SCHEDULED MAINTENANCE
51
BURNERS
WARNING
HIGH
VOLTAGE
E
LECTRICAL COMPONENTS ARE CONTAINED IN BOTH
COMPARTMENTS.
T
O AVOID ELECTRICAL SHOCK, INJURY OR
DEATH, DO NOT REMOVE ANY INTERNAL COMPARTMENT COVERS
OR ATTEMPT ANY ADJUSTMENT.
C
ONTACT A QUALIFIED
SERVICE AGENT AT ONCE IF AN ABNORMAL FLAME
APPEARANCE SHOULD DEVELOP.
Periodically during the heating season make a visual check
of the burner flames. Turn the furnace on at the thermostat.
Wait a few minutes since any dislodged dust will alter the
normal flame appearance. Flames should be stable, quiet,
soft and blue with slightly orange tips. They should not be
yellow. They should extend directly outward from the burner
ports without curling downward, floating or lifting off the ports.
Check the
Burner Flames for:
1. Stable, soft and blue.
2. Not curling, floating
or lifting off.
Burner Flame
Proper equipment promotes faster, more efficient service and
accurate repairs resulting in fewer call backs.
HEATING PERFORMANCE TEST
Before attempting to diagnose an operating fault, run a heating
performance test and apply the results to the
Service Problem
Analysis Guide.
To conduct a heating performance test, the BTU input to the
furnace must be calculated.
After the heating cycle has been in operation for at least fifteen
minutes and with all other gas appliances turned off, the gas
meter should be clocked.
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 num
-
ber 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 1,025 BTU per cubic foot.
Multiplying the ninety (90) cubic feet by 1,025 BTU per cubic
foot gives us an input of 92,250 BTUH.
Checking the BTU input on the rating plate of the furnace
being tested.
EXAMPLE:
INPUT:
92,000 BTU/HR
OUTPUT CAP:
84,000
A
LWAYS CONNECT A MONOMETER TO THE OUTLET TAP AT THE GAS
VALVE BEFORE ADJUSTING THE PRESSURE REGULATOR.
I
N 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 (coun
-
terclockwise) to decrease pressure and input.
The dissipation of the heat transferred to the heat exchanger is
now controlled by the amount of air circulated over its surface.
The amount (CFM) of air circulated is governed by the external
static pressure in inches of water column of duct work, cooling
coil, registers, etc., applied externally to the unit versus the
motor speed tap (direct drive) or pulley adjustments of the
motor and blower (belt drive).
A properly operating unit must have the BTU per hour 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.
