HydroTherm GX Series User manual

HydroTherm GX2-707
ODEL
INSTALLATI
ANT
GES G
UAL
Modulating, Direct Vent, Gas-Fired Condensing
Natural Or Propane
150,000 to 399,000 Btuh Input
Boilers
see note
Do not store or use gasoline or other flammable vapors and liquids in the vicinity of
this or any other appliance.
WHATTO DO IFYOU 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 neighbor's 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
the gas supplier.
INSTALLER: THESE INSTRUCTIONS MUST BE AFFIXED ADJACENT TO THE BOILER.
CONSUMER: RETAIN THESE INSTRUCTIONS FOR FUTURE REFERENCE PURPOSES.
Note: For LP gas use conversion kit: GX82650-1 on GX-150 & 200, GX83017-1 on GX-400
Advanced Thermal Hydronics
IN UNITED STATES: 260 NORTH ELM ST., WESTFIELD, MA 01085 ,,[phone] FAX [phone]
IN CANADA: 7555 TRANMERE DRIVE, MlSSlSSAUGA, ONTARIO L5S 1L4 • [phone] FAX [phone]

Page 2 GX INSTALLATION AND OPERATION INSTRUCTIONS
CONTENTS
Before You Start ................................................. page 2
Boiler Ratings & Capacities ............................... page 2
Boiler Location ................................................... page 3
Clearances to Combustible Construction .......... page 3
Combustion Air .................................................. page 4
General Venting Guidelines ............................... page 4
Horizontal Direct Vent Systems ......................... page 5
Vertical Direct Vent Systems ............................... page 9
Condensate Drain ............................................ page 10
General Plumbing Guidelines .......................... page 11
Primary Loop Plumbing ................................... page 13
Multiple Boiler Primary Loop Plumbing ........... page 13
Secondary Loop Plumbing .............................. page 13
Gas Supply Piping ........................................... page 18
Electrical Wiring ............................................... page 19
Sentry 2100 Controller .................................... page 26
Boiler Set Up ................................................... page 29
Operating Instructions ..................................... page 29
Boiler Checking & Adjusting ............................ page 33
Gas Pressure Adjustment ................................ page 33
Boiler Maintenance .......................................... page 34
Wall Hung Conversion ..................................... page 35
Trouble Shooting ............................................. page 36
Replacement Parts .......................................... page 41
BEFORE YOU START
These instructions cover the GX Series gas fired, direct
vent, low pressure, hot water boiler. GX boilers have been
design certified by CSA for use with natural and propane
gas under the latest edition of ANSI-Z21.13/CSA 4.9,
Gas-Fired Low Pressure Steam and Hot Water Boilers.
Each unit has been constructed and hydrostatically
tested for a maximum working pressure of 30 psi,
207 kPa, in accordance with Section IV of the ASME
Boiler and Pressure Vessel Code. Each boiler has been
equipped with a 30 psi, 207 kPa pressure relief valve.
This manual covers the application, installation, operation
and maintenance of a GX Series low pressure hot water
boiler.
To obtain the safe, dependable, efficient operation
and long life for which this boiler was designed, these
instructions must be read, understood and followed.
Direct all questions to your Hydrotherm distributor or
to the Customer Service Department, 260 North Elm
Street, Westfield, MA 01085. Always include the model
and serial numbers from the rating plate of the boiler in
question.
The owner should maintain a record of all service work
performed with the date and a description of the work
done. Include the name of the service organization for
future reference.
Where required by the authority having jurisdiction, the
installation must conform to the Standard for Controls
and Safety Devices for Automatically Fired Boilers,
ANSI/ASME CSD-1.
The installation must conform to the requirements of the
authority having jurisdiction or, in the absence of such
requirements, to the National Fuel Gas Code, ANSI
Z223.1-1atest revision. In Canada, the installation must
be in accordance with the requirements of CSA B149.1
or B149.2 Installation Code for Gas Burning Appliances
and Equipment.
If installed in the Commonwealth of Massachusetts, you
MUST FOLLOW the additional instructions contained in
Hydrotherm's instruction sheet MA IOM. Ifyou don't have
a copy call your Hydrotherm distributor or Hydrotherm.
BOILER RATINGS & CAPACITIES
Before undertaking the installation of the GX check the
boiler rating plate to ensure that the boiler is the proper
size for the job.
Also ensure that the boiler has been set up for the type
of gas available at the installation site. Other important
considerations are the availability of an adequate
electrical supply, fresh air for combustion and proximity
a suitable outside wall.
High Altitude Operation
The GX boiler is designed to operate to capacity in
installations with 2000 ft, 610 m of elevation or less. At
elevations higher than 2000 ft, 610 mthe unit will de-rate
due to the lower air density, see Figure 1.
NOTE: It is the Installers resPonsibilitFto check
the combustion, and to adjust the combustion in
accordance to Operating instructions Section.

GXINSTALLATIONANDOPERATIONINSTRUCTIONS Page3
Figure 1=Input vs Elevation Graph
400 ,, - _
3004
200 J
1004
z
04
0-2000 3000 4000 5000 6000 7000 8000 9000 10000
Elevation (ft)
-- 200 m m m 400 I
i
=_m== 150
BOILER LOCATION
CAUTION: This boiler is designed to operate only
in residential and commercial heating systems, it is
not intended for:
1. Outdoor installations, or unheated spaces, which
can cause freezing.
2. Process heating of potable water, or any other
fluids.
3. Un=pressurized, and gravity feed heating
systems.
4. Heating systems with very low pressures or
flow.
Improper use or installation will seriously damage
the boiler, voiding warranty!
,Locate the boiler in an area that provides good
access to the unit. Keep in mind that servicing may
require the removal of jacket panels. Accessibility
clearances should take precedence over fire
protection clearances. Table 1 lists the minimum
clearances for servicing, however 24 in, 610 mm is
recommended.
2. An optimum site will be level, central to the hot water
piping system and close to an outside wall.
NOTE: This boiler is designed for direct placement
on a combustible floor. Never install this boiler on
carpeting!
,DO NOT install this boiler in a location that would
subject any of the gas ignition components to direct
contact with water or excessive moisture during
operation or servicing. The boiler location ambient
temperature must be no less than 50°F, 10°C
including the condensate line.
4. NEVER store objects on or around the boiler.
5. This boiler may be wall mounted. See the Wall Hung
Conversion section listed in the table of contents.

