Need some HVAC guidance (furnace flue venting)

[rbstern]

We're building a ranch over a walk-out basement. The plans call for a mechanical room in the basement, at the front of the house. Contractor figured out late in the game the flue penetration for the furnaces would have to be through the front side roofline if they were located in the mechanical room, because there was no practical way to route the flue to the rear of the roofline. So he asked to install the furnace in a different part of the basement, in a room that is to be my workshop. I relented, too quickly, I realized. The rough in has been done, and the installation looks like crap. Ducts running every which way, not compact at all, intruding not only on my workspace, but also displacing a planned workshop sink that has already been rough-plumbed.

I realize now (without help from the contractor), we could have opted for higher efficiency furnaces that could have been vented out the side of the house. Or, it might be possible to build a soffit in a small section of the basement to conceal a horizontal run (about 10 to 15 feet) to where the pipe then goes vertical to the rear roofline. This in the basement where the flue would run from the mechanical room to the rear roof vertical location will eventually be finished, so concealment is important.

The furnaces are 4 ton and 2 ton, propane fired, Trane brand, mid efficiency (80%?) models, I believe.

Can these furnaces have a horizontal run (sloping up) of about 12', before going vertical to the roof?

EDIT: The vertical portion of the flue is about 20'.

 

[RNeumann]

Each furnace will have very clear flue specs in the installation manual. It will list total runs, max horizontal and max vertical.

The easiest time to “fix” this is now. I’d have them redo the duct work to where you want and, if needed is an HE furnace and run the line out of the wall.
Heck of a lot of compromise for a roof penetration.

 

[Groo]

power vent is probably what you want

 

[rbstern]

The easiest time to “fix” this is now. I’d have them redo the duct work to where you want and, if needed is an HE furnace and run the line out of the wall.
Heck of a lot of compromise for a roof penetration.

Completely agree. If I had known what a clownish install the HVAC vendor would perform, I never would have consented to this change. HVAC supervisor has already been called out to the build site for other issues I haven't bothered to describe here. We've had some excellent subs on this house project (framers, roofers, electricians), but the HVAC vendor's crew turned out to be a total dud. They took a bunch of shortcuts, and a lot of stuff has to be redone. Contractor is dealing with those issues, and awaiting my feedback on what I want to do about the workshop location issues. Trying to do my research so we can get it right. Pissed that the contractor didn't foresee more of this.

 

[rbstern]

power vent is probably what you want

Possibly.

 

[Sigarms]

To answer your question, "probably yes", but always refer to the install manual.

If the furnace isn't installed yet, better yet still in the box, you can return it. Believe me.

You didn't mention if you're on natural gas or propane, but if you're on LP, go with a 95% AFUE or better. If you are on LP, you better be getting a heat pump outdoor unit to "dual fuel" the system so you don't have to run LP everytime you're calling for heat.

 

[Deere Dude]

What a screwed up contractor not to mention HE furnaces ahead of time. 2" PVC in and out the sidewall is the way to go. Try to get it changed back weven if you need to send the units back, if you can. HEs are more expensive though but have a neat installation/

 

[rbstern]

To answer your question, "probably yes", but always refer to the install manual.

If the furnace isn't installed yet, better yet still in the box, you can return it. Believe me.

You didn't mention if you're on natural gas or propane, but if you're on LP, go with a 95% AFUE or better. If you are on LP, you better be getting a heat pump outdoor unit to "dual fuel" the system so you don't have to run LP everytime you're calling for heat.

Propane. Not dual fuel. We'll supplement with fireplace during the couple of months of actual "winter" we have here in GA. We are pretty frugral with dinosaur-fueled heat (use an electric blanket, programming the thermostat for night/away, etc.). We spend more on AC than heat in these parts.

 

[BrokeFarmerJohn]

What a screwed up contractor not to mention HE furnaces ahead of time. 2" PVC in and out the sidewall is the way to go. Try to get it changed back weven if you need to send the units back, if you can. HEs are more expensive though but have a neat installation/

Here in Columbus Ohio, nobody puts 80%ers in a new construction, only place 80%ers go anymore is existing apartment complex/ condos where running PVC is out of the question.

There is both side discharge and above roof concentric kits for forced air flues, the ones that shoot out the side are flat, kinda oval shaped and can match the siding, the roof concentric is kinda large and looks like 4in PVC with a nozzle

I’m curious if they just plan to double wall pipe the flue all the way to the roof? Double wall pipe and fittings are not cheap, more expensive then pvc.

If you plan to stay in the house a long time, I wouldn’t want metal flue, I have replaced enough of old rusty LEAKING incomplete combustion in the house to know it doesn’t last as long as PVC (if PVC is properly glued, it fights you sometimes and doesn’t seal, has to be cut out and re done).

 

[rbstern]

Here in Columbus Ohio, nobody puts 80%ers in a new construction, only place 80%ers go anymore is existing apartment complex/ condos where running PVC is out of the question.

There is both side discharge and above roof concentric kits for forced air flues, the ones that shoot out the side are flat, kinda oval shaped and can match the siding, the roof concentric is kinda large and looks like 4in PVC with a nozzle View attachment 560382View attachment 560383

I’m curious if they just plan to double wall pipe the flue all the way to the roof? Double wall pipe and fittings are not cheap, more expensive then pvc.

If you plan to stay in the house a long time, I wouldn’t want metal flue, I have replaced enough of old rusty LEAKING incomplete combustion in the house to know it doesn’t last as long as PVC (if PVC is properly glued, it fights you sometimes and doesn’t seal, has to be cut out and re done).

I'm guessing it's 80%. Could be higher. I'll research the model numbers.

Regarding metal flues: Maybe the location makes a difference? Last house I bought (new construction) had a metal flue, and it was still in perfect shape when we sold the house after 26 years.