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OT - electric auxiliary heat for shop

Marty Feldman

Titanium
Joined
Feb 21, 2005
Location
Owl's Head, Maine
Under certain cold conditions I like to pump some auxiliary heat into the shop. For doing this, I typically use two freestanding 20-lb propane tanks, each with a heating head; the faces of these heads glow redhot and put out a lot of heat. I would like to find a 3rd heater, for emergency use when a tank runs out of propane, to add to the mix, and I would like a heater that is electrical, with a 120v plugin. I had one, an old fan forced GE baseboard heater that had excellent heat output, but it quit and I tossed it. In modern times, I think that thing would be judged dangerous and kept off the market. If anyone knows of an electric heater that might fit the bill, I would appreciate recommendations. I am not interested in the many "1500 watt" household heaters that are pictured keeping mommy and baby warm and cozy in the playroom. Also would like to avoid big dog heaters, like salamanders, that use kero or similar and need better ventilation that I will have in the space where the heater will be used.

-Marty-
 

gustafson

Diamond
Joined
Sep 4, 2002
Location
People's Republic
Budget?

Size of shop?

I have used a 240v rectangular box heater available at many places. I put an auxiliary thermostat on it so I could lower the temp to the 40s


Ponder also a hyper heat type mini split. They run 1500 bucks online and require hvac install, but might do what you want, and run cheaply


if you run K1 in a salamander, they do not smoke, just a tiny puff at startup, so if you set it hi to warm the place up then shut it off, it is really pretty good. Of course one would not take a nap will running it
 

Biolog

Aluminum
Joined
Aug 8, 2018
The 240 volt box heaters that hang from the ceiling like a gas furnace work well if the space is not too big. I have one in the garage that is set at 50 degrees to keep everything from freezing out there. They can put out 5,000 watts without being too large. They are only 200-400 dollars. If you get a 3 phase one the output is much greater. I only use open flame propane supplemental heat in an emergency. Dont like the carbon monoxide and moisture that gets cranked out. Almost died from CO when I was a kid.
 

Garwood

Diamond
Joined
Oct 10, 2009
Location
Oregon
For a couple years I used an air handler w/electric coils from a home furnace system. I paid $50 for it, replaced all the thermal cutouts and wired it in with a pair of 240V dryer plugs.

in a 7K sq ft shop it didn't do much, but in a smaller building with some insulation it'd probably cook you out.
 

EPAIII

Diamond
Joined
Nov 23, 2003
Location
Beaumont, TX, USA
You want 120 Volt plug in? And a 1500 Watt unit is no good.

Power (in Watts) = V x I

That's basic physics and the only way to get more heat than that from electricity is to use a heat pump.

You are limiting this to 120 Volts and the largest 120 Volt circuit that you are likely to have is going to be 20 Amps, many are only 15 Amps. So...

P = 120 V x 20 A = 2400 Watts.

That is a total maximum amount of heat that is possible on a single 120 Volt circuit. But 120 Volts is not often what you get. 115 Volts is more like it. And drawing a full 20 Amps is a good way to have the breaker pop and no manufacturer wants returns because your breaker is a bit weak. They do not make appliances that draw a full 20 Amps. So lets say you find a unit that draws 18 Amps. Now you are down to:

P = 115 V x 18 A = 2070 Watts.

You would be better off (3000 Watts) with two of the "household" heaters that you don't want. Or you will have to give up that 115 V thing and get something that runs on 230 V.

Beyond that, something troubles me here. You say you have TWO propane, stand alone heaters that you use all the time. AND you are still alive. Alive, as in not a victim of CO or CO2.

Therefore you must have a LOT of outside air coming into the shop. In the winter that would be COLD air that is coming in. You are fighting things here.

I would first talk to a real HVAC tech. about a real heating system. And then, after that is installed, talk to a contractor about sealing up your building and adding some effective insulation. That is the real solution here. Not just adding a band-aid on top of a totally wrong situation.

If you must have a temporary solution, get two or even three of the radiator style, free standing, electric heaters. They are fairly inexpensive and can be plugged into 115 Volt outlets. They do work. I have used them for emergency heat in my trailer when I was living in Iowa. I have one in my bedroom and another one in my shop right now. They work. And nothing you can buy, other than a heat pump, will give you more heat on a given electrical circuit. Black holes can break the laws of physics, but your shop heater can not.