Page4 GXINSTALLATIONANDOPERATIONINSTRUCTIONS
Table1=Clearances
Surface
Front
Back
Sides
Top
Bottom-150&200
Bottom-400
Flue Pipe -enclosed
Flue Pipe -in free air
Combustible Service
Clearance Clearance
in mm in mm
0024 610
0000
0012 305
0012 305
0012 305
0000
251 n/a n/a
00n/a n/a
COMBUSTION AIR
One of the following materials is to be used for the air
intake pipe:
GX-150 & 200:3 in, 76 mm, PVC Sch.40 pipe or
Galvanized Steel pipe.
GX-400:4 in, 102 mm or 6 in 152 mm, PVC Sch.40
pipe or Galvanized Steel pipe.
See Table 2 for the maximum equivalent air intake
system length.
CAUTION: Combustion air contaminated with fluoro=
carbons or other halogenated compounds such as
cleaning solvents, refrigerants, chloride, flouride,
bromine or iodine will result in the formation of
acids in the combustion chamber. These acids will
cause premature failure of the boiler voiding the
warranty!
GENERAL VENTING GUIDELINES
To operate properly and safely this boiler requires a
continuous supply of air for combustion. NEVER store
objects around the air inlet!
Use appropriate adapters to increase the 11/2in,
38 mm air inlet collar to 3 in, 76 mm at the boiler,
GX-150 & 200, Figure 2. Use a 2 in, 51 mm to 4 in,
102 mm adapter on the GX-400. Terminate the air inlet
system per the instructions found in the venting sections
that follow.
NOTE: Compliance with code requirements doesn't
insure a satisfactory installation; good common
sense must also be applied.
Figure 2 =Air Inlet System Attachment

GXINSTALLATIONANDOPERATIONINSTRUCTIONS Page5
TheGXcondensinggasboilerisa highefficiency
boilerutilizinginducedpowerventing.It isdesigned
tobeventeddirectlytotheoutdoorsusingtheventing
methodsandmaterialsdetailedinthissection.The
ventsystemmustbebothgastightandwatertight.All
horizontalventpipingmustbeslopedbacktotheboiler
aminimumof1/4in/if,21mm/m of vent.
NOTE: Steps must be taken to ensure that condensate
does not collect in the venting system or the boiler
will not operate properly.
This boiler may be vented using the following materials,
but local codes must be followed:
GX150 & 200:3 in, 76 mm, PVC Sch.40 solid core
pipe, CPVC Sch.40 pipe, AL29-4C Flex Stainless Vent
or AL29-4C Rigid Stainless Vent.
GX=400:4 in, 102 mm or 6 in, 152 mm, PVC Sch.40
solid core pipe, CPVC Sch.40 pipe, AL29-4C Flex
Stainless Vent or AL29-4C Rigid Stainless Vent.
CAUTION: All vent systems must be fully supported
by the building structure. The vent connection and
vent piping MUST be perfectly aligned to the boiler
connection, Figure 3. It MUST NOT APPLY ANY
WEIGHT OR LATERAL FORCE TO THE FLUE BOX or
the flue box will be damaged voiding the warranty!
Appropriate adapters must be used to increase the
2in, 51 mm vent collar to 3 in, 76 mm at the boiler,
GX-150 & 200, Figure 3. On the GX-400 the 4 in,
102 mm long 4 inch diameter ABS pipe provided with
the boiler must be inserted into the exhaust connection
on the top of the boiler and tightened in place with the
supplied clamp.
Figure 3=Vent Pipe To Boiler Attachment
Table 2 =Vent & Air Intake System Sizing
Model
Number
GX-150
GX-200
GX-400
PGX-150
PGX-200
PGX-400
Equivalent Vent & Air Intake
System Length (see note)
105 ft, 32 m
105 ft, 32 m
4"-30ft, 9m 6"-65ft, 20m
50ft, 15m
50 ft, 15 m
4"-30ft_9m 6"-65ft, 20m
Note: The lengths listed is for each direction. Subtract 5 ft, 1.5 m,
for each 90° elbow except for the vent and air intake elbows. These
don't need to be considered. The length of the air inlet system
must never exceed the length of the vent system. The vent system
length may exceed the air inlet system length by no more than
20 equivalent ft, 6.1 equivalent m.
HORIZONTAL
DIRECT VENT SYSTEMS
Read the information in the GENERAL VENTING
GUIDELINES section. It is recommended that two
elbows be used, so that the 1/4 in/ft, 21mm/m slope of
the horizontal vent system does not affect the vertical
plumb of the pipe connected to the boiler, Figure 4.
Figure 4 -Vent System Attachment
ELBOWS
RECOMMENDED
EXHAUST 2 IN TO 3 IN
ADAPTER
When horizontal vent runs exceed 5 ft, 1.5m, they must
be supported at 3 ft, 0.9 m, intervals with overhead
hangers, 4 ft, 1.2 m for 6" pipe. The vent system must
be pitched down, toward the boiler, 1/4 in/ft, 21mm/m.
of vent. Structural penetrations must be made using
approved thimbles.
The maximum combined equivalent vent and intake
pipe lengths are listed in Table 2. The length specified
is the equivalent vent length added to the equivalent
intake length.

