Robertshaw 780-845 User Manual

C38

GAS IGNITION CONTROLS

780-845

24 VAC INTERMITTENT PILOT
IGNITION CONTROLS

When the thermostat calls for heat, the 780-845 control simultaneously ini­tiates ignition sparking and opens the pilot valve portion of the gas valve.
Pilot flame recognition stops ignition sparking and opens the main valve
portion of the gas valve. Pilot burner flame is continuously monitored at a
synchronous frequency for the duration of the heating cycle. Should the
pilot flame fail during the heating cycle, the control will shut off the main
valve until the pilot flame is established.

The 708-845 lockout ignition control provides 90 seconds of spark, fol­lowed by a 6 minute time delay (purge) between ignition attempts. After
three tries, if no pilot flame is sensed, the control goes into a one-hour
lockout period. At the end of the lockout period, if the demand for heat is
still present, the unit will repeat the three tries for ignition.

NOTE: During lockout, you may override the auto-system, and manually
reset the unit at the thermostat.

780-845

NOTE: The green diagnostic LED will be on continuously for normal
operation. The LED will be off for internal lockout and will flash con­tinuously for problems external to the control (ie. not sensing flame).

Identifying Your Robertshaw ICU Terminals

MV Main valve
PV Pilot valve
LED Dagnostic LED
TH 24V thermostat
PV-MV Gas valve common
TR Transformer ground
GND Main Burner Ground
SENSE Internal/external sense terminal
SPARK Spark output

Input Voltage 24 VAC to 50/60 Hz
Transformer 24 VAC / 20 VA
Safety lockout timing 90 seconds
Spark rate 4 to 15 sparks per second
Relay contact ratings

Pilot valve 1 amp at .5 PF
Main valve 1 amp at .5 PF

Combined load 1.5 at .4 PF
Flame sense current .7 µA DC @ 25°C / 24 VAC
Maximum total current load 1.5 amp
Flame failure reignition time 2 seconds maximum
Ambient temperature rating –40 to 175° (–40 to 80°C)
Relative humidity 95% noncondensing at 104°F

780-845 SPECIFICATIONS