Unit heater vs. furnace

[Netman]

Came across this forum while searching shop related stuff. I am ready to supply heat to my shop and had a few questions that might sway me one way or the other. My shop is approx. 30' x 40' with a ceiling height of about 9'8". For the most part it will be used for woodwork but I have allowed one bay as the section for the mid life crisis car. I have narrowed it to either a unit heater such as the Reznor 65k btu or a regular residential furnace mounted on the ceiling.

With the furnace I have the option to run ducting along the wall but cannot with the unit heater. This is where I am undecided. For those that have one or the other or used both at sometime in the past, which were you happier with? Being a woodwork shop as the most usage, is one safer than the other? I will obviously have dust control but one can never eliminate it 100%. Is the unit heater going to supply enough heat to the far end of the shop which is 40' away or is the option of ducting a viable one? The shop is well insulated but I am in northern British Columbia and the weather can get a bit chilly at times. I would keep the heat above zero to keep things from freezing up but would like to come home after work and not have to wait an hour for the shop to get warm enough to do some work.

Any input would be greatly appreciated. Thanks.

 

[burnedzr2]

My shop is the same and I have used a unit heater for a few years and I have saw dust collector in another room and never had a problem. I have the heater at a 45 degree angle in a corner it blows across the room and into the wall across then down. I have the thermostat at the far end of the shop and a small fan that helps move it to the far corner. After the heat has been on for a couple of hours the whole shop is fine.

 

[James-W]

I have a 24 X 36 garage/shop with 8 ft ceilings. I am using a Hot Dawg 60,000 BTU heater mounted on the ceiling in one corner and angled at the opposite corner. Heats the building very nicely and I have not noticed any "cold spots" anywhere, although I am sure if you put a whole bunch of thermometers all around the garage you would no doubt see a couple degrees of difference in different areas. But you do not notice it while working on a project, at least I haven't noticed it.

 

[nadogail]

Decisions, Decisions, and More Decisions

Scratch you head, or something else, and debate the costs versus the benefits.

I have ordered an Electric Garage Heater for my two car garage workshop.

Pluses: Our San Diego climate is moderate, I once scraped frost from my windshield maybe 10 years ago.
I will only be working in the shop for a few hours at a time, during daytime, and maybe three or four days in a busy week.
We have solar electric panels on the roof.
Electric heat will be much easier to install. One circuit as opposed to gas and vent pipes.
Small size, the heater is about as big as a breadbox, not as big as a refrigerator.
Hanging the heater from the bottom chord of the roof trusses takes less room than a furnace and ducting.

But your considerations will most certainly be different from mine, so try to pick what will work best for you and where you are.

 

[dave*99]

I think you will be fine with a unit heating mounted in a corner at a 45 degree angle.

You could consider 2 unit heaters of smaller size if you want to distribute the heat better, but in an open shop with no partition walls it would probably not be worth the extra expense.

 

[Showkey]

I think the real advantages of the furnace is 96% efficient, outside air for combustion, filter system available for the cold air return, and easy venting with PVC.
If my shop heater goes bad ( likely from rust) I will replace with a home style furnace.

 

[finn]

I think the real advantages of the furnace is 96% efficient, outside air for combustion, filter system available for the cold air return, and easy venting with PVC.
If my shop heater goes bad ( likely from rust) I will replace with a home style furnace.

Only problem with the 96% furnace is that it commits you to heating 24/7 to avoid freezing the condensate.

 

[ambenz]

I don't know where you live, but around these parts, natural gas has been relatively inexpensive.
I heat my 22x30x10 garage, 24/7, with a ventless furnace... which costed less than $200 US
With a box fan, I keep the space 55F during the winter. It's been pretty cost effective.

 

[k-os]

I don't know where you live, but around these parts, natural gas has been relatively inexpensive.
I heat my 22x30x10 garage, 24/7, with a ventless furnace... which costed less than $200 US
With a box fan, I keep the space 55F during the winter. It's been pretty cost effective.

I have a similar size space in almost the same climate that I plan on switching from my current oil furnace to using a Natural Gas heater. Is that $200 for the whole year?

 

[Showkey]

Only problem with the 96% furnace is that it commits you to heating 24/7 to avoid freezing the condensate.

Agree..........with a wood working shop and the crisis car storage.........continuous climate control would be important if not critical.

In my case I keep the shop at a minimum 40-50* depending on the current projects.

 

[finn]

I don't know where you live, but around these parts, natural gas has been relatively inexpensive.
I heat my 22x30x10 garage, 24/7, with a ventless furnace... which costed less than $200 US
With a box fan, I keep the space 55F during the winter. It's been pretty cost effective.

I lived in and around Naperville for 30 years, but now I'm 440 miles north.

So far this year I've burned 30 gallons of propane (hanging heater) and 105 gallons on heating oil (radiant in-floor) keeping a ~32'X75'X16' work area and 16'X16'X8' bathroom & office heated to a nominal 42 degrees.

The propane is kicked in (to about 55-65 degrees) when I am working. The nearest NG pipeline is 5 miles from my building.

It's been an exceptionally warm winter, though.

