Well-mcLain GV90+3 User manual

®
• Installation
• Startup
• Maintenance
• Parts
Boiler Manual
Gas-Fired Water Boilers
Thismanualmustonlybeusedby a qualified heating installer/servicetechnician.BEFOREinstalling,read
all instructions in this manual and all other information shipped with the boiler.Perform steps in the order
given.Failure to comply could result in severe personal injury, death or substantial property damage.
Part number 550-142-054/1211

Part number 550-142-054/1211
GV90+ gas-fired water boiler — Boiler Manual
2
1 Integrated boiler control
The integrated boiler control (IBC) responds to signals from the room thermostat, air
pressure switch, inlet water sensor and boiler limit circuit to operate the circulators,
gas valve, igniter and blower. When a room thermostat calls for heat, the IBC starts the
system circulator and blower.
The IBC runs the blower to purge the boiler flue passages, then turns on the igniter and
lets it warm up.
After igniter warm-up, the IBC opens the gas valve, turns the igniter off, and checks for
flame. The flame must come on within 4 seconds or the IBC will shut down and try the
full cycle again.
When the room thermostat is satisfied, the IBC turns off the boiler components and
waits for the next heat call.
The IBC indicator lights show normal sequence when the lights are on steady. When a
problem occurs, the IBC flashes combinations of lights which indicate the most likely
reason for the problem.
2 Transformer
The control transformer reduces line voltage to 24 volts for the gas valve and limit
circuit.
3 Blower
The blower pulls in air and mixes it with gas from the gas valve. The blower forces this
mixture into the burner for combustion inside the boiler chamber.
4 Recuperator
The recuperator is a stainless steel heat exchanger that increases boiler efficiency by ex-
tracting additional heat from the flue gases.Return water passes through the recuperator
before entering the boiler.
5 Water temperature limit switch
The water temperature limit switch turns off the gas valve if the temperature in the
boiler goes above its setting. (The circulators will continue to run as long as there is a
call for heat.)
6 System circulator
The system circulator circulates water through the external (system) piping. The flow
rate of the circulator is controlled by the IBC,depending on the temperature of the water
entering the boiler sections. Pump must remain on boiler — do not remove.
7 Bypass circulator
The IBC operates the bypass circulator to mix hot water from the boiler outlet with
colder return water from the system as needed to prevent condensation of flue gases in
the cast iron heat exchanger.
When the water returning to the boiler is below 140°F, the IBC regulates the bypass cir-
culator and system circulator flow rates to raise the return water temperature up to 140°F
before it enters the cast iron sections. By balancing these flow rates, the IBC can protect
against condensation in the cast iron heat exchanger even if return water is as low as 60°F.
Pump must remain on boiler — do not remove.
8 Air pressure switch
The air pressure switch signals the IBC, telling the control whether air is moving through
the blower.
9 Water temperature sensor
The water temperature sensor monitors the temperature of the water entering the boiler
sections. The sensor sends this information to the IBC. The IBC determines how much
to adjust the circulator flow rates to provide at least 140°F water to the cast iron heat
exchanger.
How it works . . .
LEGEND
a Supply to system, 1” NPT
b Return from system, 1” NPT
c Combustion air inlet fitting —
3” PVC connection
d Flue outlet — 3” PVC connec-
tion
e Gas valve — negative pressure
regulated gas control
f Pressure/temperature gauge
g Flueway inspection port cover
h Sensor hose trap
i Manual air vent
j Relief valve
k Thermal fuse — a one-time fuse
device that shuts boiler off if flue
temperature exceeds its setpoint
m Condensate trap line — shipped
loose with boiler, field installed
n Condensate drain connection —
½” PVC female
This boiler uses a negative-pressure-
regulated gas valve, set for an outlet
pressure approximately –0.20” water
column.
DO NOT set the outlet pressure higher
than factory setting.

