I have an Alpha 280E that supplies only tepid water when the CH is off;
very hot with CH on. After examining the boiler I can confirm that the
DHW microswitch is being actuated correctly and the rubber diaphragm in
the DHW assembly is not perished. When hot water taps are opened the
outgoing CH pipes get hotter than the corresponding DHW pipes. Can you
give advice on which component is responsible? The boiler is operating
100% in every other way.

Thanks,
Adam

On Mon, 11 Dec 2006 02:50:15 -0800, adam wrote:

I have an Alpha 280E that supplies only tepid water when the CH is off;
very hot with CH on. After examining the boiler I can confirm that the
DHW microswitch is being actuated correctly and the rubber diaphragm in
the DHW assembly is not perished. When hot water taps are opened the
outgoing CH pipes get hotter than the corresponding DHW pipes. Can you
give advice on which component is responsible? The boiler is operating
100% in every other way.

Thanks,
Adam

It's the diverter valve. Which is stuck on its gland or due to crud in the
primary circuit, also sometimes a very scaled up secondary heat exchanger
can cause some sort of problem that molests the diverter valve.

The valve can be replaced or overhauled (there are service kits for it).


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards