Laars VW User manual

Installation, Operation and Maintenance Instructions Document 2051C
H0147500C
Installation, Operation
and Maintenance
Instructions for
Mighty Therm
Volume Water Heaters
Model VW-PW
Sizes 175-400
FOR YOUR SAFETY: This product must be installed and serviced by a professional service technician,
qualified in hot water heater installation and maintenance. Improper installation and/or operation could
create carbon monoxide gas in flue gases which could cause serious injury, property damage, or death.
Improper installation and/or operation will void the warranty.
WARNING
If the information in this manual is not followed exactly, a fire or explosion may result
causing property damage, personal injury or loss of life.
Do not store or use gasoline or other flammable 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 fire department.
Installation and service must be performed by a qualified installer, service agency, or gas
supplier.

LAARS HEATING SYSTEMS
Page 2
TABLE OF CONTENTS
SECTION 1.
General Information
1A. Introduction.................................................... 3
1B. Warranty........................................................ 3
1C. Technical Assistance..................................... 3
SECTION 2.
Installation Instructions
2A. General Information....................................... 4
2B. Field Assembly .............................................. 4
2C. Site Location.................................................. 5
2C-1. Installation Information .................................. 5
2C-2. Outdoor Installation (U.S. only) ..................... 5
2C-3. Flooring - Typical Installation......................... 6
2D. Combustion and Ventilation Air Supply ......... 6
2D-1. Outdoor Air Supply ........................................ 7
2D-2. Indoor Air Supply...........................................7
2D-3. Exhaust Fans or Vents .................................. 7
2E. Venting of Combustion Products ................... 7
2E-1. General Information....................................... 7
2E-2. Replacement of Existing Heater .................... 8
2F. Water Flow .................................................... 8
2F-1. Reversible Water Connections......................8
2F-2. Water Chemistry.......................................... 11
2F-3. Freeze Protection ........................................ 11
2F-4 Water Hardness .......................................... 11
2F-5. Pump Requirements.................................... 11
2F-6. Pressure Buildup in Water System.............. 11
2F-7. Pressure Relief Valve.................................. 14
2F-8. Water Pressure ........................................... 14
2F-9. Pump Installation ......................................... 14
2F-10. Storage Tank Installation............................. 14
2F-11. Thermal Circulation of Hot Water in
Cold Water Supply Lines.............................15
2G. Gas Supply and Piping................................15
2G-1. General Instructions .................................... 15
2G-2. Special Precautions for Propane Gas ......... 16
2H. Electrical Wiring........................................... 16
2I. Combined Space Heating/Potable
Water Heating Systems............................... 16
2I-1. Combined Space Heating ........................... 16
2I-2. Potable Water Heating ................................ 16
SECTION 3.
Operating Instructions
3A. Normal Operating Sequence.......................17
3B. Start-Up Procedure ..................................... 17
3C. Setting the Temperature Controls ............... 17
3D. Adjustment for Minimum Input Rate
(models with modulating gas valve) ............ 20
3E. Hi-Limit Switch Checkout ............................ 20
3F. Shut-Down Procedure ................................. 20
SECTION 4.
Maintenance
4A. General Instructions .................................... 20
4B. Replacement of Gas Controls ..................... 21
4C. Heat Exchanger........................................... 22
4C-1. Inspecting the Heat Exchanger ................... 22
4C-2. Cleaning the Heat Exchanger ..................... 23
SECTION 5.
Troubleshooting
5A. Gas Pressure Tests..................................... 23
5A-1. Checking the Main Line Gas Pressure ........ 23
5A-2. Checking the Manifold
Regulated Gas Pressure .............................24
5B. Electrical Troubleshooting ........................... 24
5B-1. Heater Does Not Come On ......................... 24
5B-2. Testing the Transformer .............................. 25
5B-3. Testing the Electrical Power Supply ............ 25
5B-4. Testing the Manual Reset
Hi-Limit Switch............................................. 25
5B-5. Testing the Flow Switch............................... 25
5B-6. Testing the Fusible Link
(Flame roll-out switch) ................................. 26
5B-7. Testing the Fuse.......................................... 26
5B-8. Testing the Ignition Control
(for spark ignition)........................................ 26
5B-9. Testing the Ignition Control
(for standing pilot)........................................ 27
5B-10. Testing the High Voltage Ignition Lead........ 27
5B-11. Testing the Safety Shutoff
(for standing pilot)........................................ 28
5B-12. Testing the Safety Shutoff
(for automatic pilot)...................................... 28
5B-13. Testing the Igniter Electrode........................28
5B-14. Testing the Pilot Thermocouple
(for standing pilot)........................................ 28
5B-15. Testing for Pilot burner
(for spark ignition)........................................ 28
5B-16. Testing for Burner Ignition
(for standing pilot)........................................ 29
5B-17. Heater Will Not Shut Off .............................. 29
5B-18. On-Off Main Burner Cycling ........................ 29
5B-19. Testing the Terminal Strip/External
Controls ....................................................... 29
SECTION 6.
Parts List
6A. General Information..................................... 30
6B. Parts List ..................................................... 30

