Airmark GFW SERIES Manual

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©2013 AirMark
GFW SERIES
INSTALLATION & OPERATING INSTRUCTIONS
HIGH EFFICIENCY X13
VERTICAL WALL MOUNT AIR HANDLER
(HYDRONIC)
MODEL
(INCLUDING HEATER MODEL #) ________________________________
SERIAL #____________________________________________________
INSTALLER __________________________________________________
INSTALLATION DATE _________________________________________
These instructions should be retained and kept adjacent to the unit for future use
373 Atascocita Rd.
Humble, TX 77396
Phone [phone]
Fax [phone]
www.airmark-ac.com

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Safety Instruction
Potential safety hazards are alerted using 
symbol. The symbol is used in conjunction with
terms that indicate the intensity of the hazard.
 WARNING This symbol indicates a potentially
hazardous situation which if not avoided, could
result in serious injury, property damage, product
damage or death.

CAUTION This symbol indicates a potentially
hazardous situation which if not avoided, may
result in moderate injury or property damage.

WARNING Certified technicians or those
individuals meeting the requirements specified
by NATE may use this information. Property
and product damage or personal injury hazard
may occur without such background.
 WARNING All power sources should be
disconnected prior to servicing. Failure to do so
may cause personal injury or property damage.
 WARNING Product designed and
manufactured to permit installation in accordance
with local and national building codes. It is the
installer’s responsibility to ensure that product is
installed in strict compliance with national and local
codes. Manufacturer takes no responsibility for
damage (personal, product or property) caused
due to installations violating regulations. In
absence of local/state codes, refer to National
Electric Code: NFPA 90A & 90B Uniform
Mechanical Code.
 WARNING When this unit is installed in an
enclosed area, such as a garage or utility room
with any Carbon Monoxide producing devices (i.e.
automobile, space heater, water heater etc.)
ensure that the enclosed area is properly
ventilated.
 CAUTION Only factory authorized kits and
accessories should be used when installing or
modifying this unit unless it is so noted in these
instructions. Some localities may require a licensed
installer/service personnel.

WARNING Unit is not approved for outdoor
installations.
 WARNING The unit is designed for operation
with 108/120 V, single phase, 60 Hz power supply.
Airmark will not be responsible for damages
caused due to modification of the unit to operate
with alternative power sources.
Inspection
On receiving the product, visually inspect it for any
major shipping related damages. Shipping
damages are the carrier’s responsibility. Inspect
the product labels to verify that the model number
and options are in accordance with your order.
Manufacturer will not accept damage claims for
incorrectly shipped product.
Installation Preparation
Read all the instructions in this guideline carefully
while paying special attention to the WARNING
and CAUTION alerts. If any of the instructions are
unclear; clarify with certified technicians. Gather all
the tools needed for successful installation of the
unit prior to beginning on the installation.
This unit is designed for zero clearance installation
on three sides and adequate clearance to provide
access for service in the front. A min of 2.5 – 3.5
feet clearance is recommended on the front end.
These units are designed to be installed on top of
a water heater or recessed into a wall. The unit
should be installed in Vertical Upflow position
ONLY. While installing the unit into a recessed
wall, attach unit to "4"2 framing stud along the
front flange. These air handlers are provided with
an offset hanging bracket at the rear for certain
wall mount applications.
The drain lines must be installed with ¼” per foot
pitch to provide free drainage. A condensate trap
MUST be installed on the primary drain line to
ensure proper drainage of the condensate. The
trap must be installed in the drain line below the
bottom of the drain pan. Figure 1 illustrates the
typical drain trap installation.
These units are equipped with a bottom primary
and secondary drain and a single side primary OR
secondary. When utilizing the unit, disable switch
on the secondary line. It must be located on the
side connection to avoid a false shutdown created
by condensate droplets falling into the bottom
secondary connection. The switch should be
adjusted to permit normal operation of the unit and
disable the unit in the event of a clogged primary
before the condensate spills over the pan. In lieu of
this a hood may be field fabricated to slide over the

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secondary to keep droplets out but allow trapped
condensate into secondary fittings.

