Alpha CB28 Combi - Luke warm water

markwm · 24 Jun 2008

The only way we can get 'hot' water from our boiler is to adjust the isolation valve that's on the cold water inlet just before it goes into the boiler. If I close the valve slighlty we can get what I'd call hot water.

The problem is when the valve is half open/half closed it makes a right racket every time we turn on the tap.

With the valve fully open, it doesn't make a noise but the water is just warm, not hot. I have the controls set to max temp and have tried released pressure and reseting using the switch on the front.

gas4you · 24 Jun 2008

Could be diaphragm, flow switch or maybe even just in need of a good service and the gas pressures checked and set correctly.

ChrisR · 25 Jun 2008

Check the actual flow rate with a bucket (usually 9 litres). You should be getting 10 - 12 liytres/minute at showering temperature.

gasinstaller · 6 Jul 2009

Bugger all of that if the boiler is firing up it is not the diaphram. Anyway i would be surprised if it had a diaphram as most manufacturers started using flow switches years ago. And if it is firing up with the inlet turned down it is definately not the problem. As for gas pressures *******s. inefficancey and other problem but not lack of DHW.

it will almost definately be the DHW thermistor around £20 and an hours labour to fit.
dead easy.

If you want to change it yourself look for the GC numbere on the boiler go to your local parts supplier and get one. Take the casing of the boiler off follow the DHW pipe and after the plate heat exchanger you will see the thermistor. it will turn with a 13mm spanner. just turn the water off and place a basin underneath the boiler to catch the water

glasgowgas · 6 Jul 2009

new to the site???

you are replying to year old posts.

Legion · 6 Jul 2009

nickso · 6 Jul 2009

whoa speedy....an hour to fit a thermistor? glazier has new competition for the slowest RGI on here.

gasinstaller · 7 Jul 2009

It takes about 10 mins to change a DHW thermistor but i charge min 1 Hr labour.

I spoent a winter one year changing 4-5 thermistors a day on the ferolli optima 701 combi. The Housing association i subbied for all had the same boiler fitted . I was getting the thermistors for just £5 incl VAT.. good times. 1 Call out charge and £25 per thermistor( changed the CH at the same time)

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Alpha CB28 Combi - Luke warm water

Legion

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