Servicing - Amana PHB**C Service Instructions Manual

SERVICING

To find the BTU input, multiply the number of cubic feet of
gas consumed per hour by the heating value of the gas being
used. (The calorific value of the gas being used is found by
contacting your local utility.)
Example:
It is found by the gas meter, that it takes forty (40) seconds
for the hand on the cubic foot dial to make one complete
revolution, with all appliances off, except the furnace. Take
this information and locate it on the gas rate chart. Observe
the forty (40) seconds, locate and read across to the one (1)
cubic foot dial column. There we find the number 90, which
shows that ninety (90) cubic feet of gas will be consumed in
one (1) hour.
Let's assume the local gas utility has stated that the calorific
value of the gas is 1025 BTU.
Multiplying the ninety (90) cubic feet by 1025 BTU gives us
an input of 92,250 BTUH.
Checking the BTU input on the rating plate of the furnace
being tested.
EXAMPLE: PGB30C0902D
INPUT: 90,000 BTU/HR
OUTPUT CAP: 72,000
Should the figure you calculated not fall within five (5) percent
of the nameplate rating of the unit, adjust the gas valve pres-
sure regulator or resize orifices. In no case should the
input exceed that shown on the rating plate.
A
LWAYS CONNECT A MANOMETER TO THE 1/8" PIPE TAP AT THE GAS VALVE
BEFORE ADJUSTING THE PRESSURE REGULATOR. IN NO CASE SHOULD THE
FINAL MANIFOLD PRESSURE VARY MORE THAN PLUS OR MINUS .3 INCHES
WATER COLUMN FROM 3.5 INCHES WATER COLUMN FOR NATURAL GAS OR
10 INCHES WATER COLUMN FOR PROPANE GAS.
CAUTION
To adjust the pressure regulator on the gas valve, turn down
(clockwise) to increase pressure and input, and out (counter-
clockwise) to decrease pressure and input.
Since normally propane gas is not installed with a gas meter,
clocking will be virtually impossible. The gas orifices used
with propane are calculated for 2500 BTU gas and with proper
inlet pressures and correct piping size, full capacity will be
obtained.
With propane gas, no unit gas valve regulator is used; how-
ever, the second stage supply line pressure regulator should
be adjusted to give 11" water column with all other gas con-
suming appliances running.
The dissipation of the heat transferred to the heat exchanger
is now controlled by the amount of air circulated over its sur-
face.
The amount (CFM) of air circulated is governed by the exter-
nal static pressure in inches of water column of duct work,
cooling coil, registers and etc., applied externally to the unit
versus the motor speed tap.
A properly operating unit must have the BTU input and CFM
of air, within the limits shown to prevent short cycling of the
equipment. As the external static pressure goes up, the
temperature rise will also increase. Consult the proper tables
for temperature rise limitation.
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