Electric heaters and extension cords

[StaggeringGoat]

Long story short, I no longer have gas service to my shop. I already have four 1500w ceramic heaters and plan on buying some more for a total of 10.5kw. Each heater will be plugged into it's own 120v 20A circuit through a subpanel setup just for the heaters.

The problem is wiring, my power source is a long way from where I would like the heaters, and I don't want to spend a ton of money on copper. I was thinking about hooking each heater up to it's own dedicated 16ga 25-50 foot extension cord, as they are rather cheap.

The heaters have a warning on them not to plug into an extension cord. I understand this could overload in some circumstances. That said, the heaters are about 12.5 amps and 16 gauge cords are rated for 13 amps. I tried using a 50' cord with a heater and got about 4v drop across the cord which equates to about 45 watts being wasted in the cord. The cord gets slightly warm to the touch, but again, it's rated for 13 amps.

Do you think it would be a problem to run my heaters from these small gauge extension cords? I know they would work fine if I wanted to buy a bunch of 10 or 12 gauge cords, but I don't want to spend that kind of cash.

 

[geologist]

I've burned the socket of an extension cord by running a heater off of it. It wasn't a ceramic, but one of those fan-type heaters.

Happy holidays.

-Steven

 

[njride]

The breaker is sized to protect the wire, running 16 guage cord on a twenty amp breaker as a permanent setup for electric heat is something I wouldn't do. Go buy some twelve guage sj cord(sjo heavy duty if you feel spendy) and make up your own ends. A 20 amp breaker wont trip even after the 16 guage cord is overloaded, it can't serve its purpose, which is the protection of the wire and your property.

12.5 amps requires 12 guage wire and a twenty amp breaker. You cant size the breaker right and undersize the wire, its a recipe for bad things on a permanent installation with space heaters. Might it last for a long time with no ill effects, yes , its your risk to take, the codes are the way they are for a reason.

 

[StaggeringGoat]

The breaker is sized to protect the wire, running 16 guage cord on a twenty amp breaker as a permanent setup for electric heat is something I wouldn't do. Go buy some twelve guage sj cord(sjo heavy duty if you feel spendy) and make up your own ends. A 20 amp breaker wont trip even after the 16 guage cord is overloaded, it can't serve its purpose, which is the protection of the wire and your property.

12.5 amps requires 12 guage wire and a twenty amp breaker. You cant size the breaker right and undersize the wire, its a recipe for bad things on a permanent installation with space heaters. Might it last for a long time with no ill effects, yes , its your risk to take, the codes are the way they are for a reason.

I'm talking about setting up a subpanel with six 20A outlets and plugging a heater into each, not hard wiring any of the heaters. Not a "permanent" setup. I'll put it away in the summer. Nothing wrong with plugging a smaller extension cord into a larger amperage outlet. Like I said, 16ga extension cords are rated for 13 amps as per their UL sticker. I guess I could use 15A breakers instead of 20 for each heater.

The only problem here as it relates to the instructions that come with the product say not to use the heater with any extension cord, but that is popycock, a large enough cord will do the job. I just wonder if 16ga is big enough - technically it should be. I know the wire gets a tad warm but I'm trying to make heat anyway. The cord that comes with the heater is 16 gauge.

I would love to use 12ga wire instead, but that is simply not in the budget. I'd have to go without heat first.

Edit: for example, this cord claims a capacity of 13 amps or 1625 watts.
http://www.homedepot.com/h_d1/N-5yc...Id=10051&catalogId=10053&superSkuId=202891131

 

[matt151617]

You're doing something risky to save a little money. How did you plan on hooking up multiple extension cords to a subpanel? That sounds dangerous as hell. Even if you someone rig it up, you absolutely cannot use a breaker rated higher than the max capacity of the wire. If a fault occurs, the wire could heat up and start a fire before the breaker trips. Since 16 gauge wire is not used for any kind of household wiring, you won't find a breaker lower than 15 amps.

Why not just upgrade the wire running into the garage to provide enough power for the heaters and other stuff? You don't have to use copper, the larger cables are aluminum.

There's two ways you can do it: the right way, which will cost you more, and the half-assed way. In the meantime just hook up a propane heater.

