i have a problem with a customers higflow 400, i ve not worked on many of these boilers and wondered if any of you more experienced guys could shed some light on my problem.

since changing all the 'o' rings around and on the dhw heat exchanger i ve had a problem with poor dhw flow rate and h/w not as hot as i used to be, as these boilers have a thermal store do the use the pump for the h/w? i know the pump is faulty as its running very hot after just a few mins of operating, i m returning to fit a new 15-50 head tomorrow, i m just wondering if theres anything else that could cause this poor flow and temp probs.

also, i m assuming really, that if the tap is turned on, regardless of the hw in the store, that i should get a demand light on the fascia? and if i m not getting it could it be the flow switch that is the problem?

sorry for asking, but this is the first time i ve worked on a thermal store combi and hopefully i wont be working on many more after the hassle the dhw h/e was giving me with leaks!

thanks in advance

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23 Feb 2007
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United Kingdom
I also don't know much about these, or in fact any crap WB boilers, but I think the pump kicks in to heat the plate HE as in a combi to re-charge the store.

If the store runs out you are left with a pathetic 23Kw combi, if I remember correctly.
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