Mighty Therm VW - PW Volume Water Heaters Page 3
A
8-1/2 in.
(216mm) INLET OUTLET
TOP VIEW CC
OPTIONAL
VENT CAP FOR
OUTDOOR USE DRAFTHOOD
DRAFTHOOD MUST
BE INSTALLED IN
THE FIELD
HEADER
LOCATION
OUTLET
40-9/16 in. (1030mm)
INLET
5-1/2 in.
(140mm)
26-1/2 in.
(673mm)
SIDE VIEW
V
30-3/16 in. (767mm)
B
SECTION 1.
General Information
1A. Introduction
This manual provides installation, operating, and
maintenance instructions for Models VW and PW
Volume Water Heaters, Sizes 175 through 400. Review
all application and installation procedures completely
before proceeding with the installation. Experience has
shown that most operating problems are caused by
improper installation.
The VW-PW heaters are offered in a basic
configuration (see Figure 1). On PW heaters the pump
is factory installed. On VW heaters the pump is field
installed.
1B. Warranty
The VW-PW heaters are sold with a limited
factory warranty.
Make all warranty claims to an authorized Laars
representative or directly to the factory. Claims must
include the heater 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. Inspect everything for damage immediately
upon delivery, and advise the transporter of any
shortages or damage. Any such claims should be filed
with the transporter. The transporter will not accept a
claim from the shipper, Laars.
The warranty does not cover damage caused by
improper installation, operation, or field modification.
1C. Technical Assistance
Consult Laars or your local wholesaler with any
questions or problems involving the specification,
installation and operation of Laars equipment. An
experienced technical support staff is ready to assist in
assuring the proper performance and application of
Laars products.
Gas Connection
Size Water C CV
Connect. U.S. Only (Indoor) Vent
Nat. Propane Size A B (Outdoor) Dia.
Size in.
mm in. mm in. mm in. mm in. mm in. mm in. mm in. mm
175 3/4 19
1/2
13 11/2 38 18 457 261/2 673 141/16 357 23/2 597 6 152
250 3/4 19
1/2
13 11/2 38 221/2 572 31 787 181/16 473 243/4 629 7 178
325 3/4 19
1/2
13 11/2 38 263/4 679 353/4 908 193/16 488 257/8 657 8 203
400 3/4 19
1/2
13 11/2 38 313/4 806 401/4 1022 225/8 575 267/8 683 9 229
Note: Dimensions may vary.
Figure 1. General configuration.

LAARS HEATING SYSTEMS
Page 4
HOT
HOT
number for the drafthood is on the heater rating plate.
Follow this procedure to make the conversion:
a. Remove the top filler plate, stamped “HOT”, by
slipping a fine-blade screwdriver into the slot at
the rear of the plate and gently prying it up (see
Figure 2).
b. Remove the two screws attaching the adapter
plate to the top assembly and lift it out (see
Figure 3).
c. Remove the vent cap or drafthood from its
package.
SECTION 2.
Installation Instructions
2A. General Information
WARNING
Follow local regulations with respect to installation
of carbon monoxide (CO) detectors and
manufacturer's maintenance schedule of the
heater.
Install the VW-PW heaters in accordance with
the procedures in this manual (or the Laars warranty
may be voided), local codes and ordinances. In the
absence of such codes, install the heaters in accordance
with the latest edition of the National Fuel Gas Code,
ANSI Z223.1. In Canada, the installation must be in
accordance with CAN1-B149.1 or .2 and local codes.
The authority having jurisdiction may require the
installation conform to the Standard for Controls and
Safety Devices for Automatically Fired Heaters,
ANSI/ASME CSD-1. Any changes to the heater, gas
controls, gas orifices, wiring or draft diverter may void
the warranty. If field conditions require a change to
any of the above, consult the factory.
All gas-fired products require correct installation
to assure safe operation. The requirements for heaters
include the following:
1. Field assembly of drafthood or vent cap (see
Section 2B).
2. Appropriate site location (clearances) and
flooring.
3. Sufficient combustion and ventilation air.
4. Adequate venting of combustion products.
5. Adequate water flow.
6. Properly sized gas meter and piping.
7. Proper electrical wiring.
This manual provides the information needed to
meet these requirements. Review all application and
installation procedures completely before continuing
the installation.
2B. Field Assembly
The VW-PW heater is shipped from the factory
with the top assembly in the low-profile configuration
for outdoor installations.
The VW-PW heater is design certified for indoor
installation when equipped with a special drafthood,
which must be installed without modification. The part
Figure 2. Top filler plate. Figure 3. Adapter plate.
Figure 4. Flue transition Figure 5. Vent cap with
ring. adapter plate
(outdoor).
Figure 6. Drafthood with Figure 7. Drafthood switch
adapter plate receptacle.
(indoor).

