Intermittent hot water - Vokera Compact 24

Hi,

I have the above boiler providing intermittent hot water. The central heating works fine and the hot water used to be worse when the central heating was on at the same time. With the warmer weather the ch is now off and the hot water WAS being more behaved. Unfortunatley now its getting worse again.

The boiler fires, cuts out, fires, cuts out and then eventually fires for 60 seconds or so then cuts out. The system pressure is good @ 1.5 bar.

After a few minutes of this it will eventually sort itself out and keep the hot water flowing.

Suggestions please, is the first thing to look at the diaphragm?

Cheers

Phil

This is a new one on me. If I were called out to this defect, I would start looking at why the boiler behaves this way when it is fine for CH. Almost all the functional components are used for both CH and HW. It is possible your boiler does not 'see' HW demand, so during CH demand it gives you tepid (not hot) water.

When you ask for HW with CH off, HW demand might be intermittent due to bad connection or similar. This is what one would be looking to find during diagnostics. Good luck.

i had something similar with one of these a few months back , and after a long winded proccess of replacing the board and valve i happened to speak to a usefull tech advisor who pointed me to the ign pot on the board, as the prob seemed gas pressure related, which solved the prob . this ign pot was not mentioned anywhere in the mi. cheers vokera.

thanks for those replies ..

something else to add is that when it is misbehaving and providing short burts of hot water .. that water is effing hot!!! Could some kind of safety device be switching off the boiler because of this?

Its frustrating it was playing up yesterday and today it worked fine ...

Sounds to me like the ol' notoroius Vokera thermistor problem. the DHW thermistor will be faulty. Ive seen a few do exactly what your describing and found the resisitance of the DHW thermistor to be way wrong. Replacing sorts it.

HarrogateGas said:

Sounds to me like the ol' notoroius Vokera thermistor problem. the DHW thermistor will be faulty. Ive seen a few do exactly what your describing and found the resisitance of the DHW thermistor to be way wrong. Replacing sorts it.

Click to expand...

ok ta, ive got a multimeter somewhere .. any ideas on the correct resistance? Or is it a very model specific thing rather than a general rule?

Hi, I was just wondering if you have managed to get the intermittent hot water fixed?

I'm also looking for a second opinion with regards to the same problem with the same combi boiler (Vokera Compact 24 MTN), but did not want to start a new thread as found this one.

The intermittent hot water gets worse with warmer weather outside. I got into a habit of switching it off completely and running the tap for a minute to flush it (as in to cool it inside) before every shower which seemed to do the trick during winter but not so much now. It also seems to be worse with the shower upstairs (gravity?, restrictive shower = less water flow?, it's a normal mixer shower not the thermostatic one), then with taps downstairs.

No red lights on but it also makes quite loud boiling noise around the time it's firing up.

We had an engineer in and were just told we "need a new boiler as this one is old and there is no point fixing it, £1600".

Any suggestions?