90% Gas Furnace Installation in Unconditioned Attic

[montoy]

Can you install a 90% Gas Furnace in an unconditioned attic? We are a Mechanical Contractor and plan to install a 90% Gas Furnace in the attic for a Townhouse project. My questions are:
1. Freezing an issue? condensation from the furnace.
2. Would there will be a Gas Furnace performance issue?
3. What are our alternatives? 80% Gas Furnace? Install the 90% Gas Furnace in conditioned space? Ductless mini split?
Please advise. Thank you in advance.

 

[willard3]

What is the climate where this project is located?

 

[msquared48]

Aside from the obvious heat issues, I would be very worried about vibrations being transmitted throughout the structure. This can be very annoying.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[GMcD]

The Local Building Codes will also have a lot to say about this. In my area, gas-fired appliances sometimes need to be in a separate fire-rated room/enclosure, especially in a wood-framed structure. Even if the local Codes allow it, it's still a bad idea to put the furnace in an unconditioned space, where maintenance access is difficult.

 

[cdxx139]

Check the manufacturer's recommendation. Is it condensing? Would that have a chance of freezing?

knowledge is power

 

[montoy]

The project is located in new jersey.

 

[KiwiMace]

You could insulate the vent pipe, but the trap will still freeze. Perhaps build up an insulated and appropriately fire rated closet for the whole furnace. Passive ventilate and self heat with small grille.
I agree with maintaining accessibility per comments above.

 

[willard3]

Given that this is in a cold climate, I wouldn't mount it in the attic for safety and maintenance issues.

 

[cry22]

Insulate and heat trace you condensate line, 5 Watts per linear foot of pipe should do you.

 

[berkshire]

Is this a condensing furnace with the exhaust and intake contained in a double walled plastic pipe?
I do not know about other manufacturers, but Carrier has some very specific recommendations for this type of installation.
B.E.

 

[carlosgw]

I am putting a furnace in an unconditioned space in the north contry of NY. I thought the manufacturer (Carrier and a couple others)would not allow it but all I found was an option for heat trace on the cond. trap.

 

[roberthvacpro]

All duct-work will have to be insulated and sealed. Filter access will have to be on the return grills. You will also have to heat your condensate trap and drain lines.

http://pdf.directindustry.com/pdf/o...s-with-integrated-thermostat/12323-60280.html

Check the installation manual for any other requirements for installing in unconditioned spaces.

 

[dbarry14]

You can heat trace your condensate trap, or run the drain below the attic into a plenum space above a ceiling (if available). Locate the trap in this plenum space.