Laars Rheos RHCH User manual

Installation and Operation Instructions Document 1170F
H2300300F
Installation and Operation
Instructions for
RheosTM
Modulating Boiler
Model RHCH
Modulating Water Heater
Model RHCV
U.S. Patent No. 6,644,393
Canada Patent Pending
WARNING
If the information in this manual is not
followed exactly, a re or explosion may
result causing property damage, personal
injury or loss of life.
Do not store or use gasoline or other
ammable vapors and liquids in the vicinity
of this or any other appliance.
WHAT TO DO IF YOU SMELL GAS
• Do not try to light any appliance.
• Do not touch any electrical switch; do not
use any phone in your building.
• Immediately call your gas supplier from a
nearby phone. Follow the gas supplier's
instructions.
• If you cannot reach your gas supplier, call
the re department.
Installation and service must be performed
by a qualied installer, service agency, or gas
supplier.
FOR YOUR SAFETY: This product must be installed and serviced by a professional service technician,
qualied in hot water boiler installation and maintenance. Improper installation and/or operation could
create carbon monoxide gas in ue gases which could cause serious injury, property damage, or death.
Improper installation and/or operation will void the warranty.
AVERTISSEMENT
Assurez-vous de bien suivres les instructions
données dans cette notice pour réduire au
minimum le risque d’incendie ou d’explosion
ou pour éviter tout dommage matériel, toute
blessure ou la mort.
Ne pas entreposer ni utiliser d’essence ni
d’autres vapeurs ou liquides inammables dans
le voisinage de cet appareil ou de tout autre
appareil.
QUE FAIRE SI VOUS SENTEZ UNE ODEUR DE GAZ:
• Ne pas tenter d’allumer d’appareils.
• Ne touchez à aucun interrupteur. Ne pas vous
servir des téléphones dansle bâtiment où vous
vous trouvez.
• Appelez immédiatement votre fournisseur de
gaz depuis un voisin. Suivez les instructions
du fournisseur.
• Si vous ne pouvez rejoindre le fournisseur de
gaz, appelez le sservice des incendies.
L’installation et l’entretien doivent être assurés par
un installateur ou un service d’entretien qualié ou
par le fournisseur de gaz.

LAARS Heating Systems
Page 2
TABLE OF CONTENTS
SECTION 1.
General Information
1.1 Introduction ........................................................ 3
1.2 Model Identication............................................ 3
1.3 Warranty ............................................................ 4
1.4 Dimensions ........................................................ 4
1.5 Outdoor Installations .......................................... 6
1.6 Locating the Appliance....................................... 6
1.7 Locating Pump-Mounted Water
Heater with Respect to Storage Tank(s) ............ 6
1.8 Locating Pump-Mounted Boiler with
Respect to Return/Supply Header ..................... 6
1.9 Locating Appliance for Correct Vent Distance
From Outside Wall or Roof Termination............. 6
SECTION 2.
Venting and Combustion Air
2.1 Combustion Air .................................................. 7
2.1.1 Combustion Air From Room .............................. 7
2.1.2 Intake Combustion Air........................................ 7
2.2 Venting............................................................... 9
2.3 Locating Vent & Combustion Air Terminals........ 9
2.3.1 Side Wall Vent Terminal ..................................... 9
2.3.2 Side Wall Combustion Air Terminal...................11
2.3.3 Vertical Vent Terminal .......................................11
2.3.4 Vertical Combustion Air Terminal ..................... 15
2.4 Common Vent Test – Boilers............................ 15
SECTION 3.
Gas Supply and Piping
3.1 Gas Supply and Piping .................................... 15
SECTION 4A.
Water Connections – Rheos Boiler
4A.1 Heating System Piping:
Hot Supply Connections – Boiler ..................... 18
4A.2 Cold Water Make-Up – Boiler .......................... 18
4A.3 Water Flow Requirements – Boiler .................. 18
4A.4 Freeze Protection – Boiler ............................... 19
SECTION 4B.
Water Connections – Rheos Water Heater
4B.1 Water System Piping – Water Heater .............. 19
4B.2 Hot Water Supply Piping – Water Heater......... 19
4B.3 Water Flow Requirements – Water Heater ...... 20
4B.4 Combined Water (potable)
Heating and Space Heating............................. 20
4B.5 Freeze Protection — Water Heater.................. 20
SECTION 5.
Electrical Connections
5.1 Main Power...................................................... 21
5.2 Pump Connections .......................................... 21
5.3 Temperature Control – Boiler........................... 21
5.4 Temperature Control – Water Heater............... 21
5.4.1 Remote Water Heater Temperature Control .... 21
5.4.2 Internal Water Heater Temperature Control ..... 22
5.5 Temperature Control Features......................... 22
5.5.1 Temperature Setpoint ...................................... 24
5.5.2 Differential Setting............................................ 24
5.5.3 Offset ............................................................... 24
5.5.4 Throttling Range .............................................. 24
5.5.5 Minimum Output Setting .................................. 24
5.5.6 Integration Constant ........................................ 24
5.6 External Control Connections .......................... 25
5.7 Wiring Diagrams .............................................. 25
SECTION 6.
Operating Instructions
6.1 Filling the Boiler System .................................. 38
6.2 Operating the Burner and Set Up .................... 38
6.3 Shutting Down the Rheos ................................ 40
6.4 To Restart the Rheos ....................................... 40
SECTION 7.
Maintenance
7.1 System Maintenance ....................................... 40
7.2 Appliance Maintenance and
Component Description ................................... 40
7.2.1 Burner .............................................................. 41
7.2.2 Filter................................................................. 41
7.2.3 Modulating Gas Valve ...................................... 41
7.2.4 Safety Gas Valve ............................................. 41
7.2.5 Manual Reset High Limit Control ..................... 41
7.2.6 Temperature Control ........................................ 41
7.2.7 Ignition Control................................................. 41
7.2.8 Ignitor / Flame Sensor Assembly ..................... 42
7.2.9 Transformers.................................................... 42
7.2.10 Blower............................................................ 42
7.2.11 Flow Switch.................................................... 42
7.2.12 Heat Exchanger Coil...................................... 42
7.2.13 Normally Open Vent Valve............................. 43
7.2.14 Motorized Safety Valve.................................. 43
7.2.15 Gas Pressure Switches ................................. 44
SECTION 8.
Trouble Shooting
8.1 Sequence of Operation.................................... 45
8.2 Resolving Lockouts.......................................... 45
8.3 Delayed Ignition – Possible Causes ................ 45
8.3.1 High Lockup Pressure (LP Appliances)
- Occurs on Start-up ........................................ 45
8.3.2 Gas Valve Regulation ...................................... 45
8.3.3 Defective Burner - Occurs on
Startup or at Burner Shutdown ........................ 46
8.4 Short Cycling – Boiler ...................................... 46
8.5 Short Cycling – Water Heater .......................... 46
8.6 High Gas Consumption.................................... 46
SECTION 9.
Replacement Parts
9.1 General Information ......................................... 46
9.2 Parts List.......................................................... 47
Tables Listing ................................................................. 56
Figures Listing .............................................................. 56

Rheos Boiler and Water Heater Page 3
SECTION 1.
General Information
USING THIS MANUAL – Because the Rheos
Boilers and Rheos Water Heaters are identical
appliances, with the exception of materials of
manufacture, labels and ultimate use application,
this manual provides information for the proper
installation, operation and maintenance of both
products. Where differences exist between the
application of the appliances and their operation,
the sections pertinent to only one appliance or the
other will be so identied.
WARNING
The Rheos hydronic, boiler or water heater must be
installed in accordance with the procedures detailed
in this manual, or the Laars Heating Systems
warranty will be voided. The installation must
conform to the requirements of the local jurisdiction
having authority, and, in the United States, to the
latest edition of the National Fuel Gas Code, ANSI
Z223.1/NFPA54. In Canada, the installation must
conform to the latest edition of CSA B149.1 Natural
Gas and Propane Gas Installation Code, and/or
local codes. Where required by the authority having
jurisdiction, the installation of Rheos boilers must
conform to the Standard for Controls and Safety
Devices for Automatically Fired Boilers, ANSI/ASME
CSD-1. Any modications to the boiler, its gas
controls, or wiring may void the warranty. If eld
conditions require modications, consult the factory
representative before initiating such modications.
1.1 Introduction
This manual provides information necessary for
the installation, operation, and maintenance of Laars
Heating Systems Rheos (copper tube or cupronickel
tubes) appliances. Read it carefully before installation.
All application and installation procedures
should be reviewed completely before proceeding
with the installation. Consult the Laars Heating
Systems factory, or local factory representative, with
any problems or questions regarding this equipment.
Experience has shown that most operating problems
are caused by improper installation.
The Rheos appliance is protected against over
pressurization. A pressure relief valve is tted to all
appliances. It is installed inside the jacket, at the water
outlet of the unit.
IMPORTANT: The inlet gas pressure to the appliance
must not exceed 13" W.C. (3.2kPa).
All installations must be made in accordance
with 1) American National Standard Z223.1/NFPA54-
Latest Edition “National Fuel Gas Code” or 2) CSA
B149.1 “Natural Gas and Propane Installation Code”
and with the requirement of the local utility or other
authorities having jurisdiction. Such applicable
requirements take precedence over the general
instructions contained herein.
All electrical wiring is to be done in accordance
with the local codes, or in the absence of local codes,
with: 1) The National Electrical Code ANSI/NFPA No.
70-latest Edition, or 2) CSA STD. C22.1 “Canadian
Electrical Code - Part 1”. This appliance must be
electrically grounded in accordance with these codes.
1.2 Model Identication
Consult the rating plate on the unit. The
following information describes the model number
structure.
(1-2) Model Series Designation
R H = Rheos mid-sized commercial
(3) Model Efciency
C = Mid Efciency (non-condensing)
H = High Efciency (condensing)
(4) Usage
H = Hydronic
V = Volume Water
(5-8) Size
1 2 0 0 = 1,200,000 BTU/hr input
1 6 0 0 = 1,600,000 BTU/hr input
2 0 0 0 = 2,000,000 BTU/hr input
2 4 0 0 = 2,400,000 BTU/hr input
Model Designation
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
R H 0 0 A F
SERIES
R H C
H
USAGE
H
V
SIZE
1 2 0 0
1 6 0 0
2 0 0 0
2 4 0 0
FUEL
N
P
ALTITUDE
A
FIRING
MODE
F
LOCATION
I
C
REVISION
1
2
HEAT
EXCHANGER
E
F
OPTION
CODES
X X
A H
B N
C S
D
E
F
G

