Vokera Compact 28kw SE intermittent HW

[GQuigley67]

don't do many repairs but went to this boiler today, am i right in thinking it can only either be the thermistor or blocked PHE??

I tested thermistor and got good readings, water went hot and cold like clockwork, so have suggested replacing PHE.

Anyone know how much the PHE are for these boilers ?

thanks in advance

 

[mcniven]

al put some input in dont know where it will help ..

why would replacing a heat exchanger fix the problem if its goin hot and cold? it will be thermistor imo cutting boiler on and off when temp rises and drops. thats my tuppins

 

[mcniven]

and is the compact not a dual heat exchanger

 

[mcniven]

Dual HE

 

[GQuigley67]

thermistor readings were fine though, and its not a HE boiler

plate heat exchanger when blocked goes hot and cold because it overheats then cuts out and so on

 

[GQuigley67]

saying that just looked at the manual, i dont even think its that boiler, it comes up on the system as a compact but doesnt look like the same boiler

 

[mcniven]

thats the boiler im on about mate, i dont think it has a plate heat exchanger its a dual heat exchanger in this boiler

 

[mcniven]

do we get many blocked heat exchangers in glasgow, our water is soft aswell.

 

[GQuigley67]

this is the one

http://vokera.co.uk/wp-content/uploads/2009/04/compact-se-installation-and-servicing-manual.pdf

it doesnt seem to have a plate heat exchanger, feel like a tit now

but thermistor seemed ok

 

[GQuigley67]

do we get many blocked heat exchangers in glasgow, our water is soft aswell.

the plate heat exchanger gets clogged up with sludge i thought causing it to overheat and cut out then once cold water passes through fires up again

 

[GQuigley67]

looking more at the manual i tested the secondary thermistor, if the primary one was faulty would it cause this ?

i was in a bit of a rush and had it in my mind that it was a plate heat exchanger, so was assuming this was the DHW thermistor:13:

 

[TFGplumbing]

I went out to a Worcester 24 lpg not so long ago, Hw would run for a few mins then it would go cold, Turns out 3 of the bottles were empty and the one full one was only open a crack. Opened the bottle valve up fully, problem solved. Customer was not best pleased haha ;-)

 

[mcniven]

Or high limit stat change them all cheap

 

[CES]

McNivens is bang on the money Gerry. I was out at one of these this morning in Edinburgh. It was the DHW thermistor. The primary overides the secondary when its fecked, boiler lights then goes out on the primary thermistor.

 

[GrahamM]

thermistor readings were fine though, and its not a HE boiler

plate heat exchanger when blocked goes hot and cold because it overheats then cuts out and so on

Out of interest what resistance readings were you getting hot and cold?

As lads have mentioned thermistor issues in Compacts are an extremely common fault and is one thermistor I always have a handful of in van. For sake of few quid change them.
If still issues would maybe consider board.

 

[aggis]

Hi. On the compact, if the burner is going out when running dhw [hot then cold water & hot again] & the ntc's are correct, connect a spare ntc to the primary ntc wire, hold it away from the boiler, turn on the dhw. If the burner continually heats the water & doesn't turn the burner off. It's the main heat exchanger that's blocked. Remove & clean with a strong cleanser like FX2 in the heating & then dhw tubes, or replace with new heat exchanger.

 

[GQuigley67]

cheers lads, i dont like going to other jobs after finishing a long install when your hank marvin and all you can think about is your dinner, so was in a rush. Need the cash

customer is understanding anyway, going back tomorrow to change primary thermistor and high limit stat, if that fails i will remove heat exchanger and clean it

the secondary thermistor was doing all the correct things, giving a steady reading, high when cold and low when hot

 

[GQuigley67]

well little update here, think the problem was down to poor flow rate ! guy has just had an extension so plumber has worked in the house, with the HW thermostat at the boiler down on low setting the boiler was doing its job by cutting it out when it overheated, with the thermostat up full it didnt cut out but the water was roasting, opened stopcock fully and problem solved.

All checks on thermistors and High limit stats showed them to be in good working order, also min and max gas pressure were spot on.

 

[jordand]

What made you think of that? Poor flow rate?

 

[GQuigley67]

well i was left scratching my head when all the components i tested were fine and the boiler seemed to be doing its job properly, quick call to manufacturers and they suggested flow problems, put 2 and 2 together and the plumber must of not opened stopcock fully when he was done

even with the HW thermostat at low setting, the water would get scalding hot then the burner would go out then relight after a few seconds

 

[GQuigley67]

on another note parts centre charged me around £11 and £7 plus vate for the high limit stat and thermistor, bit steep if you ask me, went down to question price but there was no record on my account so i will keep quiet for now but seems hell of a steep for someone whos ment to be giving you discounts

 

[CES]

Probably not much use to you now Gerry seeing as you will be up to your danglies in Kangaroo dung soon but

TS 132 Vokera Compact 10027352