RAVENHEAT sequence of operation

[ls8state]

RSF 84ET/84E.100ET./100E.82E/82ET
C.S.I 85E/C.S.I 85ET


* Control panel contains main selector switch, heating & hot water potentiomoters, manual overheat reset button(located under plastic cap on left hand side), 3 function LED's and the presssure guage.

* The LED's will show:

* Top (yellow)=mains power
Middle (red)= overheat, this is a manual re-settable thermostat(left hand side of control panel
under plastic cap)

* Bottom (orange)= ignition lockout, this is reset by switching main switch to zero and then back
to the on position.

* Low water pressure switch fitted to the boilers. The boiler will not operate if the system
pressure is low or the switch is faulty, also it will not display a fault condition.

* If C'HTG sensor is defective the pump will run constantly with no demand ( boiler will not fire)

HOT WATER DEMAND


1. Demand for DHW
2. Domestic hot water flow switch operates (continuity)
3. Control PCB sends 240Vac to the pump and the pump runs.
*** If the pump fails no fault condition is displayed, but boiler will still operate
4. The C'HTG (primary) NTC is checked to see if in range.
*** If the primary NTC is faulty then only the pump will run. Also if the DHW NTC is faulty, it
will not cause the boiler to fail.
5. Ignition PCB checks Air Pressure Switch for closed circuit(continuity) between Common and
Normally Closed
6. Ignition PCB sends 240Vac to the fan and the fan runs.
7. Air Pressure Switch operates giving continuity between Common and Normally Open.
***If no continuity the fan continues to run for 60 seconds, the Orange Flame Failure light
illuminates and the fan stops.
8. Ignition PCB energises spark generator and spark commences.
9. Simultaneously the PCB sends 240Vac to the Pilot Solenoid on the gas valve and the pilot lights.
10. Flame rectification takes place and 240Vac is sent to the main Gas Valve Solenoid, allowing
gas to the burner.
11. Main burner ignites, and the voltage at the modureg increases to give the required gas
pressure (max voltage 15Vdc, this giving full gas pressure)
***Any failure at points 7,8 and 9 will result in flame failure fault condition-
after approx 40 seconds the orange Flame Failure Light will illuminate, the appliance will
lockout and the pump will run continuously.
12. Water temperatures are maintained under the control of the DHW NTC in conjunction with the
gas valve (modureg), hot water potentiometer and the PCB.
*** If the DHW NTC fails then HW is still provided but no modulation of the gas valve takes
place and the water temperature is higher with much more boiler noise




Central Heating Demand

1. Heating demand from external controls.
2. Control PCB sends 240Vac to the pump and the pump runs
***If the pump fails to run the boiler continues to fire until the C'HTG NTC gets to its highest
temperature (less than 5ohms)- which will shut down the burner, but it will refire when the
temperature drops, or the overheat device trips. Which illuminates the Red Flame Failure Light
and will require manually resetting.
3. Ignition PCB checks APS for closed circuit (continuity) between common and normally closed.
4. Ignition PCB sends 240Vac to the fan and the fan runs.
5. APS operates giving continuity between Common and Normally Open
***If no continuity the fan continues to run for 60 seconds, the Orange Flame Failure Light
illuminates and the fan stops.
6. Ignition PCB energises spark generator and spark commences.
7. Simultaneously the PCB sends 240Vac to the pilot solenoid on the gas valve and the pilot lights.
8. Flame rectification takes place and 240Vac is sent to the Main Gas Valve Solenoid allowing gas
to the burner.
9. Burner lights on minimum gas pressure for 1minute(approx), it then ramps up to the required
gas pressure dependant upon the appliance temperature
10. Water temperatures are maintained under the control of the C'HTG NTC in conjunction with the
the gas valve (modureg), heating potentiometer and the PCB.
11. Anti cycle time is 2.5 minutes
12. Demand ends, fan and burner cease.
13. After demand, pump will overrun for 4-8 minutes.


DATA...............


THERMISTORS(NTC): HTG AND Hot Water 20Kohms cold
to 5Kohms@ 82 degrees
HTG thermistor is primary NTC

GAS VALVE: HONEYWELL 2 coils=240Vac pilot solenoid and 240Vac main
solenoid.
Both coils approx. 4ohms


MODUREG HONEYWELL 15Vdc Full gas pressure
COIL approx. 120 ohms
down to 40 ohms

FAN RL.97BC.S.I R 108 1 SPEED 240Vac
COIL approx. 55ohms

LOW WATER PRESSURE SWITCH? CONTINUITY AT BLACK AND BLUE
CONNECTIONS ON SWITCH WHEN
APPLIANCE PRESSURE IS CORRECT


This should work for any conventional boiler? many boilers have an ignition pcb? those without will have it built into main PCB. the new condensing boilers will operate similarly but fan proving devices will be different.
little star and silver star boilers will operate the same as above. but the DHW flow rate for these boiler is 5l/min. if the manual says its 9-10l/min pls phone ravenheat for confirmation on this, as i believe the manuals are wrong? the plate heat exchanger on the little star and silver star is too small to provide 9-10l/min

FOR RAVENHEAT LO NOX AND little star(silver star) boilers pls check my nxt post