Alpha 240p H/W

[Gasguru]

Expansion vessel will hopefully be OK now for a few years.

DHW sensor probably £10 - £15. Can't say whether to replace it I am not a parts swapper - like to test things first!

I can't go through testing sensors - not practical really.

You may have to call out an engineer - Alpha may be able to give you someone on their books.

 

[gr8nty]

Thank you.

 

[Keith9534]

I would be interested if you found a soloution to this problem as I am experiencing similar problems.

Thank you

 

[gr8nty]

It is still not resolved . Nothing wrong with Temp. sensor .Boiler is running better with the expansion vessel charged . I am not a boiler expert , but I think the boiler is not modulating , i.e. it is running flat out and going off on a high temperature interlock ,starting up again etc . New gas valve costs 100 `s of pounds unless you can change a coil in it . I would be interested to hear your probs.

 

[ChrisR]

Either test or clean or exchange both the sensors. Alpha make them expensive I think £18 each or something.
Should be 10k cold and about 4k at 80º
CH one needs conductive paste, IIRC. You get wet for the HW one.
Gas should go down, not out, when the hw gets hot. If it's going out then its either sensor or gas valve adjustment - corgi thing. (or its still dirt in the system slowing the response so temp overshoots.)

"We" would just put a couple of meters (one on each sensor, one on gas valve), a gas pressure gauge and a contact thermometer or two on it all at once, while you play with the taps doing what you're told. We do the hard bit watching things, while drinking your tea. Piece of cake? Yes please.

 

[Agile]

You have told us that there is nothing wrong with the sensor. I would question how you have come to that conclusion.

The major two operating components which have not apparently been confirmed as operating properly are the fan/aps and the gas valve. These however both require a competent CORGI registered engineer.

For the regulars, I went last week to one which was not working after a CORGI had been trying to fix it. I found the APS was not operating correctly. The venturi had been removed and replaced backwards!

Another tonight started leaking from the pressure gauge capillary. Very luckily I had a spare gauge with me.

Tony

 

[ChrisR]

A panel light comes on if the aps or primary flow isn't operating correctly on this one I believe.

 

[Keith9534]

I think the light comes on to show that the fan/APS has opereated and stays on if there is a problem. If it goes out the manual says that the fan and APS switch have been proved.

Can you tell me if the same light indicates anything for the primary circuit though?

Sorry to hijack the thread but I have very similar problems to this....happy to start another thread but thought it better to watch this one...don`t want to upset anyone!

 

[gr8nty]

Mine does have a light which indicates that the fan is interlocking out the boiler . the light is not on whem the boiler drops out.

 

[ChrisR]

Can you tell me if the same light indicates anything for the primary circuit though?

It does - it'll come on of the primary flow is not ok. Piece of cake to check - switch on top of the diverter valve.

Gr8nty it could be your gas valve needs adjustment, which needs a corgi. Even a new valve has to be commissioned! COuld also be heat conduction problems around the sensor. Impossible to check unless you have the test kit and some knowledge.

HIjacking the thread confuses things - most of these problems are due to dirt in the primary of the hw heat exchanger.

 

[gr8nty]

I have finaly got around to changing the DHW temperature sensor . The boiler is working . Lovely modulation seen at burners , happy days . I have been draining boiler through safety valve when I work on it and now I am loosing pressure I think through the through the safety valve (when boiler back in service water weaping outside) . Is it possible that its not seating properly ?

 

[Gasguru]

Yes...replace the safety valve if it's dripping, Alpha conveniently fit a drain-off valve just behind the safety valve....for draining the boiler