Page6 GXINSTALLATIONANDOPERATIONINSTRUCTIONS
Theventterminalshallnotterminate:
*Directly above a paved sidewalk or a paved drive-way
that is located between two buildings, and that serves
both buildings;
*Less than 7 ft, 2.1 m above grade where located
adjacent to a paved driveway or public walkway.
*Within 3 ft, 0.9 m, horizontally of a window or door that
can be opened, or non-mechanical air supply inlet to
any building.
*Within 6 ft, 1.8 m, of a mechanical air supply inlet to
any building or roof eve containing soffit openings.
*Above a meter/regulator assembly within 3 ft, 0.9 m,
horizontally of the vertical centerline of the regulator.
*Within 6 ft, 1.8 m, of any gas service regulator vent
outlet.
*Less than 30 in, 762 mm, plus snow allowance above
grade, or any surface that will support snow, ice, or
debris. The exhaust must be a minimum of 18 in,
457 mm, above the air inlet, and the air inlet must
always be a minimum of 12 in, 305 ram. plus snow
allowance above any surface that will support
snow. A 24 in, 610 ram, plus snow allowance is
highly recommended. Consult your weather office,
for the maximum typical snowfall for your region.
*Underneath a verandah, porch, or deck.
*So situated that the flue gases are directed towards
brickwork, siding, or other construction, in such
a manner that may cause damage from heat or
condensate from the flue gases.
*Less than 3 ft, 0.9 m, from an inside corner of an
L-shaped structure including walls and fences.
Under normal operating conditions this appliance will
produce a plume of water vapor, and should be taken
into consideration when selecting an adequate vent
terminal location. A 3 ft, 0.9 m, diameter stainless,
plastic, or vinyl shield can be used to flash the exterior
of the residence to protect is from damage.
Separate Air Intake and Vent Terminals
It is highly recommended that the air intake and vent
terminals not be located where they will be exposed to
normal prevailing winds, Both terminals must be on the
same wall,
The vent terminal must be a minimum of 18 in,
457mm above the air inlet terminal. The air inlet terminal
must always be a minimum of 12 in, 305 mm, plus the
snow allowance above any surface that will support
snow, however a snow allowance of two feet is highly
recommended Figure 5, 6, 7 & 8.
Consult your weather office for the maximum typical
snowfall for your region. For example, in Boston MA the
maximum typical snowfall is 12 in, 305 mm. Therefore
the inlet must be 24 in, 610 mm, above any surface
that will support snow and the exhaust must be 42 in,
1067 mm, above this surface.
The horizontal centerline distance between the inlet
and exhaust terminals must be a minimum of 4 in,
102 mm. If the horizontal distance between the inlet
and exhaust is more than 12 in, 305 mm, increase the
vertical separation by the same amount to prevent flue
gas recirculation.
For example, if the horizontal separation is 24 in,
610 mm, a minimum vertical separation of 18 in,
457mm, + 12 in, 305mm, = 30 in, 762 mm is required,.
If the horizontal distance is greater than 6 ft, 1.8 m,
no additional vertical spacing is required. The vertical
separation is never required to be greater then 36 in,
914 mm.
Figure 5 =Horizontal Terminal Locations
WINDOW
OUTSIDE _ I_
36
4 IN MIN

GX INSTALLATION AND OPERATION INSTRUCTIONS Page 7
When penetrating an outside wall the air intake and vent
pipes must be constrained as shown in Figure 6. The
openings through which the air intake and vent pipes
pass must be properly sealed to prevent products of
combustion from entering the building.
Figure 6 =Wall Penetration Detail
THEVERTICALPORTIONOFTHE
EXHAUSTTERMINATIONDOES
NOT REQUIRE INSULATION IF
LESS THAN 5 FEET IN TOTAL I
12 IN PLUS
ALLOWANCE
For installations that have to exit the foundation below
grade excavate the site as shown in Figure 8 to a point
below where the pipes exit the building. Maintain the
proper vent clearances as outlined above. Attach the vent
and air intake pipes to the outside of the building using
special bracket 82075. Ensure that the wall penetrations
are properly sealed before backfilling the site.
Figure 8 =Below Grade Installation
IN MIN
PLUS SNOW
ALLOWANCE
AIR
18 IN MIN.
AND ELBOW TO
BE AGAINST WALL - 1/2 IN
PLAY IS ACCEPTABLE
In some cases it may be necessary to attach the air
intake and vent pipes to the outside wall for added rigidity,
Figure 7. If this is the case, special bracket GX-82075
must be ordered for each pipe. Proper clearances must
be maintained.
Figure 7 =Air Intake & Vent Pipe Attachment
MIN 30 IN MIN
PLUS SNOW
ALLOWANCE
UPPORT 2 IN MIN
ATTACHED TO PLUS SNOW
BUILDING ALLOWANCE
If required, the air intake and vent systems may be run
along an outside wall, Figure 9, providing the following
conditions are met:
1. The maximum length on the outside of the building
is not more than 20 ft, 6.1 m.
2. All normal termination clearances are maintained.
3. The entire vent system external to the building is
insulated using closed cell foamed polyolefin tubing
having a minimum wall thickness of 1/2 in, 13 mm.
4. The air intake and vent systems are supported
every 24 in, 610 mm.
5. The air intake and vent systems are sloped 1/4 in/if,
21mm/m back toward the boiler.

Page8 GXINSTALLATIONANDOPERATIONINSTRUCTIONS
Figure 9-External Air Intake and Vent Systems
ORTS EVERY 24 IN
EXHAUST ",
Figure 11= Horizontal Concentric Terminal Location
4 IN OR GREATER
THAN 24 IN
36 IN
USING ONLY 3" PIPE ON
THE 150 & 200 AND 4"
PIPE ON THE 400
12 IN ABOVE MAXIMUM
SNOW LINE
The debris screens provided with the boiler must be
installed in both the air intake and vent terminals. Install
the screens in the outer most opening then glue a 1 in,
25 mm length of pipe into the opening to retain them,
Figure 10.
Figure 10 =Debris Screen Installation
÷÷÷÷÷÷_÷÷_÷÷
_÷÷÷÷÷÷÷
SNOW ALLOWANCE
Figure 12 =Vertical Concentric Terminal Location
IN
MINIMUM
48 IN ÷÷÷÷_
Concentric Air Intake and Vent Terminal
GX-150 &200 Only
If a concentric terminal is used it must be Hydrotherm
part number GX-82666 orYork part number 1CT0303.
The concentric terminal must be located at least 12 in,
305 mm, above the normal snow line, Figure 11. Position
the air intake pipe on the top or to the side to prevent rain
from entering the boiler, Figure 13.
When terminals from multiple boiler installations exit a
common wall the following conditions must apply:
1. If limited to two terminals the horizontal centerline
distance must be 4 in, 102 mm, or greater than
24 in, 610 mm, to prevent flue gas recirculation.
For more than two terminals located along a
horizontal plane, the centerline distance between
them must be 24 in, 610 mm, Figure 11.
2. If the terminals are located in a vertical plane the
centerline distance between them must be at least
48 in, 1220 mm, Figure 12.
MINIMUM 12 IN
PLUS S
ALLOWANCE
When penetrating an outside wall the concentric terminal
must be constrained as shown in Figure 13.The opening
through which the concentric terminal passes must be
properly sealed to prevent products of combustion from
entering the building. The air intake of the boiler must
be connected to the terminal!

