Condensing boiler flue temperature?

Assuming this is a concentric flue, then the outside case temperature should be very low on a condenser - in fact even the inner pipe should not be much above 60 deg C.

Thanks John - thats what I wanted to hear! Its not hot now, but then I havent turned the central heating on yet

Anna

Typically you'll find that the boiler is only running at full whack when reheating the HW cylinder or producing HW if it's a combi.

For heating, it will normally be running at a much lower level because it modulates down.

I believe that there is a requirement that boilers should be mounted on a non combustible surface, but there are separate requirements for any enclosure around it - e.g. compartment ventilation in a kitchen cupboard (or not). However, usually that's about access for service.

I suppose the only other thing is that the boiler in general will radiate/convect a couple of kW anyway and whether that would be deleterious to your hessian?

Different boilers have different requirements as to ventilation boxing etc. As your boiler is new you should have been left the manufactures installation instructions by the installer. You should find the information regarding your particular boiler there.