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I'm not sure if we have any gas Heating Engineers on here, but if we have I could really do with your help.

Is it possible for the mains cold water feed to be fitted to a Combi-boiler on the wrong side and still produce hot water by that I mean the cold water supply is fitted to the Combi-boiler where the Domestic Hot Water should be coming out of it

Thanks in advance,

Chris.

Hi Chris,
Yes, in theory it is possible. It's an open circuit, no solenoid valves or such. There is a flow sensor (which tells the boiler to fire up) and a thermocouple to tell the boiler what temperature is being achieved. If it was backwards, the boiler would only see cold water at the thermocouple and would run flat out to try and achieve the temp that is set on the thermostat, so you would have scalding water out of the taps.
It would be a monumental rock up to plumb them backwards.... There's normally no isolating valve on the hot water outlet either, a really big giveaway.
If you want to post a pic of the plumbing connections I can identify for you.

bigbadjonno wrote: ↑Sun Sep 15, 2019 6:55 pm Hi Chris,
Yes, in theory it is possible. It's an open circuit, no solenoid valves or such. There is a flow sensor (which tells the boiler to fire up) and a thermocouple to tell the boiler what temperature is being achieved. If it was backwards, the boiler would only see cold water at the thermocouple and would run flat out to try and achieve the temp that is set on the thermostat, so you would have scalding water out of the taps.
It would be a monumental rock up to plumb them backwards.... There's normally no isolating valve on the hot water outlet either, a really big giveaway.
If you want to post a pic of the plumbing connections I can identify for you.

Many thanks for posting that with such great detail, that is a big help

It definitely appears to be plumbed in the wrong way around, although strangely enough it's working okay-ish, the water isn't scalding hot though. I do understand how a thermocouple should work.
The only problem is, first thing in the morning with the hot tap fully on a sink full of water needs to be drain off, other-wise the boiler doesn't fire up. Once I've got it working it's fine for the rest of the day, most days. I realise this problem may not be related.

I was really more concerned about any possible damage that could be done in the event of it being plumbed in the wrong way around. Now you've given me an idea of what is in there that is probably not the case. There is an isolating valve on the hot water outlet, but none on the mains water cold feed.

If I need any further help I'll get back to you,

Thanks Jonno,

Chris.

You should be able to feel the temp of the inlet side feed with your hand.