Mighty Therm VW - PW Volume Water Heaters Page 5
d. Disengage the flue transition ring from the stack
extension and place it on top of the collector
assembly as shown in Figure 4.
e. Slide the adapter plate over the bottom of the
stack extension as shown in Figure 5. Fit the
stack extension down over the flue transition
ring. Seat the adapter plate on the top assembly
and secure it with two screws (see Figure 6).
f. Indoor models, size 175 and 250 only, require an
adapter cable (included with product). The cable
connects the blocked vent safety switch (BVSS)
on the bell of the external draft hood to the 6-
position Molex plug on the side of the unit (see
Figure 7). Refer to instruction sheet included
with cable.
2C. Site Location
2C-1. Installation Information
WARNING
Improper installation or maintenance can cause
nausea or asphyxiation from carbon monoxide in
flue gases which could result in severe injury,
property damage, or death.
Avoid placing the heater in locations where it can
be damaged by water or condensate leakage. If this is
not possible, provide a suitable drain pan to catch and
divert any leakage. The pan must not block natural
flow of air around the heater.
Locate the heater to provide adequate clearance
on all sides for inspection, service and to provide
adequate air circulation for proper operation.
Locate the heater so the clearances from
combustible surfaces shown in Table 1 and Figure 8
are met.
Figure 8. Alcove installation.
Closet Installation
(unacceptable)
A closet is any 4 sided enclosure
which is less than 16* times the
total volume of all the gas fired
appliances within the enclosure.
Room Installation
(acceptable)
A room is any enclosure which is
at least 16* times greater than the
total volume of all the gas fired
appliances within the enclosure
Alcove Installation
(acceptable)
An alcove suitable for the
installation of a heater is a
restricted section of a room not
separated from the room by a door
or partition and which meets the
minimum clearances specified in
this manual.
* When the ceiling height exceeds 8 feet, you are only allowed to consider
8 feet when calculating the total volume of the enclosure.
Indoors Outdoors
Clearance from: inch mm inch mm
Top 37 940 Unobstructed
Water conn. side 12
305 Unobstructed
Opposite side 6
152 6 152
Front Alcove Unobstructed
Rear 6
152 6 152
Vent* 6 152 —
Flooring Combustible Combustible
Service clearance = 36 inches (914mm) at front of heater,
and 18 inches (457mm) at water connection side.
*1" (25mm) if double wall vent is used.
Table 1. Minimum Boiler Clearances
from Combustible Surfaces.
Locate the heater on a waterproof floor with a
floor drain and a 6 inch (152 mm) minimum curb on
all four sides to protect the building if heater repairs
are needed.
2C-2. Outdoor Installation (U.S. Only)
Caution
Outdoor installations are not recommended in areas
where the danger of snow blockage exists. VW-PW
heaters can be installed in the standard low-profile,
grate top configuration as received from the factory,
or with an optional vent cap.
Locate the heater in an open, unroofed area. Do
not locate the heater below or adjacent to any doors,
windows, louvers, grills, etc., which connect in any
way with an inhabited area of a building, even though
the access might be through another structure such as a
garage or utility room (see Figure 9 and Table 1).
There must be a minimum of 4 feet (1.22 m)
horizontally and vertically between the heater and any
door, window, or gravity inlet to a building (see
Figure 10).
If the heater is installed close to a structure,
protect it from rain water runoff with rain gutters on
the roof or other measures. Do not locate the heater
near sprinkler systems that could spray water on it.