Also, the reason the heater says not to use an extension cord is because extension cords are dangerous. They cause fires, it's a known fact.

 

[StaggeringGoat]

You're doing something risky to save a little money. How did you plan on hooking up multiple extension cords to a subpanel? That sounds dangerous as hell. Even if you someone rig it up, you absolutely cannot use a breaker rated higher than the max capacity of the wire.

You're missing the point. The subpanel would have six standard 15 or 20 amp outlets. Into each outlet would be plugged an extension cord. There is nothing dangerous about that. It's the same as plugging an extension cord into the wall. Yes, you can plug a 13 amp extension cord into a 15 amp outlet. That is all UL approved.

 

[StaggeringGoat]

Let me just ask a more simple question. Why can't I plug a 1500w 120v heater into an extension cord rated for 13 amps/1625 watts?

 

[nehog]

... own dedicated 16ga 25-50 foot extension cord, as they are rather cheap.

The heaters have a warning on them not to plug into an extension cord. I understand this could overload in some circumstances. That said, the heaters are about 12.5 amps and 16 gauge cords are rated for 13 amps. I tried using a 50' cord with a heater and got about 4v drop across the cord which equates to about 45 watts being wasted in the cord. The cord gets slightly warm to the touch, but again, it's rated for 13 amps.

Let me just ask a more simple question. Why can't I plug a 1500w 120v heater into an extension cord rated for 13 amps/1625 watts?

You must use a 12 AWG cord. Even a 14 AWG is too small. Also you would need a high quality one (not a garden variety homeowner's type of cord, but one with commercial ends) to be even remotely safe.

Bottom line is extension cords for a resistance heater is not a good idea.

BTW, 7 of those heaters will make your meter spin like there's no tomorrow. Not cost effective unless you have really, really cheap electricity. I'd suggest propane as an alternative.

 

[Sureshot]

I personally think those 16 gauge cords should be banned. Unless you can run it in your walls why across the floor etc. If you have a breaker rated for 20 you should have a cord rated for it also. The 16 will "work" until the cheap POS starts to short and starts on fire and the breaker doesn't trip. How much savings is it really and then to add to the power bill? How much is your time and worth if your place did burn even if fully insured? I wouldn't hesitate to use one if I needed and had no alternative but not planning to have them permanent like that. I am not a scaredy cat type either as I have welded propane tanks, rode without a helmet, do my own front end work, use plastic air hoses, and most other things people here usually flame a person for. JMHO from my experience using heaters on the Canadian prairies.

 

[mrb]

the heater is a continuous load, so whatever is powering it needs an ampacity of 15.625 amps (20% derating)

 

[mrb]

maybe find a used electric heat furance, locate it near your panel, and run flex duct to where you want heat

 

[matt151617]

You're missing the point. The subpanel would have six standard 15 or 20 amp outlets. Into each outlet would be plugged an extension cord. There is nothing dangerous about that. It's the same as plugging an extension cord into the wall. Yes, you can plug a 13 amp extension cord into a 15 amp outlet. That is all UL approved.

I get that, but each outlet would need to be on its own circuit to do that.

Bottom line, what you want to do will be very expensive and time consuming to set up properly, and expensive to run. If you're dead-set on using electric to heat, hardwire some baseboard heaters in.

 

[Charles (in GA)]

You must use a 12 AWG cord. Even a 14 AWG is too small. Also you would need a high quality one (not a garden variety homeowner's type of cord, but one with commercial ends) to be even remotely safe.

Bottom line is extension cords for a resistance heater is not a good idea.

BTW, 7 of those heaters will make your meter spin like there's no tomorrow. Not cost effective unless you have really, really cheap electricity. I'd suggest propane as an alternative.

I agree with this.......... Get the "right" cord if you have to do this, do not cheap out.

Leave the shop and fail to turn one off, and guess what? it overheats and burns..................

Charles

 

[StaggeringGoat]

BTW, 7 of those heaters will make your meter spin like there's no tomorrow. Not cost effective unless you have really, really cheap electricity. I'd suggest propane as an alternative.