CAUTION Since coil is upstream of the
blower; all drains MUST be trapped or sealed.
Failure to do so will result in condensate overflow
from the drain pan. Airmark will NOT be
responsible for any damages resulting from failure
to follow these instructions.
2" MINIMUM
3" MINIM
U
FLEXIBLE
TUBING-HOSE
OR PIPE
A POSITIVE
LIQUID SEAL IS
REQUIRED
DRAIN
CONNECTION
Fig.1. Typical drain line trap set up
Ductwork
Duct systems should be installed in accordance
with standards for air-conditioning systems,
National Fire Protection Association Pamphlet No.
90A or 90B. They should be sized in accordance
with National Environmental System Contractors
Association Manual K, or whichever is applicable.
On any job, non-flammable flexible collars should
be used for the return air and discharge
connections to prevent transmission of vibration.
Although these units have been specially designed
for quiet vibration-free operation, air ducts can act
as soundboards can, if poorly installed, amplify the
slightest vibration to the annoyance level.
All main supply and return air drops should be
properly sized as determined by the designer of
the duct system and should not necessarily be the
size of the duct flange openings of the unit.
These models have a bottom or front return.
Discard the drain access panel in the bottom of the
unit if this is a bottom return application. In case of
a front return application, the front access panel
should be removed and discarded. If an accessory
grill as shown in Fig 2. is being used; the front
access panel should be removed and discarded.
A filter rack is provided for "20"20"1


nominal
size filter. Inspect and clean or replace fliter every
month. A blocked filter can reduce air flow to the
coil and hinder the performance of the system.
It is recommended that wherever supply and return
air sheet metal ducts pass through unconditioned
areas, they be insulated to prevent excessive heat
loss during heating operation. When applied in
conjunction with summer air conditioning, sheet
metal duct routed through unconditioned areas
should be insulated and have an outside vapor
barrier to prevent formation of condensation.
Fig.2. GFW air handler grill and drain connections
Installation
 CAUTION Ensure that the unit is adequately
sized. The tonnage of the outdoor unit should
never exceed the tonnage of this unit.
 WARNING The coil was manufactured with a
dry nitrogen pre-charge. Release the pressure
through the Schrader valve test port prior to
installation. If holding pressure is not present,
return coil to distributor for exchange.
Clean coil fins with degreasing agent or mild
detergent and rinse fins clean prior to installation.
All connection joints should be burr-free and clean.
Not removing burr and cleaning may increase the
chance of a leak. It is recommended to use a pipe
cutter to remove the spun closed end of the
suction line.

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To avoid damage to grommets (where present),
remove these prior to brazing by sliding over the
lines. Use a quenching cloth or allow the lines to
cool before reinstalling the grommets.
 CAUTION Some Airmark coils may include a
Schrader valve on the suction manifold. Ensure
that the Schrader valve and valve core (where
present) are protected from heat during brazing
and installation to prevent leakage.
Metering Device
Airmark coils are available with two kinds of
metering devices a) flowrator or b) TXV.
Instructions below are separated in sections
according to the metering device. Ensure that the
applicable section is thoroughly read and
understood.
Flowrator Coils:
PISTON
DISTRIBUTOR
TAIL PIECE
13/16" NUT
TEFLON O-RING
Fig.3. Flowrator assy components
 CAUTION Use Piston sizes recommended by
the outdoor unit manufacturer whenever possible.
The piston should be sized according to the
capacity of the outdoor unit.

