Combi boiler burner keeps coming on and off

tommyl18 · 4 Oct 2010

got a Halstead combi 102 combination boiler and when you switch the hot water on the burner comes on and off intimitantly which in turn is only giving us luke warm water. When you switch it to heating it stays on but then when you turn the water on again same thing happens

the pressure is good on the boiler am i right in saying it could be the hot water switch that is faulty?

tininho · 4 Oct 2010

Hi,

Don't know the boiler particuarly well, but sounds like a DHW thermistor fault to me.

Hopefully, someone else here knows the appliance better than i do.

Martin

picasso · 4 Oct 2010

As above or blocked plate heat exchanger.

tommyl18 · 5 Oct 2010

what a thermistor do?

picasso · 5 Oct 2010

A thermistor do temperature sensing as in THERMal resISTOR.

tommyl18 · 5 Oct 2010

so would it be turning the burner off then because its malfunctioning and telling the boiler its overheating??

tininho · 5 Oct 2010

Hi

a thermistor works based on resistance. the higher the temp of the water the greater the resistance across the thermistor, thus modulating the burner down to maintain a constant temp.

In essence the thermistor resistance could be higher than it should be, in effect telling the boiler that the water is at the correct temp, or higher and shutting the burner down, when it shouldn't....

That is basically how it works.

Martin

Gavska · 5 Oct 2010

Hi Halstead boilers are generally the lower end of the market quality wise and are a fav of the landlord.
The DHW thermistor is a common fault and is also a cheap part to replace first.

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Combi boiler burner keeps coming on and off

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