Gas flue replacing with wood burner flue

[Abi Cott]

A friend at the pub wants to install a multifuel stove in his kitchen. He's had one quote and they have kicked up a stink because there is currently a gas flue liner in there. They are suggesting it can't be removed and talking about adding a smaller bore liner within it. This is pricey (by his standards) and could give a poor draw. The existing liner has capping at top and bottom with 'some' insulation but is not insulated along the full length of the liner.

I know hetas can be buggers. What's the perceived wisdom?

 

[Flyfisher]

I can't answer your specific question but assuming your friend wishes to comply with the relevant regulations (and for a business offering a public service, that would seem to be very sensible due to all manner of potential liability issues!) then the final installation must be certified by a HETAS professional OR the local council building control department. Thus, it's not strictly necessary for a HETAS professional to do the installation and DIY is perfectly acceptable AS LONG AS the work complies with the relevant regulations, in which case the relevant local building control officer should be able to certify.

So, in this particular situation, I would start from the certification requirement and work backwards to find out what is required for the installation to be approved.

A quick search uncovered this info, which suggests that gas flue linings are single-walled and not suitable for multi-fuel stoves: http://www.diydoctor.org.uk/forums/can-you-use-a-flue-fitted-for-a-gas-fire-for-a-woodburner-t23678.html. But that's quite old information and the HETAS regs do change (they changed during the 3-4 years in which we had our stoves installed!) so be careful to check the latest requirements.

If it was me, I'd ask two or three HETAS installers what is required and see if the story is consistent. Otherwise, perhaps contact the local building control people and ask them. Whatever, I'd want to ensure that any work done will meet the HETAS certification requirements. No certificate, no payment!

Another consideration is the size of the stove as different models require different diameter flues. Connecting a small stove flue into a larger chimney flue is OK but not the other way around. Thus, if it is required to re-line the existing gas liner then that may also limit the size of the stove that can be connected.

 

[88v8]

Coal burns hotter than gas, so even if he only intends to burn wood there has to be the presumption that at some point someone might burn coal.
As FF says, gas liners are single skin, no good.

It might be possible to haul the liner out and fit a jacket, but for the cost it's probably not worth the bother. Might as well have a new doubleskin with a full-length jacket.

Dropping a secondary liner inside may be an ingenious skinflint solution, although I'm struggling to imagine how it could be supported at the top.
But don't go below 6". Few stoves have 5" outlets, and most HETAS engineers won't certify a 5" liner for fear that some future ninny will connect a bigger appliance to it.

Ivor

 

[bobby spray]

your friend has been told twaddle. liners are held at the top of the chimney and normally inset into mortar. Removing the liner is simple enough by removing the mortar and pulling through.

 

[Abi Cott]

But don't go below 6". Few stoves have 5" outlets, and most HETAS engineers won't certify a 5" liner for fear that some future ninny will connect a bigger appliance to it.

Ivor

This was what really concerned me about the "pipe within a pipe" option, so thanks for the details on sizing.

I will pass everyone's advice on. Cheers