Last year was exceptionally cold (and the boiler was dirty) and I burned somewhere around 600-650 (didn't write it down and I have CRS) gallons of fuel oil. I installed the hanging heater this fall (75K)

The heating people here don't recommend high efficiency condensing equipment for a shop unless you are absolutely positively committed to heating 24/7 because of the freezing issue in the event you want to shut down the building for some reason (like going south for the winter).

 

[Netman]

Thanks for the input. There are good and bad points for both so that creates the dilemma. While the furnace has ducting capabilities if I was to decide I needed them, it is quite a bulky looking unit with the plenum etc. It is more efficient but is that really necessary for a shop that is not a living quarters (yet that is). I like the compact look of a unit heater and that was my second choice behind a radiant heater which I decided against because of the lower ceiling. My only concern was the ability for it to heat the entire area without having cold zones. The Reznor heater seems to have a good following and available where I'm located. If I go with the unit heater, am I better off with 60 or 70k BTU's for that area? As a side note it is suppose to drop to a balmy -20 this weekend. Thanks again for the above info.

 

[Showkey]

The heating people here don't recommend high efficiency condensing equipment for a shop unless you are absolutely positively committed to heating 24/7 because of the freezing issue in the event you want to shut down the building for some reason (like going south for the winter).

If your heating the building on and off as the norm condensate would be a hassle.

If you need to shut the hi eff heating system down in freezing location .......it is a simple fix to empty the condensate drain trap. Would take less than 5 minutes.
If you need to install a 96% in freezing location there is a low temp drain kit to stop the condensate from freezing.

For a 20% saving in fuel cost the extra step is worth the "hassle" if the heat is on as the norm.

 

[GYPSY400]

I have a 45k btu Reznor in a 24x36.. with a programmable thermostat its very comfortable. . I keep it about 10 during the day, and about 16-17 when im working in there.

Sent from my SGH-I747M using Tapatalk

 

[jeepinerdeep]

Good topic. Subbed.

 

[ltusler]

I think the furnace route is better, they are quieter than the unit heaters.

 

[cos]

Hello Biggest problem with condensing furnaces is return air temps must be 60-80 degrees. So keeping shop at 50 degrees when not in use could be a problem. Been thinking how to get around this. Maybe returning some heated air into cold air return with temp controlled damper until return temps are up. Ducted systems are less noise, better coverage (two level shop), more efficient unit. simply to vent. Assuming you keep building at 45-50 degrees all the time.

 

[Showkey]

*^^^^^^^^^
Please provide more info on the return air temp requirements..........my Goodman makes no mention of this ???

I have read that some shop heaters should not be set lower than 50* and 40* set temp causes rust ?????? Not sure if it's fact or garage legend ??????

 

[Netman]

I would keep it above freezing when not in use so glues and finishes won't freeze up. Days off and evenings it would be cranked up to a tolerable working temperature. That said, there may be stretches of a week or two that it won't be worked in. Summer is obviously not a factor but that season is always too short.

 

[SuperD]

Glad someone posted the fact that you must keep the shop from freezing whenever using a condensate furnace in the freezing shop atmosphere!

I have now made the decision to go with the Mr Heater hanging furnace rather than a 97% high efficiency furnace since I may go certain weeks or months without heat in there. Thanks.

 

[cos]

Hello Showkey asked about low return air temps for condensing (95%) furnaces. You can google it for general info or look for info in installation manuals for lennox,Trane,Carrier brand furnaces. My research tells me the problem is low return air temp causes condensation in primary heat exchanger (to much cooling) which it is not designed for (Carbon steel). The moisture will rust out first in line exchanger. I don't know if anyone makes a furnace with both heat exchangers that are stainless steel. Who like to put one my shop, But, will have to figure out a way around this.

 

[jmiller_2308]

I had a HD60 unit heater before the garage addition and gladly went to a ceiling mount furnace to replace it.

The unit heater did fine to heat the original 900 sqft garage but the fan was obnoxiously loud and blew things around too much. I did experience hot and cold spots as well. But when I wanted to add A/C the unit heater meant I had to buy another whole system. Because I didn't have a window and didn't want to cut stucco I ended up using a Mr. Slim. All in all, the unit heater + the mini-split cost me more than a conventional furnace would have.

When the addition went on I had to heat another 800 sqft. and buying another unit heater and more A/C was ridiculous. I ripped out the unit heater and mini-split and put in an 80% ceiling mount furnace complete with air exchanger and outside compressor and boy am I glad I did! It is a lot quieter and the duct work means not only do I spread the heat/cooling everywhere but it also allowed me to zone the original garage and the new addition as separate spaces. It is also nice that the force of the air coming out of the ducts is not blowing my paper, calendars, and work around. Nothing ***** more than having the calendar babes all torn up.

I'm not sure if it was because it was a garage or some other loop hole but I was able to install a furnace that was less than 96% so I don't have the condensate issues that people have been talking about.

 

[vicegripbloodblister]

Combustible air inlet kit for your hanging heater is money well spent. No worry about make-up air or your heater sucking in wood dust or flammable fumes.