GXINSTALLATIONANDOPERATIONINSTRUCTIONS Page9
Figure 13 =Wail Penetration Detail
-- INLET AIR
_] EXHAUST
MUST BE
1 IN FROM
WALL
The debris screen provided with the boiler must be
installed in the concentric terminal as shown in Figure
14.
Figure 14 =Debris Screen Installation
Consult your weather office for the maximum typical
snowfall for your region. For example, in Boston MA the
maximum typical snowfall is 12 in, 305 mm. Therefore
the inlet must be 24 in, 610 mm, above any surface that
will support snow. The exhaust must be 42 in, 1067mm,
above this surface.
Figure 15 =Two Pipe Through the Roof
EXHAI
\
IN MINIMUM
12 IN MINUMUM PLUS
SNOW ALLOWANCE
4 IN
MINIMUM
VERTICAL DIRECT VENT SYSTEMS
Read the information in the GENERAL VENTING
GUIDELINES section before proceeding.
The GX can be vented vertically directly through the
building's roof or through a dormant chimney used as
a chase, Figures 15 & 16. All roof penetrations must be
properly flashed and sealed.
Separate Air Intake and Vent Terminals
The discharge of the vent terminal must point away
from the pitch of the roof. The vent terminal must be a
minimum of 18 in, 457mm, above the air inlet terminal.
The vent terminal must also be 24 in, 610 mm, above
any roof surface within a horizontal distance of 10 ft,
3 m. The air inlet terminal must always be a minimum
of 12 in, 305 mm, plus the snow allowance above
any surface that will support snow, however a snow
allowance of 24 in, 610 mm, is highly recommended
Figures 15 & 16.
The horizontal centerline distance between the inlet
and exhaust terminals must be a minimum of 4 in,
102 ram. If the horizontal distance between the inlet
and exhaust is more than 12 in, 305 ram, increase
the vertical separation by the same amount. For
example, if the horizontal separation is 24 in, 610 ram,
a minimum vertical separationof 30 in, 762 mm,
is required, 18in, 457mm, + 12 in, 305ram, = 30 in,
762 ram. If the horizontal distance is greater then
6 ft, 1.8 m no additional vertical spacing is required.
The vertical separation is never required to be greater
then 36 in, 914 mm.
A dormant chimney can be used as a chase through
which the air intake and vent pipes can be run, Figure
16. The chimney must not be connected to a fireplace,
water heater or any other heating appliance.
Figure 16 =Two Pipe Using Dormant Chimney
IN MINIMUM
ABOVE AIR INLET
12 IN PLUS SNOW
ALLOWANCE

Page 10 GX INSTALLATION AND OPERATION INSTRUCTIONS
Install and seal a rain cap over the dormant chimney
opening to prevent water from entering the building.
Use only ABS, PVCs°h.4°,CPVC, or AL294C pipe for the
air inlet and vent systems as stated previously. Ensure
that the air inlet and vent system lengths are within the
maximums specified in Table 2.
The debris screens provided with the boiler must be
installed in both the air intake and vent terminals. Install
the screens in the outer most opening then glue a 1 in,
25 mm, length of pipe into the opening to retain them,
Figure 9.
Concentric Air Intake and Vent Terminal
GX-150 &200 Only
If a concentric terminal is used it must be Hydrotherm
part number GX-82666 orYork part number 1CT0303.
The concentric terminal must be located at least 24 in,
610 mm, above the normal snow line, Figure 17. The
building structure must support the air inlet and vent
systems. All roof penetrations must be properly flashed
and sealed. A dormant chimney can be used as a chase
through which the air intake and vent pipes can be run.
All previous instructions and warnings apply.
When terminals from multiple boiler installations exit a
roof the following conditions must apply:
If limited to two terminals the horizontal centerline
distance must be 4 in, 102 mm or greater than 24 in,
610 mm, to prevent flue gas recirculation. For more
than two terminals located along a given plane, the
centerline distance between them must be 24 in,
610 mm, Figure 18.
Figure 17 =Concentric Through the Roof
EXHAUST
I
I
Figure 18 =Multiple Concentric Through the Roof
EXHAUST
,.J
1
i
I
I
AIR INLET
181N
MINIMUM
--i
]- 24 IN MINIMUM
1
1
CONDENSATE DRAIN
This unit produces water as a byproduct of combustion.
Much of this water condenses on the heat exchanger
and in the venting system. Condensate must be drained
from the boiler into a household drain as shown in
Figure 19.
Figure 19 -Condensate Piping
;ATE
FROMBOILER
CONDENSATE
SIPHON --_
--CONDENSATE
DRAIN PIPE
MUST NOT BE
SEALED
DRAIN MUST NOT
EXCEED HEIGHT
OF HOLE IN
CABINET
BACK PANEL CONDENSATE TRAP
AND DRAIN
NOTE: Check with your municipality, or local gas
company to determine if disposal of untreated
combustion condensate is permitted, if not, the
condensate will have to be neutralized with lime
crystals, marble chips or phosphate chips.

