Grommets for central heating boiler

Are you sure they do anything functional other than silence vibrations? Brian

I applied for a maintenance contract, and the engineer who inspected the boiler said it wasn't safe, as it wasn't room-sealed.

However, it's not a boiler he's ever seen before, so he may just have been looking for an excuse to turn it down.

A model number would be a big help.

Generally non-condensing "room sealed" boilers will have a balanced flue, meaning that air for combustion is taken from outside. Grommets around pipes shouldn't affect the "room sealed" status as they will be between the case and the combustion chamber, not between the inside and outside of the combustion chamber.

If it doesn't have a balanced flue then it draws its air from inside the house and whilst "less safe" than a room sealed boiler if it's working properly, isn't "unsafe".

Basically he's probably just telling you to buy a new boiler and not interested in servicing an old one that's probably too reliable for him to make much money out of. ;-)

Tim

It's a Geminox thr 10-50c. It's a modulating condensing boiler.

It's now a balanced flue boiler, but it was originally installed to discharge into the chimney.

Maybe I'm mistaken, but I've always associated the term "balanced flue" with room sealed boilers but without fan assistance. If it's a condensing boiler the exhaust gasses would be way too cool to discharge into a chimney without fan assistance.

Anyhow, even if it hasn't got a fan, to have a balance flue it must be room sealed. Looking at a French manual (which is all I can seem to find on-line) it does seem to have a fan.

Anyhow, all this lends support to my suspicion that the grommets are only there to cut noise and aren't part of the combustion chamber sealing. I think your "engineer" was just trying to scare you into a more lucrative boiler replacement option.

Tim

That is my suspicion too.

Interesting. Never heard of a condensing boiler that wasn't room sealed.

But are you certain those grommets are part of the room sealed bit? That normally only applies to the combustion side.

It's got a sealed combustion chamber, but I spoke to the manufacturers, who said they think it would be better if the case were sealed. It's all a bit vague. As the boiler can be used either balanced flue or taking air from the room, it's designed with that in mind, and the room-sealed-ness is a bit of an after-thought, perhaps to suit the uk market.

Do you really mean "balanced flue" or are you mixing it up with a coaxial or concentric flue?

It's just that a "balanced flue" is un-fanned and uses the energy in the exhaust gases to draw fresh air in. I can't see this working well in a condensing boiler where the exhaust gases are much cooler.

The whole condensing/open-flued/balanced flue combination just seems unlikely to me and doesn't fit with the only pictures I can find on-line of your boiler.

Tim

I'm sorry. I can hear the fan running when it starts up, so I must mean coaxial, not balanced.

And I found the fan on the exploded view:

And it's a condensing boiler?