Part number 550-142-054/1211 3
GV90+ gas-fired water boiler — Boiler Manual
GV90+ Water Boiler

Part number 550-142-054/1211
GV90+ gas-fired water boiler — Boiler Manual
4
How it works . . . . . . . . . . . . . . 2
GV90+ Water Boiler . . . . . . . . . 3
Please read before proceeding . . . 5
Prepare boiler location . . . . . . .6
Installations must follow these codes: . . . 6
High altitude installations. . . . . . . . . . 6
Residential garage installation . . . . . . . 7
Check orifice plate — replace if necessary . 8
Install condensate trap. . . . . . . . . . . . 9
Install high altitude air pressure switch when
required (only above 5,550 feet) . . . . . . 9
Rotate the boiler into position . . . . . . 10
Perform hydrostatic pressure test. . . . . 11
Install water piping . . . . . . . . 12
General piping information. . . . . . . . 12
Install relief valve . . . . . . . . . . . . . 12
Expansion tank. . . . . . . . . . . . . . . 13
System water piping methods. . . . . . . 15
Circulators . . . . . . . . . . . . . . . . . 15
Simplified pipe/circulator selection . . . 15
Baseboard system piping — CIRCULATOR
zoning (primary/secondary) . . . . . . . 16
Baseboard system piping — ZONE VALVE
zoning (direct connection) . . . . . . . . 16
Radiator system piping . . . . . . . . . . 18
Single-zone radiant heating or heat pump 19
Adjust balancing valves . . . . . . . . . . 19
Multi-zone radiant heating system . . . . 20
Piping snow melt systems or combination
snow melt/space heating systems . . . . . 21
Water chiller systems . . . . . . . . . . . 22
Multiple boiler installations . . . . 23
Placing multiple boilers . . . . . . . . . . 23
Controlling multiple GV90+ boilers . . . 23
Piping multiple GV90+ boilers . . . . . . 23
Multiple boiler water piping. . . . 24
Easy-Fit® piping installation . . . . . . . 24
Venting & air — general . . . . . . 29
When removing a boiler from an existing
common vent system . . . . . . . . . . . 29
Existing vent test procedure. . . . . . . . 29
Provide combustion air: . . . . . . . . . . 30
Vent and air termination options. . . . . 30
DIRECT VENT installations . . . . . . . 30
DIRECT EXHAUST installations. . . . . 30
Combustion air contamination: . . . . . 30
Manifolded combustion air option for
DIRECT VENT multiple boiler installations
31
Air manifold sizing . . . . . . . . . . . . 31
Commonwealth of Massachusetts
installations . . . . . . . . . . . . 34
Vent termination requirements . . 35
DIRECT VENT — Boiler room air
openings . . . . . . . . . . . . . . 36
DIRECT VENT — Sidewall with W-M
vent/air plate . . . . . . . . . . . . 37
DIRECT VENT — Sidewall with sepa-
rate pipes. . . . . . . . . . . . . . 39
DIRECT VENT — Sidewall with 3”
concentric . . . . . . . . . . . . . 41
DIRECT VENT — Vertical with sepa-
rate pipes. . . . . . . . . . . . . . 43
DIRECT VENT — Vertical with 3”
concentric . . . . . . . . . . . . . 45
Concentric termination assembly
(sidewall or vertical). . . . . . . . 47
Vent and air piping and boiler con-
nections . . . . . . . . . . . . . . 48
DIRECT EXHAUST & DIRECT VENT . 48
Follow termination instructions . . . . . 48
Installing vent and air piping . . . . . . . 48
DIRECT EXHAUST ONLY . . . . . . . . 48
DIRECT EXHAUST — Boiler room air
openings . . . . . . . . . . . . . . 49
Combustion air provision. . . . . . . . . 49
Sizing combustion air openings . . . . . 49
Special considerations . . . . . . . . . . . 49
GV90+ boiler WITHOUT other appliances
in room . . . . . . . . . . . . . . . . . . . 50
Air openings . . . . . . . . . . . . . . . . 50
GV90+ boiler WITH other appliances in
room . . . . . . . . . . . . . . . . . . . . 50
DIRECT EXHAUST — Sidewall . . 51
DIRECT EXHAUST — Vertical . . . 53
Gas piping . . . . . . . . . . . . . 54
Connecting gas supply piping. . . . . . . 54