LAARS Heating Systems
Page 4
(9) Fuel
N = Natural Gas
P = Liquid Propane
(10) Altitude
A = Universal Altitude (0' to 10,000') (0m to 3050m)
(11) Location
C = Indoor and Outdoor (for non-condensing units)
I = Indoor (for condensing units)
(12) Firing Mode
F = Modulating
(13) Revision
1 = First version
2 = Second version
(14) Heat Exchanger
E = Glass-lined steel with copper tubes
F = Glass-lined steel with cupronickel tubes
(15) Control Option Code
X = Standard, meets CSD-1 boiler standard
A = Control Pack A: CSD-1, CA, FM, IL, IRI,
Alarm Bell
B = Control Pack B: CSD-1, CA, FM, IL, LDS, MN
C = Control Pack C: with 200°F (93°C) max.
control (KY)
D = Control Pack A with 200°F (93°C) max. control
E = Control Pack B with 200°F (93°C) max. control
F = Non CSD-1
G = Non CSD-1 with 200°F (93°C) max. control
(16) Pump Options
X = No Pump
H = Pump mounted, hard water pump
N = Pump mounted, normal pump
S = Pump mounted, soft water pump (volume
water, high efciency (condensing) model only)
1.3 Warranty
Laars Heating Systems’ Rheos appliances are
covered by a limited warranty. The owner should ll
out the warranty registration card and return it to Laars
Heating Systems.
All warranty claims must be made to an
authorized Laars Heating Systems representative or
directly to the factory. Claims must include the serial
number and model (this information can be found
on the rating plate), installation date, and name of
the installer. Shipping costs are not included in the
warranty coverage.
Some accessory items are shipped in separate
packages. Verify receipt of all packages listed on
the packing slip. Inspect everything for damage
immediately upon delivery, and advise the carrier of
any shortages or damage. Any such claims should be
led with the carrier. The carrier, not the shipper, is
responsible for shortages and damage to the shipment
whether visible or concealed.
1.4 Dimensions
The overall dimensions are 34.5" (88cm)
wide, 65.75" (167cm) tall, 55" (140cm) deep. Other
dimensions can be found in Figure 1.

Rheos Boiler and Water Heater Page 5
3.75
10
65.75
167
55
140
CB
D
7.75
20
"S" WATER OUTLET
"W" WATER INLET
NON-PUMP-MOUNTED UNIT
"P" WATER INLET PUMP-MOUNTED UNIT
13
33
48
122
17.25
44
30.5
77
53
135
"G" GAS CONNECTION
"A" AIR INLET
WITH AIR FILTER
"V" FLUE VENT (CAT. IV) OUTLET
34.5
88
Figure 1. Dimensional Drawing.
Dimensions shown in inches cm.
Model "V" Vent Outlet
Connection
"A" Air Inlet Con-
nection
"W" Inlet Water
Connection Non-
Pump-Mounted
"P" Inlet Water
Connection Pump-
Mounted
"S" Outlet Water
Connection All
Models
inches cm inches cm NPT NPT NPT
1200 6 15 615 2-1/2" 2-1/2" 2-1/2"
1600 6 15 820 2-1/2" 3" 2-1/2"
2000 7 18 820 3" 2-1/2" 3"
2400 10 25 820 3" 3" 3"
Model "G" Gas Con-
nects. Std/Control
Pk A Nat/LP
Control
Pk B & E
Nat
Control
Pk B & E
LP
"B" "C" "D"
NPT NPT NPT inches cm inches cm inches cm
1200 1" 1-1/2" 1-1/2" 34-1/4 87 27-3/4 70 9-3/4 25
1600 1-1/2" 2" 2" 34-1/4 87 25-1/2 65 10-1/2 27
2000 1-1/2" 2" 1" 34-1/4 87 24-3/4 63 9-3/4 25
2400 1-1/2" 2" 2" 32 81 22-1/2 57 10-1/2 27

LAARS Heating Systems
Page 6
1.5 Outdoor Installations
Attach the appropriate termination and appliance
adaptor to the vent outlet (see Table 1). Units are
shipped with a louvered cover over the ducted air
connection. Do not remove this cover, and/or add any
piping to the ducted air connection. The unit will take
its combustion air through the louvers in the jacket.
WARNING
The outdoor terminal gets hot. Unit must be
installed in such a way as to reduce the risk of
burns from contact with the vent terminal.
The dimensions and requirements that are shown
in Table 2 should be met when choosing the locations
for the appliance:
Required Suggested
Clearance From Service
Appliance Combustible Material Clearance
Surface inches cm inches cm
Piping Side 1 2.5 24 61
Opposite Side 1 2.5 24 61
Top 1 2.5 24 61
Back 1 2.5 36 91
Front 1 2.5 36 91
Vent per UL1738 venting system
supplier's instructions
Table 2. Clearances.
1.7 Locating Pump-Mounted Water Heater
with Respect to Storage Tank(s)
For best results a pump-mounted Rheos water
heater should be located within 15 feet (4.6m) of the
storage tank(s). The pump is sized for 30 feet (9.1m)
of piping.
Water heater pumps are sized for water hardness;
7.6 to 17 grains per gallon for normal water, and
greater than 17 grains per gallon for hard water. If
the system has soft water (1 to 7.5 grains per gallon
hardness), but the Rheos has a normal water pump
mounted in it, please consult the factory for assistance.
If the appliance must be installed with longer
piping runs, then larger diameter pipe or tubing may be
able to be used, in some instances. Consult the factory
for assistance.
1.8 Locating Pump-Mounted Boiler with
Respect to Return/Supply Header
For the best results a pump-mounted Rheos
Boiler should be located within 15 feet (4.6m) of
the supply and return headers. The pump is sized for
30 feet (9.1m) of piping, in most cases, enough for
primary-secondary piping systems.
If the appliance must be installed with longer
piping runs, then larger diameter tubing may be able
to be used, in some instances. Consult the factory for
assistance.
1.9 Locating Appliance for Correct Vent
Distance From Outside Wall or
Roof Termination
The forced draft combustion air blower in the
appliance has sufcient power to vent properly when
the guidelines in Table 3 are followed.
NOTE: When located on the same wall, the Rheos
combustion air intake terminal must be installed
a minimum of 12" (30cm) below the exhaust vent
terminal and separated by a minimum of 36 inches
(91cm) horizontally.
Model (Size) Termination Appliance Adapter
1200 D2008300 D2008500
1600 D2008300 D2008500
2000 D2008400 D2008600
2400 D2007500 D2007600
Table 1. Terminals for Outdoor Installation.
In installations where the air temperature may
go below 15°F (-9°C), a valve heater kit, part number
R2010100, must be installed on the operating gas
valve. Instructions for the installation of the valve
heater are included with the kit.
NOTE: Units built with control packs B and E
have two actuators. Therefore, two heater kits must be
used.
1.6 Locating the Appliance
The appliance should be located to provide
clearances on all sides for maintenance and inspection.
It should not be located in an area where leakage of
any connections will result in damage to the area
adjacent to the appliance or to lower oors of the
structure.
When such a location is not available, it is
recommended that a suitable drain pan, adequately
drained, be installed under the appliance.
The appliance is design certied by CSA-
International for installation on combustible ooring;
in basements; in closets, utility rooms or alcoves.
Rheos Boilers or Water Heaters must never be
installed on carpeting. The location for the appliance
should be chosen with regard to the vent pipe lengths
and external plumbing. The unit shall be installed such
that the gas ignition system components are protected
from water (dripping, spraying, rain, etc.) during
operation and service (circulator replacement, control
replacement, etc.). When vented vertically, the Rheos
must be located as close as practical to a chimney
or gas vent. If the vent terminal and/or combustion
air terminal terminate through a wall, and there is
potential for snow accumulation in the local area, both
terminals should be installed at an appropriate level
above grade.

