Bryant GAS-FIRED 454 - Manual (Page 8)

Cycle of Operation VIII. BALANCING THE SYSTEM
The 36-454 is equipped with a fan/pump motor
control (Bryant Model 821), an auxiliary
SPST relay and a sail switch. The fan/pump
motor control is a single pole, single throw
low voltage switch actuated by a heat motor
(low voltage electric resistance coil fastened
to mono-metal strip next to the switch). When
the thermostat calls for cooling, electric
current energizes the resistance coil in the
Model 821 control and in approximately one
minute the low voltage switch closes, ener­
gizing the auxiliary relay which starts the
condenser fan motor and solution pump-water
pump motor. The opening of the gas valve
will be delayed slightly until the condenser
fan is moving a sufficient amount of air
through the unit to activate the sail switch.
On shutdown by the thermostat, the gas valve
will close immediately; however, the balance
of the unit will continue to run for ap­
proximately 3 minutes until the low voltage
switch in the Model 821 control opens.
V I I . ADJUST GAS INPUT
The gas input must be checked and adjusted if
necessary to agree with the input shown on
the unit's rating plate.
The natural gas units are equipped with ad­
justable gas pressure regulators set at
factory for 4.2 inches w.c. manifold pres­
sure .
units by the following Check natural
method:
gas
1. Measure gas at meter. Be sure all other
gas appliances are turned off. Increase or
decrease input to burners by adjusting the
gas pressure regulator.
Caution: The unit may be run for short
periods with the panel removed. Prolonged
operation with panels removed should not be
attempted.
After the unit is in operation and the input
has been measured and adjusted to agree with
the rating plate requirements, the system
must be balanced.
Any approved method of checking the air flow
over the water coil may be utilized. Refer to
the Bryant Service Manual on Gas Air Con­
ditioners for a review of standard methods.
IX. FREEZING WEATHER PROTECTION
Gas Air Conditioner
The unit has built-in freeze protection suf­
ficient to protect the chiller and pump.
Chilled Water Pipes
If hard pipe (non-plastic) is used for thé
chilled water lines, it will be necessary to
drain the lines or add antifreeze . The recom­
mended antifreeze is Zerex. The chilled
water additive must be used in the same
proportion as indicated in Section V when
antifreeze treatment is required.
Chilled Water Coil
Chilled water coils cannot be completely
drained; therefore, if the water coil is sub­
ject to freezing temperatures, protect it by
adding antifreeze. The chilled water additive
must be used in the same proportion as indi­
cated in Section V when antifreeze treatment
is required.
Operation at Freezing Temperatures
The unit cannot be operated at temperatures
below 40° F.
36/454
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