Vokera Compact 24 (No CH)

[catnipcatnip]

Hello

Got a Vokera Compact 24 Boiler in a sealed CH system.

Boiler works fine with hot water but when asked to serve CH it fires up fine but cuts out after 25 secs and keeps trying every 4-5 mins...no radiators are getting warm and the return flow pipe is cold...there is no external thermostats or valves and heat is set to max.

I have checked the pump is working and is turning strongly (ie I can't stop it with a screwdriver) and I've also replaced the Main NCT Thermister/Sensor...also power flushed and bled all rads.

Any ideas?

Many thanks in advance

 

[tonybhoy]

Iso valve turned off under boiler or a blockage on the pipework somewhere.

There are two thermistors on this boiler, you should have changed both at the same time BTW.

 

[catnipcatnip]

Iso valve turned off under boiler or a blockage on the pipework somewhere.

No valves have been touched, so can't have turned off...pipework seems pretty free when I drained and flushed the system...and how would boiler know to shut off so soon if there was a blockage?

There are two thermistors on this boiler, you should have changed both at the same time BTW.

I know there is another one on the hot water side of the boiler....there is another sensor on the CH side that is a primary sensor as lead to believe...think I will change this one tomorrow

 

[picasso]

have you got the HE version or the older non condensing one ?

 

[tonybhoy]

Iso valve turned off under boiler or a blockage on the pipework somewhere.

No valves have been touched, so can't have turned off...pipework seems pretty free when I drained and flushed the system...and how would boiler know to shut off so soon if there was a blockage?

There's an overheat stat on the boiler that will shut off the boiler or one of the thermistors will when it senses no flow or too much heat or more accurately the boiler's satisfied for heat and of course the boiler stat will be satisfied so shuts down the boiler.

 

[catnipcatnip]

There's an overheat stat on the boiler that will shut off the boiler or one of the thermistors will when it senses no flow or too much heat or more accurately the boiler's satisfied for heat and of course the boiler stat will be satisfied so shuts down the boiler.

Any further suggestions Tony?

 

[HarrogateGas]

Iso valve turned off under boiler or a blockage on the pipework somewhere.

There are two thermistors on this boiler, you should have changed both at the same time BTW.

Why change both when only one is potentially faulty? Seem amaturish fault finding to me!

 

[tonybhoy]

Iso valve turned off under boiler or a blockage on the pipework somewhere.

There are two thermistors on this boiler, you should have changed both at the same time BTW.

Why change both when only one is potentially faulty? Seem amaturish fault finding to me!

At £15 for two are you kidding?

 

[catnipcatnip]

Why change both when only one is potentially faulty? Seem amaturish fault finding to me!

I changed the one on the CH side...if HW side is working then why would I change that?....backing up your comment Harrogate

 

[tonybhoy]

There's an overheat stat on the boiler that will shut off the boiler or one of the thermistors will when it senses no flow or too much heat or more accurately the boiler's satisfied for heat and of course the boiler stat will be satisfied so shuts down the boiler.

Any further suggestions Tony?

Something's stopping the flow of water mate so that's where I would be looking. Hot water is fine so everthing's working that will be working for heating, pump, fan, aps etc, only with heating the water isn't going anywhere so the boiler is shutting down due to being satisfied for heat.

Why did you power flush?

 

[catnipcatnip]

Why did you power flush?

Because I initially thought the fault was sludged up rads....but when I flushed the water came out pretty clear....and also run the system for a day with Sentinal cleaner.

Should I remove every rad and manually flush them?

 

[tonybhoy]

You need to find out if the water is going out from the boiler and going back to the boiler so I would start at the boiler's heating iso valves but first in my amaturish way I would fire a new pump head on the pump but that's £35 for you mate and nothing for me cause I keep pumps from boiler replacements however £35 isn't that much if if it saves you a load of time and your getting a new pump on an older boiler which eliminates the pump.

Wonder if your man above will come up with a better solution

 

[catnipcatnip]

You need to find out if the water is going out from the boiler and going back to the boiler so I would start at the boiler's heating iso valves but first in my amaturish way I would fire a new pump head on the pump but that's £35 for you mate and nothing for me cause I keep pumps from boiler replacements however £35 isn't that much if if it saves you a load of time and your getting a new pump on an older boiler which eliminates the pump.

Wonder if your man above will come up with a better solution

I was going to replace the pump, but two things...pump seemed strong and not been quoted owt near £35!!!

ps...I'm liking this handbags at dawn thing! lol

 

[HarrogateGas]

Common fault on the Compact...............blocked filter on the return.

 

[HarrogateGas]

Iso valve turned off under boiler or a blockage on the pipework somewhere.

There are two thermistors on this boiler, you should have changed both at the same time BTW.

Why change both when only one is potentially faulty? Seem amaturish fault finding to me!

At £15 for two are you kidding?

Why £15 for two when its £7.50 for the faulty one? thant 3 pints, a cd, 7 litres of diesel, a decent book, a nice lunch in cafe, a toy for a child, a nw tie........................get the idea?