Noisy Glow Worm

[Dr Spock]

Hi

I have a GW 18hxi, installed in a conventional open system in my 3 bedroom house. The boiler is in what used to be the garage, with the flue going vertical through the flat roof, with termination kit. It's been fitted about a year.

The boiler emits what can only be described as a howl from the flue on initial fire-up from cold, lasting a few seconds. It can be heard all over the house, and even 2 doors down the road ! Once running, all seems OK.

The engineer thought it might be high gas pressure, and he has checked that, but it's nigh-on the 8" WG recommended. He's now at a bit of a loss.

The flue is well fixed, and I've even tried to hold it when it starts up, as I thought it might be a resonance of some sort. Didn't make any difference.

Has anybody had a similar experience ?

 

[EliteHeat]

Wouldn't a howling noise point to the fan?

 

[Dr Spock]

Yes. it sounds like an air movement problem. Could the fan be coming on too fast or too soon, before the combustion is properly underway ? What could cause this ?

 

[gas4you]

I assume Elite meant the fan bearings

 

[Rob]

Incorrect mixture?

 

[Dr Spock]

Thanks for the suggestions. It doesn't sound like bearings, and why would the noise disappear after a few seconds ?

The mixture settings I assume are factory set. There's no mention of any adjustment in the Installation info.

 

[gas4you]

As this is a discontinued Vaillant Ecomax Pro there should be an adjustment to set the gas mixture (co2) content.

 

[Agile]

The mixture settings I assume are factory set. There's no mention of any adjustment in the Installation info.

You may assume things but part of the commissioning process is to check the CO² percentage with a flue gas analyser.

Did the CORGI installer complete the Benchmark Certificate or was it a cowboy installation?

Tony

 

[Dr Spock]

You were correct about probably being to do with the mixture. I sent the GW Tech Dept an email, and received the following response:

" The problem you have is fairly common with these type of appliances. I
think you have an issue with your gas/air mixture which is slightly out,
resulting in a noise on firing.

It is very easy to rectify. The engineer needs to get his flue gas
analyzer on the appliance and carry out a check on the CO2 % level while
the appliance is locked at both a high and low rate of ignition. This is
all specified in the installation manual in the servicing section.

Reasons for this problem other that the mixture being slightly out could
be low inlet gas pressure to the appliance, or a restriction on the air
inlet side of the flue, but in most cases, once the engineer has
analyzed the products, and made adjustments on the gas valve as
necessary, the noise will go away. "

Full marks to GW for a prompt and reasoned response, and thanks to you guys for your comments and pointers.