Gloworm 30hxi - cuts out & won't do a powerful burn

[RWhites]

Hi all.
I've got a Gloworm 30hxi boiler on an open vented system.

When going at 'full pelt' it used to make quite a lot of noise - sounding like a fan, and shoot a good powerful plume out of the flue.

Last week I noticed an odd noise - I'm not sure whether to describe it as a buzzing or a squeaking noise, but my gut feeling is that it was to do with the/a fan.

Today, I've noticed that on a couple of occasions the boiler has tried to get up to 'full pelt', but the flow temp went up to about 85deg (usually 80), then the whole thing 'trips' and shuts down for a few minutes, eventually deciding to operate at more of a 'tickover', very quiet, and no significant plume so much as a gradual puff of vapour coming out of the flue.

I can no longer hear the fan unless it is just before it 'trips' the boiler off.

The boiler heats up a 350lt thermal store, and there is a TMV in the return pipe to deliver the return water at 55 deg (though I've never tested this temp with anything). The idea of the system is supposed to be that the store is allowed to cool to about 60deg before triggering a long efficient burn from the boiler to get it back up to 80deg.

My gut tells me that there is a fan in the boiler that has died.

Can anyone confirm this? And is there anything I can do / am allowed to do as a DIYer? I'm quite happy to have a go at changing the fan if it is something I'm permitted to do - but a bit of expert guidance would be a massive help!!!

Alternatively, am I barking up the wrong tree?? Any other thoughts?

 

[ollski]

if its 85 degrees and going nowhere I'd start at the pump.

 

[RWhites]

The pump is fine. It isn't that its 'going nowhere', it just seems that the boiler isnt running at full pelt anymore, and I'm trying to work out why.

 

[ollski]

but if it's reading a flow temp of 85 degrees it won't need to go full pelt as its as hot as it ever needs to get?

 

[RWhites]

but if it's reading a flow temp of 85 degrees it won't need to go full pelt as its as hot as it ever needs to get?

Fair point, but:
- It is taking a lot longer to heat up the store than it did a couple of weeks ago.
- It is a lot quieter (because there is no fan noise).
- I'm assuming there is some kind of internal flow regulator (???) to restrict the flow to produce the 80deg flow temp, rather than the unrestricted flow being heated to exactly 80deg by chance.

I don't know the finer details of how the innards of a boiler work, so I'm making a number of assumptions.... can anyone clarify any of it for me?

 

[RWhites]

The pump is fine. It isn't that its 'going nowhere', it just seems that the boiler isnt running at full pelt anymore, and I'm trying to work out why.

The more I thought about this, the more it was bugging me that all the symptoms seem to point to a pump problem or other flow issues, so I've today:

- Swapped the pump for an identical 'known good' pump.
- Installed an additional bleed vent on the flow pipe in the one spot where I thought there could be a potential build-up of air.
- Double checked all other potential problem points, emptied magnaclean etc.

And the result??
No change.

I'm all out of ideas now.... can anyone help?

 

[picasso]

Perhaps he TMV has failed and the boiler is getting 80c return and shutting down to tickover until the temp drops.

 

[ollski]

what are your actual problems with the heating or hot water delivery?

 

[bolshy]

Time to call a heating engineer - your boiler modulates according to load - it monitors your flow and return temperatures and adjusts its burner rate accordingly. You may have a fan control/combustion problem. And you can't sort this yourself. It could also be a thermistor fault, but I suggest you get a professional in now.

 

[RWhites]

Perhaps he TMV has failed and the boiler is getting 80c return and shutting down to tickover until the temp drops.

I've just checked the pipe temps with a probe on a multimeter. It isn't bang on, but close enough. I'm getting readings of 52deg on the return, and 78deg on the flow. Both temps taken about 300mm along the pipe just above the boiler.

So I guess we can rule that out.

 

[RWhites]

what are your actual problems with the heating or hot water delivery?

I know this is an odd reply, but neither - both heating and hot water are fine for now (I'm hoping the boiler will keep up with the Monday morning rush, but I guess we'll see!)

My problem is that I've noticed that the boiler isn't behaving the same as it used to, and it is taking longer to reheat the thermal store, so I know something is wrong, and it probably isn't working at maximum efficiency either.

 

[RWhites]

Time to call a heating engineer - your boiler modulates according to load - it monitors your flow and return temperatures and adjusts its burner rate accordingly. You may have a fan control/combustion problem. And you can't sort this yourself. It could also be a thermistor fault, but I suggest you get a professional in now.

So not a simple pcb swap? I know there are a lot of knowledgable guys on here, but the only heating engineers I've ever had the pleasure of having in my house have either been:

- Manufacturer's own (Baxi Heat Team) - know the product well, lots of parts in the van, usually fairly quick and efficient, but montorously expensive. (Solved the problem the previous guy couldn't (see below).

- Generic repairman who faffed around for ages, charged me by the 1/4 hr for making my appliance worse than it was before he came, and still charged a fortune.

I've never had the good fortune to land the holy grail of boiler repairmen - someone who knows his stuff, gets on with it, and charges a fair amount for a job well done. (For the record, I'm not saying I don't want to pay, just that I don't want to pay a numpty for making it worse).

Where does one find a decent heating engineer?

 

[RWhites]

Update...
So, I start to think about calling someone in, and now it has just decided to revert to where it was a couple of days ago - making the 'buzzing' fan noise.

Does anyone know if I can do anything useful to alleviate it - like taking off the fan, giving it a squirt of WD40? Or am I wasting my time even attempting it?

 

[hazetimesfive]

wd40 is flammable...

just thought you should know.

 

[RWhites]

wd40 is flammable...

just thought you should know.

3 in 1.... ?