Vokera Compact 28 - drain water

[vokeraques]

Hi there,

I have a Vokera Compact 28 combi boiler.

It's been playing up a bit recently, the hot water is cycling between hot & cold, and the boiler also goes off an on which matches the hot and cold water cycling. The water doesnt go completely cold, but goes from luke warm to very hot. I believe, that when it reaches very hot, the boiler switches itself off.

Its around 9 years old now and has by and large performed without fault up till now. Reading up a little, I think the issue is possibly with the Thermistors, primary or secondary. The Heat exchanger being clogged with accumulated debris over the years, or something to do with the gas feeding the flames not being regulated correctly - gas pressures?

The only thing I could attempt to fix myself here are changing the thermistors. This will be the cheapest and easiest thing to change to try and fix or rule out that as the issue.

I'm not sure I would want to attempt to descale the heat exchanger, and obviously wont be touching anything gas related.

So the question I have is, does this sound like I'm on the right lines? And if so, how does one go about draining the boiler of water before removing and replacing the thermistors. They seem easy enough to get access to, but I think if i remove them, water will jet out of the hole?

Thanks for any tips, or recommendations..

David

 

[ianmcd]

saying you have a Vokera compact is like saying you have a Ford car and looking for advice, there are loads of different models of compact, if you cant find the data badge post a pic and I will tell you which one you have.

 

[vokeraques]

Hi Ian,

Thanks for your reply. Here are some pics of the boiler. I can see there is a plastic tube which looks like ti could drain water, just not sure where the valve is to open the drain? Also, in the manual it says once the boiler is drained, the remaining water should be drained via an external outlet.. I guess this means a mains hot water tap?

Thanks,
David

 

[dilalio]

When you replace that cover, how will you know that it's not leaking POC's?

 

[vokeraques]

Products of combustion? No clue tbh.. Is there something wrong with the setup in there?

Thanks!

 

[Madrab]

@vokeraques, @dilalio is referring to you opening up the room sealed portion of the boiler. i.e. The front cover off the combustion space (that metal plate that you had to undo the bottom 2 snap clips to remove). Only an RGI with the correct training/equipment should be in there. On that model removing and flushing the Heat Exchanger is not a DIY job. For you and yours safety you'll need to get a gas safe registered engineer in now to ensure that cover is refitted properly and then perform checks that it has re-sealed properly. He should also perform check to diagnose your problem at the same time.

 

[Ihavenojob]

I had one last week, same symptoms. It wasn't modulating down, so when it got hot it went off, then came back on. Easy enough to sort, but as already mentioned, you will need specialist equipment & knowledge to test it & ensure it is safe.

 

[vokeraques]

Thanks guys, will have to have a wee think about what to do next.. probably get an engineer out then..

 

[vokeraques]

Well, it turns out the heat exchanger was blocked.. when they took it off, all these little black stones of sorts came out of it.. I'm guessing mineral deposits from the water over the years.. It was cleaned out, then put back in place. Issue with cycling has now gone, and hopefully will stay gone fingers crossed..

 

[JohnD]

have you still got any of this black deposit? And a magnet? you do mean it came from the inside, where the heated water flows?

or did you mean from the surfaces that the flame plays on?

 

[vokeraques]

All the black deposit was flushed down the toilet.. I don think it was checked with a magnet.. It came from inside the heat exchanger, in particular, at one of the 4 openings. Looked like a combination of little flakes, black diamonds, and soot..