Troubleshooting - Honeywell R7795A Manual

The first step in troubleshooting the R7795 is to deter-
mine the location of the trouble in the system. Reset the
safety switch and operate the system on a normal start.
Refer to the OPERATION section for details of the normal
operating sequence. Observe the operation carefully to
determine exactly when the trouble occurs. Refer to the list
below and follow the procedures outlined.
IMPORTANT: At the completion of any troubleshooting
procedure, be sure to perform the checkout tests
listed in the CHECKOUT section.
EQUIPMENT REQUIRED
Voltmeter (Honeywell W136A or equivalent): with 0 to
300 Vac scale.
Microammeter (Honeywell W136A or equivalent) with 0 to
25 microampere range and SPL scale with damping.
Meter connector plug part no. 196146 or equivalent.
123514A Flame Simulator: for use with the R7795B,D
(rectification models).
123514B Flame Simulator: for use with the R7795A,C
(ultraviolet models).
Watch or clock: with second hand.
Manometer (or gauge): to measure pilot gas pressure.
Thermometer or thermocouple: to measure temperature at
the flame detector.
Orifice plates (aperture discs) or filters: to adjust the sensi-
tivity of flame detector(s).
PRELIMINARY INSPECTION
1. Disconnect the power to the R7795 by opening the
system disconnect switch.
2. Reset the safety switch.
TROUBLE LIST
Compare the following list of possible system troubles
with the actual deviations from the normal operating
sequence. Select the appropriate symptoms by letter and
proceed to that troubleshooting procedure. (See Fig. 11
for relays.)
A. Relay 3K does not respond to a call for heat.
B. Relay 3K pulls in but the burner motor does not
start.
C. Control locks out during prepurge.
D. Burner motor starts but prepurge does not stop at
the end of purge timing (relay 1K does not pull in).
E. Relay 1K pulls in but the pilot does not light, igni-
tion does not occur, or the pilot valve does not open.
F. Pilot lights but Flame Indicator LED does not come
on (control locks out without lighting main burner).
G. Pilot lights and the Flame Indicator LED comes on
but the main burner does not light.
H. Flame Indicator LED remains on after the flame
goes out.

Troubleshooting

Fig. 11—R7795 Relay location.
TROUBLESHOOTING PROCEDURES
!
CAUTION
1. Be very careful when troubleshooting the
R7795; line voltage is present on most contacts
when the power is on.
2. To prevent electrical shock or equipment dam-
age, disconnect the power supply before clean-
ing any contacts, or removing and reinstalling
the R7795 from the subbase.
IMPORTANT:
1. Output terminals MUST NOT BE SHORTED TO L2.
Shorted output terminals will cause permanent dam-
age to the R7795.
2. If, after performing an applicable troubleshooting
procedure, proper operation cannot be obtained,
replace the R7795 (except the ST795A Purge Timer,
unless noted).
A. Relay 3K does not respond to a call for heat:
1. Make sure that the safety switch is reset.
2. Check the power at terminals L1 and 16 with the
controller calling for heat.
a. Voltage must be between plus 10 and minus 15 per-
cent of the rated voltage for dependable operation.
b. If the voltage is zero, check the power supply and
the continuity of the limit and controller contacts.
Look for blown fuses, open switches, and bad
wiring connections.
17
R7795A,B,C,D
TROUBLESHOOTING
66-2001—2