Natural Gas. . . . . . . . . . . . . . . . . 55
Propane Gas . . . . . . . . . . . . . . . . 55
Wiring . . . . . . . . . . . . . . . 56
Field wiring. . . . . . . . . . . . . . . . . 56
Start-up. . . . . . . . . . . . . . . 59
Freeze protection (when used) . . . . . . 59
Clean system to remove sediment . . . . 59
Water chemistry . . . . . . . . . . . . . . 59
Antifreeze. . . . . . . . . . . . . . . . . . 59
Check for gas leaks. . . . . . . . . . . . . 60
Fill and test water system . . . . . . . . . 60
Verify gas/air orifice plate . . . . . . . . . 61
Check thermostat circuit(s) . . . . . . . . 61
Inspect/fill condensate system . . . . . . 61
Final checks before starting boiler . . . . 62
To start the boiler . . . . . . . . . . . . . 62
If boiler does not start correctly . . . . . 62
Check system and boiler after start-up. . 62
Gas valve adjustment — altitude over 5,500
feet ONLY . . . . . . . . . . . . . . . . . 62
Final checklist . . . . . . . . . . . . . . . 64
Annual start-up and general mainte-
nance schedule . . . . . . . . . . 67
Annual start-up . . . . . . . . . . 68
Address reported problems . . . . . . . . 68
Inspect boiler area . . . . . . . . . . . . . 68
Inspect boiler interior . . . . . . . . . . . 68
Inspect condensate drain system . . . . . 68
Inspect all piping for leaks . . . . . . . . 68
Inspect gas piping . . . . . . . . . . . . . 68
Inspect the water system. . . . . . . . . . 68
Inspect expansion tank . . . . . . . . . . 68
Inspect air openings . . . . . . . . . . . . 69
Inspect vent system and air piping . . . . 69
Inspect boiler heating surfaces . . . . . . 69
Inspect recuperator . . . . . . . . . . . . 69
Inspect igniter . . . . . . . . . . . . . . . 69
Inspect temperature mixing system . . . 70
Inspect limit controls and cutoffs. . . . . 70
Inspect gauges . . . . . . . . . . . . . . . 70
Inspect blower motor . . . . . . . . . . . 70
Inspect oiled-bearing circulators . . . . . 70
Inspect boiler relief valve . . . . . . . . . 71
To complete Annual Start-up, perform
startup and checks: . . . . . . . . . . . . 71
Review with owner. . . . . . . . . . . . . 71
Service & maintenance . . . . . . 72
Cleaning boiler heating surfaces . . . . . 72
Inspecting and cleaning the recuperator . 73
Troubleshooting . . . . . . . . . . 75
VERIFY PROPER OPERATION AFTER
SERVICING. . . . . . . . . . . . . . . . . 75
Before troubleshooting . . . . . . . . . . 75
Check the following . . . . . . . . . . . . 75
Checking the air pressure switch . . . . . 75
Igniter. . . . . . . . . . . . . . . . . . . . 76
Gas Valve . . . . . . . . . . . . . . . . . . 76
Blower Housing . . . . . . . . . . . . . . 76
Thermal fuse . . . . . . . . . . . . . . . . 76
Return temperature sensor . . . . . . . . 76
IBC (integrated boiler control) . . . . . . 77
IBC indicator lights — lockout modes . . 77
IBC indicator lights — non-lockout modes
77
Replacement parts . . . . . . . . 89
Dimensions and ratings. . . . . 100
NOTES . . . . . . . . . . . . . . 104
NOTES . . . . . . . . . . . . . . 106
Handling ceramic ber and ber-
glass materials. . . . . . . . . . 107
Installation and service
certicate . . . . . . . . . . . . 108
Contents

Part number 550-142-054/1211 5
GV90+ gas-fired water boiler — Boiler Manual
Failure to adhere to the guidelines on this
page can result in severe personal injury,
death or substantial property damage.
When servicing boiler —
• To avoid electric shock, disconnect electrical supply
before performing maintenance.
• To avoid severe burns, allow boiler to cool before
performing maintenance.
• This boiler contains ceramic fiber and fiberglass
materials. Refer to the WARNING and instructions
on page 107.
Boiler operation —
• Do not block flow of combustion or ventilation air
to boiler.