GXINSTALLATIONANDOPERATIONINSTRUCTIONS Page11
Thefollowingareimportantrulesthatmustbefollowed
whenconstructingthecondensatesystem:
1. Connectthecondensatetrapto thedrainusing
1/2in, 13 mm, silicone, rubber, reinforced nylon, or
PEX tubing. Long runs must be properly pitched
and supported to prevent blockage.
2. Do not use nylon tubing, as it will collapse, blocking
drainage. This could damage the boiler.
3. Do not seal the opening between the condensate pipe
and the condensate drain pipe, Figure 19. Inthe event
of a blocked drain the opening will allow the condensate
to overflow and prevent the boiler from flooding.
4. Never have the drain pipe higher than the hole in the
back cabinet, this will flood the boiler.
5. Never allow the drain to freeze or become blocked.
This will cause condensate to fill the combustion
chamber resulting in a no heat condition and damage
to the boiler.
6. NEVER use copper, steel, or galvanized piping in
the construction of the condensate system.
7. When a condensate pump is used or required, select
a pump that is designed for residential furnaces.
GENERAL PLUMBING GUIDELINES
If connecting this boiler to a system containing cast iron
radiation, be sure to add a strainer to the system to trap
any sediment that may dislodge. Failure to do this could
harm the heat exchanger and void the warranty! The
use of non-oxygen barrier radiant tubing is acceptable,
provided that non-ferrous pipe, valves, and fittings are
used throughout the entire hydronic system.
CAUTION: All heating system piping must be
installed in accordance with the ANSI/ASME Boiler
and Pressure Vessel Code, Section IV.All applicable
local codes and ordinances must also be followed, if
the boiler is installed above any radiation elements
it must be fitted with a low water cutoff device
installed above the normal boiler water level!
CAUTION: This boiler must have adequate water
flowing through it whenever the burner is on.
Failure to do this will damage the unit and void the
warranty!
CAUTION: All systems must be flushed to remove
sediment, flux, filings and other foreign matter.
Use products such as Fernox "Superfloc" for new
installations and CHR "Central Heating Restorer"
for retrofits. Also add an inhibitor to the system
water to prevent limestone and magnetite deposits
from forming and to protect the boiler from galvanic
corrosion. An inhibitor such as CliP, "Central
Heating Protector" from Fernox is recomended.
if connecting this boiler to a system containing
cast iron radiation, be sure to add a strainer to the
system to trap any sediment that may dislodge.
Failure to do this could harm the heat exchanger
and void the warranty!
The use of non-oxygen barrier radiant tubing is
acceptable, provided that non-ferrous pipe, valves,
and fittings are used throughout the entire hydronic
system. Failure to comply with these instructions
will seriously damage the boiler, voiding warranty!
CAUTION: The boiler fittings cannot support any
weight. The plumbing system must be supported by
the building structure. A wrench must be used to
hold the boiler fittings when installing the heating
system piping. Failure to do so can seriously
damage the boiler, voiding warranty!
The GX hot water boiler comes from the factory ready
to be piped to the heating system. The boiler must be
used only in a Primary/Secondary pumping system to
avoid cycling problems in systems that have poor flow
or heating zones with very small capacities.
CAUTION: A11/4in, 32 mm, primary loop system
must be used for GX-150 &200 models regardless of
the configuration of the secondary system design.
A 11/2in, 38 mm, primary loop system must be used
for the GX-400. Failure to properly plumb the boiler
may void the warranty!

Page12 GXINSTALLATIONANDOPERATIONINSTRUCTIONS
Understandandfollowtheplumbingrequirements
providedinthissection.Keepserviceabilityin mind
wheninstallingplumbingaroundtheboilercabinetry.
Installfittingsthatwillallowthesystemtobeflushedif
neededduringannualcheck-ups.Addaninhibitortothe
systemwatertopreventlimeandmagnetitedeposits
fromforming,andtoprotecttheboilerfromgalvanic
corrosion.Aminimumclearanceof 1in,25 mm must
be maintained between heating system pipes and all
combustible construction. All heating system piping must
be supported by suitable hangers not the boiler. The
thermal expansion of the system must be considered
when supporting the system. A minimum system
pressure of 12 psig, 84 kPa must be maintained.
Hot water boilers are designed to operate with airless
water in the system. The GX boiler is provided with
a 1/8 in, 3 mm, air vent located on the top of the unit.
This air vent is intended to vent the boiler on initial
startup. This device will NOT continuously vent air
collecting in the primary loop and is not intended
to be the primary venting device. The air scoop as
shown in Figure 21 is the primary venting location. It is
recommended that an additional air scoop be used in
the secondary plumbing. If air continues to be a problem
an air scrubber must be used.
NOTE: Only inhibited propylene glycol solutions
should be used if freeze protection is required.
Avoid using mixtures greater than 30%, unless
the size of the boilers' circulator(s) is increased
accordingly. Under no circumstances should a 50%
mixture be exceeded.
Pressure Relief Valve
Each boiler is equipped with a 30 psi pressure relief
valve that must be piped in accordance with the ANSI/
ASME Boiler and Pressure Vessel Code, Section IV to
prevent scalding of persons with hot liquid or vapor in
the event of a discharge, see Figure 20.
Support the relief valve discharge piping to prevent
strain on the valve body. Leave the open end of the relief
valve discharge pipe visible for periodic inspection.
NOTE: The discharge pipe diameter must be the
same at the relief valve output diameter. Never
restrict the outlet relief valve.
Figure 20 -Relief Valve Piping
Non ASME Model 150 All ASME Models

GX INSTALLATION AND OPERATION INSTRUCTIONS Page 13
Low Water Cut Off, LWCO
If a LWCO is used ensure that the water line of the "Low
Water Cutoff" isat least 6 in, 152mm, above the top of the
boiler, Figure 21. It is recommended that the LWCO be
situated so that it can be tested without removing water
from the boiler. Tri-cocks and a gauge glass are highly
recommended. Valves shall not be installed between
the LWCO and the boiler. Use an air vent if installed as
per our diagram to be used as a vacuum breaker and to
eliminate air upon filling.
Figure 21 =LWCO &Air Vent Piping
SYSTEM AIR
VENT _IcOW WATER
UTOFF
W_ER LINE
SECONDL_Yp_ I
6 IN
MINIMUM
I
PRIMARY LOOP PLUMBING
This low mass boiler requires a continuous minimum
water flow for proper operation. The heat exchanger in
this boiler is more restrictive than a conventional boiler.
The system pump must be sized to overcome the head
loss of the boiler, Figure 22. Greater consideration must
be given to the capabilities of the circulating pump(s) in
the primary-loop. This includes the pump used for an
indirect tank.
Figure 22 -Boiler Head Loss
-- 150 _ 200 ....... 400
60
= 40
o2o
L_-
o2 4 6 8 10 12 14 16 18 20 22 24 26 27
GPMus
Table 3 lists the recommended circulators for use as the
primary and indirect loop pumps.
Figure 23 shows the proper way to plumb a primary loop
for single boiler installations.
MULTIPLE BOILER PRIMARY LOOP
Figure 24 show's the proper way to plumb a primary loop
for multiple boiler installations.
SECONDARY LOOP PLUMBING
Figures 25 and 26 show some typical primary/secondary
piping systems. It is the responsibility of the installing
contractor to determine which system best meets the
need of the installation. Contractor modifications to these
instructions may be required, based upon the existing
piping and system design.
Table 3=Recommended Primary and Indirect Loop Circulators
Minimum
Restriction Flow
Model Head Loss GPM, L/s
GX-150 7It at 6 GPM,2.1 mat 0.4 L/s 6, 0.4
GX-200 10 ft at 8 GPM,3mat 0.5 L/s 8, 0.5
GX-400 10 It at20 GPM,3mat 1.25L/s 13, 0.8
Max. Temp.
Rise
°F, °C
45, 25
45, 25
57, 45
Minimum Primary &
Indirect Pump Size
B&G Grundlos Taco
NRF-33 UP26-64 0010
PL-36 UP26-99 0011
PL-36 UP26-99 0011