It's no different than any other electric heat. To buy a 4kw "shop" heater at Home Depot is like $200, while their 1500w heaters are only $20 each. Yes I know electricity is expensive heat but that's my only option right now. Propane works out to around the same cost as electricity - with fumes. Electric bill is still only around $50/month.

If 16 gauge cords are so dangerous...why does the heater come from the factory with a 16 gauge cord?

 

[gatchel]

I would also suggest you follow the 80% rule like sizing circuit breakers. It's a small price to pay for piece of mind.

 

[theoldwizard1]

Let me just ask a more simple question. Why can't I plug a 1500w 120v heater into an extension cord rated for 13 amps/1625 watts?

Personally, I would not. I would pay the extra money and get 14 gauge cords which are rated at 15 amps/1875 watts (if under 50 feet).

 

[Sureshot]

I'm talking about setting up a subpanel with six 20A outlets and plugging a heater into each, not hard wiring any of the heaters. Not a "permanent" setup. I'll put it away in the summer. Nothing wrong with plugging a smaller extension cord into a larger amperage outlet. Like I said, 16ga extension cords are rated for 13 amps as per their UL sticker. I guess I could use 15A breakers instead of 20 for each heater.

The only problem here as it relates to the instructions that come with the product say not to use the heater with any extension cord, but that is popycock, a large enough cord will do the job. I just wonder if 16ga is big enough - technically it should be. I know the wire gets a tad warm but I'm trying to make heat anyway. The cord that comes with the heater is 16 gauge.

I would love to use 12ga wire instead, but that is simply not in the budget. I'd have to go without heat first.

Edit: for example, this cord claims a capacity of 13 amps or 1625 watts.
http://www.homedepot.com/h_d1/N-5yc...Id=10051&catalogId=10053&superSkuId=202891131

It's no different than any other electric heat. To buy a 4kw "shop" heater at Home Depot is like $200, while their 1500w heaters are only $20 each. Yes I know electricity is expensive heat but that's my only option right now. Propane works out to around the same cost as electricity - with fumes. Electric bill is still only around $50/month.

If 16 gauge cords are so dangerous...why does the heater come from the factory with a 16 gauge cord?

Not sure I follow the logic. Subpanel,6 breakers,3 split outlets,extension cords,heaters vs a $200 heater and 1 run of wire. Must be more to this story.

 

[Aceman]

Just do it.

I have a better idea, why don't you put a splitter in the end and run two off the same cord? That'll save you even more money.

I mean, what's the point of having fire insurance if you never use it?

 

[olytdi]

Look, there's no free lunch with regard to wire sizing and in fact there is a huge cost in terms of burning down your shop if you under-size the wire.

The heater can get away with using a 16g cord because of the length. In other words, it's safe at 3 ft of length (or whatever the factory length is). The math has been done on this.

So, firstly, you should be oversizing the wire in ANY extension cord length and upsizing yet again for for each 50 ft. So to be safe, you should be using 12g.

Look at it this way, 12 g is what would be hard wired in a 20A circuit that you would then use for a heater. The only valid thinking here is that you intend to separate each heater on it's own circuit.

Do it right and safely. And as someone already has pointed-out, you'll be in for less if you swap those six 20A breakers for one 30A 220v and hard wire an electric unit heater.

 

[StaggeringGoat]

And as someone already has pointed-out, you'll be in for less if you swap those six 20A breakers for one 30A 220v and hard wire an electric unit heater.

Do you realize how much an "electric unit heater" big enough for a 40x60 cost? Small heaters are by far the cheapest. For $100 I can get 7.5kw. A unit heater will be around 5-10kw and cost several hundred. And I'd probably need two.

The problem is the only electrical hookup I have is on top of my loft above my office. Putting heaters up there is just going to heat the ceiling. If I put each on a 25' cord I can bring them down to the floor.

I like the idea of compromising with 14ga cords, 80% of 15 amps is 12. The 15 amp circuits in my house are all wired with 14ga wiring and I plug a heater into that...

 

[mrb]

the heaters might only cost 100 but all the extension cords, subpanel, breakers, boxes, receptacles, etc is going to cost another couple hundred..