Rheos Boiler and Water Heater Page 7
SECTION 2.
Venting and Combustion Air
2.1 Combustion Air
Rheos boilers and water heaters must have
provisions for combustion and ventilation air in
accordance with section 5.3, Air for Combustion and
Ventilation, of the National Fuel Gas Code, ANSI
Z223.1, or Sections 7.2, 7.3 or 7.4 of CSA B149.1,
Installation Codes, and applicable provisions of the
local building codes.
A Rheos unit can take combustion air from the
space in which it is installed, or the combustion air can
be ducted directly to the unit. Ventilation air must be
provided in either case.
2.1.1 Combustion Air From Room
In the United States, the most common
requirements specify that the space shall communicate
with the outdoors in accordance with method 1 or 2,
which follow. Where ducts are used, they shall be of
the same cross-sectional area as the free area of the
openings to which they connect.
Method 1: Two permanent openings, one
commencing within 12" (300mm) of the top and one
commencing within 12" (300mm) of the bottom, of
the enclosure shall be provided. The openings shall
communicate directly, or by ducts, with the outdoors
or spaces that freely communicate with the outdoors.
When directly communicating with the outdoors, or
when communicating to the outdoors through vertical
ducts, each opening shall have a minimum free area
of 1 square inch per 4000 Btu/hr (550 square mm/kW)
of total input rating of all equipment in the enclosure.
When communicating to the outdoors through
horizontal ducts, each opening shall have a minimum
free area of not less than 1 square inch per 2000 Btu/hr
(1100 square mm/kW) of total input rating of all
equipment in the enclosure.
Method 2: One permanent opening, commencing
within 12" (300mm) of the top of the enclosure, shall
be permitted. The opening shall directly communicate
with the outdoors or shall communicate through a
vertical or horizontal duct to the outdoors or spaces
that directly communicate with the outdoors and shall
have a minimum free area of 1 square inch per 3000
Btu/hr (734 square mm/kW) of the total input rating of
all equipment located in the enclosure. This opening
must not be less than the sum of the areas of all vent
connectors in the conned space.
Other methods of introducing combustion and
ventilation air are acceptable, providing they conform
to the requirements in the applicable codes listed
above.
In Canada, consult local building and safety
codes or, in absence of such requirements, follow
CAN/CGA B149.
2.1.2 Intake Combustion Air
The combustion air can be taken through the
wall, or through the roof. When taken from the wall, it
must be taken from out-of-doors by means of the Laars
horizontal wall terminal, shown in Table 4. See Table 3
to select the appropriate diameter air pipe. When taken
from the roof, a eld-supplied rain cap or an elbow
arrangement must be used to prevent entry of rain
water (see Figure 2).
Use single-wall galvanized pipe for the
combustion air intake (see Table 5), sized per Section
1.8. Route the intake to the heater as directly as
possible. Seal all joints with tape. Provide adequate
hangers. The unit must not support the weight of the
combustion air intake pipe. Maximum linear pipe
length allowed is 50 feet (15.2m). Up to ve elbows
can be used with the 50 feet of pipe. Subtract 10
allowable linear feet for every additional elbow used.
Figure 2. Combustion Air and Vent Through Roof.
Model Intake Exhaust Intake Exhaust
Size Size Maximum Run Maximum Run
1200 6" (15 cm) dia. 6" (15 cm) dia. 50 linear feet with 5 elbows 50 linear feet with 5 elbows
1600 8" (20 cm) dia. 6" (15 cm) dia. 50 linear feet with 5 elbows 50 linear feet with 5 elbows
2000 8" (20 cm) dia. 7" (18 cm) dia. 50 linear feet with 5 elbows 50 linear feet with 5 elbows
2400 8" (20 cm) dia. 10" (25 cm) dia. 50 linear feet with 5 elbows 50 linear feet with 5 elbows
Table 3. Vent / Air Pipe Sizes.

LAARS Heating Systems
Page 8
Figure 3. Combustion Air and Vent Through Side Wall.
U.S. Installations (see note 1) Canadian Installations (see note 2)
A= Clearance above grade, veranda, porch, 12 inches (30 cm) 12 inches (30 cm)
deck, or balcony
B= Clearance to window or door that may be 4 feet (1.2 m) below or to side of opening; 36 inches (91 cm)
opened 1 foot (30 cm) above opening
C= Clearance to permanently closed window See note 4 See note 5
D= Vertical clearance to ventilated soft located
above the terminal within a horizontal See note 4 See note 5
distance of 2 feet (61cm) from the center line
of the terminal
E= Clearance to unventilated soft See note 4 See note 5
F= Clearance to outside corner See note 4 See note 5
G= Clearance to inside corner See note 4 See note 5
H= Clearance to each side of center line 3 feet (91 cm) within a height 15 feet above
extended above meter/regulator assembly See note 4 the meter/regulator assembly
I= Clearance to service regulator vent outlet See note 4 3 feet (91 cm)
J= Clearance to nonmechanical air supply inlet
to building or the combustion air inlet to 4 feet (1.2 m) below or to side of opening; 36 inches (91 cm)
any other appliance 1 foot (30 cm) above opening
K= Clearance to a mechanical air supply inlet 3 feet (91 cm) above if within 10 feet (3 m) 6 feet (1.83 m)
horizontally
Vent termination not allowed in this location for
Vent termination not allowed in this location category IV appliances. A vent shall not
L= Clearance above paved sidewalk or paved for category IV appliances. For Category III terminate directly above a sidewalk or paved
driveway located on public property appliances, vent must terminate at least 7 driveway that is located between two single
feet (2.13m) above the sidewalk or driveway. family dwellings and serves both dwellings.
For Category III appliances that do not violate
the previous condition, vent must terminate at
least 7 feet (2.13m) above the sidewalk or
driveway.
M= Clearance under veranda, porch, deck, See note 4 12 inches (30 cm) (see note 3)
or balcony
Notes:
1. In accordance with the current ANSI Z223.1 / NFPA 54 National Fuel Gas Code.
2. In accordance with the current CAN/CGA-B149 Installation Codes.
3. Permitted only if veranda, porch, deck, or balcony is fully open on a minimum of two sides beneath the oor.
4. For clearances not specied in ANSI Z223.1 / NFPA 54, clearance is in accordance with local installation codes and the requirements of the
gas supplier.
5. For clearances not specied in CAN/CGA-B149, clearance is in accordance with local installation codes and the requirements of the gas
supplier.

Rheos Boiler and Water Heater Page 9
Model Horizontal Combustion Horizontal Vent
Air Terminal Terminal
1200 20260701 D2004500
1600 20260703 D2004500
2000 20260703 D2004600
2400 20260703 D2006200
Table 4. Horizontal Vent and Air Terminals
For Indoor Installations.
Term Description
Pipe Single-wall galvanized steel pipe, 24 gauge
minimum (sized per section 1.9)
Joint Permanent duct tape or aluminum tape
Sealing
Insulation Not required, but recommended R5 insulation
for cold installations (consult American Society
of Heating, Refrigerating, and Air Conditioning
Engineers (ASHRAE) handbook)
Table 5. Required Combustion Air Piping Material.
The connection for the intake air pipe is in the
back of the unit. Take the plate off the back to reveal
the collar on the lter box. Run a bead of silicone
around the collar and slide the pipe over the collar.
Secure with sheet metal screws.
In addition to air needed for combustion, air
shall also be supplied for ventilation, including all air
required for comfort and proper working conditions
for personnel. The Rheos loses less than 1 percent of
its input rating to the room, but other heat sources may
be present.
2.2 Venting
The Rheos is a Category IV appliance and must
be installed with a stainless steel venting system
that complies with the UL 1738 Standard (see Table
6). It must be installed per this installation manual
and the venting system manufacturer’s Installation
Instructions. The unit’s vent can terminate through the
roof, or through an outside wall. It can be installed
through walls that are from 3" (7.6cm) to 12" (30cm)
in thickness.
See Table 3 to select the appropriate vent pipe
diameter. The rst section of venting attached to the
boiler must include a condensate drain tting and
condensate trap. Route the vent pipe to the heater
as directly as possible. Seal all joints and provide
adequate hangers as required in the venting system
manufacturer’s Installation Instructions. Horizontal
portions of the venting system must be supported to
prevent sagging and may not have any low sections
that could trap condensate. The unit must not support
the weight of the vent pipe. Horizontal runs must slope
upwards not less than ¼ inch per foot (21mm/m) from
the unit to the vent terminal. Up to ve elbows can
be used with the 50 feet (15.2m) of pipe. Subtract 10
allowable linear feet for every additional elbow used.
IMPORTANT NOTE ABOUT COMMON VENTING:
A single vent that is shared by multiple Rheos
units MUST be engineered by a competent venting
specialist, and involves the selection of draft inducing
equipment, hardware and controls to properly balance
ue gas pressures. Do not common vent Rheos
units unless the vent system meets this requirement.
Rheos units are never permitted to share a vent with
Category I applliances.
For outdoor applications, see Section 1.5.
Condensate Drain Connection: A condensate
drain connection shall be provided on the rst section
of venting attached to the boiler. Connect a clear
plastic tube between that drain connection on the
vent and a oor drain (or optional condensate pump
if a oor drain is not accessible). The plastic tube
shall be formed into a loop (trap) to drain condensate
that collects in the vent system without permitting
ue gases to escape. The condensate drain must be
installed so as to prevent accumulation of condensate.
Consult local codes for disposal method.
Term Description
Venting Heat-Fab®, Inc. Saf-T Vent®GC or CI,
System Metal-Fab®, Inc. Corr/Guard, or
equivalent sealed stainless steel
system certied to UL1738.
Insulation Not required, but recommended R5
insulation with protective cover for cold
installations (consult American Society of
Heating, Refrigerating, and Air Conditioning
Engineers (ASHRAE) handbook)
Table 6. Required Venting Material.
2.3 Locating Vent & Combustion Air
Terminals
2.3.1 Side Wall Vent Terminal
The appropriate Laars side wall vent hood must
be used, and is listed in the installation and operation
manual. The terminal provides a means of installing
the vent piping through the building wall, and must
be located in accordance with ANSI Z223.1/NFPA 54
and applicable local codes. In Canada, the installation
must be in accordance with CSA B149.1 or .2 and
local applicable codes. Consider the following when
installing the terminal:
1. The gure in this addendum shows the
requirements for mechanical vent terminal
clearances for the U.S. and Canada.
2. Vent terminals for condensing appliances or
appliances with condensing vents are not
permitted to terminate above a public walkway,
or over an area where condensate or vapor could
create a nuisance or hazard.

