Vent Furnace Exhaust through shop wall?

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2fs2ns

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Joined
Nov 13, 2012
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Quick background, we're building a house and during the construction phase we're going to be staying in a 36' travel trailer inside an insulated metal building.  I don't want to run the furnace as there is not adequate ventilation to avoid co2 buildup. So electric space heaters become the next best option. However, would it be possible to pipe the exhaust through the building wall?  I could even have a 2nd pipe for the furnace intake.  I'm concerned that it would not seal very well, but if it was a large enough exhaust/intake pipe there shouldn't be any pressure buildup.

Just thinking of ways to keep warm and not kill myself :)

Dan
2005 Fleetwood Prowler
 
Dan,

Talk to any auto or truck shop to see what they use and follow their lead as they have the problem well in hand.  There is a heat resistant hose that is made specifically just for this situation.  Your local atuo store may have it or can order it for you.
 
Dan,
Be very careful! Adding length to the exhaust vent on the furnace will add a pressure drop to the system no matter what size, and may not vent or burn properly. I believe the $/BTU for LP and Electric are very close at this time. Electric heat would be much easier. 
 
If you have sufficient electric available, use that.  You may be able to rig an exhaust & intake hose to the RV furnace, but getting an adequate seal on the RV end seems problematic and the risk that the operation of the furnace would be affected is more than slight.  For some reason RV furnaces are EXTREMELY sensitive to having a unobstructed path for air intake and exhaust! It doesn't take much to throw the air/fuel mixture out of whack, leading to (at best) non-ignition or (at worst) CO and fumes inside the RV.
 
I just had some problems at my house worked on and learned some things that may apply for you.  The biggest probelm with exhausting seems to be that the flue gas must stay warm until it is near the outlet.  If you run it through a cool building to get to the building walls, it will cool off enough that is will not vent properly.  I was told you need to keep the size of the pipe small and to line it or use a lined pipe to keep it cool until it is outside.  What you are suggesting seems like it could work but it might be wise to involve somebody in the business, to make sure you size the pipe correctly and set it up properly.  And if the electric costs about the same, and does as well, that certainly eliminates all these concerns I was faced with.  I have a furnace that heats my whole house and it is rated for a 4" to 5" pipe according to my contractor.  I have a 50,000 BTU furnace in my wood shop and it is rated for 3".  Don't oversize, at least on the inner pipe.  You can run that inside a larger pipe to keep it warm but too large is surprisingly a problem with air flow and venting.
 
I too would recommend using electric heat. DO NOT neglect the wet bays. Or use the "Cheap Heat" system (Which adds electric to your furnace) and disconnect the gas solenoid on the furnace to insure it does not come on.

However,,, If you were to extend with fairly large exhaust hose I do not think there should be much of a problem.. Or, (Alt route)

Do the "Gen-turi" think  In this case run oh, about a 4" PVC up through the roof and use a sweep elbow to inject the furnace exhaust just above the bottom center of the pipe.  TEST by holding a leaf or piece of paper at the bottom of the PVC when the furnace is in "Blower start up" mode.  Theory has it said paper should exit the roof.
 
2fs2ns said:
Quick background, we're building a house and during the construction phase we're going to be staying in a 36' travel trailer inside an insulated metal building.

Easiest thing may be to heat the building

I don't want to run the furnace as there is not adequate ventilation to avoid co2 buildup. So electric space heaters become the next best option. However, would it be possible to pipe the exhaust through the building wall?  I could even have a 2nd pipe for the furnace intake.  I'm concerned that it would not seal very well, but if it was a large enough exhaust/intake pipe there shouldn't be any pressure buildup.

Just thinking of ways to keep warm and not kill myself :)

I guess I wouldn't try that.  The better answer would be to ensure that there's enough ventilation by leaving doors open or running vent blowers in the building so that there would be no buildup of combustion products.

 
Hi Dan,

What did you end up doing with your exhaust? And would you do it again?

RBL
 
RBL66 said:
Hi Dan,

What did you end up doing with your exhaust? And would you do it again?

RBL

Don't expect a reply. The last time he was here was on November 2012 when he registered and ask the original question and hasn't been back since.
 
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