Worcester Highflow 400 RSF intermittent DHW

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ktnabd

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Aberdeen
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Guys,
Drained the CH system, replaced expansion vessel and currently on Sentinel x400 since 1.5 weeks ...but notice DHW water burner is cutting out time to time when on constant hot water demand! think should remain constant and so water temp fluctuate bit. More noticeable when on shower, not major issue at kitchen tap.

That may be its due to the temperature sensor or the DHW thermo stat/dial?

Where is the DHW temp sensor located; is that the one in front/left of storage tank with 2 pink wires? if so what should be the resistance across? Is this direct screwed to tank or thermowell and does not need tank emptied?

and also anyway to test thermostat too - check resistance or voltage etc?

Cheers
 
Maybe diverter valve or blocked plate heat exchanger. When you run the tap does any of the central heating pipes get hot under the boiler?
 
@adam911 , managed to get checked.
yeah when DHW on ... CH supply pipe is hot (radiator seems not hot but notice supply at one of the nearest radiator valve is little hot).. infect CH out pipe feels hotter than DHW out!
FYI also i have checked tank sensor + DHW sensor resistance and it reads around 1.38/1.58kohm, which seems inline with what's mention in fault finding.
 
Yeh probably blocked plate heat exchanger. Its block so hot water is going into ch instead.
 
I love this boiler with a passion
Is it a 400 or a 400 electronic? Big difference
Forget stats and get down to basics. What is dhw temp....pump ok?

It moves over to central heating...dhw is default.....any questions ask me....( it’s a £ a question )
 
boilerdoktor said:
I love this boiler with a passion
Is it a 400 or a 400 electronic? Big difference
Forget stats and get down to basics. What is dhw temp....pump ok?

It moves over to central heating...dhw is default.....any questions ask me....( it’s a £ a question )
Click to expand...

Hey BD, do you guys still cover this boiler, but you stopped covering the 280 and 350, similar vintage aren't they.?
 
Think the 400 was after them, the original highflow ....can’t remember the name @jiminblack might remember it was around with them
The 400 electronic was still being made when we went over to condensers
 
Not sure if they take the 400 on a fixed price. The electronic version yes.
 
Don't forget. If you're lucky there is a mesh filter in the top manifold, cleaning it can save the day. underneath the brass plug. (on the 400 there is temp Phial inserted in there)
 
Guys, me back here; on to the same issue!. We had CH ok (all radiator heating perfect hot) but DHW cutting out. SSE engineers were out and thought its diverter valve.
which was replaced today; but seems situation at boiler ended up bit worst... we had DHW cutting out before; but now its cutting out on both CH and DHW! - asked the guys to check small weep tube at the back for the blockage but he was so sure that's not a problem and not checked.

Now they think its HE, and ordered heat exchanger and coming back to change, hope that sorts the issue. However can't see why change of diverter makes things worst! and cutting out both CH/DHW.
 
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