 

[StaggeringGoat]

the heaters might only cost 100 but all the extension cords, subpanel, breakers, boxes, receptacles, etc is going to cost another couple hundred..

Subpanel = free, already have it
15A breakers = cheap, already have a few
100' 14ga cord = $39.99
Misc. parts = maybe $25

My only other choice would be an electric unit heater like this, most likely 2 or 3 of them:
http://www.northerntool.com/shop/tools/product_200307927_200307927
Plus the associated wiring....

 

[matt151617]

12 gauge wire is the proper way to go. If the heaters are rated for 12.5 amps, you can't say it's "close enough" and choose 14 gauge wire that is rated at 12 amps at 80%.

You said it's 25 feet to bring a heater to the floor? So you'll need 6 individual circuits of at least 25 feet each, plan on 30-35 feet of wire to accomidate for bends, slack, etc. A 250 foot roll of 12 gauge Romex is about $100, so you're really not saving any extra money.

Also, what is the wire size coming into the shop's subpanel? Is there enough current available to safely run that kind of amperage?

 

[nehog]

I was going to answer your points, but I see you've already decided to go ahead with this as a viable solution. Good luck. Let us know in March just how well it worked.

 

[closetoreality]

its pretty simple. the money you save now creating a dangerous hack-job is going to be spent on the utility bill.

heat it right or don't heat it at all?

 

[sberry]

Running a 1500 watt heater on a 14 cord wouldn't cause me a great deal of sleep loss and yes the heater is supplied with a 16 but 3 ft long hasn't got much to do with it.

 

[TxPowderCoater]

just do it.
You came on asking if it was ok to do, you have been told by many its unsafe and they actually stated their reasoning and proof, even with all of that, you still argue and toss up your reasoning for it being cheap and ok.
whatever, just do it and next time, try not to create a thread with questions if your not going to heed the warnings anyways.

 

[Strouty]

My father is the same way, he is always lucky, nothing bad ever happens, so he continues on with unsafe practices. I would rather not risk losing my belongings over some heaters. I use a house furnace that runs off oil, it has one big duct and it heats my 60x30 (12.5 tall) well, but it uses about 175 gallons a month to keep it at 55 most of the time. I have electric spot heaters to use, but most of the time I keep the temp at 45 so nothing freezes. I will turn it up when I am there. I don't see how those small heaters would ever heat a 60x40 shop, I use a small oil filled one to keep my office warmer and it raises my electric bill $30 a month. I think that if you don't have the money to get two larger units, I would get one and a good pair of insulated bib overalls. That was how I started in my shop before the heat.

 

[theoldwizard1]

If you are paranoid (which is a good thing is this case) unplug the extension cords when the shop is not occupied.

While you are buying your extension cords at Walmart, pick up a couple of fire extinguisher. Seriously ! Cheap insurance.

 

[50cal]

I've burned the socket of an extension cord by running a heater off of it. It wasn't a ceramic, but one of those fan-type heaters.

Happy holidays.

-Steven

I will second that got a arc flash out of one on a extension cord. Glad I was home, it went straight to the trash bin. I was looking at heaters at big box store all of them siad to plug directly into wall socket, no extension cord.

 

[50cal]

If you are paranoid (which is a good thing is this case) unplug the extension cords when the shop is not occupied.

While you are buying your extension cords at Walmart, pick up a couple of fire extinguisher. Seriously ! Cheap insurance.

I agree mine was plugged into a # 12 extension cord the arc flash could have caused a fire before the breaker tripped. I have extinguishers.

 

[Random Guy]

Another thing I would recommenced is replacing the cheap ends that come on extension cords with some higher quality ones. The last thing you want with a 12.5 amp load is the extension cord have a poor connection to the heater plug.

 

[VHF]

I would agree that when it comes to purchase price you can't get much cheaper per BTU than 1500W residential space heaters, and the ceramic ones seem to be pretty safe--safer than some of the 4000W "garage heaters"!

How about the following setup for each *pair* of 1500W heaters? A 20A double-pole breaker in your subpannel feeding a 120/240V 20A twistlock recepticle (L14-20) mounted on the wall. Then make up an extension cable using 4-conductor #12 SJ portable cord with a twistlock plug on one end and a box containing a regular duplex recepticle on the other end. The duplex receptical would be split with each half connecting to one hot leg, in effect giving you a MWBC. You would plug two heaters into each receptical.

