Heating Shop: Electric Alternatives

[David Hostetler]

Just to run your numbers, 20x25 (500sq ft) with 8 ft ceilings gives you 4000 cubic feet to heat.

Now let's assume for a minute that you have R30 in the ceiling, and R13 in the walls. (I am assuming 2x4 stud contstruction, YMMV). Your biggest heat loss at that point would be the big gaping door, with, most likely leaky seals, or no seals what so ever...

Sealing up the door should be no big deal. At least top and bottom. I have seen rubber seals for the sides as well, but they are few and far between... Insulating the doors themselves is a good idea. I personally am going the Reflectix route as it offers both radiant, and convection heat gain / loss insulation. I think foam board would be better for convection, but does nothing for radiant which is my biggest problem here in the south...

Dollars to run wise, electric is a pretty poor choice. I would think you would be far better off money wise providing combustion air venting for a propane or gas unit.

[Michael Wetzel]

I actually put a pellet stove in my shop. A more expensive initial cost but it heats the shop rather nicely.

[Wayne Cannon]

I would expect that the thermostat could be the greatest concern for igniting flammables, as it switches the heater on and off. Low amperage thermostats these days are all solid-state or mercury switches, but I don't know about the thermostats for higher amperage electric heaters.

[Justin M Rovang]

I just finished installing the Farenheat version of this - I had to exchange the first one because the fan wasn't blowing as expected - but the new one so far in ~30 degree outside temps, gets my insulated 24x24 garage up near 60. within 30mins.

I did use a plug - basically wired up my 10-3 to a 30A rated dryer receptacle along with a corresponding plug/wire and haven't felt any indicative warmth. (30A rated double pole breaker, wire, and plug - the load from this is ~21A.). There -IS- a 7.5kW equivelant of those heaters that needs 40A circuit. I'm not an EE - but I do know dryers, ovens and various shop equipment are mostly plug based and hot hardwired, (Being able to pull a plug is a mechanism of safety itself)

As for electric vs. gas, it's a tossup depending on where you live. I wouldn't go as far to call it a 'Poor' choice.

Even in off-peak, my number crunching indicates it'd take me about 4+ seasons to have a gas alternative pay for itself. (Cost of heater and cost of running a pretty short gas line).

I'd say run the wire - and get one to try it out - worst case scenario you're out the price of a 240V hookup in the garage. That's the approach I did/am doing and so far I'm happy as a clam.

[Ralph Lindberg]

I also heat with the similar (Northern Tool sold) fixed heater and it has worked for years and years.

That being said I am looking at replacing it with either a packaged Heat-Pump or mini-split (ductless) Heat Pump

They cost more (roughly $1,000) and use less power, and also allow cooling. They do require either a plumping run outside (mini-split) or a sealed hole in the wall.

The packaged heat-pump is the style of heat used in most hotel/motel rooms

[Gary Radice]

I purchased the same unit listed from Northern above last year.
I hard wired my unit but a electrician told me it was code in his area to use a plug. Why? So the unit could be unplugged by a service tech if work was needed.

Are you sure you heard that right? My understanding is that these should always be hardwired (because of the fire hazard of a plug as discussed above—which is why they come without power cords) and that the code was that a service disconnect, such as the breaker box that feeds it, should be in line of sight so that the service tech could confirm that it is off before service.

But I'm not an electrician and I don't know the code in your area.

[Dave Lehnert]

Are you sure you heard that right? My understanding is that these should always be hardwired (because of the fire hazard of a plug as discussed above—which is why they come without power cords) and that the code was that a service disconnect, such as the breaker box that feeds it, should be in line of sight so that the service tech could confirm that it is off before service.

But I'm not an electrician and I don't know the code in your area.

Yes, This is an electrician we use at work that only does industrial work. Maybe it is different for home use???

[Leo Vogel]

Augusto - this was a reply I got from another post why not to use a plug (thanks again Charley). I thought the reply was good and well worth mentioning again.

"Any poor connection in the plug, the outlet, their internal wire connections, or the blade contact between the plug and the outlet, can be the cause of this. When the connection is poor, it has resistance to the current flow and gets hot. How hot is determined by the appliance load and how much resistance is in the bad connection. Of course, the hotter it gets, the higher the connection resistance gets causing an out of control thermal runaway then ends up in the fire that you had and the destruction of the plug and receptacle.

Motor loads only draw high current when they are starting, so your saw connected to this outlet isn't pulling full current for a very long period of time and it's duty cycle is comparatively short. The heater, however, is a different story. It will draw max current continuously until the room reaches temperature, allowing this poor connection to heat up, and continue to heat up, until it burst into flames. At no time did this situation draw more current than the breaker was rated for, so the breaker never tripped. You just had two heat sources connected in series with each other, your heating unit and the poor connection at the plug/receptacle.