• Should overheating occur or gas supply fail to
shut off, DO NOT turn off or disconnect electrical
supply to circulator. Instead, shut off the gas supply
at a location external to the appliance.
• Do not use this boiler if any part has been under
water. Immediately call a qualified service techni-
cian to inspect the boiler and to replace any part of
the control system and any gas control that has been
under water.
Combustion air —
• DO NOT install combustion air intake where there
is a risk of combustion air contamination.
Carbon monoxide detector —
• For Direct Exhaust units, a carbon monoxide detec-
tor is required in the boiler room. The carbon mon-
oxide detector must be wired on the same electrical
circuit as the boiler.
• For Direct Vent units, a carbon monoxide detector
that is wired on the same electrical circuit as the boiler
is strongly recommended.
Boiler water —
• Thoroughly flush the system (without boiler con-
nected) to remove sediment. The high-efficiency heat
exchanger can be damaged by build-up or corrosion
due to sediment.
• Do not use petroleum-based cleaning or sealing
compounds in boiler system. Gaskets and seals in the
system may be damaged. This can result in substantial
property damage.
• Leaks in boiler or piping must be repaired at once
to prevent make-up water. Use this boiler ONLY
in a closed-loop system. Continual fresh make-up
water will reduce boiler life. Mineral buildup in heat
exchangers reduces heat transfer, overheats the mate-
rials, and causes failure.Addition of oxygen carried in
by make-up water can cause internal corrosion.
• Do not add cold water to hot boiler. Thermal shock
can cause heat exchanger to crack.
Freeze protection uids —
• NEVER use automotive or standard glycol antifreeze.
Use only freeze-protection fluids made for hydronic
systems. Follow all guidelines given by the antifreeze
manufacturer. Thoroughly clean and flush any re-
placement boiler system that has used glycol before
installing the new boiler.
Please read before proceeding
Installer— Read all instructions, including this
manual and all other information shipped with the
boiler, before installing. Perform steps in the order
given.
User — This manual is for use only by a qualified
heating installer/service technician. Refer to User’s
Information Manual for your reference.
User — Have this boiler serviced/inspected by a
qualified service technician, at least annually.
Failure to comply with the above could result in
severe personal injury, death or substantial property
damage.
Write in the CP number in the space provided on
the Installation certificate on page 108 if not already
shown.
When calling or writing about the boiler— Please
have the boiler model number from the boiler rating
label and the CP number from the boiler jacket.
Consider piping and installation when determining
boiler location.
Any claims for damage or shortage in shipment
must be filed immediately against the transportation
company by the consignee.
Commonwealth of Massachusetts
When the boiler is installed within the Commonwealth of Mas-
sachusetts, comply with the following.
• This product must be installed by a licensed plumber or gas
fitter.
• If antifreeze is used, a reduced pressure back-flow preventer
device shall be used.
• If sidewall vent or vent/air is installed, see instructions on
page 34.
Hazard denitions
The following defined terms are used throughout this manual to
bring attention to the presence of hazards of various risk levels or
to important information concerning the life of the product.
Indicates presence of hazards that will cause severe
personal injury, death or substantial property dam-
age.
Indicates presence of hazards that can cause severe
personal injury, death or substantial property dam-
age.
Indicates presence of hazards that will or can cause
minor personal injury or property damage.
Indicates special instructions on installation, op-
eration or maintenance that are important but not
related to personal injury or property damage.

Part number 550-142-054/1211
GV90+ gas-fired water boiler — Boiler Manual
6
Figure 1 Estimated GV90+ input at altitude
Altitude
(feet) % Sea level input
1,000 97
2,000 93
3,000 90
4,000 87
5,000 83
5,500 82
6,000 80
7,000 77
8,000 74
9,000 72
10,000 69
Figure 2 Service clearances (recommended)
Prepare boiler location
Installations must follow these codes:
• Local, state, provincial, national codes, laws, regulations and ordinances.
• NationalFuelGasCode,ANSIZ223.1-latestedition.
• StandardforControlsandSafetyDevicesforAutomaticallyFiredBoil-
ers, ANSI/ASME CSD-1, when required.
• NationalElectricalCode.
