Electrical question for heater

[John Torchick]

My shop is very cold. Right now, two 110V 1500W heaters take about two hours to bring the temp from mid 50s to about 66-68 degrees. Looking for a 240V electric heater of about 4800-5000W to heat about 350 SF. Heaters spec to 400 SF. Plug-in units have the #6-30NEMA plug. Plug has two horizontal blades and the round ground. Specs on several heaters say to use a 30 amp double breaker; got that. First- I'm thinking this would take black/white.ground with the black going to one pole and the white to the other pole on the breaker. Ground is self explanatory. I have done electrical but want to make sure I'm on the right track. Not looked at the breakers as Lowe's is completely reworking the store and many aisles are blocked. Is there any way to determine on the breaker where the two wires attach or does it matter? Second- would 12/3 or 10/3 be best for this application? If I can get the shop warmed in a decent time, I can turn more or work on other projects that are on the list. Many thanks.

 

[Roger Wiegand]

you need 10 gauge for a 30A breaker. Unless the device requires a neutral (that plug doesn't give you one) then you want 10-2 w/ground for wire. It doesn't matter which conductor is attached to which pole in the breaker (the ground, of course goes to ground). You should mark the white wire at both ends with black or red electrical tape to indicate it is being used as a conductor rather than as a neutral.

You may well want to consider an air source heat pump. That big a heater is going to cost a bunch to run.

 

[Mark Jundanian]

I don't recall the specs on my 240V heater, but the circuit is 40 amps. When I first started running it I did some back of the envelope calcs and I figure it costs about a dollar an hour to run.

 

[Ron Solfest]

I also put in a heater this winter, and am very happy to have it; same as with AC I added last summer - now I don’t ‘avoid’ going out to the shop.

I have a 450sq ft shop, 9ft ceilings; well insulated on the plateau in TN (typical lows ~20-35, highs ~30-50). I put in a 4000W wall heater, hardwired 10-2 with gnd, and 20A 240v breaker. Takes my shop from mid 50’s to mid-60’s where I like it within about 10-15minutes.

 

[Chris Lawrence]

I bought a Dr. Heater 3000/6000 watt forced air heater a couple years ago. I run it on the 3000 watt setting most of the time and have no problems heating up my 340sq ft garage to 65 pretty fast. I did do a good job insulating it including 8 inches of blown in above the ceiling. When i am running it during the winter it kicks on for a couple minutes every 30 minutes or so. I wired an energy monitor on it to watch how much power it consumes and its not as bad as i thought it would be.

 

[John Torchick]

you need 10 gauge for a 30A breaker. Unless the device requires a neutral (that plug doesn't give you one) then you want 10-2 w/ground for wire. It doesn't matter which conductor is attached to which pole in the breaker (the ground, of course goes to ground). You should mark the white wire at both ends with black or red electrical tape to indicate it is being used as a conductor rather than as a neutral.

You may well want to consider an air source heat pump. That big a heater is going to cost a bunch to run.

Thanks but the budget doesn't all for that type of expense or room for installation. The heater won't be running all the time so power use won't be too bad. At the worst, it will offset the blasted pool pump that I tossed last year along with the pool. Plus the $$$ for chemical.

 

[Mark Jundanian]

The heater won't be running all the time so power use won't be too bad.

That is my thinking, too. Although I confess I have forgotten it on overnight more than once.

I have an observation I'd share. Having a fan of some kind to help circulate the warm air makes a big difference in shop comfort for me. Back when I first put the heater in I just had an oscillating fan, which worked well (but was probably stirring up dust). Since then I installed a Jet air filtration system and use that in conjunction with the heater to mix and spread the air.

The heater hangs from the ceiling in the NW corner and blows across the room diagonally (past the turning station) to the SE. The air filtration system is on the S wall and intakes from the SE corner. It sends the warm air around the room. If the AFS is off the W and N sides of the shop are noticeably colder.

Just some food for thought as you plan your install.

 

[Matthew Ferriter]

Has anyone used a portable AC/heat-pump unit? We have a portable AC system in an upstairs bedroom for the summer months that works well (have to vent the exhaust out through a window), but there is another version that also has a heat pump built in. I think you have to run a drain line to the outside or a floor drain.