Under certain cold conditions I like to pump some auxiliary heat into the shop. For doing this, I typically use two freestanding 20-lb propane tanks, each with a heating head; the faces of these heads glow redhot and put out a lot of heat. I would like to find a 3rd heater, for emergency use when a tank runs out of propane, to add to the mix, and I would like a heater that is electrical, with a 120v plugin. I had one, an old fan forced GE baseboard heater that had excellent heat output, but it quit and I tossed it. In modern times, I think that thing would be judged dangerous and kept off the market. If anyone knows of an electric heater that might fit the bill, I would appreciate recommendations. I am not interested in the many "1500 watt" household heaters that are pictured keeping mommy and baby warm and cozy in the playroom. Also would like to avoid big dog heaters, like salamanders, that use kero or similar and need better ventilation that I will have in the space where the heater will be used.

-Marty-
 

country_boy

Aluminum
Joined
Nov 22, 2004
Location
Alabama/Georgia
Owning a 110 V heater is handy for various reasons. Not sure why you don’t like a heater designed to warm mommy and baby, but they will warm you shop as fast as anything designed for a 15 A 120 V receptical.

Note a 15 A circuit should not be loaded continuously over 12 A (1440 watts), a 20 A plug/circuit (with one blade perpendicular to the other) over 16 A ( 1920 watts). Those radiant heaters fitting on top of a 20# LP tank produce 10,000 BTU/ burner- about 3000 watts each so prepare your expectations.

The 220 V 20A heaters ( Northern Tool sales them) are stable, compact, and produce twice the heat- plus they have a small fan.

In the cold of winter, the extra moisture added by propane is nice- eventually you can add too much and get moisture problems- a disaster arround machine tools. 1 lb of burned propane produces 1.6 lbs of water ( as vapor)
 

Chip Chester

Diamond
Joined
Dec 13, 2007
Location
Central Ohio USA
I'm standing up my radiant in-floor heating in the shop over the next few days. I'll be ridding myself of 3 of the red box 220V fan heaters, and a 3-phase ceiling-hanging fan heater. Central Ohio location if anyone's interested. Haven't put them on CL or anything yet -- more focused on getting the in-floor stuff running first.

I'll add specific brands and models as time permits.
 

Chip Chester

Diamond
Joined
Dec 13, 2007
Location
Central Ohio USA
Bought a place that had a 30-year-old barn that was in nice shape, but it had a gravel floor. So we took the gravel out down to 8", (and built a nice parking pad with it next to barn/shop). Then insulated beneath and around the slab-to-be, put down heavy-duty vapor barrier, wire reinforcing mesh, then PEX tie-wrapped to the mesh. Place 6" slab on top, with no slope, fiberglass, or expansion joints/cuts. Level and smooth like a warehouse. A little slick when coming in from the snow -- door mats should help. Intent is as a shop with a divided-off office. Separate hydronic zones for each.

Excavation and concrete was $13k for essentially 36x40. I did vapor barrier, placed supplied mesh, and all PEX layout. Concrete was pumped in via trailer pump; 3 trucks. No damage to PEX, based on air pressure readings throughout pour.

Below-slab materials were $1400, above-slab were $3200. All pumps, valves, electric thermostats and controllers, pre-fab sectional system piping, pre-fab PEX manifolds, on-demand direct-vent water heater, and co-axial intake/vent termination included. Not included: gas line (which we had to install on the property to house and shop -- ouch.), long lengths of 3" PVC for intake/exhaust to outside, and miscellaneous copper pipe/fittings to attach above-slab to below-slab subsystems (I'll probably do this in PEX).

Water heater vent system is good for about 70 feet if angled fittings are minimized. Less so if you max the lines out with five fittings each (90 or 45). Water heater is pretty efficient, and has condensate drain, filter, etc. and more computational power than the lunar lander. Above-slab subsystem has temp and pressure gauges, valves for bleed/purge and fill, filters and air purge mechanisms, and three Grundfos pumps to circulate and distribute heated glycol mixture. It's a closed system, so no city water involved.

All install labor aside from concrete/prep and gas line work is me.

I'm several days away from firing it up. We'll see how it goes. When it's running, I can continue to work out there on the insulation (of which there was none.) I had trouble getting motivated to do that when it was 18 deg F out there...

In the summer, the office will get a window air conditioner. With the large doors and windows, I probably won't air condition the shop. We'll see. Barn has a second floor "mezzanine" that's about 24' square, open to the rest of the building. And a 10x40 porch that's currently all outside space. Will probably wall that in for vehicle parking as time permits.
 

dalmatiangirl61

Titanium
Joined
Jan 31, 2011
Location
BFE Nevada/San Marcos Tx
I use a mil surplus H81 100,000btu diesel fired heater, with an exhaust pipe to outdoors, that operates on 120v power. Depending on your shop layout it can be mounted inside with exhaust run outside, mounted thru a wall, or mounted outside with ducts for recirculation. My gripe about them is they were designed where the fan runs continuously and burner cycles on/off, and the fan is somewhat noisy, I am going to reconfigure controls so it only comes on when needed, when burner shuts off it runs for a minute or 2, then fan shuts off.H81 was first model, H82 was second, and H83 third. Picked up a couple H82's last year to use in other parts of the building so contractors can work in winter time. If you want more info just ask.

