Garage Heat

[furb]

So I got the wood stove notice from homeowners three years ago. No solid fuel stoves in garages. I ended up getting a 10000 watt 34k btu electric heater. It’s okay but I wanted something more efficient and with air conditioning. I put a Friedrich 24k mini split in. It’s the new 454 refrigerant model if that makes a difference. Some first impressions… The duraheat drew about 40 amps on high. In three hours I could bring the temp up about 15 degrees. This varied by it was a good rule of thumb so I could time when to turn it on vs when I was going to go out. The new unit took nine hours to raise the temperature 16 degrees with the help of the the duraheat on low. The mini split runs about 12 amps. The mini split does push the heat around more so it probably isn’t the best comparison. To summarize if you want quick heat and don’t want to run heat 24/7 a heat pump isn’t the solution I hoped for. I’ll be keeping the duraheat hooked up. It has a freeze protection mode that maintains between 40 and 46. It had the garage at 35 in that mode. I need to go out with a thermal imaging camera and see if it is 40 by the temp sensor or if there is an issue with it.

 

[stretch5881]

A lot of info about the heaters, but no info about the garage construction.

 

[furb]

A lot of info about the heaters, but no info about the garage construction.

28x36x10 pole barn 2” foil faced foam walls and ceiling, insulated man door, insulated overhead door.

 

[Joe Kidd]

Hard to say what the load would be not knowing your outdoor temps, but I'd go with 400sq ft per ton for that structure and you're at 30k btu's minimum. You may be a little undersized with 24k and R13 R-value. Did you get someone to do a load cal?

 

[Hoser]

Heat pumps are designed around a tight building envelope and maintaining a constant temperature (usually 65F minimum room temp) They don’t do well with large temp swings, plus some runtime is lost to the unit going into defrost.
I’ve had to go to calls for them being put in shops before with the same complaint and it’s usually just undersized, the odd time out of gas or too many non condensables in the system on install.

 

[furb]

Hard to say what the load would be not knowing your outdoor temps, but I'd go with 400sq ft per ton for that structure and you're at 30k btu's minimum. You may be a little undersized with 24k and R13 R-value. Did you get someone to do a load cal?

Around 30 today. He did the load calculation and thought we might be a bit oversized.

 

[furb]

Heat pumps are designed around a tight building envelope and maintaining a constant temperature (usually 65F minimum room temp) They don’t do well with large temp swings, plus some runtime is lost to the unit going into defrost.
I’ve had to go to calls for them being put in shops before with the same complaint and it’s usually just undersized, the odd time out of gas or too many non condensables in the system on install.

So I should keep it at 65 instead of 61. It is going into defrost. I noticed it more this morning. It’s a lot of cold junk to heat in the garage to get up to temp.

 

[Hoser]

If you’re keeping it at 65 /61 all the time yes but 61’s usually close enough. If you’re just turning it to 65 when you go into the shop it won’t catch up any faster.
Thermostats aren’t gas pedals.
Remember heat load calcs are done around a design temperature (what you’d like the building to be maintained at).
not Saturday it’s 36 in the shop so you turn the heat on to 61, go inside have a coffee and come back to a 61 degree shop.

 

[furb]

If you’re keeping it at 65 /61 all the time yes but 61’s usually close enough. If you’re just turning it to 65 when you go into the shop it won’t catch up any faster.
Thermostats aren’t gas pedals.
Remember heat load calcs are done around a design temperature (what you’d like the building to be maintained at).
not Saturday it’s 36 in the shop so you turn the heat on to 61, go inside have a coffee and come back to a 61 degree shop.

I meant as far as efficiency. I didn’t know if it’s better to try to maintain 65 vs 61. When we did the load calculation I told him it’ll probably never be over 65 in there. My house is set to 65. I’m out all day so 70 degrees is hot to me.

 

[Hoser]

It’s more for unit longevity than efficiency. Outdoor temperature dictates efficiency on an air to air heat pump

 

[stretch5881]

A lot of good info.
For a shop, we have always oversized for heat. Welding, grinding, painting, testing small engines, ect. Doors and windows get opened to clear the air or let fresh air through. An oversized furnace would catch up quick.
If we were doing sheet metal work, we needed to keep the metal as stable as possible.
I had my house load tested when installing a new furnace, but not my garage. Didn't make sense, too many doors opening and closing.

 

[Hoser]

Exactly this above. If a garage/ shop looks like a 40k load I’m fine with putting in an 80k unit heater or better yet a tube heater.
They usually won’t have short cycling issues from all the objects that are cold, and the large temp swing/ air exchanges.

 

[Bill G]

I am just amazed at who is telling you that you cannot heat with wood.

 

[Dustin4185]

Exactly this above. If a garage/ shop looks like a 40k load I’m fine with putting in an 80k unit heater or better yet a tube heater.
They usually won’t have short cycling issues from all the objects that are cold, and the large temp swing/ air exchanges.

We have a 30x60x12 shop with unknown insulation. We had the forced air LP heaters from the 1980’s but they quit working years ago. We are debating going back with new versions of them or a tube heater. We have a wood furnace but I would like something to keep it above 35-40 overnight when we aren’t there. Any suggestions?

 

[Dustin4185]

I am just amazed at who is telling you that you cannot heat with wood.

Homeowners insurance probably.

 

[Bill G]

Homeowners insurance probably.

Find a new company or sign a rider.

 

[Hoser]

If it’s 1980’s unit heaters look into fixing them if someone hasn’t, get on a ladder at the front of the unit, inspect the heat exchangers for cracks.
They’re simple tech with generic parts so the bill to repair them isn’t bad.
I have a preference for tube heaters because 1.-they’re a radiant heat
2.-the heads can be removed and cleaned easily if it’s a dusty/ dirty environment
3.-they’re usually cheaper to install/ repair then unit heaters
And at 12’ ceiling it should be enough headroom, you just can’t park something 10’ high underneath it.
But both do the job well, I work in a lot of auto shops, body shops and machine shops so I’ve seen enough of them.

 

[Bill G]

Around 35 years ago Dad was building a new shop. It was to have 16 ft ceilings, steel lined, and insulated. I wanted him to put in floor radiant hot water heat. He did not want that and went with a ceiling mounted radiant tube. I thought he was crazy but by gosh it provided some really good heat.

 

[Joe Kidd]

Unit heaters are still popular, we sell a chit load of 'em.

 

[furb]

Find a new company or sign a rider.

It’s the homeowners insurance. Any good insurance company around says no solid fuel source in accessory structures. I have an oil tank and wood stove in my basement that is a drive in basement so sometimes there is also a vehicle in there. No problem. They never inspected the stove, oil tank, boiler, anything. As far as they know it’s still the old fisher and an oil tank from 1979. The chimney on the garage gave it away and they said they could possibly come back and check. My options are Erie or State Farm if I want something with a local agent.