Boiler Fault Firing up / Hot Cold water – Hope you can Help

ade_hanks · 23 Aug 2006

Can anyone help me? I hope so.

My situation is this. I have a Worcester 24i Combi Boiler that has been playing up recently. The HW & CH is currently working intermittently. The boiler fires up when a hot tap is turned on or the CH is turned on, but around 3-4 minutes later the boiler turns itself off, It then sometimes “tries” to fire up, but can’t and after a predetermined time it does fire up again, but only for a short time. It sounds like something is overheating and needs to cool down before it can fire up again. Maybe??

To date I have taken the fan off and cleaned it and that spins perfectly. I have checked the Air Pressure Switch as per the manual using a meter and that is also fine. I have been reading a few posts that suggest maybe the Water temp sensor or the heat exchange could be scaled up. Also, it could be the pump needs bleeding and the rads need bleeding. These symptoms might not even apply to my boiler, but I was hoping you guys could point me in the right direction and maybe even eliminate possible symptoms I have suggested. I hope to get to the bottom of this problem and thank you in advance for your time and help.

Regards,

Ade Hanks

Agile · 23 Aug 2006

I would suggest that you take out the pump and make sure the impeller is clear and spins freely.

It might also have an intermittent fault whereby it stops turning when it gets hot.

Tony

Softus · 23 Aug 2006

You haven't mentioned the water pressure, so on the it might be nothing more sinister than low pressure.

I would top up the pressure, vent all rads, top up again, reset the boiler, and then see how it behaves.

If, over the coming weeks or months, you get recurring 'air' when venting, then it's likely that your system is corroding internally, in which case it would benefit from being drained, flushed and a chemical inhibitor added when refilling.

ade_hanks · 23 Aug 2006

Thanks for the sharp response guys. The pressure is set at 1.5bar and seems pretty constant. My house is mixed with old and new radiators and I know the old radiators are a bit sludgy (and probably need changing). The combi system is around 4 years old. I think my next step is to bleed all radiators and top up. I’m not sure if the pump can be bled. Do you guys know? Thanks again for your help.

Softus · 23 Aug 2006

ade_hanks said:
The pressure is set at 1.5bar and seems pretty constant.

Constant? Hmm. Are you looking at the red pointer (fixed) or the blue/black one?

If the latter, then what is the red one set to? And what happens if you rap* the gauge?

*Edit - and I don't mean do street talk to it, I mean hit it sharply with a knuckle.

ade_hanks · 23 Aug 2006

When I say constant, I mean I havn't had to top the system up at all, so it's not losing pressure.

Softus · 23 Aug 2006

ade_hanks said:
When I say constant, I mean I havn't had to top the system up at all, so it's not losing pressure.

In that case there's no need to vent the system.

So, are you looking at the red pointer, or the blue/black one?

ade_hanks · 24 Aug 2006

The black needle and the red needle are both set at 1.5bar. I thought the red needle is adjustable and just an indication needle? Is that true?

Softus · 24 Aug 2006

ade_hanks said:
Is that true?

Yes. I asked because it has been known for people to read the pressure from the red one, especiallly in dim light, and not notice that the black one is at zero.

If the black doesn't even vary by the tiniest amount then the needle is stuck or the gauge is faulty. So, if you bleed off some water from a rad vent, does the pressure reduce?

ChrisR · 24 Aug 2006

Have you checked the pump?. It won't need bleeding unless you've done something to let air in.

Softus · 24 Aug 2006

ChrisR said:
It won't need bleeding unless you've done something to let air in.

...or unless the system is corroding.

ade_hanks · 24 Aug 2006

When you say "system corroding", do you mean the central heating system or the actual combi boilier. Some of my rads are very old, but the combi is relatively new. (4 years old). How would I go about checking the pump. Do you think that the pump is overheating and cutting out and hence burner goes down?

The hot water has been suppled for a longer period of late, so I must have done something right even though I still think something is up with the system and it will get worse again.

Softus · 24 Aug 2006

ade_hanks said:
When you say "system corroding", do you mean the central heating system or the actual combi boilier.

I mean any ferrous metal in contact with water.

I don't know, without looking it up, whether your boiler has a steel heat exchanger, but the rads are steel, so they will corrode unless a chemical inhibitor has been added to the system.

Some of my rads are very old, but the combi is relatively new. (4 years old). How would I go about checking the pump. Do you think that the pump is overheating and cutting out and hence burner goes down?

Agile's suggestion, and a good one of course, was exactly that.

...I must have done something right

Er, what is it that you've done that might have had an effect?

ade_hanks · 24 Aug 2006

I know, it's a joke. I probably haven't done anything apart from the things I mentioned in my first post. I suppose intermittent is the word I need to explain the fact it is a little bit better. (As in, the water stays hotter for longer). I think I'll go with Agile's suggestion and have a look at the pump. Thanks for all your advice. (especially softus). It's much appreciated.

ade_hanks · 24 Aug 2006

One other thing to mention. While the shower was runnng the boiler was making a banging noise. It's the first time this has happened. Do you think this has any relevance or makes things clearer to the initial problem of the burner cutting out? Thanks.

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Boiler Fault Firing up / Hot Cold water – Hope you can Help

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