[MKG]

Hi All,

I've noticed that on my furnace (and other furnaces) that the PVC pipe coming from outside for combustion air to the furnace is not insulated. A quick look at my psychrometric chart and it would appear that an uninsulated pipe carrying cold air (less than 0F where I live) through a conditioned space would quickly cause condensation on the outside of the pipe. However, I've never observed this happening and no one else seems worried about it because I don't usually see these pipes insulated. What am I missing? Is PVC a good insulator or something?

Thanks!

 

[syndicated]

PVC is a good insulator!
Also warming the combustion air will increase the furnace's efficiency slightly.



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[jrbenny]

You need at least 20' of pipe for it to become an issue.

 

[James Colver]

PVC is a great insulator so I've never seen that cause a sweating problem. I wish more people around here would insulate the condensation drain line and the discharge hose for the pump. I've seen many freeze.

 

[thomasmices34]

That is a really good idea. But i am worried about how long it will last and how effective it is?

 

[dougfamous]

PVC is a great insulator so I've never seen that cause a sweating problem. I wish more people around here would insulate the condensation drain line and the discharge hose for the pump. I've seen many freeze.

This must be a region-specific issue because in 24 years I've never seen a condensate drain even sweat.

I've also never seen an intake pipe in PVC sweat.

 

[LKJoel]

This must be a region-specific issue because in 24 years I've never seen a condensate drain even sweat.

I think he was concerned about freezing not sweating.

 

[kdean1]

At 0*F there is very little moisture in the incoming air. Certainly not enough to be a potential freezing problem.
The only time I have seen a freezing problem is when the exhaust pipe is not positioned properly to disperse the gases when they exit. The vapor has occasionally frozen on the inlet of the combustion air pipe.

 

[timebuilder]

I think the concern was condensation of the indoor air moisture onto the outside of the pipe being cooled by the incoming outside air.

Good thought, but most likely not an issue.