Boiler fires up and turns off every 20 seconds

[garf900]

I have an apollo 40b boiler - fully pumped system with 3 port (mid position) valve, I've turned the CH termstat down to off, diconnected the timer and still found that the boiler and pump fire up.
The pump appears to run continually.
The boiler itself has a High and Low setting both do the same, I did try setting it to low, then waiting for it to click off then turned it to high to see if the boiler would fire up immediately...it didn't.

 

[ChrisR]

First check whether the Switched Live terminal on the boiler is live or not. Then remove the wire(s) from the terminal and test again. That will tell you whether the fault is internal or external wiring.

Last one of these I heard doing this turned out to be an internal fault which I can't quite remember - will try to find it.

 

[garf900]

I have replaced the supressor and the High thermostat.
I have tried setting the boiler to low and waiting for the thermostat to click off then turning it to high - I would have expected the boiler to click immediately on but it does not. Also I'm sure the pump is running continuously I was wondering :- If the pump-over run thermostat was not turning off that would explain the pump running continuously but would it explain why the boiler kept turning on and off so quickly. I have dis-connected all the external controls from the boiler controller/cylinder thermostat/room thermostat but still the boiler fires up and the pump runs.

 

[ndmxp07]

Did you ever get to the bottom of this problem, my apollo just started doing a similar thing, firing for 20 secs then stoping then firing.

 

[breezer]

ndmxp07, welcome, i would like to make a suggestion.

Before you pose a question, i suggest you read the date the origonal was posted. The one you are asking was posted in August 2003 by garf900 and if you look at number of posts, he only ever made 2, and they are both here