 

[Doug Freeman]

Something to consider. 2 basic approaches to hvac inthe shop area - 1) on/off - use only while in the space, 2) continuous. I worked for the largest NA hvac compressor mfr in engineering and manufacturing for ~ 30 years. After I started there, set back thermostats started becoming a big thing - save on your electric bill. Before opting in, I did what engineers do - I put together a math model to analyze continous temp vs set back. What the setback fans dont mention is how much mass of the house/bldg cools off and must be heated back up. I included the thermostat recovery function of using hp instead of strip heat to increase the temp. I played with the model over probably 6 months, tweaking it for various variables. At the end of the day any cost savings with setback is pretty questionable. when you include the mass of the structure and all things in it, not just the air, its a whole different thing.

An on/off approach to a shop is even worse and costs more $, if you are in the shop everyday. If shop use is sporadic it depends on time factors. Factor in buying and operating a larger hvac unit to get to temp quick and it costs even more $.

If your current heater setup keeps the shop warm enough, it just doesnt change it fast enough, and you use the shop pretty much every day, just let the hvac run all the time. You will be $ ahead. One exception - if you have no or really poor insulation. That changes the heat balance eq considerably, but the 1st thing to do as part of putting hvac in a shop is insulate, and insulate as well as you can.

 

[Tom De Winter]

Doug, Thanks for your insight. I've come to the same conclusions but without the research to back them up.

My shop is an attached garage of 1200 sq. ft. with an 11' ceiling. The walls are fully finished drywall with 6" studs full of fiberglass and an inch of foam on the outside. The concrete floor is poured over 2" of foam. The ceiling has 12" of fiberglass but the room above is heated anyway. The weak link is the single and double garage doors. They are foam insulated but don't seal all that great. It's heated by 50,000 btu 80% hanging heater. There's a single 54" ceiling fan to stir the air.

This winter I'm using it probably 8 hours every day. I've decided to leave the heat set to 70 and is the first time it's been really comfortable. The floor is not cold. Judging by how little the furnace runs I'm sure I'm better off not having to try to reheat all the equipment and floor. Wish I could find a good way to better seal the doors.

Of course I've got to endure my wife's remarks about it being warmer than the house and complaints about the cars setting outside.

 

[John Torchick]

No windows that opens and floor drain is out of the question. Again, many thanks for your help here. Due to cost, running wire through existing conduit, being cheap, etc., I'm going to get another heater like I have now. About $25.

 

[Russell Nugent]

I heat my 240 sq foot shop with a 1500watt infrared heater that cycles on and off. I can get the temp pretty consistent costs me 100 bucks or so a month in the winter.

 

[Doug Freeman]

I set my tstat to ~ 65F in winter. If Im cool I have a long sleeve jacket, but most of the time I wear my “ac jacket”, zip up thru the collar windbreaker with sleeves cut off and the back cut out. Main thing is to be reasonably comfortable.

BTW for those interested - you can buy a “pass through” tstat for 120v hvac operation. The 120v passes through using a cord in cord out. The unit has a programmable tstat with temp sensor, and switches pass through power on/off. It has worked great for me with a cheap 120v heater and a window ac. It actually controls the room temp well vs the crappy units mounted on the heater or ac (part of it is the location of the unit controllers but part is the actual hardware and capability) I think they are $30-$40.

 

[John Torchick]

We built a wall in front of the metal garage door and insulated it. Had temps as low as 41 degrees three years ago. This year I see temps around the mid 50s. We can't open the vents in the downstairs den, basement/garage as it takes too much from the top floor.

 

[Dean Center]

In my little garage shop (walled and insulated) I put in an electric bath wall heater which comes with a fan. It's 240v, 1500/2000 watts and it generates a tremendous amount of heat and spreads it well into the room. The shop heats up quickly so I turn it on when I'm going to work in the shop, in 20 minutes it's warm, and I can turn it off when I'm done. To avoid blowing and igniting shavings, it's installed 48" on the wall opposite the lathe and since it's mounted up in the wall, I don't trip over it or any cord. It's a Cadet brand from one of the big box stores and was not at all expensive. https://www.lowes.com/pd/Cadet-Com-...fan-Heater-9-in-L-x-12-in-H-Grille/1002731654

 

[Mike Johnson]

Radiant type heating in a cold shop area works great for heating one area with very little power used. A radiant heater directly overhead will warm up the machine and the person working in the area. Radiant heat does not heat the air but heats the objects in proximity to the radiant heater. 10awg sized conductors will carry a 30A load..

 

[John Torchick]

Dean, don't have wall space for one. Considered one.
Mike, radiant heat is good until you move out of its focal area. Used to sell gas IR burner systems for commercial and industrial applications. IR heats the matter in its "path" and that radiates to warm you; floor in a shop would act at the radiant. Example is the dash in your car in winter. It can be cold outside and windy but the dash is warm.