Is my boiler broken?

beckstrous

I just wondered if anyone might be able to advise on whether or not my boiler may be broken (I know this sounds like a daft thing to say).
It is a Potterton combi boiler...I'm not sure of the make. The central heating and hot water are fine. But if you use up all of the hot water and need to boost it, it doesn't work unless the heating is switched off, I think (from looking at the status light) because the boiler wrongly believes that the temperature is already correct.
Is this supposed to happen? I was planning on calling an engineer but don't want to waste money so wanted to ensure I know what I am talking about first.
Thanks if you can help!

EliteHeat

Are you certain that you have a combination boiler?

beckstrous

Not sure what you mean (sorry, I know very little about these things) but if you mean does the boiler take care of both the hot water and the heating, yes. I couldn't get hot water at all yesterday evening once it had run out, despite the hot water boost being on, and then hot water on constantly. It only worked, only heated up the water after the central heating had gone off. When the heating was on and I tried to boost the hot water the boiler would fire up and then go out, with a green light flashing on and off, which according to the manual means that it thinks it has reached the temperature it needs to?

beckstrous

PS We do have a hot water cylinder in the airing cupboard...

allan673

you havent got a combi then, you only have as much hot water as the hot water cylinder can hold.
it needs to be timed/turned on for an hour+ to heat a cylinder full of water up.
and therefore when youve used all the hot water it needs to be turned on again.
probably nothing wrong at all - just ensure you know how to program water & heating on the timer/programmer.

beckstrous

Thanks. But I am not sure...we used all the hot water yesterday so I turned the hot water to boost for an hour (which did nothing). So then after that I just turned the hot water on constant, for about another hour (this also did nothing). The heating was on during this time. It was only when I turned the hot water to boost after the heating had gone off that the hot water came back, after about half an hour. The timer and programmer are fine normally but the boost does not appear to work when the heating is on. Is this normal?

EliteHeat

Apologies, I was going to get involved, but I wouldn't want to step on the previous posters toes, so I'll leave it up to him to diagnose your problem.

latecomer

No. you should be able to have both on at the same time. Did it used to work?

Edit. Do you normally have the hot water on without the heating to get hot water as you say in the first post the how water is fine?

beckstrous

Thanks, yes, it did used to work...normally we have both hot water and central heating come on at the same time (apart from in summer). This still works fine, it's just that if you use all the hot water up and need to boost it, it doesn't appear to work (the boost) unless the heating is off. Which is really weird as when it comes on with the heating at 6am it's fine. I wondered if it was because the heating had reached a certain temp and so the boiler did not think that the water needed to be heated, even when boost button was pressed. What happens when I press boost is that the boiler will fire up but will go out immediately. the only other way (apart from turning the heating off) to get it to work is to turn up the heating thermostat really high, and then the boiler comes on and stays on long enough to heat the water and also increase heating temperature. So I wondered if somehow they were linked and it was confusing itself. It's a relatively new PCB (2.5 yrs old, we had it replaced).

latecomer

There is a normally a thermostat on the hot water tank which will control the temperature of the water but if that was at fault then you wouldn't get any hot water at all.

I think EliteHeats post was sarcastic so hopefully he'll come back and post again as he is a heating engineer (if thats the correct term?) and probably more qualified than most to attempt to diagnose your problems. I'm just a lowly DIYer btw so dont take anything I say as correct

beckstrous

Ahh, thanks for your help anyway :-)