Page 14 GX INSTALLATION AND OPERATION INSTRUCTIONS
Figure 23 -Single Boiler with indirect Hot Water Heater
COLD
WATER
T
T
MAX.12"
HOT
WATER
SEE
NOTE
OPTIONAL:
INDIRECT HOT
WATER HEATER.
SEE NOTE
10
_-I _ SEE
NOTE 5
SEE
NOTE 4
NOTE 5 SEE
NOTE 12
A_
SEE
NOTE 15
SEE
.OT l NOTE 7
SEE X_:::_
NOTE 6 2
BACKFLOW
PREVENTION
DEVICE
COLD
WATER
MAKE UP
SEE
NOTE 2 SIOM 90 REV 1
EXPANSION
TANK
NOTES:
1. All piping and pumps must be supported so that no loads or stresses are applied to boiler heat exchanger. To make boiler service easy
use Unions or flexible Vibration Isolation Kit.
2. This boiler is provided with a 1/8" vent that is not intended for continuous system venting.
3. For continuous system venting use a cast iron air scoop, for excessive air conditions use a Spirovent. Do not fire boiler until all air is
purged from the system piping. Heat exchanger damage caused by air is not covered by warranty.
4. See Table 3 for boiler pump flow requirements. This pump is wired to terminals C1 -L2.
5. See Table 3 for Indirect Water Heater pump flow requirements. This pump is wired to terminals AP-L2.
6. Set pressure reducing valve to 12 PSI.
7. Use 30 psi relief valve max. Locate where discharge will not cause injury or damage. Follow local codes.
8. Add an inhibitor to protect system. (CliP from Fernox)
9. Boiler circuit piping must be sized large enough to handle maximum flow through unit.
10. Suggested piping. When installing an indirect water heater consult manufacturer's manual for full details.
11. Do not install any valves between the Vacuum Relief valve and the tank.
12. Do not operate boiler with service valves closed isolating the boiler from the expansion tank.
13. Failure to follow these instructions will result in heat exchanger damage: All flux and contaminants must be flushed from piping before
connecting boiler. Do not connect this boiler to older systems with cast iron radiation without installing a fine particulate separator. TYP:
Spirotrap Junior Model TDN 125 FT. Do Not use non-oxygen barrier radiant tubing.
Notice: This drawings show suggested piping configuration and valving. Check with local codes and ordinances for specific requirements.
Pump Gate Valve Ball Valve Pressure Check Valve Pressure Thermometer Union Automatic Heating Drain Valve Backflow-Prevention
Reducing Relief Valve Air Vent Load (Typ.) Device
Valve
Q
Differential Pressure Spirotrap
Bypass Valve Fine Particulate
Separator

GX INSTALLATION AND OPERATION INSTRUCTIONS Page 15
Figure 24 =Multiple Boiler Installation
MAX. 12"
SEE
NOTE 4
EZZZ}--
sEE{}NOTE 11
COLD
WATER
MAKE UP
SEE
NOTE ,3
_ -'i)
BACKFLOW
- (}
NOTE 1 NOTE 7
SEE
NOTE 2
SIOM 91 REV 1
SEE
NOTE 6
EXPANSION
TANK
NOTES:
1. All piping and pumps must be supported so that no loads or stresses are applied to boiler heat exchanger. To make boiler service easy
use Unions or flexible Vibration Isolation Kit.
2. This boiler is provided with a 1/8" vent that is not intended for continuous system venting.
3. For continuous system venting use a cast iron air scoop, for excessive air conditions use a Spirovent. Do not fire boiler until all air is
purged from system piping. Heat exchanger damage caused by air is not covered by warranty.
4. See Table 3 for boiler pump flow requirements. This pump is wired to terminals C1 -L2.
5. Indirect Water Heater pump is wired to terminals AP-L2.
6. Set pressure reducing valve to 12 PSI.
7. Use 30 psi relief valve max. Locate where discharge will not cause injury or damage. Follow local codes.
8. Add an inhibitor to protect system. (CHP from Fernox)
9. Boiler circuit piping must be sized large enough to handle maximum flow through unit.
10. Do not operate boiler with service valves closed isolating the boiler from the expansion tank.
11. Failure to follow these instructions will result in heat exchanger damage. All flux and contaminants must be flushed from piping before
connecting boiler. Do not connect this boiler to older systems with cast iron radiation without installing a fine particulate separator. TYP:
Spirotrap Junior Model TDN 125 FT. Do not use non-oxygen barrier radiant tubing.
Notice: This drawings show suggested piping configuration and valving. Check with local codes and ordinances for specific requirements.
Pump Gate Valve Ball Valve Pressure Check Valve Pressure Thermometer Union Automatic Heating Drain Valve Backflow_Prevention
Reducing Relief Valve Air Vent Load (Typ.) Device
Valve
©
Differential Pressure Spirotrap
Bypass Valve Fine Particulate
Separator

