DIY Doctor

Extreme temperature changes in HWS

Postby Hodge » Wed Jun 25, 2008 7:41 pm

We have a Worcester 28 CDI combi boiler. When hot water is on it very quickly goes cold. Have noticed that the hot water indicator light does not light up every time the hot water taps/shower are turned on. Can anyone tell me what the problem is? Is it a pressure issue?
Basically it appears to be intermittent. We can have a hot (almost scalding) shower in the morning which goes extremely cold but it seems better in the evening. Either that or we're going mad!
Any feedback appreciated.
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Simply Build It

Postby htg engineer » Thu Jun 26, 2008 3:16 pm

Possibly a fault with the diverter valve, the diaphragm may be split or stretched.

When the water is at high demand, on mornings and evening when everyone in the street is going to work or getting home from work, it can be noticeable as the pressure is not great enough to push the diaphragm and pin up to operate the microswitch.

Also worth checking, is the cold mains pressure decent ? water companies have a legal requirement to provide a minimum uninterrupted supply of water to your house.

If you turn the hot tap on, and the HW indicator light does not light up - it's more than likely to be the diverter at fault.

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