Adding drain in garage for furnace and A/C?

[N969DP]

I want quiet heat in the garage and the Mrs wants A/C when it’s really hot to make more use of the space. That makes me want to install a normal house furnace and A/C for just the garage. There’s not currently a drain I can run the condensate pipes to. What’s the best realistic option?

Drill a small hole through the floor as deep as possible to stuff a pvc pip down and just let the slow trickle of condensation permeate through the sandy ground below?

Mount the whole system in the unconditioned attic where a bathroom roof drain stack vent can be tapped into for condensation. Then box out and insulate around the whole system to make it conditioned space?

Something else I’m not thinking of?

I get a hole drilled in the floor isnt ideal and can slowly erode the fill under the concrete. Along with it not being the cleanest install having the furnace/ductwork mounted at the ceiling out of the way but with a pip coming down to the floor. It would also not be fun to service a furnace installed in the attic with a small room built around it even though there’s enough space and height it could be it’s own legit room.

 

[65ranchero]

Why not route the drain through the side wall to the outside?
What about a mini split?

 

[larry4406]

If you have a roof vent, can you not get access to a drain stack elsewhere?

AC is summer so out the wall it can go without freezing.

Furnace type? 80+ no condensate generated so no winter freezing concern. 90+ furnace you generate condensate while heating.

 

[N969DP]

The house is in Minnesota. Any drain through the wall would freeze unless heat tape or something like it was used to keep it warm. That could he an option but still not ideal

 

[N969DP]

And yes I meant drain stack that vents out the roof. If I put the system in the attic.

If I get A/C I’d want a 90%+ furnace since I’d have to deal with condensate anyway.

 

[Dagny]

I have done many farm shops out the wall. The best is Raychem self regulating heat tape the 6 footer work well. We have been using them for years in walk in freezers on the drain lines.

 

[Jackfre]

A condensing furnace has condensate in the neighborhood of 3.2 pH. While your plan may work, be advised taht it can eat the slab from the bottom up. I think your best bet is a mini-split.

 

[PoorUB]

I know of a contractor that has put high efficiency furnaces in garages with no drains. He takes a piece of 1/2" plumbers copper and flattens the end shut so it forms a nozzle. He sticks it through the wall at a 45 degree angle going up to the outside so about 6-8"is outside. Mount it fairly high up, 5-6 feet or more. Solder on a 45 degree elbow inside and run about 12" of copper down the wall. This is to add heat to the outdoor section. He also insulates the outside portion of the copper. The slope to that inside helps it drain back so it doesn't freeze. He drains the condensate into a better condensate pump like a Little Giant VCMA-20 and pumps it through this nozzle. Pretty sure he said to remove the check valve at the pump in the 3/8" barb fitting so the water drains back. You want the pump pretty close to the nozzle so there is not a a lot of water to run back and refill the tank on the pump. I asked him if he ends up with an iceberg outside and he said you might notice bit more "snow", but it is pretty unnoticeable.

You can not drill a hole in the floor and hope it drains. A high efficiency furnace can produce 10-15 gallons a day. Too much for a haphazard drain.

Your air conditioner condensate can go to a gravity drain just outside along the building beings it will drain only in the summer.

 

[PoorUB]

And yes I meant drain stack that vents out the roof. If I put the system in the attic.

If I get A/C I’d want a 90%+ furnace since I’d have to deal with condensate anyway.

Two different situations as you can drain the AC right out the wall onto the ground.

Also you can not put a high efficiency furnace in an unheated space. It will freeze up at some point and then you have a mess on your hands. I worked in HVAC for years and we put a few furnaces in attics, but the customer had a carpenter come in and build us a small room for the furnace and also install an electric strip heater turned down as low as it will go just to make sure the space has some heat if the furnace fails.

I had one customer that never got a strip heater installed. One winter night when it was -20F and blowing the furnace quit. By the time I got there the furnace room was well below freezing. I ran extension cords up tp the room and ran then all day until the furnace and condensate lines thawed out and the condensate drained. He wasn't happy as he had to heat the house with a few electric heaters all day. He got a strip heater installed right after that! He was lucky as we have had secondary heat exchanges split open from frozen condensate. You need a secondary heat source if you put them in an attic room.

 

[nadogail]

Have your equipment drain into a collection basin and use an automatic pump to move the condensate to a plumbing drain as it accumulates.

 

[PoorUB]

Is this an attached garage?

