Glowworm HXi noise at starting

[matgriff]

Hi

I have a CH system in our house (10 yrs old from new) 18 rads, fully balanced, Grundfoss 15/60 pump set on speed 3, open vented.

System is spotlessly clean inside, has been flushed twice & drained in past ten yrs, always treated with fernox.

Rads were balanced a couple of yrs ago, I also confimed the temp differential accross the flow/return of the boiler is 20C at max modulation. I had the CO2 checked by my central heating fitter buddy, we replaced the burner gaskets with graphite ones and everything was spot on, clean as a whistle inside & the condensate trap is also clean n leak free.

Basically the system works fine, I set the boiler temp at around 68C and I checked the return temp to ensure it's running in condensate mode when the CH's on and it is.

The only problem I have, is that sometimes when the boiler fires up, on demand from either the HW or CH it makes a kind of shuddering noise for about 2-3 seconds which is quite loud, after that it seems to be fine, runs quietly & modulates correctly.

Any ideas ???

Thx

 

[gazdaz36]

Possibly due to the gas valve struggling to open up so when it goes through the ignition and lights up the mixtures are wrong causing the noise. Then after it's opened fully it works normally. It's difficult to be 100% sure due to the fact that combustion readings will always be funny during the ignition sequence giving high co readings until it runs for a few mins and settles down

 

[matgriff]

Thx for the reply...

I've listened to it a bit more, and it sounds quite like something's not quite right with the ignition sequence, the noise is more like a loud whooshing noise that lasts for a second or so as it fires up.

If I could describe the sound, its a bit like when you try to light the gas cooker or BBQ and the gas doesn't ignite immediately, so builds up a little bit then as it ignites it goes with a bit of a surge until it burns off the excess.

 

[Agile]

So I suppose that you have never bothered to get the boiler serviced?

Tony

 

[matgriff]

Why would you assume I've never "bothered" to get it serviced ??

Yes it has been serviced.... that's when we replaced the heat exchanger seals with new graphite ones & checked the Co2 levels and cleaned out the condensate trap etc.

This problem did not exist then, it's started recently

Thx

 

[hazetimesfive]

did we? i dont recall

 

[matgriff]

If anyone has any sensible suggestions, I'd be glad to hear them.


If you're just bored & like typing...please don't bother

 

[David937]

With your symptoms pointing towards a combustion issue, it's out of scope for DIY. Best to get an RGI in to have a look

 

[Agile]

How long ago was it serviced?

A proper service involves measuring the combustion products and adjusting to within the makers spec.

Your problem sounds like a combustion issue and as such we don't give advice on them here.

The obvious solution is to call a competent boiler engineer with an FGA.

Tony

 

[matgriff]

It was serviced last year... the combustion was checked at that time and adjusted correctly (after a new set of heat exchanger gaskets were fitted.... as stated in my original post. In fact after the new gaskets were fitted it only needed a tiny trim to get it within spec.

My next door neighbour (and friend) is a heating engineer, he'll sort it for me , he's just flat out busy at the moment, so I thought I'd ask to get a heads upon the problem first.


Mat

 

[hazetimesfive]

i wonder if he is your friend too