# Question Help me decide on a garage shop heating solution



## hhrahman (Dec 25, 2015)

Hi,

This is my first post. I'm looking for some advice from you knowledgable folks. Any help is much appreciated!

I'm looking at having a Carrier 58CTA070 (http://www.carrier.com/residential/en/us/products/gas-furnaces/58cta/) unit installed in my garage attic (the manual actually has instructions for an attic specific installation). I plan on setting up a woodworking shop in this garage. I will be using a dust collector and for now it is a 1HP with a 1 micron bag. My HVAC guy says he will install a couple of ducts on both sides of the garage and put in a chimney to vent to the outside above the garage.

What I'm unsure about is, because this unit is not sealed combustion, is it safe to use in a woodworking shop or even a garage? My HVAC guys says there isn't a problem but will not install it if I am not comfortable. The other option is a hot dawg ceiling mounted heater, I'm not sure if those are sealed combustion either but seem to be a popular choice. The Carrier unit will cost me $650 less so I'll definitely go with that if it's a safe and good solution.

Hope that made sense and please ask any questions. Really looking to get this installed in the next few days so I can start setting up my shop!

Thanks.


----------



## a1Jim (Aug 9, 2008)

Welcome to Ljs
I'm not a HVAC guy so I would tend to listen to one that you feel he knows what he's talking about or get a second opinion.


----------



## wapakfred (Jul 29, 2011)

The furnaces that aren't direct vented draw their combustion air from the room they're in, so if that's the shop itself it sucks in any any flammable vapors, ambient dust, and whatever. But having it in the attic just means it will draw attic air, which I would think is free of the problem materials from the shop…and i suppose if it's made for the attic it has some kind of dust trap/filter for the combustion air it draws from the attic. I think you're good to go, one thing I see you didn't mention: will there be a cold air return to the shop?


----------



## TinWhiskers (Oct 17, 2015)

You should give us info on size of shop and insulation. Texas or Alaska? What do you fear blowing up? Fumes? Sawdust?

You have a huge shop? Mine is 24×36 x10 insulated to the max. I have a 35K BTU Hot Dawg. I am happy.


----------



## GT350 (Dec 22, 2012)

I have a ceiling mounted gas furnace in my shop that pulls combustion air from inside the shop. I have never had a problem, but I run dust collection and I don't think that you can get enough dust in the air in a home shop where it is explosive. If you are spraying finish you probably should be exhausting the vapor anyway. I don't think I would want ducted heating because no matter how good your dust collection is you are still going to have dust buildup in the ducts.
Mike


----------



## WoodNSawdust (Mar 7, 2015)

Beyond heating, will you ever need AC? Even if you don't install it now the furnace needs different ducts to allow space for the AC's A coil to be installed.


----------



## LostHasher (Dec 6, 2015)

Talked to one of my propane guys about refurbishing my giant garage heater, so I can work in the winter. He noticed the chemicals I had and said "Do NOT use propane or natural gas if you're going to be refinishing furniture." Essentially, he didn't want to see me blowing myself up.

With the information you supplied, it sounds like you might need a second opinion. Maybe call the gas company directly with what you plan to do. (I'm not trying to sound like I know what I'm talking about, or that the propane guy was right… just passing this along.)


----------



## bearkatwood (Aug 19, 2015)

I have the ceiling mounted 220V heater style and I have not had any problems with it and the bill has been very low so far for the last two years. About every 3 months I hit it with a burst of air from my compressor as my shop can get really dusty. I also have an old wood stove in the back corner of my shop and if there was to be any issues with finishing or dust explosions you would think that would do it, but I haven't had any problems. I don't spray finish, but I have had a run of 12 chairs being finished with the stove going and not had any issues.


----------



## hhrahman (Dec 25, 2015)

Thanks for all the feedback, it's very helpful.

My garage is a 20×20x10 in Toronto, Canada. It will be fully insulated and drywalled. Initially my concern is only sawdust and humidity but eventually I will be spraying finishes too.

I asked about the cold air return and my guy said both supply and return will be from the shop so that doesn't sound good with regards to open flame and filters.

I am also looking into gas radiant tube heating.


----------



## hhrahman (Dec 25, 2015)

GT350, do you have any issues with filter changes? How frequently do you have to swap them out?


----------



## TinWhiskers (Oct 17, 2015)

I am curious on your pricing. Is that a 70K BTU furnace?

A 45 K BTU Hot Dawg will run $600. I am adequate with a 35 K BTU in north Ohio with a larger area. You may be a tad colder as in one heating zone. Maybe a second opinion on size?

