Boiler on and off constantly
Discussion
Hi everyone, I hope someone can shed some light on what my boiler is doing!
I've just moved into a new place and the boiler seems to be cycling on and off (the actual ignition and sequence and flame) a hell of a lot. I got a gas safety cert done a month ago which said all was safe but that the boiler does not 'regulate down properly'-this apparently means it gets to top temperature and where it should cool down slightly to regulate the thermostat temperature, it's actualy switching off and starting over again. It does this approx every 5 minutes.
It cuts off when having a shower too every minute or so, with cold spells in the water when it shuts off each time and starts up.
Could the boiler be getting too hot as it cant regulate correctly and cutting out as a safety feature?
Does anyone know how I may fix this an why it may be doing it? It just seems to be doing a lot and cant be a good thing; especially efficiency wise!
Thanks for any help.
I've just moved into a new place and the boiler seems to be cycling on and off (the actual ignition and sequence and flame) a hell of a lot. I got a gas safety cert done a month ago which said all was safe but that the boiler does not 'regulate down properly'-this apparently means it gets to top temperature and where it should cool down slightly to regulate the thermostat temperature, it's actualy switching off and starting over again. It does this approx every 5 minutes.
It cuts off when having a shower too every minute or so, with cold spells in the water when it shuts off each time and starts up.
Could the boiler be getting too hot as it cant regulate correctly and cutting out as a safety feature?
Does anyone know how I may fix this an why it may be doing it? It just seems to be doing a lot and cant be a good thing; especially efficiency wise!
Thanks for any help.
Edited by vescaegg on Wednesday 4th May 22:55
cal72 said:
We had a similar issue with ours recently, engineer tried gas valves(thought it worked but 2 days later), circuit board, thermostat, even tried emptying boiler and re-presurise it and nothing fixed it.
We got a new boiler in the end.
God dont say that!We got a new boiler in the end.
I have been advised by a plumber (over the phone without seeing it) that it sounds like the heat exchanger may be scaled up and causing the issue. Hopefully it is and wont be too expensive

Sorry if this sounds a bit basic but I assume you have checked that the system pressure is ok? my combi boiler (also a Worcester of that age but cant remember model no) exhibited similar symptoms and it was just a case of the system pressure being too low. repressurised it and problem solved.
My boiler does a similar thing. It'll run the CH for 5 minutes, then turn off for 5 minutes, repeat.
We don't have a thermostat in the house, and my plumber said that it was getting the water (for the rads) upto temp then shutting off, as it had no other way to know if it was hot enough. Problem was, we'd have to keep turning the boiler on/off when it was too cold/hot.
We don't have a thermostat in the house, and my plumber said that it was getting the water (for the rads) upto temp then shutting off, as it had no other way to know if it was hot enough. Problem was, we'd have to keep turning the boiler on/off when it was too cold/hot.
Pete Franklin said:
Sorry if this sounds a bit basic but I assume you have checked that the system pressure is ok? my combi boiler (also a Worcester of that age but cant remember model no) exhibited similar symptoms and it was just a case of the system pressure being too low. repressurised it and problem solved.
Out of interest what pressure does yours run at? Mine hovers around 1 bar when in use. But it drops away quickly if i leave it for a few days. A week sees me having to recharge from nothing......vescaegg said:
It's a Worcester 24cdi approx 6 years old.
My daughter's house has, if not the same boiler, then one from that series, about the same age, and I'm convinced it's not modulating.Look at the chart at the back of the instuction book (download it if you haven't got it).
When it's running the CH it should start at a low level for a minute, then ramp up, then modulate back to maintain the flow temp. Her's stays at full power and so the boiler quickly hits its high limit and cuts out. It won't refire then for 3 mins, after which the cycle repeats.
On HW it should come on at full power, then back-off to maintain a steady temp. Her's does same as your's - on/off so the the water termperature oscillates.
She was able to take out a BG service contract without an inspection as the previous owner had one, so we're leaving it a few mths and will get them in.
Edited by Deva Link on Thursday 5th May 23:25
vescaegg said:
Out of interest what pressure does yours run at? Mine hovers around 1 bar when in use. But it drops away quickly if i leave it for a few days. A week sees me having to recharge from nothing......
If the pressure is dropping you either have a leak in the system or it is exhausting out of the safety/pressure valve. You should not need to top up the pressure if all is working well.I suspect water is exhausting from the valve. There should be a drain pipe come from the back of the boiler to the outside, see if any water is come out of this, you may need to tie a plastic bag over the end of the pipe to see if it fills with water. If so this is a symptom of your problem.
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