If yes, is it possible to drain the condensate to the basement, assuming you have one?

I would buy a horizontal hung furnace and mount it against the ceiling in a place that is out of the way and impractical to use for anything else. Installing it in an attic is a pain in the kester.

A minisplit like a Mitsubishi Hyper heat would work too except in extreme cold.

 

[Larrywv]

When I did my 90% couple years ago I put a condensate pump on the side of furnace and pumped it up and around the wall and tied into the sewer vent stack.

 

[finn]

My condensate line runs under the uninsulated slab through a 16’wide unheated and uninsulated enclosed lean to. It’s probably six to twelve inches below the four inch slab.

It froze. The condensate line is pumped from a regular condensate pump / trap.

I have also had sump pump discharge lines freeze solid in suburban Chicago.

I wouldn’t rely on heat strips to keep the line flowing.

If you don’t have a floor drain, the only foolproof solutions are to drill through the slab and out, under the footing, below the frost line, to a French drain, or somehow get access to your sewer line.

That, or abandon the idea of a condensing furnace altogether.

I ended up putting three and a half inches of foam and a false floor over my slab (4’x16’), above the buried drain line to keep my drain from freezing. Seemed to work last winter.

 

[LS6 Tommy]

Just some things to keep in mind, condensing fuel burning appliances must have a neutralizer on the condensate drain line. The condensate drain line must have a trap, regardless of air handler design. If you drain into a vent, the vent receiver must have an air break between the condensate line outlet and the receiver.

Tommy

 

[sixty4]

We used to run them out all the time by increasing the size (we did 2"), never had one freeze yet. Make sure it pitches down to the outside, inside at least a foot in before bushing down to 3/4". If you think about it your exhaust is 2" depending on btu's. Yes neutralizers are great if you plan on hiding with a shrub or bush so it don't die.

 

[finn]

We used to run them out all the time by increasing the size (we did 2"), never had one freeze yet. Make sure it pitches down to the outside, inside at least a foot in before bushing down to 3/4". If you think about it your exhaust is 2" depending on btu's. Yes neutralizers are great if you plan on hiding with a shrub or bush so it don't die.

Freezing of the exhaust line is a common problem in cold, snowy climates..

Probably not an issue in mild climates like Ct, but we have to chip the ice off of the neighbor’s exhaust every January. Yes, the pipe is properly pitched. The ice builds up until the pressure switch shuts off the propane.

Happened to two of my own heaters, a boiler and a forced air furnace. Common problem here, per a couple of hvac technicians

A drain is worse.

Neither would be issues in mild climates.

 

[greenskeeper]

condensate pump

 

[ambenz]

Unless you have a tight sealed garage and 20+ R value on the ceiling and walls, why bother with a 90%+ efficient????
You could probably get away with a ventless wall heater and a window AC unit like I do in my 660 sq feet of 10 foot tall ceiling garage.
For less than $700, you could have what you want without spending $4K or more...your efficiency logic for a garage eludes me.

 

[finn]

Unless you have a tight sealed garage and 20+ R value on the ceiling and walls, why bother with a 90%+ efficient????
You could probably get away with a ventless wall heater and a window AC unit like I do in my 660 sq feet of 10 foot tall ceiling garage.
For less than $700, you could have what you want without spending $4K or more...your efficiency logic for a garage eludes me.

Biggest reason is probably the wide availability of wall hung boilers, when floor space is at a premium, and the simple pvc exhaust piping with a high efficiency boiler.

Otherwise, I also question the suitability of condensing hvac equipment for a shop or outbuilding. They pretty much lock you in to 24/7 heating and all the issues that go with condensate handling and disposal, as well as exhaust icing.

 

[PoorUB]

I have no issue with high efficiency heating equipment for a shop or a garage. Yes it is better to have good insulation, but either way going from 80% to 95% will save you money no matter how well the building is insulated.

 

[N969DP]

After more thought I just bought a 50K btu unit heater and will do a mini split if we decide we still want A/C later. It just wasn’t worth the hassle for drains. As for insulation it’s R19 in exterior walls and door with R50 in the ceiling. Should work good for the 27’x42’ attached garage that will be heated all winter. Hopefully with a “smaller” unit heater it won’t be as loud.

 

[PoorUB]

The 50K heater is more than enough. When you look into a mini split you might look for one that will heat in cold weather so you have options for heat.