You seem concerned if your furnace will blow up with your activity. If your explosive levels are that high, don't forget that any spark from motor startup, light switch…will cause an explosion too.


----------



## jumbojack (Mar 20, 2011)

Is there no way to draw the combustible air from outside?


----------



## GT350 (Dec 22, 2012)

Hhrahman, I don't have filters on the furnace because it is just one of the old ceiling mounted gas furnaces, I just occasionally blow the dust off but not much accumulates. As far as my dust collectors, I have two that hang from the ceiling with 3 filters each, a fiberglass filter then a pleated filter and then a bag filter and I just blow them out outsode every few months. I also built the cyclone dust collector that Wood Magazine featured several years ago with a diesel truck filter and every month or so I blow that out.
Mike


----------



## hhrahman (Dec 25, 2015)

The carrier unit is 70k BTUs and will cost me $1000 installed. The hot dawg unit is 60k BTUs and will cost me $1650 installed. I can ask about a lower BTU unit, I have read about a few people using 45k units.

Jumbojack, I thought the forced air unit would draw air from the outside and vent to the outside too but maybe that's a more expensive unit that allows that. I did tell my HVAC guy that o was on a tight budget and he's been trying to source cheaper units for me.


----------



## hhrahman (Dec 25, 2015)

> Hhrahman, I don t have filters on the furnace because it is just one of the old ceiling mounted gas furnaces, I just occasionally blow the dust off but not much accumulates. As far as my dust collectors, I have two that hang from the ceiling with 3 filters each, a fiberglass filter then a pleated filter and then a bag filter and I just blow them out outsode every few months. I also built the cyclone dust collector that Wood Magazine featured several years ago with a diesel truck filter and every month or so I blow that out.
> Mike
> 
> - GT350


Nice! Sounds like a good setup you got there.


----------



## TinWhiskers (Oct 17, 2015)

Just to give you an example of what a 35K unit would do in Ohio…To go from 50F to 65F would take up to an hour. To maintain a warm temp of 65F is easily done. 24×36x10 area. I have kept it warmer for drying varnish with no problems. A 70K unit for me would be too much which is bad.


----------



## Ger21 (Oct 29, 2009)

A 45,000 btu furnace is all you need. 
I have a 60,000 Reznor that's similar to the hot dawg, and it will warm the air in a 30°F shop in a few minutes. I only purchased the 60K unit because I got it cheaper than a 45K unit.

Dust is not an issue, but I don't run the furnace if I'm using flammable finishes. I'll keep the garage warmed up, and turn off at the end of the day, and do my finishing then. Or, If I'm finishing during the day, I'll turn off the furnace while the finish dries, then open the door to air out the garage for a few minutes, then turn the heat back on and close the door. A minor inconvenience to save $500-$1000

This is all you really need, but it will probably be about 40% more in Canada.
http://www.amazon.com/Modine-HD45AS0111Natural-Garage-80-Percent-Efficiency/dp/B0096MJ522

Sounds like your heating guy is looking at the models that draw combustion air from outside.

I'm in Detroit, so not too far from you, with similar climates.


----------



## wapakfred (Jul 29, 2011)

> I asked about the cold air return and my guy said both supply and return will be from the shop so that doesn t sound good with regards to open flame and filters.
> 
> - hhrahman


You've misinterpreted what that means (I think). Only the air going over the heat exchanger will be moving through the cold air return and back into the room, the combustion compartment is still isolated from the shop…and from the air that goes back and forth to the shop. I still think you will be fine, but whatever you choose to do I wish you the best.


----------



## FancyShoes (Aug 31, 2014)

Im a hvac guy, so first thing I suggest is that it will work, its no different than any other type of heating system. Second thing I suggest is that you should add in a 20"x25" return duct work, then pick up a pocket filter for it, and then a 20"x25"x5" pleated filter to catch all the small particles before the pocket filter, and you wont need to install one of those delta or jet air filters, it will do the same thing and be much much cheaper! Just make sure you turn the fan on when you are in the shop.

If you are worried about stuff getting into the combustion area like funes or sawsust, which really shouldnt, pick up a 95% efficiency furnace, and ask them to have it suck fresh air in, from outside the shop for the combustion.

Let me know if you have any other questions.


----------



## hhrahman (Dec 25, 2015)

Thanks again to everyone who replied! Pleasantly surprised at the great info I received. I'll review the solution with my HVAC guy and hopefully be able to post back here with what I end up with.


----------