LAARS Heating Systems
Page 10
Model and Distance from Gas Meter or Last Stage Regulator
Gas Type 0-50 feet 0-15m 50-100 feet 15-31m 100-200 feet 31-61m 200-300 feet 61-91m
1200 natural 2" 5.1cm 2-1/2" 6.4cm 2-1/2" 6.4cm 3" 7.6cm
1200 propane 1-1/2" 3.8cm 2" 5.1cm 2" 5.1cm 2-1/2" 6.4cm
1600 natural 2-1/2" 6.4cm 2-1/2" 6.4cm 3" 7.6cm 3" 7.6cm
1600 propane 2" 5.1cm 2" 5.1cm 2-1/2" 6.4cm 2-1/2" 6.4cm
2000 natural 2-1/2" 6.4cm 3" 7.6cm 3" 7.6cm 3-1/2" 8.9cm
2000 propane 2-1/2" 6.4cm 2-1/2" 6.4cm 2-1/2" 6.4cm 3" 7.6cm
2400 natural 2-1/2" 6.4cm 3" 7.6cm 3" 7.6cm 3-1/2" 8.9cm
2400 propane 2" 5.1cm 2-1/2" 6.4cm 2-1/2" 6.4cm 3" 7.6cm
Notes: 1. These gures are based on 1/2" 0.12kPa water column pressure drop.
2. Check supply pressure and local code requirements before proceeding with work.
3. Pipe ttings must be considered when determining gas pipe sizing.
Table 7. Gas Piping Sizes.
3. Locate the vent terminal so that vent gases cannot
be drawn into air conditioning system inlets.
4. Locate the vent terminal so that vent gases cannot
enter the building through doors, windows,
gravity inlets or other openings. Whenever
possible, locations under windows or near doors
should be avoided.
5. Locate the vent terminal so that it cannot be
blocked by snow. The installer may determine
that a vent terminal must be higher than the
minimum shown in codes, depending upon local
conditions.
6. Locate the terminal so the vent exhaust does
not settle on building surfaces or other nearby
objects. Vent products may damage such
surfaces or objects.
7. If the boiler or water heater uses ducted
combustion air from an intake terminal located
on the same wall, locate the vent terminal at least
3 feet (0.9m) horizontally from the combustion
air terminal, and locate the vent terminal at least
1 foot (0.3m) above the combustion air terminal.
From Massachusetts Rules and Regulations
248 CMR 5.08:
(a) For all side wall horizontally vented gas
fueled equipment installed in every dwelling,
building or structure used in whole or inpart
for residential purposes, including those
owned or operated by the Commonwealth and
where the side wall exhaust vent termination
is less than seven (7) feet above nished grade
in the area of the venting, including but not
limited to decks and porches, the following
requirements shall be satised:
1. INSTALLATION OF CARBON MONOXIDE
DETECTORS.
At the time of installation of the side wall
horizontal vented gas fueled equipment, the
installing plumber or gastter shall observe that
a hard-wired carbon monoxide detector with
an alarm and battery back-up is installed on
the oor level where the gas equipment is to be
installed. In addition, the installing plumber or
gastter shall observe that a battery operated or
hard-wired carbon monoxide detector with an
alarm is installed on each additional level of the
dwelling, building or structure served by the side
wall horizontal vented gas fueled equipment.
It shall be the responsibility of the property
owner to secure the services of qualied licensed
professionals for the installation of hard-wired
carbon monoxide detectors.
a. In the event that the side wall
horizontally vented gas fueled equipment is
installed in a crawl space or an attic, thehard-
wired carbon monoxide detector with alarm
and battery back-up may be installed on the
next adjacent oor level.
b. In the event that the requirements of
this subdivision cannot be met at the time of
completion of installation, the owner shall
have a period of thirty (30) days to comply
with the above requirements; provided,
however, that during said thirty (30) day
period, a battery operated carbon monoxide
detector with an alarm shall be installed.
2. APPROVED CARBON MONOXIDE
DETECTORS.
Each carbon monoxide detector as required
in accordance with the above provisions shall
comply with NFPA 720 and be ANSI/UL 2034
listed and IAS certied.
3. SIGNAGE.
A metal or plastic identication plate shall be
permanently mounted to the exterior of the
building at a minimum height of eight (8) feet

Rheos Boiler and Water Heater Page 11
above grade directly in line with the exhaust vent
terminal for the horizontally vented gas fueled
heating appliance or equipment. The sign shall
read, in print size no less than one-half (½) inch
in size, “GAS VENT DIRECTLY BELOW.
KEEP CLEAR OF ALL OBSTRUCTIONS”.
4. INSPECTION.
The state or local gas inspector of the side
wall horizontally vented gas fueled equipment
shall not approve the installation unless, upon
inspection, the inspector observes carbon
monoxide detectors and signage installed in
accordance with the provisions of 248 CMR
5.08(2)(a) 1 through 4.
(b) EXEMPTIONS: The following equipment is
exempt from 248 CMR 5.08(2)(a) 1 through 4:
1. The equipment listed in Chapter 10 entitled
“Equipment Not Required To Be Vented” in the
most current edition of NFPA 54 as adopted by
the Board; and
2. Product Approved side wall horizontal vented gas
fueled equipment installed in a room or structure
separate from the dwelling, building or structure
used in whole or in part for residential purposes.
(c) MANUFACTURER REQUIREMENTS
– GAS EQUIPMENT VENTING SYSTEM
PROVIDED. When the manufacturer of
Product Approved side wall horizontally
vented gas equipment provides a venting
system design or venting system components
with the equipment, the instructions provided
by the manufacturer for installation of the
equipment and the venting system shall
include:
1. Detailed instructions for the installation of the
venting system design or the venting system
components; and
2. A complete parts list for the venting system
design or venting system.
(d) MANUFACTURER REQUIREMENTS –
GAS EQUIPMENT VENTING SYSTEMNOT
PROVIDED. When the manufacturer of a
Product Approved side wall horizontally
vented gas fueled equipment does not
provide the parts for venting the fuel gases,
but identies “special venting systems”, the
following requirements shall be satised by
the manufacturer:
1. The identication of each “special venting
system” shall include either the listing of the
website, phone number or manufacturer’s address
where the venting system installation instructions
can be obtained; and
2. The “special venting systems” shall be Product
Approved by the Board, and the instructions
provided with that system shall include a parts
list and detailed installation instructions.
(e) A copy of all installation instructions for the
Product Approved side wall horizontally
vented gas fueled equipment, and all the
venting instructions, parts lists, and/or design
instructions for the venting system shall
remain with the appliance or equipment at the
completion of the installation.
Manufacturers' websites where venting system
installation instructions may be obtained is
located on the Laars website at: http://www.
laars.com.
2.3.2 Side Wall Combustion Air Terminal
The Laars side wall combustion air terminal (see
Table 4) must be used when the heater takes air from a
side wall. Consider the following when installing the
terminal:
1. Do not locate the air inlet terminal near a source
of corrosive chemical fumes (e.g., cleaning uid,
chlorine compounds, etc.)
2. Locate the terminal so that it will not be subject
to damage by accident or vandalism. It must be at
least 7 feet (2.1m) above a public walkway.
3. Locate the combustion air terminal so that it
cannot be blocked by snow. The National Fuel
Gas Code requires that it be at least 12 inches
(30cm) above grade, but the installer may
determine it should be higher, depending upon
local conditions.
4. If the Rheos is side-wall vented to the same wall,
locate the vent terminal at least 3 feet (0.9m)
horizontally from the combustion air terminal,
and locate the vent terminal at least 1 foot (0.3m)
above the combustion air terminal (see Figure 3).
2.3.3 Vertical Vent Terminal
When the unit is vented through the roof, the
vent must extend at least 3 feet (0.9m) above the point
at which it penetrates the roof. It must extend at least
2 feet (0.6m) higher than any portion of a building
within a horizontal distance of 10 feet (3.0m), and high
enough above the roof line to prevent blockage from
snow. When the combustion air is taken from the roof,
the combustion air must terminate at least 12" (30cm)
below the vent terminal (see Figure 2).