Page 16 GX INSTALLATION AND OPERATION INSTRUCTIONS
Figure 25 =Multiple Zones Using Circulators
MAX. 12"
SEE _1_
NOTE 1 1
SEE
SEE __
NOTE .3
NOTE 1
I INOTE2
EXPANSION ,_
TANK _
ow
DEVICE _
COLD
WATER
MAKE UP
StOM 92 REV 1
NOTES:
1. All piping and pumps must be supported so that no loads or stresses are applied to boiler heat exchanger. To make boiler service easy
use Unions or flexible Vibration Isolation Kit.
2. This boiler is provided with a 1/8" vent that is not intended for continuous system venting.
3. For continuous system venting use a cast iron air scoop, for excessive air conditions use a Spirovent. Do not fire boiler until all air is
purged from the system piping. Heat exchanger damage caused by air is not covered by warranty.
4. See Table 3 for boiler pump flow requirements. This pump is wired to terminals C1 -L2.
5. Indirect Water Heater pump is wired to terminals AP-L2.
6. Set pressure reducing valve to 12 PSI.
7. Use 30 psi relief valve max. Locate where discharge will not cause injury or damage. Follow local codes.
8. Add an inhibitor to protect system. (CHP from Fernox)
9. Boiler circuit piping must be sized large enough to handle maximum flow through unit.
10. Do not operate boiler with service valves closed isolating the boiler from the expansion tank.
11. Failure to follow these instructions will result in heat exchanger damage: All flux and contaminants must be flushed from piping before
connecting boiler. Do not connect this boiler to older systems with cast iron radiation without installing a fine particulate separator. TYP:
Spirotrap Junior Model TDN 125 FT. Do Not use non-oxygen barrier radiant tubing.
Notice: This drawings show suggested piping configuration and valving. Check with local codes and ordinances for specific requirements.
Expansion Pump Zone Ball Valve
Valve
Tank N 2
Check Valve Automatic Heating Drain Valve
Air Vent Load (Typ.)
Differential Pressure
Bypass Valve
©
Spirotrap
Fine Particulate
Separator

GX INSTALLATION AND OPERATION INSTRUCTIONS Page 17
Figure 26 -Multiple Zones Valves with Bypass Valve
SEE NOTE
zz
m
zz
m
zz
SEE
Note: Velocity noise may be NOTE12
aproblem when the entire |E_ 0
output of the system pump is
flowing through the zone with SEE
the highest pressure drop. NOTE1
Adjust the differential bypass
valve to eliminate noise. sEE
_ NOTE 7
I NOTE 2
t EXPANSION
TANK
BACKF,OW _)
PREVENTION
DEVICE
COLD
WATER
MAKE UP
SIOM 95 REV 1
NOTES:
1. All piping and pumps must be supported so that no loads or stresses are applied to boiler heat exchanger. To make boiler service easy
use Unions or flexible Vibration Isolation Kit.
2. This boiler is provided with a 1/8" vent that is not intended for continuous system venting.
3. For continuous system venting use a cast iron air scoop, for excessive air conditions use a Spirovent. Do not fire boiler until all air is
purged from system piping. Heat exchanger damage caused by air is not covered by warranty.
4. See Table 3 for boiler pump flow requirements. This pump is wired to terminals C1 -L2.
5. Indirect Water Heater pump is wired to terminals AP-L2.
6. Set pressure reducing valve to 12 PSI.
7. Use 30 psi relief valve max. Locate where discharge will not cause injury or damage. Follow local codes.
8. Add an inhibitor to protect system. (CHP from Fernox)
9. Boiler circuit piping must be sized large enough to handle maximum flow through unit.
10. Do not operate boiler with service valves closed isolating the boiler from the expansion tank.
11. Failure to follow these instructions will result in heat exchanger damage. All flux and contaminants must be flushed from piping before
connecting boiler. Do not connect this boiler to older systems with cast iron radiation without installing a fine particulate separator. TYP:
Spirotrap Junior Model TDN 125 FT. Do not use non-oxygen barrier radiant tubing.
Notice: This drawings show suggested piping configuration and valving. Check with local codes and ordinances for specific requirements.
Expansion Pump Zone Ball Valve
Valve
Tank
Check Valve Automatic Heating
Air Vent Load
©
Spirotrap
Fine Particulate
Separator

Page 18 GX INSTALLATION AND OPERATION INSTRUCTIONS
GAS SUPPLY PIPING
The GX hot water boiler comes from the factory ready to
be piped to the gas supply.The National Fuel Gas Code,
ANSI Z223.1/NFPA 54 and local codes for gas piping
requirements and sizing must be followed. If for any
reason the boiler is not for the type of gas available at the
installation site, call the nearest Hydrotherm distributor
to resolve the problem.
Figure 27 depicts the proper way to connect the boiler to
the gas supply piping.The manual shut-off valve MUST be
installed in the supply piping. It should be approximately
5 ft, 1.5m, above the floor. Provide a sediment trap/drip
leg at the bottom of the vertical section of the gas supply
pipe. A ground joint union should be installed between
the boiler gas controls and the supply piping. Each of
these items is needed to ensure long life and ease of
servicing. Always use a pipe sealant that is suitable for
use with LP gas. Flexible gas piping is recommended if
accepted by the local codes. Make sure the gas piping
doesn't hinder boiler access.
CAUTION: Always use a wrench on the gas valve
body when making gas connections to it. Never over=
tighten the piping entering the gas valve body or the
gas valve will be damaged voiding the warranty!
CAUTION: The gas piping must be properly supported
by the building structure and not by the boiler or the
gas valve will be damaged voiding the warranty!
Figure 27 =Gas Supply Piping
GAS COCK SHUT OFF
VALVE TO BE "T" TYPE HANDLEI_U
GAS VA_
J
-----FLEXIBLE GAS PIPE
Safe lighting and other performance criteria were met
with the gas manifold and control assembly provided on
the boiler when the boiler underwent tests specified in
ANSI Z21.13/CSA 4.9. All gas connections MUST be leak
tested before putting the boiler into operation.
Table 4 -Gas Pipe Capacity
Nominal Pipe Length
iron Pipe 10' 20' 30' 40' 50' 60' 80' 100' 150'
Size Gas Pipe Capacity (fP/hr)
3/4" 278 190 152 130 115 105 90 79 64
1" 520 350 285 245 215 195 170 150 120
1 1/4" 1050 730 590 500 440 400 350 305 250
1 1/2" 1600 1100 890 760 670 610 530 460 380
Note: Maximum pipe capacity in fP/hr is based on a 0.60 specific gravity
gas at a pressure of 0.5 psig and a 0.3" WC pressure drop.
Table 5 -Equivalent Pipe Length Chart
Nominal Type of Pipe Fitting
Iron Tee Gate Valve
90 ° Gas Cocks
Pipe (branch flow) (full port)
Size Equivalent length of pipe fittings in feet
3/4" 2.06 4.12 0.48 1.25
1" 2.62 5.24 0.61 1.60
1 1/4" 3.45 6.90 0.81 2.15
1 1/2" 4.02 8.04 0.94 2.50
Whenever the gas supply piping is pressure tested the
boiler gas controls must be protected. Ifthe test pressure
is equal to, or less than 1/2 psi, 3.5 kPa, isolate the boiler
by closing it's manual shut off valve, see Figure 27. If the
test pressure is greater than 1/2 psi, 3.5 kPa, disconnect
the boiler and it's individual shut-off valve from the gas
supply piping.
Table 4 should be used to ensure that the gas supply
piping is sized properly. If more than one appliance is
supplied by the same supply pipe, the piping must be
sized based on the maximum possible demand. Do not
neglect the pressure drop due to pipe fittings. Table 5
should be used in conjunction with Table 4 to ensure that
the gas supply piping is sized properly.

