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big1bird
Nov 26, 2006, 07:29 PM
I'm wondering what options I have for outside supply and discharge? The appliance is a high efficiency York NG furnace (small, less than 60K BTU.).

The installation manual shows what could just be PVC elbows. I'm wondering if there are other options.

The furnace is intended as backup heat, with the primary heat being a ground source heatpump (just spent the last 10 weeks trenching in the wells, and installing.). So it will be used only intermittently, and is intended for use in the winter when there are extended power outages.
(Mentioning this in case it influences any choices.)

Any pointers?

Thanks.

NorthernHeat
Nov 27, 2006, 04:03 PM
Why not PVC? Just don't use the lighter, cheaper, foam core pipe.

big1bird
Nov 27, 2006, 04:15 PM
PVC is fine for getting there... I'm wondering if I leave exposed pipe or if there are fixtures which can be mounted on the side of the house.

If I use just PVC pipes, I'd probably put screens over them. The animals here will pack any opening with seeds and nuts, and nothing would work when needed.

NorthernHeat
Nov 27, 2006, 04:22 PM
Putting a screen on the exhaust will cause the condensation to freeze the opening closed. It should only be a 2" pipe right? Trane makes a very nice termination kit for 90+ furnaces.

labman
Nov 27, 2006, 04:26 PM
Besides being cheap and easy to work with, PVC naturally burns very poorly, and can be formulated to be even more fire resistant. The base PVC resin has enough chlorine in it to not burn well, and nearly always is compounded with ground limestone further reducing its burning. Heated hot enough, the limestone gives off the same carbon dioxide found in some fire extinguishers.

Vinyl may not burn, but it does give off toxic fumes.

big1bird
Nov 30, 2006, 08:53 PM
I'm not real worried about the PVC burning, but I am worried about the termination. I'll look again for the Trane kit, thanks.

By screen over the PVC, I'm thinking 1/4" rat wire. I agree that anything finer would freeze. Perhaps 1/4" will freeze.

BTW, mentioned this before, but the 90+ furnace is intended primarily as backup for powerfailures. A radical shift in utility pricing could change that.

Any other termination ideas?