LAARS Heating Systems
Page 12
SYSTEM
BOILER CIRC.
PUMP
SYSTEM PUMP
THERMOMETER
GLOBE VALV E
CHECK VALV E
PRESSURE REDUCING VALV E
W/ FAST FILL BYPASS
EXPANSION TANK
WITH AIR SCOOP AND
AUTO AIR VENT
PUMP
LEGEND
VALV E
TEMPERATURE
SENSOR
3-WAY VALVE
PURGE
VALV E
C
COLD WATER
MAKE-UP
OPTIONAL PUMP MOUNTED UNIT AVAILABLE
C
RETURN
SYSTEM
SUPPLY
INSTALL AIR VENTS AT HIGH POINTS IN SYSTEM
PIPING&SIZING OF EXPANSION TANK
PER TANK MANUFACTURER'S INSTRUCTIONS
PRIMARY/SECONDARY MANDITORY FOR ALL
VARIABLE FLOW SYSTEMS
DIMENSION ''C'' TO BE4PIPE DIAMETERS
BOILER CIRC. PUMP SIZED FOR FLOW THROUGH BOILER
BOILER CIRC. PUMP TO BE USED WITH EM
DOTTED DEVICES INDICATE ALTERNATE LOCATIONS
BOILER CIRCUIT PIPING MUST BE EQUAL TO
BOILER WATER CONNECTION SIZE
SYSTEM TEMP. INTERLOCK REQUIRED
MULTIPLE STAGE BOILERS RECOMMENDED
2
CAUTION: THIS DRAWING SHOWS SUGGESTED
PIPING CONFIGURATION AND VALVING. CHECK
WITH LOCAL CODES AND ORDINANCES FOR
ADDITIONAL REQUIREMENTS.
D D
DIMENSION ''D'' TO BE 18" MINIMUM
THERMOMETER
GLOBE VALVE
CHECK VALVE
PRESSURE REDUCING VALVE
W/ FAST FILL BYPASS
EXPANSION TANK
WITH AIR SCOOP AND
AUTO AIR VENT
PUMP
LEGEND
VALVE
TEMPERATURE
SENSOR
3-WAY VALVE
PURGE
VALVE
SYSTEM
RETURN SYSTEM
SUPPLY
INSTALL AIR VENTS AT HIGH POINTS IN SYSTEM
PIPING&SIZING OF EXPANSION TANK
PER TANK MANUFACTURER'S INSTRUCTIONS
PRIMARY/SECONDARY MANDITORY FOR ALL
VARIABLE FLOW SYSTEMS
BOILER CIRC. PUMP SIZED FOR FLOW THROUGH BOILER
BOILER CIRC. PUMP TO BE USED WITH EM
DOTTED DEVICES INDICATE ALTERNATE LOCATIONS
BOILER CIRCUIT PIPING MUST BE EQUAL TO
BOILER WATER CONNECTION SIZE
SYSTEM TEMP. INTERLOCK REQUIRED
MULTIPLE STAGE BOILERS RECOMMENDED
2
CAUTION: THIS DRAWING SHOWS SUGGESTED
PIPING CONFIGURATION AND VALVING. CHECK
WITH LOCAL CODES AND ORDINANCES FOR
ADDITIONAL REQUIREMENTS.
BOILER CIRC.
PUMP
C
A
B
T1
ADJUSTMENT PROCEDURE TO MAINTAIN 130°FINLET TEMP.
1. Turn on heater and open valves A&B
3. If T1 is greater than 130° F, slowly
close valve A until T1 dropsto 130° F
4. Check after system operating temperature has
2. After steady-state operation, if T1 is less than
130° F, slowly close valve B until T1 climbs to 130° F
stabilized. Make final adjustments
OPTIONAL PUMP MOUNTED
UNIT AVAILABLE
COLD WATER
MAKE-UP
SYSTEM PUMP
B
C
A
B
T1
DD
DIMENSION ''C'' TO BE4PIPE DIAMETERS
DIMENSION ''D'' TO BE 18" MINIMUM
Figure 4. Hydronic Piping — Multiple Boilers, Primary Secondary System.
Figure 5. Hydronic Piping — Multiple Boilers, Low Temperature System.

Rheos Boiler and Water Heater Page 13
THERMOMETER
GLOBE VALV E
CHECK VALV E
PRESSURE REDUCING VALV E
W/ FAST FILL BYPASS
EXPANSION TANK
WITH AIR SCOOP AND
AUTO AIR VENT
PUMP
LEGEND
VALV E
TEMPERATURE
SENSOR
3-WAY VALVE
PURGE
VALV E
INSTALL AIR VENTS AT HIGH POINTS IN SYSTEM
PIPING&SIZING OF EXPANSION TANK
PER TANK MANUFACTURER'S INSTRUCTIONS
PRIMARY/SECONDARY MANDITORY FOR ALL
VARIABLE FLOW SYSTEMS
BOILER CIRC. PUMP SIZED FOR FLOW THROUGH BOILER
BOILER CIRC. PUMP TO BE USED WITH EM
DOTTED DEVICES INDICATE ALTERNATE LOCATIONS
BOILER CIRCUIT PIPING MUST BE EQUAL TO
BOILER WATER CONNECTION SIZE
SYSTEM TEMP. INTERLOCK REQUIRED
MULTIPLE STAGE BOILERS RECOMMENDED
2
CAUTION: THIS DRAWING SHOWS SUGGESTED
PIPING CONFIGURATION AND VALVING. CHECK
WITH LOCAL CODES AND ORDINANCES FOR
ADDITIONAL REQUIREMENTS.
BOILER CIRC.
PUMP
SYSTEM PUMP
C
C
C
180° F
180° F
140° F
120° F
NOTES:
1. BOILER LOOP TO BE MAINTAINED AT 180° F.
2. ZONE THERMOSTATSTOBE INTERLOCKED WITH BOILER.
BOILER TO FIRE UPON CALL FOR HEAT FROM ANY ZONE.
3. ZONE PIPING AND INTERLOCK WIRING TO BE
DESIGNED BY SYSTEM DESIGNER.
COLD WATER
MAKE-UP
OPTIONAL PUMP MOUNTED UNIT AVAILABLE
C
D
D
D
DIMENSION ''C'' TO BE4PIPE DIAMETERS
DIMENSION ''D'' TO BE 18" MINIMUM
Figure 6. Hydronic Piping — One Boiler, Multi-Temperature System.
Temperature Rise in Degrees (°F/°C)
20°F 11°C 25°F 14°C 30°F 17°C
Model Flow H/L Flow H/L Flow H/L Flow H/L Flow H/L Flow H/L
(Size) gpm feet lpm m gpm feet lpm m gpm feet lpm m
1200 104 18 395 5.5 84 12 316 3.7 70 8 264 2.4
1600 139 22 527 6.7 111 14 422 4.3 93 10 351 3.0
2000 174 20 659 6.1 139 13 527 4.0 116 9 439 2.7
2400 209 18 791 5.5 167 12 632 3.7 139 8 527 2.4
NOTE: Maximum temperature rise is 30°F (17°C), as shown. Headloss is for boiler’s heat exchanger only.
Table 8. Water Flow Requirements, RHCH (Boiler).