Edit: I tried two 30,000btu unvented propane heaters in my shop, they ran non-stop for 2 days, the shop was not any warmer, and the fumes were wicked.
 

CITIZEN F16

Banned
Joined
May 2, 2021
If you are limited to 120 volts your not going to get anything better than the 1500 watt heater that keep mom and baby warm in the playroom. There is no such thing as a high efficiency electric heater. All 1500 watt heaters are pretty much created equal.
 

CITIZEN F16

Banned
Joined
May 2, 2021
Edit: I tried two 30,000btu unvented propane heaters in my shop, they ran non-stop for 2 days, the shop was not any warmer, and the fumes were wicked.

I have a couple kerosene heaters that look like overgrown Coleman lanterns, if they need cleaning they can start belching thick black smoke in an instant. I learned that the hard way, firing them up in the morning then going to cook and eat breakfast, came back to a shop full of smoke.
 

dalmatiangirl61

Titanium
Joined
Jan 31, 2011
Location
BFE Nevada/San Marcos Tx
I have a couple kerosene heaters that look like overgrown Coleman lanterns, if they need cleaning they can start belching thick black smoke in an instant. I learned that the hard way, firing them up in the morning then going to cook and eat breakfast, came back to a shop full of smoke.

I tried one of those too, fumes were not any better, gave it away. Here is a short vid on the H82 heater.
Space heater test, 120K BTU, HDU-36E, H82, Military, Engineered Air Systems - YouTube
 

Chip Chester

Diamond
Joined
Dec 13, 2007
Location
Central Ohio USA
A couple heat things: If you're going electric 120V, a heater that works well is the oil-filled radiator style. Thermostat for on and off, but when they're off the residual heat is still available. A low-speed fan behind them can help stir up the air, as long as it's gentle enough to avoid a wind chill factor.

Next, consider 'heat chimneys' to get the heat from up high down to where you can appreciate it. A 4" light-gauge PVC pipe, or similar straight, open-ended ducting, mounted vertically in the shop, with a fan at the bottom, and the top up near the apex of the ceiling. Fan sucks warm air from up high to down low, circulating as it goes. A couple of those can help recover the heat you've already paid for before it "leaks" out the roof...
 

Phil in Montana

Stainless
Joined
Jul 31, 2007
Location
Missoula Mt
Unless you have free electricity its a real bad Idea! 10kw in montana cost 1.20 a hour plus 120.00 demand or 29 bucks a day plus 120.00 demand so 149.00 the first day you use it and 29 bucks a day till the end of the mounth. To run it a mounth the bill would be 990.00 bucks cheap heat ha ha...Phil
 

MrWhoopee

Cast Iron
Joined
Nov 8, 2017
If you are limited to 120 volts your not going to get anything better than the 1500 watt heater that keep mom and baby warm in the playroom. There is no such thing as a high efficiency electric heater. All 1500 watt heaters are pretty much created equal.

I've tried to explain this to several people who fell for the latest miracle electric heater advertised on TV. There's no free lunch, the conversion from electric power to heat is mathematically defined and not negotiable.

I used one of the radiator style electric heaters with a box fan for my greenhouse full of tropical ferns, primarily because of the gentle, non-drying nature of the heat. They may not be suitable for on-demand heating as it takes some time for the oil to heat up.
 

EPAIII

Diamond
Joined
Nov 23, 2003
Location
Beaumont, TX, USA
This was my point, exactly.

But the heat pump is the one exception that I know about. Heat pumps work like air conditioning but in reverse. They actually move or pump heat energy from the outside where things are colder in the winter into the building. And a well designed heat pump will also direct a good fraction of the electric energy that they use into the interior space as well. This again is the opposite of what an AC unit does with as much of the electrical energy's heat is directed to the outside.

So a heat pump working under favorable conditions can actually produce more heat than the electrical power equation (P = VA) would predict. Unfortunately heat pumps work best when the outside temperature is higher so more heat energy is available and is easier to pump to the interior. As the exterior temperature drops, the efficiency of a heat pump drops and eventually it is only as good or even worse than a simple, resistance based (P = VA) heating element.



I've tried to explain this to several people who fell for the latest miracle electric heater advertised on TV. There's no free lunch, the conversion from electric power to heat is mathematically defined and not negotiable.

I used one of the radiator style electric heaters with a box fan for my greenhouse full of tropical ferns, primarily because of the gentle, non-drying nature of the heat. They may not be suitable for on-demand heating as it takes some time for the oil to heat up.
 








 
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