WARNING Failure to install the proper piston
can lead to poor system performance and possible
compressor damage.
During some installations a piston change may be
required. If so the installer MUST change the
piston. As stated earlier, use piston sizes
recommended by the outdoor unit manufacturer. If
a sizing chart is not available, use Table 1 below to
size the required piston. The size of the piston is
stamped on the piston body.
Instruction for piston change
1) Turn the 13/16 nut once to release any
residual pressure in the coil.
2) After ensuring that the coil is free of any
residual pressure, disassemble the
flowrator body completely using two
wrenches. Distortion of the feeder tubes
should be avoided.
3) The wrench used to clasp the nut should
be turned in a counter-clockwise direction
to unscrew the nut.
4) Slide the 13/16 nut over the line set and
separate the two halves of the flowrator.
Outdoor
Capacity Orifice Size–R22 Orifice Size- R410A
12,000 0.041 N/A
18,000 0.055 0.049
24,000 0.059 0.055
30,000 0.068 0.059
36,000 0.074 0.068
42,000 0.080 0.074
48,000 0.084 0.080
60,000 0.092 0.089
Table.1. Piston Size Chart
 CAUTION Pay close attention to the Teflon O-
ring. Be sure to replace the O-ring to attain a
proper seal. (The Teflon O-ring is located between
the two halves of the flowrator)
5) Pull the piston out using a small wire or
pick. Verify the piston size (size is typically
stamped on the body of the piston). If a
different piston size is required by the
outdoor unit manufacturer replace the
piston using the small wire provided with
the piston kit.
 CAUTION Pay close attention to the piston
orientation. The pointed end of the piston
MUST go into the distributor body/towards the
coil. Failure to ensure this orientation will
cause the piston to be bypassed during
operation which might damage the outdoor
unit.
6) Assemble the two halves correctly and
ensure that the white Teflon O-ring is
present between the two halves.

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7) Slide the 13/16 nut onto the distributor
body.
8) Tighten the nut to a torque of
approximately 10-30 ft-lbs. Do NOT over
tighten the nut. This will hamper the piston
movement during operation.
9) Slide the grommet back to position to
prevent air leakage.
TXV Coils:
 WARNING The sensing bulb and TXV body
MUST be protected from overheating during
brazing. The sensing bulb and TXV body must be
covered using a quench cloth or wet cloth when
brazing. Pointing the brazing flame away from the
valve and sensing bulb provide partial protection
only.
 CAUTION Ensure that the TXV selected is
compatible with the refrigerant used in the outdoor
system (R22 or R410A). TXV caps are painted
green for R22 or pink for R410A. In absence of
color, the caps will be marked with the compatible
refrigerant.
 CAUTION The valves should be sized
according to the capacity of the outdoor unit.
Failure to install the right valve can lead to poor
performance and possible compressor damage.
TXV Bulb Mounting
The orientation and location of the TXV bulb has a
major influence on the system performance.
 CAUTION Ensure that the TXV bulb is in
direct contact with the suction/vapor line. Gaps
between the bulb and tube should be avoided.
Failure to eliminate gaps will impair the proper
functioning of the TXV valve.
It is recommended that the TXV bulb be installed
parallel to the ground (in a horizontal plane). The
bulb position should be above and between 4
o’clock and 8 o’clock. Fig. 4 shows the
recommended position for the TXV bulb installation
in the horizontal plane.
The TXV sensing bulb SHOULD be mounted using
the metal clamp provided. In order to obtain a good
temperature reading and correct superheat control,
the TXV sensing bulb must conform to ALL of the
following criteria:
1) The sensing bulb MUST be in direct and
continuous contact with the suction line
2) The sensing bulb should be mounted
horizontally on the suction line.
3) The sensing bulb must be mounted above
and between the 4 and 8 o’clock position
on the circumference of the suction line.
4) The sensing bulb MUST be insulated from
outside air.
TXV BULB POSITION
4 O' CLOCK OR
8 O' CLOCK
METAL STRAP
SUCTI O N/ VA PO R LI NE
Fig.4. Recommended location of the TXV bulb in a
horizontal orientation
The mounting location and insulation guards the
sensing bulb from false reading due to hot outside
air or liquid refrigerant formed inside the
suction/vapor line.
As recommended earlier, the TXV sensing bulb
should be mounted in a horizontal plane in relation
to the suction/vapor line. However, in case such a
mounting is not feasible and the sensing bulb has
to be mounted vertically; then place the bulb as
shown in Fig.5.

