Bryant 452W - Manual (Page 10)

TABLE VI—Manifold Pressure
(Inches W.C.)
0)
3 '
03 >
OQ
Specific Gravity
0.59 0.61 0.63 0.65 0.67
900 3.9” 4.0” 4.1” 4.2” 4.3”
950 3.5” 3.6” 3.7” 3.8” 3.9”
1000 3.1” 3.2” 3.3” 3.4” 3.5”
1025 3.0” 3.1” 3.2” 3.3” 3.4”
1050 2.8” 2.9” 3.0” 3.1” 3.2”
1100 2.6” 2.7” 2.8” 2.9” 3.0”
For manifold pressures exceeding 3.0 inches ±¡.3 inches, consult
your Bryant Distributor.
heater circuit that permits operation of the unit at
outdoor ambient temperatures down to -30°F. The
pump heater circuit consists of a hydraulic pump
heater (11A2) and a pump heater relay (2B).
The pump heater is connected in series with the nor­
mally closed contacts of the pump heater relay.
Current flows through the heater only when there is
no demand for cooling hy the thermostat. When the
thermostat calls for cooling, the pump heater relay
winding is energized and opens the normally closed
contacts of the pump heater relay and removes the
power supply voltage from the pump heater.
VII. ADJUSTING GAS INPUT
The gas input must be checked and adjusted if
necessary to agree with that shown on the rating plate
of the unit (246,000 Btuh). The burners are equipped
with fixed orifices drilled as follows; Natural gas No.
36 drill; Propane gas No. 52 drill.
The natm-al gas units are equipped with adjustable
gas pressure regulators set at factory for 3.0-inches
w.c. manifold pressure. The propane gas units are not
equipped with a pressure regulator.
Check natural gas units by one of the following
methods:
1. Measxrre gas at meter. Be sure all other gas ap­
pliances are turned off. Increase or decrease in­
put to burners by adjustment of gas pressure
regulator.
2. Set manifold pressure according to Table VI for
Btu value and specific gravity of gas to be sup­
plied to unit. Connect manometer to 1/8-inch
pressure tap on manifold and, with unit in
operation, set correct pressure by adjustment of
gas pressure regulator.
Example: Natrual Gas
1025 Btu
0.63 Specific Gravity
1. From Table VI, manifold pressure is 3.2 inches
w.c.
2. With manometer connected to manifold, set
pressure at 3.2 inches by adjusting gas pressure
regulator.
Check propane gas units as follows:
The burner orifices are sized for rated input with a
manifold pressure of 11.0 inches w.c. Connect
manometer to 1/8-inch pressure tap on unit manifold
and adjust regulator at supply tank to provide a
manifold pressure of 11.0 inches w.c.
CAUTION: The unit may be run for short periods
with the panel removed. Proloiif;ed operatioti with
panels removed sliould not he attempted.
VIII. BALANCING THE SYSTEM
After the unit is operating and the input has been
measured and adjusted to agree with the rating plate
requirements, balance the system.
Any approved method of checking the a:irflow over the
water coil may be utilized. Reference is made to the
Bryant Service Manual on Gas Air Conditioning for a
review of standard methods. Do not purge non­
condensibles or check solution level.
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