York W)036 THRU 060 Specifications download pdf (Page 55)

542300-YIM-A-1009

Johnson Controls Unitary Products 55

not clean, then clean, reinstall and adjust pilot per the start

up procedures.

2. If the flame is weak or unstable in the flame sensor area,

then verify the gas inlet pressure. If gas inlet pressure is

above the minimum inlet pressure stated on unit data label,

then adjust the pilot pressure per the start up procedures. If

the pilot cannot be adjusted to obtain a strong and stable

flame in the flame sensor area, then remove the burner

assembly and verify the pilot burner assembly is open

internally and the holes in the burner are clean. Check the

pilot orifice size to the unit data plate and the cleanliness of

the pilot orifice. Verify that the flame sensor electrode is

clean and is adjusted properly. After cleaning or

replacement of the pilot assembly components, reinstall the

burner assembly and adjust pilot per the start up procedure.

Primary or Aux Temperature Limit

The temperature limits limit the temperature in the furnace to a

safe level. If a temperature higher than the preset limit is

achieved due to low or no air flow through the furnace, then the

temperature limits opens and the ICB closes the gas valve and

flashes code 6. The primary limit is automatic reset type while

the auxiliary limit is manual reset type. If either one opens, then

the ICB removes power to the gas valve and the UCB

energizes the indoor blower until the primary limit automatically

resets or the auxiliary limit is manually reset. Verify adequate air

flow through the furnace. If air flow is nonexistent or weak, then

troubleshoot and repair the conditioned space air circulation

system as necessary. Reset the auxiliary limit and verify proper

operation of the furnace. If airflow is normal, then verify the gas

input rate to the furnace following the start up procedures

(auxiliary limit must be reset before the furnace will operate). If

after verifying the circulating air system, the input rate to the

furnace and that the air temperature rise through the furnace is

within the rise range on the unit data plate the flash code still

exists, then set the gas valve to the off position and temporarily

apply control voltage (~24 volts) to pin 9 of the 9 pin ICB

connector. With power applied to the unit, if the ICB LED

continues to flash a code 6, then replace the ICB and return unit

to operation (you must remove the temporary voltage to pin 9

before the gas valve is turned on). If the ICB LED flashes a

heartbeat, then replace the limit that is opening, remove the

temporary voltage applied to pin 9, turn on the gas valve, restart

the furnace and verify proper operation of the furnace.

Rollout Switch

The rollout switch is installed to protect the furnace from

damage due to excessive heat in the burner area. There are 4

main reasons the rollout switch will open (flash code 7) due to

excessive heat in the burner area. You must remove power to

the unit for 20 seconds to reset the ICB.

1. A blocked flue outlet is the most common cause for the

rollout switch to open. Check the flue outlet for debris and

clear if necessary.

2. Loose blower wheel on draft motor. Verify that the blower

wheel is securely fastened to the draft motor shaft.

3. Unit operating outside the air temperature rise range stated

on the unit data plate. Either the air flow through the

furnace is not sufficient or the gas input rate to the furnace

exceeds the recommended rate. Verify both conditions are

within the published ranges.

4. Cracked heat exchanger tube(s). If a heat exchanger tube or

tubes is cracked, then the flow through the heat exchanger

is restricted and the flame will either roll out of the tube inlet

or heat will build to an abnormal level in the burner area.

This can usually be determined by observing burner flame

with and without indoor blower operation. If the flame

changes when the blower is running compared to when it is

not, then visually inspect the heat exchanger tubes.

If all of the above are found to be in good condition or within the

operating ranges, then set the gas valve to the off position and

temporarily apply control voltage (~24 volts) to pin 6 of the 9 pin

ICB connector. With power applied to the unit, if the ICB LED

continues to flash a code 7, then replace the ICB and return unit

to operation (you must remove the temporary voltage to pin 6

before the gas valve is turned on). If the ICB LED flashes a

heartbeat, then replace the rollout switch, remove the

temporary voltage applied to pin 6, turn on the gas valve, restart

the furnace and verify proper operation of the furnace.

Unexpected Flame Presence

If a flame is present without a call for heat (flash code 8), then

the ICB will continue operation of the draft motor and the UCB

will call for indoor operation when either of the temperature limit

opens. If the unit is correctly wired and there is not a call for

heat, then check for control voltage to the gas valve. If control

voltage exists at the gas valve, then replace the ICB. If voltage

is not present at the gas valve, then replace the gas valve.

Gas Valve Stuck Off or On

If the pilot and/or the main valves are sensed to be off more

than 1 second when commanded to be on, the control will shut

off all outputs and enter a hard lockout (flash code 9). Likewise,

if the pilot and/or the main valves are sensed to be on more

than 1 second when commanded to be off, the control will shut

off all outputs and enter a hard lockout (flash code 9). The

control will not respond to thermostat demands during a hard

lockout. The only way to recover from a hard lockout is to

remove and reapply 24VAC power to the control.

Flame Sense Circuit Failure

If the control detects an internal hardware failure in the flame

sense circuit, it shuts off all outputs and enters a hard lockout

(flash code 10). The control will not respond to thermostat

demands during a hard lockout. The only way to recover from a

hard lockout is to remove and reapply 24VAC power to the

control. If problem persists after removal and reapplication of

24VAC power, the board may need to be replaced.

Symptomatic Troubleshooting

On calls for heating, the draft motor operates and the furnace

lights but the supply air blower motor does not energize after a

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York W)036 THRU 060 Specifications Page 55

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