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Fig.5. Figure showing the sensing bulb mounted in a
vertical orientation
 CAUTION If the TXV sensing bulb is mounted
vertically; the capillary MUST be directed upwards.
The bulb must be mounted on the wall opposite to
that being directly hit by the refrigerant and oil
leaving the distributor tubes.
Field – Installed Expansion Valve Coils
Remove the valve identification sticker from the
valve and place it adjacent to the Airmark model
number on unit name plate.
When installing an expansion valve, it is not
necessary to remove all the access panels and
slide the coil out of the housing.
1) Disassemble the flowrator body using two
wrenches. Unscrew the body with a
counter-clockwise motion.
2) Replace the white Teflon seal in place
(located between the halves).
3) Remove the existing flowrator piston using
a small wire or pick.
4) Inspect the TXV box to confirm that the
valve is compatible with the refrigerant in
the system.
5) Remove the valve from the box and note
the location of the inlet side (threaded
male port) and the outlet side (female
swivel nut port).
6) After ensuring that the white Teflon seal is
still in place inside the flowrator body,
screw the female swivel nut onto the
flowrator body.
7) Place the attachment nut on the liquid line.
8) Braze the stub-out portion to the liquid line
and let cool.

WARNING Do not attempt to touch the braze
joint while hot. Touching it may cause severe
burns.
9) Remove the additional white Teflon seal
ring from the box and place on the
shoulder just inside the inlet port. Screw
the nut attached to the stub-out portion of
the flowrator body onto the inlet port of the
TXV.
10) Tighten all connections taking care to use
proper back up.
Some Airmark coils come with a Schrader valve on
the suction line. If a Schrader port is present
11) Remove valve stem from the Schrader port
mounted on the suction line
12) Screw flare nut on TXV equalization tube
in to the Schrader valve stem
Coils without Schrader Ports
13) Locate a convenient spot on the suction
line and punch a ¼” hole with a pick or
other suitable tool.

CAUTION Do NOT drill a hole as chips will
enter suction manifold.
14) Insert TXV equalizer tube approximately
3/8” into the hole and apply solder to seal.

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Fig. 6. shows the components of a typical TXV
assembly
TXV BULB
TAIL PIECE
DISTRIBUTOR
TEFL ON O-RINGS
Fig.6. Components of a typical TXV assembly

CAUTION Using a non-bleed expansion valve
may require the use of a hard-start kit. Follow the
outdoor unit manufacturer’s guidelines.
Electrical Installation
These units are designed for single phase 120
volts, 60 Hz power supply. Wire selection and
wiring must be in accordance with the National
Electric Code and/or local codes. Unit terminals
are designed to accommodate copper and
aluminum wirings. If aluminum wiring is used;
please observe special precautions relative to
sizing, wire connections and corrosion protection.
Fig.7 shows the typical electrical connections
required for A/C only and heat pump applications.
The unit ships with a micro-processor based board
which controls the electrical functioning of the unit.
An inspection of the controls is recommended prior
to start-up.
Fig.8 provides a schematic of the control board
present in the unit. The units ship from the factory
with the aquastat jumper in the OFF position (right
two pins) and the heating selector in the HW
position (right two pins). If an aquastat is used in
the application; the jumper should be changed to
ON position (left two pins).
Note: Terminals T and N located on the top right
side of the board are not intended for field use and
should be left un-connected.

CAUTION The aquastat (AQ) jumper must be
in the OFF position at all times; except for when an
aquastat is used. If the jumper is moved to the ON
position without installing an aquastat the blower
will not be energized.
When an aquastat is present, the blower will be
energized at the aquastat temperature settings.
Fig 7. Electric connections
On units shipped from factory with a pump installed
the pump will be energized on call for heat.
In units that were shipped without factory installed
pumps, two black wires should be connected to the
boiler terminals T T. In applications where a boiler
provides the hot water supply, these wires shouId
be connected to the boiler. Terminals T T are
normally open dry contacts.
In applications where a valve is used to regulate
hot water supply, the two black wires located on
the T T terminals should be removed and placed
on the two terminals reading “VALVE”. The open
ends of the wires should be connected to the valve
according to local requirements and instructions of
the valve manufacturer. On call for heat, 24V will
be sent to the field-installed valve or pump relay.
On call for heat water will circulate through the
water (hydronic) coil for 60 secs prior to energizing
the blower. After the thermostat is satisfied, the
blower will continue to stay energized for a
minimum of 30 secs. This helps maximize heating
efficiency.