• ForCanadaonly:B149.1orB149.2InstallationCodeandCSAC22.1
Canadian Electrical Code Part 1 and any local codes.
The GV90+ boiler gas manifold and controls met safe lighting and other
performance criteria when boiler underwent tests specified in ANSI Z21.13
— latest edition.
For the Commonwealth of Massachusetts, read and follow
the special instructions located on page 34 of this manual.
Install the boiler so control system components are protected
from dripping or spraying water or rain during operation.
Allowing these components to become wet could cause a
boiler failure, resulting in severe personal injury, death or
substantial property damage.
High altitude installations
GV90+ boiler controls automatically reduce input with increasing altitude.
See Figure 1 for estimated input at altitude as a percentage of sea level
input. Multiply the boiler sea level input by this percentage to obtain the
estimated high altitude input. Note that the length of the venting system
will also have a minor impact on input. Refer to the vent supplement for
further information.
No modifications to the boiler should be necessary for installations up to
5,500 feet above sea level. For higher elevations, the air pressure switch
must be changed to a special high altitude switch. Refer to the high altitude
kit instructions, page 10. Note that the gas valve outlet pressure must be
checked (and adjusted if necessary) following instructions on page 62.
DO NOT sidewall vent DIRECT EXHAUST APPLICATIONS
at altitudes above 5,500 feet. Sidewall venting is only allowed
for DIRECT VENT applications (ducted combustion air) at
altitudes above 5,500 feet.
Vent length also affects boiler input — the boiler automati-
cally derates to compensate for pressure loss through the vent.
See the derate values given in Figure 109, page 101. For high
altitude installations, multiply the % in Figure 1 times the
value shown in Figure 109 to determine input vs sea level.
Service clearances
When possible, install GV90+ boilers with clearances at least as large as
shown in Figure 2 for best service access.
Flooring
The GV90+ boiler is approved for installation on combustible flooring,
but must never be installed on carpeting.
Do not install boiler on carpeting even if foundation is used.
Fire can result, causing severe personal injury, death or sub-
stantial property damage.

Part number 550-142-054/1211 7
GV90+ gas-fired water boiler — Boiler Manual
Foundation
Provide a solid brick or concrete foundation pad if any of the following
is possible:
• When the floor can become flooded.
• When the boiler mounting area is not level.
• When a high-profile condensate pump is used, provide a foundation
high enough that the GV90+ condensate connection is at least as high
as the condensate pump inlet connection.
Figure 3 Minimum foundation dimensions (inches)
Boiler model W LH *
GV90+3 / GV90+4 16 30¾ 2
GV90+5 / GV90+6 16 37¾ 2
* Increase height if needed to ensure
condensate trap outlet tee is above inlet
of condensate pump, when used.
Residential garage installation
Precautions
Take the following special precautions when installing the boiler in a
residential garage. If the boiler is located in a residential garage, per ANSI
Z223.1, paragraph 5.1.9:
• Mount the boiler a minimum of 18 inches above the oor of the
garage to assure the burner and ignition devices will be no less than
18 inches above the floor.
• Locate or protect the boiler so it cannot be damaged by a moving
vehicle.
Minimum clearances
You can install GV90+ boilers in spaces smaller than Fig-
ure 2, page 6 recommended service clearances, but never
smaller than shown in Figure 4.
Installations with clearances less than shown in Fig-
ure 2, page 6 must have air openings sized and located as
shown in Figure 4.
• Always provide at least screwdriver clearance to jacket front panel screws
for removal of front panel for inspection and minor service.
• If the boiler cannot be serviced in place, pipe the boiler with unions
and isolation valves so it can be slid out of the space and serviced in
an adjacent area.
• The space has to be equipped with a door so boiler can be accessed,
unpiped and removed.
Prepare boiler location (continued)
Figure 4 Minimum clearances — when
clearances are less than recom-
mended service clearances of Fig-
ure 2, page 6, install as shown below:
A Area adjacent to access door must be accessible
and must allow for removal of the GV90+boiler
for service.
No other appliance or air mover (exhaust fan,
etc.) may be mounted in the same space.
