Principal Technical Features; Operation - Honeywell 7800 Series Manual

Test
Test No. Jumpers Voltmeter
1 — 9 to 5
2 — 1 to 5
3 9 to 4 —
4 9 to 8 —
5 9 to 2 —
6 9 to 3 —
(alarm)
FINAL
CAUTION
Equipment Damage Hazard.
Can cause equipment damage.
After completing these tests, open the master switch, remove all test jumpers and remove any bypass jumpers
from the low fuel pressure limits to prevent equipment damage.

PRINCIPAL TECHNICAL FEATURES

The CR7890 provides all customary flame safeguard
functions as well as significant advancements in safety,
annunciation, and system diagnostics.
Safety Shutdown (Lockout) Occurs if:
1. INITIATE PERIOD
a. AC line power errors occurred, see Operation.
b. Four minute INITIATE period has been exceeded.
2. STANDBY PERIOD
a. Ignition/intermittent pilot valve output is energized.
b. Internal system fault occurred.
c. Main valve terminal is energized.
3. SAFE START CHECK
a. Ignition/intermittent pilot valve output is energized.
b. Internal system fault occurred.
c. Main valve output is energized.
4. PILOT FLAME ESTABLISHING PERIOD (PFEP)
a. Ignition/intermittent pilot valve output is not
energized.
b. Internal system fault occurred.
c. Main valve output is energized.
d. No flame present at end of PFEP.
Table 6. Static Checkout.
Normal Operation
Line voltage.
Line voltage.
Ignition spark (if ignition transformer
is connected to terminal 4.
1. Ignition spark (if ignition
transformer is connected to
terminal 8).
2. Automatic pilot valve opens (if
connected to terminal 8).
NOTE: Refer to wiring diagram of
system being tested.
Automatic fuel valve(s) open(s). If
using direct spark ignition, check the
first stage fuel valve(s) instead of the
pilot valve.
Alarm (if used) turns on.
11
CR7890B 7800 SERIES INTEGRATED BURNER CONTROL
If Operation is Abnormal, Check the Items
1. Master switch.
2. Power connected to the master switch.
3. Overload protection (fuse, circuit breaker, etc.)
has not opened the line.
1. Limits.
2. Burner control.
1. Watch for spark or listen for buzz.
a. Ignition electrodes are clean.
b. Ignition transformer is okay.
1. Watch for spark or listen for ignitor buzz.
a. Ignition electrodes are clean.
b. Ignition transformer is okay.
2. Listen for click or feel head of valve for
activation:
a. Actuator if used.
b. Pilot valve.
Same as test no. 4. If using direct spark ignition,
check the first state fuel valve(s) instead of the pilot
valve.
1. Alarm.
5. RUN PERIOD
a. Ignition output is energized.
b. Internal system fault occurred.
c. Main valve output is not energized.
d. No flame present.
e. Pilot valve output is not energized.

OPERATION

Sequence of Operation
The CR7890 has the operating sequences listed below; see
Fig. 2. The CR7890 LEDs provide positive visual indication of
the program sequence: POWER, PILOT, FLAME, MAIN and
ALARM.
Initiate
The CR7890 enters the INITIATE sequence when the relay
module is initially powered. The CR7890 can also enter the
INITIATE sequence if the relay module verifies voltage
fluctuations of +10/-15% or frequency fluctuations of ±10%
during any part of the operating sequence. The INITIATE
sequence lasts for ten seconds unless the voltage or
frequency tolerances are not met. When the tolerances are
Listed Below
65-0259—1