Filling gap between flue and hole

[frediaz]

What material is allowed to use in the gap where a flue pipe goes through a brick and block wall? the hole is overzised so mortar is not likely to do it and I want to fill all the gap properly. The flue is from an oil condensing boiler with a twin wall so the outer pipe is just the one that lets the air in.
I was thinking of expanding PU foam, but are there any issues with flammability?

 

[swbjackson]

How oversized is the hole so that mortar won't do it? If it's too large for mortar on its own use some pieces of brick to pack out the hole.

Mike

 

[kirkgas]

expanding foam will do fine, heat shouldn't be a problem as the foam will only be in contact with the outer pipe which is air intake not hot flue gas, however i do remember hearing about someone spraying it onto central heating pipes to seal them going through a wall, the heating was on so the pipes were very hot, when the foam hit the hot pipe it went on fire with enough fire to make him use his fire extinguisher,

 

[gas4you]

I always use fire resistant expanding foam. Bit more expensive but worth the peace of mind

 

[htgeng]

when the foam hit the hot pipe it went on fire with enough fire to make him use his fire extinguisher,

you are saying the hot pipe was the source of ignition?

 

[mogget]

expanding foam.....went on fire with enough fire to make him use his fire extinguisher,

I think the propellant in expanding foam is butane, so it's definitely not a good idea to spray it on anything hot or to smoke whilst using it!

 

[kirkgas]

htgeng, the foam def went on fire immediately it hit the hot pipe, this was confirmed by the supervisor who was with him, gave their pacemakers quite a boost

 

[frediaz]

htgeng, the foam def went on fire immediately it hit the hot pipe, this was confirmed by the supervisor who was with him, gave their pacemakers quite a boost

That pipe must have been at the ignition point temperature of the PU foam, 100deg? 150?

Yes, I remember now there is the fire resistant foam, better to use this one.
Thanks for the feed-back

 

[hect]

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