B Access DOOR with fresh air openings
C Provide (2) Fresh air openings — Each with at
least 1 sq. inch per 1,000 Btuh of boiler input
NOTICE SPECIAL REQUIREMENTS
FOR AIR OPENINGS: For installations
with clearances less than recommended
service clearances (Figure 2, page 6), but
no less than shown in Figure 4 — An
access door must be provided, fitted with
two air openings as shown in Figure 4.
Each opening must have a free area no
less than 1 square inch per 1000 Btuh
input of the GV90+ boiler in the space.
DO NOT apply the air opening sizes
given in Figure 42, page 36 or Fig-
ure 60, page 50.

Part number 550-142-054/1211
GV90+ gas-fired water boiler — Boiler Manual
8
Prepare the boiler (continued)
Check orifice plate — replace if necessary
The correct orice plate must be used. Failure to do so
will result in severe personal injury, death or substantial
property damage. The boiler is shipped with a natural
gas orice plate. It MUST BE CONVERTED to use
propane.
Natural gas:
For natural gas installations, inspect the silver gas/air orice plate
marking. It must be the same as the boiler size. If the orifice plate is
stamped with another size, obtain the correct plate from your whole-
saler. The boiler size is stamped where the “X” is shown in the plate
stamping, Figure 6.
Propane:
For propane installations, replace the silver gas/air orice plate
with the red/white plate, per following instructions. Ensure the red/
white plate boiler size is correct for the GV90+ boiler being installed.
The boiler size is stamped where the “X” is shown in the plate stamp-
ing, Figure 6.
Also fill out the propane label in the conversion kit and attach to the
left side of the jacket,above the gas inlet opening, as shown in Figure 5.
Orice plate installation, when required
Access the bottom of the blower housing as shown in Figure 5.
To inspect the plate only, read the marking on the plate edge. It
must read the same as the boiler size and fuel, as follows:
Boiler model Natural gas marking Propane marking
GV90+3 NG 3 SEC LP 3 SEC
GV90+4 NG 4 SEC LP 4 SEC
GV90+5 NG 5 SEC LP 5 SEC
GV90+6 NG 6 SEC LP 6 SEC
To replace the plate, using a manual screwdriver or nut driver, see
Figure 6:
1. Loosen screws 1and 2two full turns.
2. Remove screws 3and 4.
3. Pull the gas/air orifice plate forward to remove it.
4. Slide in the new plate as shown in Figure 6. The red side of a
propane plate must go next to the blower housing.
5. Replace screws 3and 4. Tighten all four screws securely and uni-
formly. DO NOT overtighten. DO NOT exceed 40 inch-pounds
torque.
6. Bend down plate label tab at score mark as shown in lower right
corner of Figure 6, item 10.
DO NOT use electric or pneumatic screwdrivers to re-
move or tighten the gas/air boss screws. Hand-tighten
only, using manual screwdriver. Should the torque exceed
40 inch-pounds, the threaded holes could strip out,
causing an inadequate seal of the orifice plate. Failure to
properly seal the plate to the housing could result in a gas
leak, causing severe personal injury, death or substantial
property damage.
Figure 5 Check for correct gas orifice plate
A Remove jacket front
panel to access the bot-
tom side of the blower
housing.
B Complete the propane
conversion label includ-
ed with the conversion
kit. Install label on jacket
left side, as shown.
Leave the boiler on its back,
on the skid as shown, until
you have checked the gas/air
orifice plate and replace it if
necessary.
Figure 6 Follow instructions to check or replace
gas orifice plate ("X" = boiler size)
1–4 Screws — follow instructions for loosening and tightening
5 Gas/air manifold
6 Front section, bottom view, component details omitted
7 Side shown must point toward air inlet hose — WARNING
label side for natural gas; WHITE side for propane gas
8 Propane orifice plate, RED one side and WHITE on the
other (red side must face the blower housing
9 Natural gas orifice plate, SILVER
10 Orifice plate after bending along score mark — label is
visible when installed

Part number 550-142-054/1211 9
GV90+ gas-fired water boiler — Boiler Manual
Prepare the boiler (continued)
Figure 7 Install condensate trap
A In-line flue drain
B Flue drain nipple
C Flue drain hose
D Flue connection
E Condensate trap tee
F U-clamp and nuts (not
shown)
G Condensate drain
nipple
H Condensate trap hose
J Hose clamps
Finished assembly
Install condensate trap
1. Before placing the boiler in position, install the condensate trap
line, shown in Figure 7. Items shown are provided with the boiler.
