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Open Thermal Protection Device
If the primary limit switch opens, the gas valve is immediately
deenergized, the induced draft and air circulating blowers
are energized. The induced draft and air circulator blowers
remain energized until the limit switch recloses. The diag-
nostic fault code for an open limit is four (4) flashes.
A primary limit will open due to excessive supply air tempera-
tures. This can be caused by a dirty filter, excessive duct
static, insufficient air flow, or a faulty limit. Check filters, total
external duct static, blower motor, blower motor speed tap
(see wiring diagram), and limit. This limit will automatically
reset once the temperature falls below a preset level.
Flame Detected with Gas Valve Closed
If flame is detected with the gas valve deenergized, the com-
bustion and air circulator blowers are energized. The diag-
nostic fault code is five (5) flashes for this condition. The
control can be reset by removing the power supply to the unit
or it will automatically reset after one hour. Miswiring is the
probable cause for this fault.
A
O
- C
BNORMAL
PERATION
Short Cycle Compressor Delay
The automatic ignition control has a built-in feature that pre-
vents damage to the compressor in short cycling situations.
In the event of intermittent power losses or intermittent ther-
mostat operation, the ignition control will delay output to the
compressor contactor for three minutes from the time power
is restored. (Compressor is off a total of three minutes). The
diagnostic LED will flash six (6) times to indicate the com-
pressor contactor output is being delayed.
NOTE: Some electronic thermostats also have a built-in
compressor short cycle timer that may be longer than the
three minute delay given above. If you are using an electronic
thermostat and the compressor has not started after three
minutes, wait an additional five minutes to allow the thermostat
to complete its short cycle delay time.
INPUT RATING
It is the responsibility of the contractor to adjust the gas input
to the unit. The input rate can be calculated by using the
formula:
3600 x HV
I
NPUT Btu/Hr =
T
WHERE:
HV = Heating value of fuel = Btu/ft of gas
T = Time in seconds per ft of gas flow as read from gas meter
Adjust input rate by varying the adjustment of the gas pres-
sure regulator on the gas valve. All adjustments must be made
with furnace operating at high fire and at normal operating
temperature. Clockwise (P) rotation of the pressure regula-
tor screw increases pressure and gas flow rate. Turn screw
counterclockwise (Q) to decrease pressure and gas flow rate.
OOLING
3
3
After adjustment the furnace temperature rise must be within
the range specified on the unit data plate. NOTE: Thermal
efficiency of the furnace is a product efficiency rating deter-
mined under continuous operating conditions independent
of any installed system.
Regulator Cover Screws
(Reg. Adj. Beneath these screws)
INLET
Gas Valve
On/Off Switch
WHITE-RODGERS 36H54 PRESSURE ADJUSTMENTS
T
O
PREVENT
UNRELIABLE
GAS
MANIFOLD
PRESSURE
. O
PLATE
NLY
MINOR
ADJUSTMENTS
THE
GAS
VALVE
PRESSURE
AIR FLOW ADJUSTMENTS
The drive on the supply fan is typically set in the middle of the
RPM range. The drive motor sheave pitch diameter is field
adjustable for the required airflow. Refer to "Drive
Adjustments" section below.
When the final adjustments are complete, the current draw
of the motor should be checked and compared to the full
load current rating of the motor. The amperage must not ex-
ceed the service factor stamped on the motor nameplate.
The total airflow must not be less than that required for op-
eration of the electric heaters or the furnace.
If an economizer is installed, check the unit operating bal-
ance with the economizer at full outside air and at minimum
outside air. Upon completion of the air flow balancing, we
recommend replacing the variable pitched motor sheave with
a properly-sized fixed sheave. A matching fixed sheave will
provide longer belt and bearing life and vibration free opera-
tion. Initially, it is best to have a variable pitched motor sheave
for the purpose of airflow balancing, but once the balance
has been achieved, fixed sheaves maintain alignment and
minimize vibration more effectively. For direct drive units, move
green wire for fan.
MOTOR SHEAVE ADJUSTMENTS
V
, V
& 2
V
L
M
VP
ARIABLE
The driving and driven motor sheaves should be in align-
ment with each other and the shafts parallel.
21
High Fire
Adjust
Low Fire
Adjust
OUTLET
CAUTION
OPERATION
OR
EQUIPMENT
DAMAGE
MUST
BE
AS
SPECIFIED
ON
THE
SHOULD
BE
MADE
BY
.
REGULATOR
P
K
T
M
ITCH
EY
YPE
OTOR
,
THE
UNIT
RATING
ADJUSTING
S
HEAVES
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