Firebird Enviromax C35 Hot Water Issue

5 Nov 2013
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South Glamorgan
United Kingdom
When we turn on the hot water tap, about 10 seconds later, we get hot water - which is great!. However, if the tap is kept running for a further 10-15 seconds, then the water actually turns cold and takes about 5 or 6 minutes to come back to temperature.

The drop in temperature coincides with the firing of the burner, i.e. the water is hot until shortly after the burner fires.

Also, this only happens after the boiler is left for more than 1/2 hour or so.

Engineer has replaced both flow switch and heat store stats but that hasn't resolved the problem. Rather than continuing to pay for parts to be replaced without the problem being solved, I was wondering if anyone could suggest what the problem/solution might be.

Thanks in advance.
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When the tap is switched on water from the heat store should be pumped around the plate heat exchange instantly to heat the hot water.

It would seem to indicate the water from the heat store is isn't warm enough or sufficient. I would say possibly a diverter valve fault.

If the boiler is fitted with a blendling valve this is another typical fault.
With a temperature probe it should be easy enough to identify the fault.

Flow switch?. Heat store stat? Good grief. Get someone else.
Thanks for the swift response.

I'm beginning to think along the same lines as you as the engineer claims to have contacted firebird and the repairs they suggest is what he's done.

Just to clarify what he's done though, he's changed the flow switch stat and the heat store stat.

I'll try and find another engineer!
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I realise this is a while ago now but did you resolve the problem? I have exactly the same problem. Firebird recommended replacing the flow switch thermistor which did not solve it and then the burner photocell which also did not solve it. How did your new engineer resolve the problem?

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