LAARS Heating Systems
Page 14
OPTIONAL PUMP MOUNTED UNIT AVALIABLE
BOILER CIRC.
PUMP
COLD WATER
MAKE-UP
SYSTEM PUMP
SYSTEM
RETURN
SYSTEM
SUPPLY
C
THERMOMETER
GLOBE VALV E
CHECK VALV E
PRESSURE REDUCING VALV E
W/ FAST FILL BYPASS
EXPANSION TANK
WITH AIR SCOOP AND
AUTO AIR VENT
PUMP
LEGEND
VALV E
TEMPERATURE
SENSOR
3-WAY VALVE
PURGE
VALV E
INSTALL AIR VENTS AT HIGH POINTS IN SYSTEM
PIPING&SIZING OF EXPANSION TANK
PER TANK MANUFACTURER'S INSTRUCTIONS
PRIMARY/SECONDARY MANDITORY FOR ALL
VARIABLE FLOW SYSTEMS
BOILER CIRC. PUMP SIZED FOR FLOW THROUGH BOILER
BOILER CIRC. PUMP TO BE USED WITH EM
DOTTED DEVICES INDICATE ALTERNATE LOCATIONS
BOILER CIRCUIT PIPING MUST BE EQUAL TO
BOILER WATER CONNECTION SIZE
SYSTEM TEMP. INTERLOCK REQUIRED
MULTIPLE STAGE BOILERS RECOMMENDED
PUT BOILER CONTROL SENSOR IN THE OUTLET
WHEN USING THIS PIPING STYLE
2
CAUTION: THIS DRAWING SHOWS SUGGESTED
PIPING CONFIGURATION AND VALVING. CHECK
WITH LOCAL CODES AND ORDINANCES FOR
ADDITIONAL REQUIREMENTS.
DIMENSION ''C'' TO BE4PIPE DIAMETERS
DIMENSION ''D'' TO BE 18" MINIMUM
D
Figure 7. Hydronic Piping - Alternate System.
Figure 8. Hydronic Piping - Alternate Low Temperature System.
OPTIONAL PUMP MOUNTED UNIT AVALIABLE
BOILER CIRC.
PUMP
COLD WATER
MAKE-UP
SYSTEM PUMP
SYSTEM
RETURN
SYSTEM
SUPPLY
ADJUSTMENT PROCEDURE TO MAINTAIN 130°FINLET TEMP.
1. Turn on heater and open valves A&B
2. After steady-state operation, if T1 is less than
130° F, slowly close valveBuntil T1 climbs to 130° F
3. If T1is greater than 130° F, slowly
close valve A until T1 dropsto 130° F
4. Check after system operating temperature has
stabilized. Make final adjustments.
A
B
A
B
THERMOMETER
GLOBE VALV E
CHECK VALV E
PRESSURE REDUCING VALV E
W/ FAST FILL BYPASS
EXPANSION TANK
WITH AIR SCOOP AND
AUTO AIR VENT
PUMP
LEGEND
VALV E
TEMPERATURE
SENSOR
3-WAY VALVE
PURGE
VALV E
INSTALL AIR VENTS AT HIGH POINTS IN SYSTEM
PIPING&SIZING OF EXPANSION TANK
PER TANK MANUFACTURER'S INSTRUCTIONS
PRIMARY/SECONDARY MANDITORY FOR ALL
VARIABLE FLOW SYSTEMS
BOILER CIRC. PUMP SIZED FOR FLOW THROUGH BOILER
BOILER CIRC. PUMP TO BE USED WITH EM
DOTTED DEVICES INDICATE ALTERNATE LOCATIONS
BOILER CIRCUIT PIPING MUST BE EQUAL TO
BOILER WATER CONNECTION SIZE
SYSTEM TEMP. INTERLOCK REQUIRED
MULTIPLE STAGE BOILERS RECOMMENDED
PUT BOILER CONTROL SENSOR IN THE OUTLET
WHEN USING THIS PIPING STYLE
2
CAUTION: THIS DRAWING SHOWS SUGGESTED
PIPING CONFIGURATION AND VALVING. CHECK
WITH LOCAL CODES AND ORDINANCES FOR
ADDITIONAL REQUIREMENTS.
DIMENSION ''C'' TO BE4PIPE DIAMETERS
DIMENSION ''D'' TO BE 18" MINIMUM
CD

Rheos Boiler and Water Heater Page 15
2.3.4 Vertical Combustion Air Terminal
When combustion air is taken from the roof, a
eld-supplied rain cap or an elbow arrangement must
be used to prevent entry of rain water (see Figure 2).
The opening on the end of the terminal must be at least
12" (30cm) above the point at which it penetrates the
roof, and high enough above the roof line to prevent
blockage from snow. When the vent terminates on the
roof, the combustion air must terminate at least 12"
(30cm) below the vent terminal.
2.4 Common Vent Test — Boilers
NOTE: This section does not describe a method for common
venting Rheos units. It describes what must be done when a unit is
removed from a common vent system. Rheos units require special
vent systems and fan for common vent. Contact the factory if you
have questions about common venting Rheos units.
When an existing boiler is removed from a
common venting system, the common venting system
is likely to be too large for proper venting of the
appliances remaining connected to it.
At the time of removal of an existing boiler, the
following steps shall be followed with each appliance
remaining connected to the common venting system
placed in operation, while the other appliances
remaining connected to the common venting system
are not in operation.
1. Seal any unused openings in the common venting
system.
2. Visually inspect the venting system for proper
size and horizontal pitch and determine there is
no blockage or restriction, leakage, corrosion and
other deciencies which could cause an unsafe
condition.
3. Insofar as it is practical, close all building doors
and windows and all doors between the space in
which the appliances remaining connected to the
common venting system are located and other
spaces of the building. Turn on clothes dryers
and any appliance not connected to the common
venting system. Turn on any exhaust fans, such
as range hoods and bathroom exhausts, so they
will operate at maximum speed. Do not operate a
summer exhaust fan. Close replace dampers.
4. Place in operation the appliance being
inspected. Follow the lighting instructions.
Adjust thermostat so appliance will operate
continuously.
5. Test for spillage at the draft hood relief opening
after 5 minutes of main burner operation. Use
the ame of a match or candle, or smoke from a
cigarette, cigar or pipe.
6. After it has been determined that each appliance
remaining connected to the common venting
system properly vents when tested as outlined
above, return doors, windows, exhaust fans,
replace dampers and any other gas burning
appliance to their previous conditions of use.
7. Any improper operation of the common venting
system should be corrected so that the installation
conforms to the National Fuel Gas Code, ANSI
Z223.1/NFPA 54 and/or CSA B149.1, Installation
Codes. When resizing any portion of the common
venting system, the common venting system
should be resized to approach the minimum size
as determined using the appropriate tables in Part
II of the National Fuel Gas Code, ANSI Z223.1
NFPA 54 and/or CSA B149.1, Installation Codes.
SECTION 3.
Gas Supply and Piping
3.1 Gas Supply and Piping
Gas piping should be supported by suitable
hangers or oor stands, not the appliance.
Review the following instructions before
proceeding with the installation.
1. Verify that the appliance is tted for the proper
type of gas by checking the rating plate. Laars
Heating Systems appliances are normally equipped
to operate at elevations up to 2000 feet (610m).
However, the appliance will function properly
without the use of high altitude modication at
elevations up to 10,000 feet (3050 m).
2. The maximum inlet gas pressure must not exceed
13" W.C. (3.2kPa). The minimum inlet natural
gas pressure is 4" W.C. (1.0kPa) and minimum
inlet propane gas pressure is 6" (1.5kPa).
3. Refer to Table 7, size supply.
Hard Water Normal Water Soft Water
Model Flow H/L Temp Flow H/L Temp Flow H/L Temp Flow H/L Temp Flow H/L Temp Flow H/L Temp
(Size) gpm feet Rise (°F) lpm m Rise (°C) gpm feet Rise (°F) lpm m Rise (°C) gpm feet Rise (°F) lpm m Rise (°C)
1200 119 20 18 449 6.1 10 93 12 23 351 3.7 13 65 6.0 32 246 1.8 18
1600 161 29 17 609 8.8 10 132 20 21 500 6.1 12 89 8.9 31 336 2.7 17
2000 182 22 19 690 6.7 11 149 15 23 565 4.6 13 100 6.6 35 379 2.0 19
2400 237 23 18 898 7.0 10 186 14 23 703 4.3 13 129 6.9 32 488 2.1 18
Note: Soft Water: 1 to 7.5 grains per gallon Note: Headloss is for heater’s heat exchanger only.
Normal Water: 7.6 to 17 grains per gallon
Hard Water: More than 17 grains per gallon
Table 9. Water Flow Requirements, RHCV (Water Heater).