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The freeze protection sensor is connected to the
FP and R terminals. These are normally open and
will close when the sensor sees 40ºF. The pump
stays ON for a minimum of 30 secs.
The board has a built-in timer which circulates hot
water 6 times a day for 60 secs each time to
prevent the coil from freezing.
Fig.8. Micro-processor control board
Start up
Ensure that motor is pre-loaded with program from
factory.

WARNING The hot water (hydronic) coil and
all water lines MUST be purged of air prior to
starting the pump. Failure to do so could result in
pump damage. Airmark will not be responsible for
any property or personnel damage caused by
failure to follow this instruction.
 WARNING Hot water flowing to the coil
should be in the range of 120º - 180º F. Water at
these temperatures can cause first-degree burns.
Use of proper safety gear while installing or
servicing the equipment is strongly recommended
as is installation of a water-tempering valve (for
water temperatures of above 140ºF) to supply
lower temperature water to fixtures in the house.
N170L series or equivalent should be used.
Connect the hydronic coil to the water heater
system as shown in Fig 9. Use flexible piping and
insulate all pipes. Plumbing must be in compliance
with state or local codes (Code CMR248 in
Massachusetts). The units for hydronic heat have
different top and heater box configurations. This
configuration is not suitable for electric heat. DO
NOT try to install hydronic heater in a unit not
equipped for it. Verify connections: hot water to “in”
and cold water to “out”. 7/8” ODstubs are provided
for plumbing connections. Bleed the air flow
system through the bleeder port or optional valve.
Purging The System
1) Open air vent and allow water heater to fill with
water. Close air vent when water heater is full
and all air has been purged.
2) Ignite water heater. Set thermostat on water
heater to 140 degrees.
3) Close the valve on the hot water supply from
the water heater ("A") and open the valve on
the cold-water return to the water heater ("B").
Then open the air vent in the fan coil. Use
bucket or hose to discard water during purging
process at air bleed valve. Purge air
completely from line.
4) Once air is purged, close return valve ("B") and
open supply valve ("A"). Purge the coil and
lines of air completely.
5) After air is purged from the system and filled
with water, open the return valve ("B") and the
supply valve ("A"). Then close the air vent in
the fan coil.
6) Apply power to the fan coil and set the room
thermostat on heat. Raise the temperature
setting to activate the circulating pump

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7) Check the pump to ensure proper operation.
The water inlet of the unit should be hot if the
water temperature in the water heater has
reached the set point. If water is not being
circulated through the coil but the pump is
running, then open the air bleed valve in the
unit and purge any air left in the system.
8) Adjust the water heater thermostat so that the
water temperature entering the hot water coils
is 120 – 180ºF depending on the amount of
heat required by the structure. This is done
with the unit energized and operating long
enough for all temperatures to stabalize.
After all connections are made, start-up and check-
up must be performed before proper evaluation of
the entire system can be made. Make sure that
heat anticipator is properly set as noted on
thermostat instructions.
Load requirements can vary in each residence and
it may be necessary for the installer or homeowner
to make slight adjustments to the heat anticipator
setting for longer or shorter cycles. It is
recommended to change the setting no more than
plus or minus 0.05 amps at a time. Greater
changes can cause the unit to rapid cycle or
remain on excessively. To properly check the unit's
operation, the installer should have an electrical
current measuring device (0-10 amp Amprobe,
Fluke), air pressure measuring device (0-1.0 in
slope gauge), and a temperature-measuring
device (0-200ºF thermometer).
Install the Amprobe to measure blower current, the
slope gauge to measure static air pressure at the
units and the temperature device to measure unit
supply and return air temperature. Before taking
measurements, be sure that all registers, grilles
and dampers are open or are set to their proper
positions. Be sure that clean filters are in place.
Temperature measuring device must be installed
to obtain average temperature at both inlet and
outlet. For outlet, measure temperature of each
main trunk at a location far enough away to avoid
heater radiation and read the average
temperatures. Table 2 below shows the CFM that
should be achieved at various external static
pressures
Fig.9. Schematic of hydronic unit set up
0.10 0.20 0.30 0.40 0.50
Tap 5 900 851 800 742 682
Tap 4 652 630 591 556 530
Tap 3 500 476 452 421 400
Tap 2 900 851 800 742 682
Tap 1 400 381 360 339 312
Tap 5 1150 1087 1030 975 910
Tap 4 1080 1048 1010 960 895
Tap 3 900 862 825 796 745
Tap 2 700 663 632 600 552
Tap 1 500 473 449 421 395
AFW18-24
AFW30-36
SPEED
TAP
MODEL
CFM V. External Static
Pressure
Table 2. CFM delivered at various external statics
GFW18-24
GFW30-36

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Electric Heat Controls
Turn on power supply. Set thermostat fan
switch to on. Set the cooling indicator to
maximum, heating to minimum. System switch
may be on heat or cool. Check slope gauge
measurement against appropriate air flow
chart. Make damper, register and motor speed
adjustments to obtain required airflow.
Set thermostat fan switch to auto, system to
heat and thermostat heating indicator to
maximum heat. Blower should start and all
heat be energized.
Check air flow using temperature rise method.

RISETEMP
BTUHOUTPUT
CFM

08.1
NOTE: BTUH output should be computed by VOLT
x AMPS x 3.4 = BTUH OUTPUT. Since line volt
can vary, do not use nameplate rating to determine
output.
Operation and Maintainance
Below are brief descriptions of the key components
of the unit and installation. This manual only
provides general idea of the components and
recommended practices. The installer should use
best judgment to ensure safe installation and
operation of the unit.
1) Room Thermostat- This is the device that
controls that operation of your heating and/or
cooling unit. It senses the indoor temperature
and signals the equipment to start or stop
maintaining the temperature you have selected
for your comfort. The room thermostat should
be in a central, draft free inside wall location
for best operation. Do not place any heat
producing apparatus such as lights, radio, etc.,
near the thermostat as this will cause erratic
operation of the comfort system. The
thermostat can accumulate dust or lint which
can affect its accuracy. It should be cleaned
annually.
2) Air Filter(s) - All central air moving comfort
systems must include air filter(s). These filters
will be located either in the equipment or in the
return air duct system upstream of the
equipment. The filter(s) removes dust and
debris from the air thus helping to keep your
air-conditioned space clean. More important,
the filter keeps dust and debris from collecting
on the heat transfer surfaces thus maintaining
optimum equipment efficiency and
performance. Inspect and clean or replace
filters every month. This routine maintenance
procedure will pay big dividends in reduced
operating cost and reduced service expense.
Never operate comfort equipment without
filter(s).
3) Fuses and/or Circuit Breakers- This comfort
equipment should be connected to the building
electric service in accordance with local and
National Electric codes. This electrical
connection will include over-current protection
in the form of circuit breakers. Have your
contractor identify the circuits and the location
of over-current protection so that you will be in
a position to make inspections or replacements
in the event the equipment fails to operate.
4) 
WARNING
a) Do not store combustible materials or use
gasoline or other flammable liquids or
vapors in the vicinity of this appliance.
b) Do not operate the comfort equipment with
panels removed.
c) Have your contractor point out and identify
the various cut-off devices, switches, etc.,
that serve your comfort equipment. There
is a main switch that will cut off energy to
your heating system. Know where they are
so that you may cut off the flow of energy
in the event of overheating.
5) Periodic Checkup and Service- This product is
designed to provide many years of
dependable, trouble-free comfort when
properly maintained. Proper maintenance will
consist of annual check-ups and cleaning of
the internal electrical and heat transfer
components by a qualified service technician.
Failure to provide periodic checkup and
cleaning can result in excessive operating cost
and/or equipment malfunction.
6) Lubrication- Direct drive blower motors are
equipped with permanently lubricated bearings
and do not require further lubrication.

