Ravenheat LS100 working well, but cycling often once hot

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Hi,

Thanks for reading this.

I have a Ravenheat Silver Star LS100 that is approx ten years old.

DHW is working fine.

CH also seems to be working well.

There is no thermostat or thermostatic valves in the house, it is just a manual on/off boiler.

The only problem is that the anti-cycling device does not seem to be working. So the pattern is as follows:

-Turn on the central heating.
-The radiators all heat up well.
-When everything gets to full temperature the boiler shuts down normally.
-Now previously it would now stay off for around 3 minutes and then refire, but now it refires after a few seconds, runs for a few seconds and then turns off, this repeats. The only issue it causes is that I thought it is probably not good for the boiler burner and fan to be constantly starting and stopping. But please note this cycling only starts AFTER the correct radiator temperature is reached.

If I turn the CH temperature knob on the front down to a lower setting, exactly the same thing happens only it happens sooner, i.e. the cycling starts at a lower overall temperature.

According to Ravenheat the anti-cycling system is on the control board and I could just get a replacement, but I wondered if there was anything else I could check first?

However, to me, the fact the boiler is working normally and switches off once it reaches temperature seems to indicate that the thermistors must be working correctly.

Thank you for any help.

Jamie
 
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The PCB provides the anti cycle delay.

Normally from a time constant depending on electrolytic capacitors! They can dry out and lose their value.

Some boilers have an engineer facility for turning off the anti cycle. Yours may not have that.

Tony
 
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If boiler temp drops below 20 degrees on heating side boiler will fire up.Thermistor fault.

Thanks for the replies. Would a faulty thermistor indicating a 20 degree drop override the anti-cycle device?

Thanks so much for your help.

Jamie
 
Take connections off thermistor, start boiler, if all well, thermistor fault. or link it and test. Depends on thermistor, try it.
 

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