High efficiency unit heater

[Max93]

Has anyone installed a high efficiency unit heater in their garage? I was planning on installing a Modine or Reznor gas heater and came across some high efficiency units. They are more expensive, but I like the idea of being able to vent with pvc and lower gas use. Are they reliable? Any reason I should not use one? Any input is appreciated. The garage is 24x40 and will be well insulated if that matters.

 

[Bert_]

Would need to heat the garage full time. Condensate will freeze.

 

[Max93]

It would be kept at 50* but turned up when I go out to work on something.

 

[TurnipTruck]

I have done several boilers, but this is my first furnace.

I found an installed-but-never-used generic 80kbtu 95% efficient furnace ($600!) and it keeps my 40x60 at 55 (50* nighttime setback), including the four rooms in the back. It makes almost 4 gallons of water overnight when it’s -22*F.

Here it’s installed in the ceiling of my tool room.

 

[PoorUB]

I question the savings versus the cost. The high efficiency Modine is roughly twice the price. It costs me somewhere around $50 average a month to heat the garage with natural gas, so maybe $250 a season. Roughly 10% savings in fuel so $25 a year. If I pay and extra $800 for the heater it will take 32 years to break even.

If it was $100 a month it would take 16 years.


Also, do you have somewhere to deal with condensate? The produce condensate like a high efficancy furnace, also you should install a neutralizer on the condensate drain.

 

[American Locomotive]

Looks like its about a $600-800 premium for the high efficiency units. That's really not too bad, and would likely pay for itself pretty quickly if you use propane. You would save on install costs by not needing a chimney or any fancy flue pipe, so the cost differential may be even lower.

 

[Sumboodie]

I have done several boilers, but this is my first furnace.

I found an installed-but-never-used generic 80kbtu 95% efficient furnace ($600!) and it keeps my 40x60 at 55 (50* nighttime setback), including the four rooms in the back. It makes almost 4 gallons of water overnight when it’s -22*F.

Here it’s installed in the ceiling of my tool room.

I was surprised how much water my combi makes. The drain pipe somehow got cracked and started leaking.

I put a 5 gal pail till I could get parts and it almost overflowed it overnight.

 

[jblnut]

To be both specific and vague at the same time I like to look at the amount of condensate produced as "roughly" 1gal of LP used. When I ran my boiler in the farm shop last year it'd produce around 20gal of condensate a day when it was windy and -20f. After a week of that last year I looked at the tank and it had used roughly 25% or 125gal in 7 days. So almost a 1 to 1 ratio. I think it is officially around 0.01gal of condensate per 1,000btus of heat so do your math accordingly. My boiler filled my 750gal holding tank over winter and I had to pump it a lot sooner than I expected. 10-20gal a day were dripping in there.

 

[HoosierBuddy]

I installed 3 of the Modine Effinity93 at work. No issues so far. The oldest was installed about 10 years ago.

 

[greatreset]

I also installed a Modine Effinity93 in my garage it’s been 6 years and no problems.

 

[Max93]

If I can come up with a good way to deal with the condensate, I think I will go with an Effinity. Any recommendations on what size? 55k or 65k btu?

 

[TurnipTruck]

I had a 24x52 with a 75kbtu, and it was more than adequate in Alaska; we don’t know where you are.

 

[Max93]

I am in Wisconsin

 

[PoorUB]

If I can come up with a good way to deal with the condensate, I think I will go with an Effinity. Any recommendations on what size? 55k or 65k btu?

Assuming reasonable insulation the 55K BTU is plenty, more than enough.

Well insulated, 30K is enough!

 

[HoosierBuddy]

Regarding condensate, in 2/3 of our installations we were able to gravity drain the condensate, but in one we had to buy a condensate pump.

Like this one: https://www.amazon.com/dp/B00BYFQQ8U/?tag=atomicindus08-20

No issues with that either. It will need to go to a drain or sewer line. You can't just run it outside, because it will freeze in the winter if you do.

 

[Max93]

That’s my biggest hold up, there is no drain to run it to. It would have to go outside. I did find a post regarding using a pump to spray it outside. Or I would need to rig up a holding tank in case if freezing.

 

[PoorUB]

That’s my biggest hold up, there is no drain to run it to. It would have to go outside. I did find a post regarding using a pump to spray it outside. Or I would need to rig up a holding tank in case if freezing.

I probably posted about spraying it outside.

Keep in mind it might produce a lot of condensate, 50 gallons a week would not surprise me. So a holding tank? How are you going to deal with that much condensate if you collect it? You could unroll a garden hose once a week and pump it on the lawn, but that is a lot of hassle.
Either spray it outside, run it to a drain or go 80%. IMO, you probably will not see a huge difference in costs.

I put an 80% in my shop simply because of the condensate. Also keep in mind the Modine 93% wants to be run all the time. You will not be shutting off the heat when you are not out there, letting the shop freeze down and turning the heat back on Saturday morning. You need to heat the building all the time or the condensate drain will freeze plus there is potential to freeze the heat exchanger and damage it.

 

[Max93]

I meant a holding tank only incase of the drain line freezing. Like an overflow tank.

 

[HoosierBuddy]

I meant a holding tank only incase of the drain line freezing. Like an overflow tank.

That would work. You'd need to plan on 1.15 gallons of condensate per 100,000 BTU's of gas. So...50,000 BTU heater running 50% of the time would be 6.9 gallons per day.