LAARS Heating Systems
Page 16
THERMOMETER
GLOBE VALVE
CHECK VALVE
PRESSURE REDUCING VALVE
W/ FAST FILL BYPASS
EXPANSION TANK
WITH AIR SCOOP AND
AUTO AIR VENT
PUMP
LEGEND
VALVE
TEMPERATURE
SENSOR
3-WAY VALVE
NOTES:
7. CAUTION: PUMP SIZING MUST BE BASED UPON WATER HARDNESS AT JOB SITE
CAUTION: THIS DRAWING SHOWS SUGGESTED
PIPING CONFIGURATION AND VALVING CHECK
PRV
WITH LOCAL CODES AND ORDINANCES FOR
ADDITIONAL REQUIREMENTS
WATER CATEGORY GRAIN
HARDNESS PER GALLON
S=SOFT 1 THROUGH 7.5
N=NORMAL 7.6 THROUGH 17
H=HARD OVER 18
17.1PARTS PER MILLION
=1GRAIN HARDNESS PER GALLON
KEY:
2
SUPPLY
RECIRC.
CWMU
1. OPTIONAL CWMU&RECIRC. LINE LOCATION.
2. WHEN USING INTERMITTENT PUMP AND EM LOCATE REMOTE AQUASTAT
WELL IN LOWER 1/3OFTANK WITH HEAT SENCEING COMPOUND.
3. BACK FLOW PREVENTER MAYBE REQUIRED CHECK LOCAL CODES.
4. THERMAL EXPANSION TANK MAYBE REQUIRED CHECK LOCAL CODES.
5. WHEN USING OPTIONAL FACTORY MOUNTED PUMP, MAX PIPE LENGTH
30'TOTAL, 6-90° ELBOWS,FULL PIPE SIZE.
6. THIS DRAWING DEPICTS A TWO-PASS HEAT EXCHANGER.
5
TPRV
34
2
1
THERMOMETER
GLOBE VALV E
CHECK VALV E
PRESSURE REDUCING VALV E
W/ FAST FILL BYPASS
EXPANSION TANK
WITH AIR SCOOP AND
AUTO AIR VENT
PUMP
LEGEND
VALV E
TEMPERATURE
SENSOR
3-WAY VALVE
CAUTION: THIS DRAWING SHOWS SUGGESTED
PIPING CONFIGURATIONAND VA LVING CHECK
PRV
WITH LOCAL CODES AND ORDINANCES FOR
ADDITIONALREQUIREMENTS
WATERCATEGORY GRAIN
HARDNESS PER GALLON
S=SOFT1THROUGH 7.5
N=NORMAL 7.6 THROUGH 17
H=HARD OVER18
KEY:
TPRV
6. THIS DRAWING DEPICTS ATWO-PASS HEAT EXCHANGER.
30'TOTAL, 6-90° ELBOWS ,FULL PIPE SIZE.
5. WHENUSINGOPTIONALFACTORY MOUNTED PUMP,MAX PIPE LENGTH
4. THERMAL EXPANSION TANK MAYBEREQUIRED CHECK LOCAL CODES.
3. BACK FLOWPREVENTER MAYBEREQUIRED CHECK LOCAL CODES.
WELL IN LOWER 1/3 OF TA NK WITH HEAT SENCEING COMPOUND.
2. WHENUSINGINTERMITTENT PUMP ANDEMLOCATE REMOTEAQUASTAT
1. OPTIONAL CWMU&RECIRC. LINELOCATION.
8. CAUTION: PUMP SIZING MUSTBE BASED UPON WATER HARDNESS AT JOB SITE
NOTES:
2
5
SUPPLY
CIRC.RETURN
2
3
CWMU
4
1
5
7. COMMON PIPING MUST BE SIZEDFOR MAXIMUM COMBINED HEATER FLOW.
7
7
17.1PARTS PER MILLION
=1GRAIN HARDNESS PER GALLON
Figure 9. Water Heater Piping — One Heater, One Tank.
Figure 10. Water Heater Piping — Multiple Heaters, One Tank.

Rheos Boiler and Water Heater Page 17
CAUTION: THIS DRAWING SHOWS SUGGESTED
PIPING CONFIGURATION AND VALVING CHECK
WITH LOCAL CODES AND ORDINANCES FOR
ADDITIONAL REQUIREMENTS
THERMOMETER
GLOBE VALVE
CHECK VALVE
PRESSURE REDUCING VALVE
W/ FAST FILL BYPASS
EXPANSION TANK
WITH AIR SCOOP AND
AUTO AIR VENT
PUMP
LEGEND
VALVE
TEMPERATURE
SENSOR
3-WAY VALVE
PRV
TPRV
6. THIS DRAWING DEPICTS A TWO-PASS HEAT EXCHANGER.
30'TOTAL, 6-90° ELBOWS,FULL PIPE SIZE.
5. WHEN USING OPTIONAL FACTORY MOUNTED PUMP, MAX PIPE LENGTH
4. THERMAL EXPANSION TANK MAYBE REQUIRED CHECK LOCAL CODES.
3. BACK FLOW PREVENTER MAYBE REQUIRED CHECK LOCAL CODES.
WELL IN LOWER 1/3OFTANK WITH HEAT SENCEING COMPOUND.
2. WHEN USING INTERMITTENT PUMP AND EM LOCATE REMOTE AQUASTAT
1. OPTIONAL CWMU&RECIRC. LINE LOCATION.
7. COMMON PIPING MUST BE SIZED FOR MAXIMUM COMBINED HEATER FLOW.
8. CAUTION: PUMP SIZING MUST BE BASED UPON WATER HARDNESS AT JOB SITE
NOTES:
2
5
SUPPLY
CIRC. RETURN
2
2
3
CWMU
4
1
5
7
7
WATER CATEGORY GRAIN
HARDNESS PER GALLON
S=SOFT 1 THROUGH 7.5
N=NORMAL 7.6 THROUGH 17
H=HARD OVER 18
17.1PARTS PER MILLION
=1GRAIN HARDNESS PER GALLON
KEY:
CAUTION: THIS DRAWING SHOWS SUGGESTED
PIPING CONFIGURATION AND VALVING CHECK
WITH LOCAL CODES AND ORDINANCES FOR
ADDITIONAL REQUIREMENTS
THERMOMETER
GLOBE VALVE
CHECK VALVE
PRESSURE REDUCING VALVE
W/ FAST FILL BYPASS
EXPANSION TANK
WITH AIR SCOOP AND
AUTO AIR VENT
PUMP
LEGEND
VALVE
TEMPERATURE
SENSOR
3-WAY VALVE
PRV
TPRV
6. THIS DRAWING DEPICTS A TWO-PASS HEAT EXCHANGER.
30'TOTAL, 6-90° ELBOWS,FULL PIPE SIZE.
5. WHEN USING OPTIONAL FACTORY MOUNTED PUMP, MAX PIPE LENGTH
4. THERMAL EXPANSION TANK MAYBE REQUIRED CHECK LOCAL CODES.
3. BACK FLOW PREVENTER MAYBE REQUIRED CHECK LOCAL CODES.
WELL IN LOWER 1/3OFTANK WITH HEAT SENCEING COMPOUND.
2. WHEN USING INTERMITTENT PUMP AND EM
1. OPTIONAL CWMU&RECIRC. LINE LOCATION.
7. CAUTION: PUMP SIZING MUST BE BASED UPON WATER HARDNESS AT JOB SITE
NOTES:
2
5
1
2
CIRC. RETURN
2
CWMU
SUPPLY
34
WATER CATEGORY GRAIN
HARDNESS PER GALLON
S=SOFT 1 THROUGH 7.5
N=NORMAL 7.6 THROUGH 17
H=HARD OVER 18
17.1PARTS PER MILLION
=1GRAIN HARDNESS PER GALLON
KEY:
Figure 11. Water Heater Piping — One Heater, Multiple Tanks.
Figure 12. Water Heater Piping — Multiple Heaters, Multiple Tanks.