I strongly recommend that you hook up the heating unit with permanent wiring and not plug it in, as plugs/receptacles are prone to having reduced quality in their connections. Also make sure that all of the electrical connections in your heater circuit are very clean and very tight. There is a special grease that is used to keep aluminum electrical connections from oxidizing, and I use it for copper connections as well, whenever the connections are likely to heat from heavy loads. I also make it a point to sand or steel wool the ends of the wires before making the connections and then use the grease as I put the connections together. The grease is designed to prevent oxygen from reaching the connection to prevent the connection from oxydizing when it heats up. Of course, it will do nothing if the connection is poor to start with."

[James Fleming]

My shop is in my 24' x40' x8' insulated garage with a high-quality insulated (R-10) 16' garage door with good seals on all four sides plus two entrance doors and one small window. My garage is on a separte meter and the monthly cost for electricity is about $70 year-round. I have a 10,000 Btu AC mounted through the wall and I have the 7500w version of the Dayton heater in your link. It is hard-wired to a 40a breaker via 6 gauge wiring and flexible conduit. I have a small fan on the wall that operates continuously to keep the temp the same at all levels so my legs don't get cold. It was fairly inexpensive and easy to install, but a gas-fired overhead heater would be cheaper to operate.

The heating element is encased in cast aluminum so I don't think there is a fume ignition problem there, but it has a snap-action line voltage thermostat which does generate a small arc when the heater shuts off. This is in an enclosed, but not air-tight compartment, so there may be some ignition issue there. But how high a concentration of fumes would be necessary to constitute an explosion hazard? Is there any tool or light switch (except mercury?) that doesn't create some tiny spark?

I try to provide extra ventilation when using finishes and thinners but never gave much thought to the possibility of igniting the fumes.

[Rod Sheridan]

I have a 4.8Kw unit heater in my insulated, single car garage.

Electricity rates are about $0.10/Kwh where I live so it's about $0.48 per hour to run the heater.

It takes about 2 hours for the garage to warm up to 15C, when the heater starts cycling.

So if I estimate 4 to 6 hours of heater use per day, it's a maximum of $3 for a day of heat.

Since I only heat it when I'm working in the garage, it's very economical for me.

Regards, Rod.

[Justin M Rovang]

I just finished installing the Farenheat version of this - I had to exchange the first one because the fan wasn't blowing as expected - but the new one so far in ~30 degree outside temps, gets my insulated 24x24 garage up near 60. within 30mins.

I did use a plug - basically wired up my 10-3 to a 30A rated dryer receptacle along with a corresponding plug/wire and haven't felt any indicative warmth. (30A rated double pole breaker, wire, and plug - the load from this is ~21A.). There -IS- a 7.5kW equivelant of those heaters that needs 40A circuit. I'm not an EE - but I do know dryers, ovens and various shop equipment are mostly plug based and hot hardwired, (Being able to pull a plug is a mechanism of safety itself)

As for electric vs. gas, it's a tossup depending on where you live. I wouldn't go as far to call it a 'Poor' choice.

Even in off-peak, my number crunching indicates it'd take me about 4+ seasons to have a gas alternative pay for itself. (Cost of heater and cost of running a pretty short gas line).

I'd say run the wire - and get one to try it out - worst case scenario you're out the price of a 240V hookup in the garage. That's the approach I did/am doing and so far I'm happy as a clam.

It's been about half a month and here's some more on my experience:

24x24x9' Insulated garage, sans doors with poor sealing.

- On a 28 degree night, the garage is about 35-40 degrees.
- Heats up to 58 in ~20mins.
- After an hour and a half I'm stretching up to turn it -down-

Last night was the coldest night we've had since it's been installed and I was nice and comfy in boxers an a T-shirt.

I am working on putting some R11 in the garage door panels (They act as cold radiators, causing convection, etc); and eventually figuring out what to do to make my seals better (BTW, anyone have any ideas? I have issues with the sides having 'play' when the wind hits)

I'm quite a happy camper.

NOTES:

I bought the 'Farenheat' version from my local Fleet Farm, and the fan was faulty, didn't blow enough. Replaced and was good to go.

If you decide to test it out and run it on a bench/table and not from the ceiling - expect better results if it was up higher - the 'throw' of the air is important; as is the air it's inducting - being higher up, it's sucking in continuously warmer air and throwing even warmer out (To a point).

No 'cold' burst of air when started, as advertised - also cools the radiator down when turning off;

Decent CFM - to the hand, maybe a bit more than a box fan in flow.

To the hand, it's not 'HOT' heat, but it's hot enough to not want to stand in front of while it's running for too long.

