Honeywell R4795A Troubleshooting, Normal Operation Refer To And, Safety Operation

		R4795A
		OPERATION • TROUBLESHOOTING
		Operation
NORMAL OPERATION (REFER TO FIG. 2 AND 3.)
Call for Heat (Limit Switch	Terminal 1 energized. Relay 3K pulls in to close contact 3K2 and energize
Closed)	terminal 8 fan or burner motor.
Airflow Proved	Low voltage airflow switch between terminals 6 and 7 closes to energize the
	purge timer.
Prepurge Complete (7, 10, 30, 60,	Relay 1K pulls in to close contact 1K4 and energize terminal 3 (pilot valve, first
or 90 Seconds)	stage oil valve(s), or expanding pilot valve) directly and terminal 4 (ignition)
	through the closed flame relay contact 2K2. Contact 1K1 closes to energize the
	safety switch heater.
Flame Proven (Pilot or First Stage	R4795A: Relay 2K pulls in. Contact 2K2 opens to cut off ignition, contact 2K3
Oil)	closes to energize the main fuel valve(s) or second stage oil valve(s). Contact
	2K1 opens to de-energize the safety switch heater and reset the purge timer.
Controller Satisfied	All relays drop out; systems shuts down.
SAFETY OPERATION
Flame Failure	R4795A: Relays 1K and 2K drop out. Contact 1K4 opens to de-energize
	terminals 3, 4, and 5. If air is still proven, the prepurge period begins. After
	prepurge, one attempt is made to start the burner.
Airflow Failure	If airflow fails at any time during the operating cycle, relay 1K drops out.
	Contact 1K4 opens to de-energize terminals 3, 4, and 5. Only terminal 8, fan or
	burner motor, remains powered. If air is re-established, the prepurge period
	starts and the startup sequence is repeated.
Prepurge Timer Failure	If the plug-in purge timer is not properly seated, or is not functioning properly,
	the fan motor will start on a call for heat, but the 1K relay will not pull in. The
	result will be a continuous purge (safe failure).
Hot Refractory Hold-in (Photocell	If hot refractory holds in the flame relay at the end of the running cycle, startup
Installations)	is prevented until the hot refractory no longer holds in the flame relay.

Troubleshooting

The first step in troubleshooting the R4795A is to deter- mine the location of the system trouble. Reset the safety switch and operate the system on a normal start. Refer to the Normal Operation subsection in the Operation section. Ob- serve the operation carefully to determine at what point the trouble occurs. Then refer to the Trouble List in the Trouble List section and follow the troubleshooting procedure.

IMPORTANT: At the completion of any troubleshooting procedure, be sure to perform the Checkout Tests listed in the Checkout section.

PRELIMINARY INSPECTION

1.Disconnect power to the R4795 by opening the sys- tem disconnect switch.

2.Remove the R4795 cover. Make sure all mounting screws are tight, and that the plug-in amplifier and purge timer are properly seated; refer to Fig. 10.

3.Reset the safety switch (push in and then release the small round button that extends through the plastic safety switch cover; see Fig. 9).

TROUBLE LIST

Compare the following list of troubles with the actual deviations from normal operating sequence. Select the appli- cable letter(s) and proceed to the corresponding Trouble- shooting Procedure(s).

A. Relay 3K does not pull in on a call for heat.

B.Relay 3K pulls in but the burner motor does not start.

C.Burner motor starts but prepurge does not stop at end of purge timing (relay 1K does not pull in).

D.Relay 1K pulls in but the pilot does not light, ignition does not occur, or expanding pilot valve does not open.

E.Pilot lights but relay 2K does not pull in (control locks out without lighting the main burner).

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