LAARS Heating Systems
Page 18
NOTE: This appliance must be installed in a closed
pressure system with a minimum of 12 psi (82.7kPa)
static pressure at the boiler.
Hot water piping should be supported by suitable
hangers or oor stands. Do not support piping with
this appliance. Due to expansion and contraction of
copper pipe, consideration should be given to the type
of hangers used. Rigid hangers may transmit noise
through the system resulting from the piping sliding in
the hangers. It is recommended that padding be used
when rigid hangers are installed. Maintain 1" (2.5cm)
clearance to combustibles for hot water pipes.
Pipe the discharge of the relief valve (full size)
to a drain or in a manner to prevent injury in the event
of pressure relief. Install an air purger, an air vent,
a diaphragm-type expansion tank, and a hydronic
ow check in the system supply loop. Minimum ll
pressure must be 12psig (82.7kPa). Install shutoff
valves where required by code.
Suggested piping diagrams are shown in Figures
4, 5, 6, 7 and 8. These diagrams are meant only as a
guide. Components required by local codes must be
properly installed.
4A.2 Cold Water Make-Up — Boiler
1. Connect the cold water supply to the inlet
connection of an automatic ll valve.
2. Install a suitable back ow preventer between the
automatic ll valve and the cold water supply.
3. Install shut off valves where required.
NOTE: The boiler, when used in connection with a refrigeration
system, must be installed so the chilled medium is piped in parallel
with the boiler with appropriate valves to prevent the chilled
medium from entering the boiler.
The boiler piping system of a hot water heating
boiler connected to heating coils located in air
handling appliances where they may be exposed to
refrigerated air circulation must be equipped with ow
control valves or other automatic means to prevent
gravity circulation of the boiler water during the
cooling cycle.
A boiler installed above radiation level, or as
required by the authority having jurisdiction, must be
provided with a low water cutoff device either as a part
of the boiler or at the time of boiler installation.
4A.3 Water Flow Requirements — Boiler
A hydronic heating (closed loop) application
recirculates the same uid in the piping system. As a
result, no new minerals or oxygen is introduced into
the system. To ensure a proper operating temperature
leading to long boiler life, a ow rate has been
established based on the uid temperature rise for this
specic size boiler.
Pump-mounted boilers can be ordered for use in
primary secondary piping systems. The pumps used
are sized for the headloss through the heater, plus 30
4. Run gas supply line in accordance with all
applicable codes.
Note: If you have a boiler/water heater with a
normally open vent valve, install a vent line from
the vent valve to an outside location as required
by your installation code or IRI requirement. Do
not remove 3/4 inch pipe plug from the vent
valve if venting from the normally open vent
valve is not required by your installation code.
5. Locate and install manual shutoff valves in
accordance with state and local requirements.
6. A sediment trap must be provided upstream of
the gas controls.
7. All threaded joints should be coated with
piping compound resistant to action of liqueed
petroleum gas.
8. The appliance and its individual shutoff valve
must be disconnected from the gas supply piping
during any pressure testing of that system at test
pressures in excess of 1/2 PSIG (3.45kpa).
9. The unit must be isolated from the gas supply
system by closing its individual manual shutoff
valve during any pressure testing of the gas
supply piping system at test pressures equal to or
less than 1/2 PSIG (3.45kpa).
10. The appliance and its gas connection must be
leak tested before placing it in operation.
11. Purge all air from gas lines.
WARNING:
Open ame can cause gas to ignite and result in
property damage, severe injury, or loss of life.
NOTE: The Rheos appliance and all other gas
appliances sharing the gas supply line must be ring
at maximum capacity to properly measure the inlet
supply pressure. The pressure can be measured at
the supply pressure port on the gas valve. Low gas
pressure could be an indication of an undersized
gas meter, undersized gas supply lines and/or an
obstructed gas supply line. A bleed line from the
diaphragm-type automatic valve shall be vented per
local code requirements. Rheos units are equipped
with low and high gas pressure switches that are
integrally vent limited. These types of devices do not
require venting to atmosphere.
SECTION 4A.
Water Connections — Rheos Boiler
4A.1 Heating System Piping:
Hot Supply Connections — Boiler

Rheos Boiler and Water Heater Page 19
Increase the head loss requirement by 20%.
IMPORTANT NOTES: Different glycol products
may provide varying degrees of protection. Glycol
products must be maintained properly in a heating
system, or they may become ineffective. Consult the
glycol specications, or the glycol manufacturer, for
information about specic products, maintenance
of solutions, and set up according to your particular
conditions.
SECTION 4B.
Water Connections —
Rheos Water Heater
4B.1 Water System Piping —
Water Heater
Hot water piping should be supported by suitable
hangers or oor stands. Do not support piping with
this appliance. Due to expansion and contraction of
copper pipe, consideration should be given to the type
of hangers used. Rigid hangers may transmit noise
through the system resulting from the piping sliding in
the hangers. It is recommended that padding be used
when rigid hangers are installed.
The Rheos can be used with several different
types of readily available storage tanks. A pump draws
water from the storage tank and pumps the water
through the heater and back into the tank. Pump-
mounted units have a circulating pump built into the
water heater.
Pipe the outlet from the heater’s relief valve
such that any discharge from the relief valve will be
conducted to a suitable place for disposal when relief
occurs. Do not reduce line size or install any valves in
this line. The line must be installed to allow complete
drainage of both the valve and the line.
Suggested piping diagrams are shown in Figures
9, 10, 11 and 12. These diagrams are meant only as a
guide. Components required by local codes must be
properly installed.
The minimum inlet water temperature for the
Rheos is 130°F (54°C) to avoid condensing on the
copper coils.
4B.2 Hot Water Supply Piping —
Water Heater
Follow the tank manufacturer’s guidelines for
completion of the hot water system connections.
feet (9.1m) of full-sized piping and a normal number
of ttings.
Table 8 species water ow rates for boilers,
which will enable the user to size a pump. The
headloss shown is for the heater only, and the user
will need to add the headloss of the system piping to
properly size the pump.
The minimum inlet water temperature for the
Rheos is 130°F (54°C) to avoid condensing on the
copper coils.
4A.4 Freeze Protection – Boiler
Proper precautions for freeze protection are
recommended for boiler installations in areas where
the danger of freezing exists.
Power outage, interruption of gas supply, failure
of system components, activation of safety devices,
etc., may prevent a boiler from ring. Any time a
boiler is subjected to freezing conditions, and the
boiler is not able to re, and/or the water is not able
to circulate, there is a risk of freezing in the boiler
or in the pipes in the system. When water freezes,
it expands. This can result in bursting of pipes in the
system, or damage to the boiler, which could result in
leaking or ooding conditions.
Do not use automotive anti-freeze. Maintaining
a mixture of minimum 50% water and maximum
50% properly inhibited HVAC glycol, which contains
an antifoamant, is the preferred method of freeze
protection for Rheos boilers. Percentage of glycol
used in the Rheos boiler must not exceed 50%.
Typically, this mixture will serve as burst protection
for temperatures down to approximately –35°F (-
30°C). To get the desired temperature rise across the
boiler when this mixture is used, increase the water
ow by 15% above the original recommendation.
Connector
Module
Dial
Setpoint Adjustment
Differential
Adjustment
Energized
Relay
LED Indicator
Relay
VDC
COM
24V
SEN
Jumper Block
Position
Heating
Cooling
Note: Jumper must
be in “Heating” mode,
or Rheos will not
operate properly.
Figure 13. Temperature Control.

LAARS Heating Systems
Page 20
NOTE: A listed temperature and pressure relief
valve listed as complying with the Standard for
Relief Valves and Automatic Gas Shutoff Devices
for Hot Water Supply Systems, 1). ANSI Z21.22
latest edition, or 2). CSA 4.4, of suitable discharge
capacity must be installed in the separate storage
tank system.
If the Rheos water heater is installed in a closed
water supply system, such as one having a backow
preventer in the cold water supply line, the relief valve
may discharge periodically, due to thermal expansion.
Means (such as a properly-sized expansion tank) shall
be provided to control thermal expansion. Contact the
water supplier or local plumbing inspector on how to
control this situation.
4B.3 Water Flow Requirements —
Water Heater
In a water heating application (an open system),
new water is constantly being introduced. With the
new water comes a fresh supply of minerals that can
be deposited on the unit’s heat exchanger. This is
commonly known as scaling. The amount of minerals
will depend upon the hardness of the water. Water can
also be aggressive, and can erode metals, including
copper, if the water is moved too quickly. The water
ow requirements for the Rheos water heater are based
upon the hardness of the water. The water ow is kept
high enough to prevent scaling, but low enough to
prevent tube erosion. For extremely soft or hard water,
cupro-nickel tubes are available. Contact a Laars
Representative if you have questions or concerns about
water quality.
Pump-mounted water heaters can be ordered
with standard pumps for soft or normal water or with
pumps for hard water. The pumps used are sized for
the headloss through the heater, plus 30 feet (9.1m) of
full-sized piping and a normal number of ttings.
Table 9 species water ow rates for water
heaters, which will enable the user to size a pump.
The headloss shown is for the heater only, and the user
will need to add the headloss of the piping system to
properly size the pump.
4B.4 Combined Water (potable) Heating
and Space Heating
NOTE: These systems are not allowed in the
Commonwealth of Massachusetts.
Piping and components connected to this water
heater for the space heating application shall be
suitable for use with potable water.
Toxic chemicals, such as used for boiler
treatment, shall not be introduced into the potable
water used for space heating.
This water heater when used to supply potable
water shall not be connected to any heating system
V C I
Cover Screws
(Quantity=4)
Integration
DIP Switch
is setto
“Medium” at
thefactory.
See Section
5.5.6for
descriptions
of other
settings.
LED Indicator
(Percent of
Output)
Module
Connector
THROT
RANGE
MIN
OUTPUT OFFSET
Reverse
Acting
Direct
Acting
Operation Mode
Jumper Positions
Figure 14. Proportional Control.
or component(s) previously used with a non-potable
water heating appliance.
When the system requires water for heating at
temperatures higher than required for other uses,
an anti-scald mixing or tempering valve shall be
installed to temper the water for those uses in order
to reduce scald hazard potential.
4B.5 Freeze Protection – Water Heater
Although Rheos water heaters are design-
certied for outdoor installations, such installations
are not recommended in areas subject to freezing
temperatures unless proper precautions are taken.
Power outage, interruption of gas supply, failure
of system components, activation of safety devices,
etc., may prevent a heater from ring. Any time a
heater is subjected to freezing conditions, and the
heater is not able to re, and/or the water is not
able to circulate, there is a risk of freezing in the
heater or in the pipes in the system. When water
freezes, it expands. This can result in bursting of pipes
in the system, or damage to the heater, which could
result in leaking or ooding conditions.
Note: Jumper must be in “Reverse Acting” mode, or Rheos will not operate properly.