Intermittent Hot Water - Alpha 240E

[davas]

Hello all,

I've got the problem that when I run the hot water tap my Alpha 240E fires up as expected and then starts to deliver hot water normally. Just as you start to get the hot water coming through the boiler shuts off the burners meaning the hot water stops. Then 10 seconds or so later fires it up again...

Cold - Warm - Hot - Warm - Cold - Warm - Hot etc.

I assume this is a pretty common problem as a combi in my student flat did the same (landlord was too tight to get it fixed - although fitted an electric shower instead! )

Any help would be appreciated!!

 

[Paul Barker]

Max gas rate needs checking and adjusting as required, thermisters checked, and temperatures monitored to make sure primary side of dhw heat exchanger isn't in need of cleansing or renewing.

 

[davas]

Max gas rate needs checking and adjusting as required, thermisters checked, and temperatures monitored to make sure primary side of dhw heat exchanger isn't in need of cleansing or renewing.

Not a DIY thing then

Thanks for your suggestion Paul

 

[Paul Barker]

Might only need thermisters if you're very very lucky, but someone competent would check the other items on the list. It's a cheap part and in my view always worth changing both.

 

[davas]

I've had a guy out to look at the offending combi and he's diagnosed that it is one of two things:

1) Thermisters need replacing (~£35 parts and £65 labour)
2) Circuit Board needs replacing (£180 part and £25 labour)

Does the diagnosis and costs involved seem reasonable? (i'm in the North East if that helps establish prices etc)

Thanks a lot

Chris

 

[Rob]

Does it work ok for HTG?

Its not the PCB

My guess is the HE blocked but worth taking the thermistors in case.

 

[GasAid]

My suggestion would also be a blocked plate heat exchanger... Might be worth you stripping it out and giving it a flush through if you are on a budget at the moment.

Otherwise, for the £10 or whatever he was gonna charge you for the thermistors; it's worthwhile. I always carry one of these on-board; they should read about 11kOhms when cold and have a negative temperature co-efficient.

 

[davas]

I think the reason he said PCB is that when the you turn the hot water tap off the boiler fires up again a couple of seconds later (the LED does not show a demand for HW or CH when it is doing this.

Does this change your views in anyway about the heat exchanger/PCB?

The HTG does seem to work OK but not as well as i remember it ("back in the day") the problem is not as obvious here though as I don't take as much notice of the output from the boiler as i do when my hand is under a tap.

Thanks a lot for your help! Do you know of any online resources for boiler maintenance manuals for boilers that might include mine?

I have found the user manual somehwere but not the installation quide etc.

Thanks again!

 

[Paul Barker]

can send pdf if have email address.

 

[davas]

Thanks a lot! [email protected]