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7) Air filter replacement: An air filter can restrict
the airflow of air to the fan coil if it is not
cleaned or replaced periodically. When
replacing the air filter, always replace with the
same type and size as originally furnished with
the unit.
GFW Hydronic Related General
Information
1) Equipment Sizing
Select an air handler with a heating output that
exceeds the space heating loss of the structure
and that has a cooling coil sized to match the
outdoor condensing unit.
Note: The heating output of the air handler or hot
water coil will not be greater than the output of the
selected hot water heater. Therefore, if the water
heater is undersized the heating BTUH of the air
handler will be LESS than its rated output.
2) Water Heater Selection
The following sizing information should only be
used as a basic guide to adequate water heater
sizing because of variations in each family's
domestic hot water requirements. For additional
assistance in water heater sizing contact a
professional engineer.
Proper water heater sizing should consider both
the gallon capacity AND the BTU input of the water
heater.
a. To determine water heater GALLON
CAPACITY: A minimum 40-gallon high recovery
and/or high efficiency gas or oil-fired water heater
is recommended. The following volume-sizing
guide is satisfactory in most areas of the country:
CFM Min Water Heater
600-800 40 gal
1000-1200 50 gal
1400-1600
2x40 gallons piped together
High input 50 gallons (63-75k Btu)
72-75gallons
2000 105k Btu
b. To determine water heater BTU INPUT
(assumes a water heater recovery efficiency of
76%): For mild climates: BTU INPUT=structure’s
heat loss x 1.51. For colder climates: BTU
INPUT=structure's heat loss x 1.58.
3) Pump Replacement
a. Disconnect electrical power to the unit before
servicing.
b. Remove access door to reveal pump. Close
supply valve ("A") and return valve ("B"). Open the
air bleed valve to de-pressurize the system and
drain water.
c. Remove the metal pump housing by loosening
the four screws on the pump. DO NOT UN-
SOLDER PUMP.
d. Replace the new pump housing assembly and
reconnect components to the pump. Before
assembling, make sure that the runner on the o-
ring is in place on the pump housing.
e. Purge the system of the air as described earlier
and re-connect the electrical power.
Common Problems and Solutions
1) Noisy Pump
System may not be totally purged of air. Purge the
system again as described in the start up section
above.
2) T&P valve on water heater weeps
This normally occurs when a backflow preventer
has been installed in the cold water supply line to
the water heater. An expansion tank may be
necessary to correct this problem. Please contact a
qualified plumbing professional for assistance.
3) Hot water is circulating through the water
coil during cooling cycle
The check valve may be stuck open and allowing
hot water to circulate through the coil.
4) Little or no heat from water coil
a. Purge the system
b. The inlet connections may be reversed at the
fan coil
c. Water heater thermostat is not set at proper
temp
d. Water heater thermostat is not calibrated
e. Dip tube in the water heater may not be installed
correctly or could be restricted.
f. Look for restrictions in heating system from water
heater to fan coil. Some water heaters are supplier

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©2013 AirMark
with check valves, remove any extra check valves
except for the one supplied with the fan coil
g. The air handler is undersized for space being
heated
h. Water heater is undersized
Note: All units installed in Massachusetts are
required to be in compliance with CMR 248
Massachusetts State Plumbing Code and/or
Massachusetts Fuel Gas Code.
These codes require the use of an optional pump
timer to circulate the hydronic loop independent of
the thermostat.

IO-123090-GFW-020113
©2013 AirMark
HIGH VOLTAGE disconnect all power sources prior to servicing. Failure might lead to safety hazard
Wiring diagram for GFW models