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re-zeroing is required, firmly hold the case of gage with one hand
and unscrew the front cover with the palm of the other hand in a
counterclockwise direction. If difficult to loosen, place a small
sheet of rubber between the cover and the palm of the hand. Zero-
adjust screw is located behind the scale at the pair marked "zero."
Use a hex/allen wrench and adjust until pointer is on zero. This
must be done with both pressure connections vented to atmo-
sphere and the gage oriented in the final mounting position. Re-
place cover.
SERVICE
CAUTION
Electric shock hazard. Disconnect power before entering or
servicing.
More than one disconnect switch may be required to de-ener-
gize the equipment.
General
1. Review Safety Considerations at beginning of these in-
structions. Good safety habits are important tools when
performing service procedures.
2. To make speed measurements, use a strobe-style tachom-
eter or calculate per Step 7 of Start-Up, Checklist for Air-
foil and Forward-Curved Fans (page 205).
Single Point Power Enclosure
At least once a year at start of operating season or whenever unit is
serviced, check field and factory made electrical connections for
condition of wiring insulation and tightness of connections.
Electric Heaters
At least once a year at start of operating season or whenever unit is
serviced, check field and factory-made electrical connections for
tightness. Also periodically clean filters, fan, airways, ductwork,
grilles, and registers as required. Differential air pressure switch is
factory set to open at 0.07 in. wg, close at 0.05 in. wg and requires
no adjustment.
Refer to the Troubleshooting section for more information. Heater
electrical data is shown in Table 40.
Gas-Fired Furnaces (Duct and Rack System)
Follow these procedures for inspection and operation check.
INSPECTION
1. The duct furnace or furnace module should be inspected
annually by a qualified service agency. The condition of
the burners, heat exchanger, draft inducer, vent system,
operating controls and wiring should be determined.
Check for obvious signs of deterioration, accumulation of
dirt and debris, and heat or water related damage. Any
damaged or deteriorated parts should be replaced before
the unit is put back into service.
2. Label all wires prior to disconnection when servicing unit,
Wiring errors can cause improper or dangerous operation.
Verify proper operation after servicing.
3. Inspect burners, heat exchanger, induced draft fan and vent
ducts and clean as necessary.
4. Check the heat exchanger for cracks. If any are present, re-
place heat exchanger before putting unit back into service.
5. Check the attachment points of the duct furnace to the cabi-
net to verify that they are air-tight. For a rack system module,
check the attachment points to the cabinet or ducts to verify
that they are air-tight.
6. Check the automatic gas valve to ensure that the gas valve
seat is not leaking.
7. Check wiring connections to be sure they are secure, and in-
spect wiring for any deterioration.
If any of the original wiring needs to be replaced, it must be
replaced with wiring materials suitable for 221°F (105°C).
Unsuitable wiring materials may cause equipment damage.
OPERATION CHECK
1.
Turn on power to the unit and set thermostat or heat controller
to call for heat, allowing duct furnace or heater assembly
module to operate.
2.
Check for proper start-up and ignition of the single unit or
each furnace in the heater assembly module. See the
section Gas-Fired Furnaces (Duct and Rack Systems) on
page 209.
3.
Check the appearance of the burner flame. See Fig. 180 on
page 210.
4.
For single units, be sure circulating air fan is operating and
verify proper airflow through duct furnace.
5.
Return thermostat or heat controller to normal setting.
Fans
FAN MOTOR REPLACEMENT ON DIRECT DRIVE FAN
ASSEMBLIES WITH NEMA MOTORS
It is recommended to replace the entire motor and fan wheel as-
sembly so that the assembly is factory balanced. It is possible to
replace only motor or fan wheel, but the motor and fan wheel as-
sembly MUST be balanced to ISO 1940 / balance grade G6.3
specifications prior to operation.
1.
Loosen and remove motor hold down bolts from motor base.
2.
Remove motor and fan assembly from the fan sled.
3.
Mark the motor shaft to indicate the mounted location of the
motor shaft bushing.
4.
Loosen and remove motor shaft bushing bolts.
5.
Remove fan from the shaft bushing.
6.
Remove shaft bushing from motor shaft.
7.
Install shaft bushing on new motor.
8.
Mount rotor on shaft bushing and install mounting bolts but
do not tighten.
9.
Position bushing at marked location on the motor shaft.
10. Partially tighten each bolt and, following a rotational pattern,
tighten all bolts until reaching final tightening torque on all
bolts as shown in Table 43.
11. Place motor and fan wheel assembly in position on motor
plate.
12. Insert motor hold down bolts but do not tighten.
13. Align fan wheel to fan inlet to dimensions shown in Table 27.
14. Tighten motor hold down bolts.
15. Balance fan wheel and motor assembly to meet ISO 1940 /
balance grade G6.3.
Direct Drive Fans with EC Motors
Direct drive plenum fans with EC motors MUST be replaced as a
complete assembly. No replacement parts are available.
1.
Review and follow all warnings and caution notes concerning
EC motors.
2.
The L10 service life of the maintenance-free ball bearings can
be taken as approx. 40,000 operating hours at an ambient
temperature of 104°F. This estimate can vary according to the
actual ambient conditions. If bearing replacement is neces-
sary after that period, contact fan supplier.
3.
Maintaining cleanliness of the fan assembly is important.
211
CAUTION
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