GXINSTALLATIONANDOPERATIONINSTRUCTIONS Page19
ELECTRICAL WIRING
CAUTION: Label all wires prior to disconnection
when servicing controls. Wiring errors can cause
improper and dangerous operation!
The electrical connections to this boiler must be made
in accordance with all applicable local codes and the
latest revision of the National Electrical Code, ANSI/
NFPA-70. Install a separate 120 volt 15 amp circuit
for the boiler, Figures 28 and 29. A properly rated shut-
off switch should be located at the boiler. The boiler
must be grounded in accordance with the authority
having jurisdiction, or if none, the latest revision of
the National Electrical Code, ANSI/NFPA-70. Line
voltage field wiring of any controls or other devices must
conform to the temperature limitation of type T wire
at 95°F, 35°C, above room temperature.Use copper
conductors with a minimum size of #14 awg. Low voltage
wiring must not be less than #18 awg with a neoprene,
thermoplastic or other equivalent insulation having a
minimum insulation thickness of 0.012 in, 3 mm.
Schematic and ladder diagrams of the boilers wiring are
shown in Figures 33 & 34.
CAUTION: The contact capacity of outputs C1or A
is 3 amps with a maximum inrush of 6 amps. If the
amp draw of the pumps exceeds these maximums,
apump controller, or isolation relay must be used
to prevent damage to the boiler. Damage caused by
improper wiring will void the warranty!
Before supplying 120 volts to the boiler, do a continuity
check between all the wires and the ground to make sure
that there are no electrical shorts that could damage the
Sentry 2100 board.
Never use magnetic tip screwdriver near the Sentry
2100.
Verify that the wires connected to the Sentry TC and
AC terminals are not grounded, or have any voltage
applied to them, or voltage to ground -dry contact
closure only,
Ensure that the probe wire is not damaged.
CAUTION: Damage to the electrical system
components caused by improper wiring will void
the warranty!
Thermostat Installation
ALWAYS follow the instructions included with the
thermostat to be used to control the boiler. Proper
location of the thermostat will ensure efficient trouble-free
operation of the boiler. Mount the thermostat to an inside
wall at a height approximately five feet above the floor.
Avoid placing the thermostat in areas that will not provide
an accurate measurement of the room temperature.
Locating the thermostat behind a door, in an alcove,
close to a source of thermal radiation or in a drafty area
will cause poor or sporadic heating.
Figure 28 - Basic Heating System Wiring
120V WIRING
4
_L1
WHITE
L2_
ELECTRICAL BOX
120/1/60 15 AMP FUSED
POWER SUPPLY
CAUTION:
CONTACTS THAT ENERGIZE
THESEINPUTS MUST BE DRY
CONTACTS ONLY
-OUTDOOR
PROBE
5 V WIRING

Page 20 GX INSTALLATION AND OPERATION INSTRUCTIONS
Figure 29 =Basic Heating System and Indirect Tank Wiring
120V WIRING
WHITE
_11 /--INDIRECT
c RcuLAT°R
_LI L2_
ELECTRICAL BOX
120/1/60 15 AMP FUSED
POWER SUPPLY
CAUTION:
CONTACTS THAT ENERGIZE
THESE INPUTS MUST BE DRY
CONTACTS ONLY
-OUTDOOR
PROBE
5 V WIRING
Multiple 4 Wire Zone Valves
Figure 30 shows the basic multiple zoned system uses
normally closed four (4) wire zone valves. This wiring
system is used with the piping shown in Figure 26.
When there is a call for heat the room thermostat closes
the circuit to the zone valve motor, thus opening the zone
valve. When the zone valve is opened, the end switch
closes the circuit between terminals T and C on the
Sentry 2100 control. The Sentry 2100 provides power to
the primary and secondary pumps via terminal C1.Once
these pumps are on, the burner fires.
Once the room thermostat is satisfied, it breaks power
to the zone valve motor. The end switch opens the circuit
between terminals T and C shutting down the pumps
and the burner.
Multiple Zones w/Taco Valve Controller
Models ZVC403 to ZVC 406
Figure 31 shows the basic multiple zoned system using
normally closed 2, 3 or 4 wire Taco zone valves. This
wiring system is used with the piping as shown in Figure
26.
When there is a call for heat the room thermostat closes
the circuit between the TT terminals on the Taco zone
controller. The controller energizes the appropriate zone
valve and closes the circuit between terminals T and C on
the Sentry 2100 control. The Sentry 2100 provides power
to the primary and secondary pumps via terminal C1.
Once these pumps are on, the burner fires.
Once the room thermostat is satisfied, it breaks power
to the zone valve motor.The end switch opens the circuit
between terminals T and C shutting down the pumps
and the burner.