Step 1 Attach the flue drain hose (C) to the in-line flue drain
nipple (B).
Step 2 Slide a screw driver or pencil through the condensate
drain nipple (G).
Slide the end of the screwdriver or pencil into the open
end of the flue drain hose (C).
Feed the in-line flue drain (A) assembly into the flue con-
nection (D), guiding the flue drain hose through the con-
densate drain nipple (G) with the screwdriver or pencil.
Step 3 Press the in-line flue drain (A) into the flue connection
(D) and through the seal ring until it reaches the stop.
Then tighten the flue connection hose clamp to secure.
The flue drain hose (C) should now extend down past the
end of the condensate drain nipple (G).
Step 4 Slide the U-clamp (F) over the condensate trap tee (E)
and into the two holes in the rail. Attach the two nuts pro-
vided to the U-clamp and tighten to secure the condensate
trap tee to the rail.
Step 5 Slide the ends of the condensate trap hose (H) onto the
condensate drain nipple (G) and the condensate trap tee
(E). Secure the condensate trap hose at each end with the
hose clamps (J).
Check the height of the condensate trap tee outlet.
Before rotating the boiler into position, measure the
distance from the condensate tee outlet to the bottom
of the boiler mounting rails. When the boiler is place in
position, the condensate tee outlet must be higher than
the condensate pump inlet connection (when a con-
densate pump is used). Increase the foundation height
if necessary.

Part number 550-142-054/1211
GV90+ gas-fired water boiler — Boiler Manual
10
Figure 8 Air pressure switch mounting
1 Interior panel top
2 Jacket left side panel
3 Air pressure switch
4 WHITE hose
5 RED hose
6 Mounting screws
Figure 9 Follow instructions to perform the steps
shown below
Prepare the boiler (continued)
Install high altitude air pressure switch
when required (only above 5,500 feet)
1. For installations at altitude more than 5,500 feet above sea level:
a. A special high altitude air pressure switch is required.
b. The gas valve outlet pressure setting must be checked, and
adjusted if necessary, per the instructions on page 62.
Failure to check gas valve outlet pressure and adjust, if
necessary, could result in severe personal injury, death
or substantial property damage. Carefully follow the
guidelines given in this manual.
2. Obtain the GV90+ high altitude kit from your local Weil-McLain
distributor. The high altitude kit contains the high altitude air
pressure switch.
3. See Figure 8 (switch shown with wires removed).
a. Remove the two (RED) control wires from the air pressure
switch spade terminals.
b. Remove the factory-installed air pressure switch (loosen top
screw and remove bottom screw holding switch to jacket in-
terior panel).
c. Install the high altitude air pressure switch in the same loca-
tion.
d. Carefully replace the hoses on the new switch, with the red hose
on the hose barb closest to the electrical spade connectors, as
shown in Figure 8. The white hose goes on the other hose barb.
e. Replace the two (RED) control wires on the new pressure
switch spade terminals.
Rotate the boiler into position
Boiler is shipped on back side. It must be taken off skid
and rotated into correct position.
After installing condensate line, inspecting (replacing if necessary) the
gas/air orifice and installing the high altitude kit (if required), move
the boiler near its position.
Figure 9 shows the boiler with the front and top panels replaced.
These panels may be left off if desired until the installation has been
completed.
Boiler is heavy and contains some sheet metal parts which
may have sharp edges. Wear gloves when handling and
take proper precautions when moving. Failure to do so
will result in severe personal injury, death or substantial
property damage.
Refer to Figure 9 for placement sequence as follows:
1 Wear heavy gloves — carefully rotate the boiler over onto its
base rail legs.
2 Clip the shipping strap securing the skid to the boiler block as-
sembly. Remove the skid and strap.
3 Attach the jacket rear panel as shown using (4) #10 x ½” screws
provided in the accessory bag.