[Doug Carpenter]

Ok I can't just glance over something like what Justin just said. He said he was comfy in a T-shirt and Boxers! I am totally getting a heater because I want to be inspired enough to work in my underwear!

Justin, if it gets any warmer in your shop you are going to have more safety issuse than fire at the plug in. I'm thinking something like a tie caught in the paper shredder. If you get my drift.

Honestly I'm glad you posted this thread because I too am considering heat. I used to have a furnace with a blower and thermostat but it died and now I want something else because I miss it dearly. I wouldn't mind AC as well for when it gets really humid. The kind of humidity that you don't even want to go outside. another time that would be good for underwear work; except the neighor across the street wouldn't appreciate it.

Finehomebuilding had an article that mentioned a PTAC unit. I guess it is like what hotel rooms have. That idea looks good to me as well. I do have a gas line so I'm not married to electric.

[Bob Borzelleri]

I have had the Dayton in my shop for about three years. It is hard wired. After checking codes, talking to electricians I know and reading the Dayton literature, that decision was simple to make. The risk of failure with a plug was not worth the convenience.

The shop is 24X24X9 but for the first year, there was nothing between the floor (raised wood foundation) and the approx 40 degree roof but trusses. The exterior walls were open studs. During that period, the Dayton was working hard and fairly long periods during the colder months (20-35 degrees).

The next year, I insulated the walls (R13), and covered them with beadboard over OSB sheathing. In addition, I covered the middle 8 feet of the trusses with flooring and an attic ladder and the rest of the ceiling had the same beadboard as the walls affixed to the bottom of the trusses (no sheathing, I seem to want to limit the time I look up as I age).

That left several 6"X24" openings between the beadboard and the flooring above and toward the center of the shop ceiling. I had some 2X6 fir that I cut up and used to fill in about 1/3 of the gaps and then I stopped for no good reason. After those mods, the Dayton really came into its own. It took about 90 minutes from virtually any low temp we ever see to get the shop to where it was easily workable (but probably not for underwear).

I still have not insulated the ceiling yet mainly because it seemed a bit dumb to do so while I still have several 6"X24" openings in the ceiling yet to fill.

As for cost of electric vs. other fuels, in my view, there ain't enough consistency anymore to make blanket judgments unless one happens to live in a place where fuel prices are regulated. Our propane costs have doubled in 4 years and now they are all over the map. An hour and a half a day of electricity to fuel the Dayton is cheaper in my view than 1 1/2 hours of runaway propane prices.

I think I'll dig around the wood stack for some more of that 2X6 fir...

Oh, I also went out and got a A/C (Haier) unit on wheels and hoses for outside air exchange. While the shop was unfinished inside, the A/C was a waste of effort. With the finish work (almost) done, I ran the A/C this past summer and it really made a difference during >90 degree days.

[Augusto Orosco]

Thank you everyone for the insight and updates. I got the Dayton G73 from ebay following Rick's great advice (at $275, it had the cheapest price at the time and the unit arrived just 2 days after I placed the order). I installed it a couple of weeks ago. It's on the ceiling in the middle of the side wall, hardwired to my subpanel using conduit (flex for the last 3 feet, to allow for tilting the unit as needed).

My garage is about 20x24x8 and un-insulated (but walls and celing are sheetrocked). Insulation will come soon.

We haven't had any really cool days yet, but so far it works great. When it's about 40F outside, the garage remains at about 50F without the unit on, and it takes about 15-20 min for the heater to bring it up to 65F, which is where I have it set up (warm enough for pants and a T-shirt, but no so for boxers ). The blower is powerful, but not loud. I can feel the warm air on the other side of the shop, 20' away.

After that, it runs about 50% of the time to keep it at the desired temp. At $0.13 Kw/h, it costs me about $0.30 an hour to run it, which is pretty reasonable given that I only work in the shop 6 hours a week if I am lucky. I am sure it will have to run a little harder when temps go down, but things should also improve with insulation.

So far, I am very pleased with it, an excited to be able to play in the shop during the winter months. My take is that this unit is great for the occasional hobbyist: It's easy to install and maintain, you don't need to worry about fuel, there are no exhaust or humidity issues to deal with and it's powerful enough to keep you warm even if your shop is not well insulated. If you don't spend a ton of time in the shop, the added cost to your electric bill should be marginal.

[Brian Tax]

Does anyone have an opinion on using a through the wall heat pump like this http://www.ajmadison.com/cgi-bin/ajm....html?mv_pc=dt for a shop?

My understand that they are about 10 times as efficient as regular electric heat, and work best if the outside temp is not really cold, is this correct?

I am in Seattle, so winter is fairly mild, not too many days below freezing. I would like to keep it on continuously, to keep the shop in the high 50s, to prevent rust etc.