Boiler coming on when no demand.

22 Jul 2018
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United Kingdom
Hi all, I’ve been looking through the forum a long time to try and isolate my issue, while similar never seams to be a solution. Basically my boiler is firing up when there’s no demand for a few seconds etc and going off. The valves seam to be working and are not stuck open. Boiler working fine otherwise (icos ihe24)

I’m losing pressure too, no idea why. My pump looks like it could have a small very slow leak. Would this be a cause for it lose pressure daily?

Pump seams to be running fine but is on when boiler off and no demand

I’m thinking it’s the cylinder thermostat but how can I check. Cylinder is OSO indirect 210
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I’m thinking it’s the cylinder thermostat but how can I check. Cylinder is OSO indirect 210
Highly doubt it’s that, as this sends a signal to the motorised valve to open. It’s likely to be a sticking/stuck microswitch in the motorised valve.
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Yes two valves, assume one ch one hw ones a Drayton the other Honeywell both with Drayton motors inside
Yes that’s right, majority of the time it’s doing that. It’s not constant. There’s demand being asked from somewhere but no idea what.
It's the motorised valves that send power to the boiler( and pump) to fire up. One of yours is faulty. You would need to do some testing at the wiring centre to establish which one.If you are not comfortable working with electrics ,you will need to bring in a professional.
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I’m fine with electrics, I’ll take a look and see what I can do.
You’ll likely have 240vac between neutral or earth and orange without any demand on your faulty valve.
in your wiring centre , you will have two grey wires in the same terminal and two orange wires in the same terminal, isoltate the power and remove and seperate the two orange wires test for continuity betwwe the grey eires and each orange wire individually, the orange wire that shows continuity is the valve with the faulty micro switch
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