Baxi combo 80e, no power to the boiler fan with DHW

[ishaqmir]

Please help,

boiler playing up. I have to keep the central heating on for the hot water to work.

i opened up the boiler and found that if only the hot water is running, there is no 240V power to the boiler fan, and therefore the boiler doesn't fire up.

when i put central heating on, there is 240V to the boiler fan and it spins freely and the boiler fires up very hot as normal. then if i turn on the hot water tap, the fan keeps live and hot water runs freely through the taps.
but if central heating off, then no power to the fan if i put hot water on.

I first thought it was the fan, but after checking power to it with a multimeter I realised it can't be the fan as its to do with the power to it.

also, even the central heating packs up intermittently, i.e. again no power to the fan, the boiler receives the signal to start etc but just doesn't power the fan and therefore nothing else can happen.

Its a baxi combi 80e

thanks

Ishaq

 

[CombustionGuy]

Go to gas safe website and look up a local engineer who will be able to fix the fault for you

 

[ishaqmir]

had one come down yesterday and just insisted i changed the boiler for a new one and pay him. he said the fan was playing up, but i know a bit about electrics, it wasn't the fan, its the power to the fan.

 

[gas112]

Start at basics is the diaphragm pin coming all way out and hitting microswitch when tap on and only HW selected .

Bottom left of boiler

 

[ishaqmir]

oh yeah, I also did that test. turned central heating completely off. just tested hot water, and diverter valve pin definitely came out and pushed the DHW switch. boiler then just waiting for fan to start up, but no power to it.
when CH on and working, i turned hot water on, pin came out as usual, but this time power to fan remains on and i get hot water.

strangely, sometimes if i had only 'just' switched the central heating off, and then tried DHW on/off on/off power would go to the fan and water piping hot as normal. but then eventually fails if taps turned off for a while.

 

[JBPHS]

Start at basics is the diaphragm pin coming all way out and hitting microswitch when tap on and only HW selected .

Bottom left of boiler

This isn't the CC gas112!!!!!!

James

 

[picasso]

This isn't the CC gas112!!!!!!

James

Whats a microswitch got to do with gas ? nothing wrong with trying to diagnose faults that dont involve the gas train/safety devices ect.

 

[JBPHS]

This isn't the CC gas112!!!!!!

James

Whats a microswitch got to do with gas ? nothing wrong with trying to diagnose faults that dont involve the gas train/safety devices ect.

Well numb nuts, how did the OP manage to test the voltage at the fan and observe it spinning?

By giving info on how to fault find, regardless of whether or not it affects gas controls, POC's, etc. gas112's advice implies that they condone the OP's previous actions. The correct way forward would have been to advise the OP of rule 10 and to hire a GSR engineer as their actions so far were incorrect. Remember that this is a public forum and a little knowledge can be dangerous!

James.

 

[picasso]

Fook off you complete to$$er

 

[gas112]

jbphs
I dont give a flying fek what you think i presumed.

Like you he may have been a pro asking a question in the open forum .

 

[muggles]

...in which case, he should have been directed to the CC to ask it there

 

[gas112]

WHY ? Are yo sayin only certain people should ask questions in certain sections , i would say every single member of the CC started off in here asking and answering questions

 

[muggles]

Indeed they did, and they were refused answers and directed to the CC, basic principle of the site

 

[gas112]

Eh no they werent the mod police on here have only really been active for a few years and dont forget the CC was a spin off from this section after quite a few years

 

[ishaqmir]

ok guys

I did the RIGHT thing and got a very good (but expensive!) gas safe plumber to take a look at the boiler.

long story short, he changed both diaphragms on the diverter valve including the nut, with original InterPart parts, and cleaned and lubed up the required areas in the diverter assembly with the correct silicone stuff (not the car grease that my previous plumber had used!!!).
He checked over the boiler thoroughly with all his high tec gear and said everything else is looking okay. BUT the problem is STILL there. No hot water if the central heating is off.

His diagnosis was this: the pin which activates the boiler fan goes high enough in good time for DHW only if the CH is on.
If the CH is OFF, then the same pin goes up for DHW but not high enough and therefore the boiler waits and waits for the fan to come on, and then eventually goes into lockout mode, requiring boiler to be switched off/on.
He thinks that it is due to sludge in the diverter assembly, and he injected Fernox F3 Super concentrate (the tube on the gun) paste into the system through a part in the boiler, so it hit the diverter valve straight away.
Now its been a day so far with heating being used and I have noticed that one radiator in the house which took a while to heat up from the bottom, is now heating up quicker.
The plumber said leave this cleaner in for a week and see if it sorts the problem.
at present, the problem is still there. only hot water when CH on.
But what I have noticed is, if central heating is switched off, the hot water DOES come on if used within 15-20 mins of CH being switched off. So i'm assuming, when the assembly cools down, the problem re-occurs.

any input would be greatly appreciated. I have a magna clean and descaler installed but magna clean definitely due for a clean as its been around 10 months.

thanks