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Plumberpro
Plumberpro, Plumber
Category: Plumbing
Satisfied Customers: 634
Experience:  Heating and plumbing answers. 20 years experience
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There, We have a Ideal ISAR Boiler - seems in good condition.

Resolved Question:

Hi there,
We have a Ideal ISAR Boiler - seems in good condition. Pressure reading seems to be fine, between 1 a 1.5.
BUT when we run any hot tap (kitchen / shower / bath) it initially runs hot before running lukewarm/cold. It sometimes kicks in again...or sometimes stays cold. Having looked at the boiler as this happens, the light indicating the burner initially comes on but then turns off again thirty seconds later.
The taps are all mixers - not sure if this makes a difference.
When we turn the central heating on it works fine - the burner lights stays on. And if you run a hot tap whilst the heating is on the water stays warm.
The pipes at the back of the boiler seem to be hot.
Submitted: 2 years ago.
Category: Plumbing
Expert:  Plumberpro replied 2 years ago.
Hi most likely the hot water remote sensor. Fairly easy to replace and costs around £20.
Other than that it will be a blocked, scaled/ sludged domestic hot water heat exchanger.this would need cleaning out or just replace.
Start with the temp sensor first , its most likely this . common fault on the ideal isar
Customer: replied 2 years ago.
Hi there - thanks for this. When you say 'hot water sensor' do you mean something like this...https://www.plumbnation.co.uk/boiler-spares/product/ideal-170996-dhw-thermistor-kit-isar/?gclid=CLH976miycgCFYgKwwodONgJywAnd in terms of fitting it - would it be along the lines of this thread...http://www.diynot.com/diy/threads/how-to-change-thermister-on-ideal-isar-he35-boiler.226092/It isn't showing an error code on the display.If this doesn't work is the exchanger job something I would need to get a plumber in for?Thanks!
Expert:  Plumberpro replied 2 years ago.
Hi , yes that's the sensor . just make sure the boile is isolated electrically and the mains waters off (or off at the boiler cold water isolation valve.
If its not that it will be the Dom hot water heat exchanger
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