This cuts down on the total amount of copper you would need to run, as two heaters are sharing a neutral and ground. (Assumes locating two heaters close together works for you.) And while the twist lock connectors are more expensive, you would only need one twistlock receptical/plug for each pair of heaters, and with these you don't need to worry about them be pulled part way out of the wall and heating up from a poor connection.

This solution may not be either NEC or OSHA compliant, and won't provide GFCI protection, but if made up with quality materials and good workmanship at least you wouldn't have to loose sleep worrying about your shop burning down because of it!

 

[theoldwizard1]

Any of you folks suggesting making your own extension cord have not shopped for "portable cordage" ! 12/3 SJT (not as good as SJ or SJO) is about $1/foot in a 250 foot spool.

Pre-made 100' SJT cords are about $0.60/foot and SJO are about $0.85/foot.

A couple of years ago, I needed about 25' of 12/3 SOOW for a portable compressor power cord. The cheapest thing to do was buy a 100' extension cord, cut my 25' off and add a new heavy duty receptacle. 2 for 1 !

 

[Zeke]

Somebody please tell Goat about voltage drop in long *** skinny cords. Is he gonna get much heat at all except for the cord ends?

 

[sberry]

A couple degrees heat loss in the cord would be pretty much irrelevant. Anything better than a 16 cord is going to be just about negligible.
The main reason the have a cord warning is some ditz broad will p-lug one into a little lamp cord, maybe even 2 of them seeing as how most have 2 recepts on the end. I almost bet that 1 heater would be more dangerous than 2, I am tempted to try it here with 2 to see if it trip a breaker on a 16 before it overheated the cord. The danger of 1 would be that it might not overheat right away, at first glance all may appear ok, leave it un attended and there be a problem.

 

[StaggeringGoat]

Somebody please tell Goat about voltage drop in long *** skinny cords. Is he gonna get much heat at all except for the cord ends?

Go back and read my FIRST post where I already measured that. The drop is 4 volts. Not excessive in my opinion.

 

[Zeke]

I'd be curious as to how you measured that.

 

[sberry]

This is just an observation The longer I walk around the less my need to over kill everything in sight wears down. When I was in my 20's a 1 V drop while using a skilsaw would almost send me into a panic attack. As I get older I find more use for the words reasonable and adequate and I know how lots of people are on the other side of this computer. Despite the world being one gigantic average one might get the idea that, and maybe so, that all of us here are way on the top end of the scale, our own opinion of this may not always be accurate.
Same guy here says,,, I would never,,, I would use 4/0, all of this and let him bid on a spec house. Number 6 alum wire to the det garage or 1 15A service circuit in one, ha
If it was mine I would replace them all, there is another one,,, or I wouldn't use that white box part, you need bx racing this or that, if it was their beater with a core value of 800$ it would get wheel bearings all the way around vs the one making a little noise.
Another one is that somehow one with license or "professional installation" is somehow automatically superior despite half of them gonna be below average. Some of the crappiest work anywhere I have seen done was by people sposed to know better.
Its a good thing to be code compliant, in some cases better and I would want to be able to pass forensic if something happened, most faults happen without tragic consequences contrary to popular belief.
For most people in this crowd a bit of common sense and a question or 2 like the op posted are good, a rule for this gang to be reasonably safe is,,,, use a cord or wire a size larger than the cord that comes on the device makes it hard to go wrong.

 

[2LTim]

But if I use propper hearing protection, it won't hurt my ears when I discharge a 357Mag. into my temple!
Let,s cover this one more time; 1: Heaters are NOT to be used on extention cords! But if you must, use a cord of the proper size, NOT JUST WHAT IS CHEAP! If the whole aspect of properly sizing a circuit (panel, breakers, wire, devices) doesn't "Make Sense" to you, then maybe you should leave it to the professionals. Some very experienced and intelligent guys have told you eight different ways that your "Plan" is a bad one. For your sake I hope your insurance agent is not a member of the Garage Journal. If you proceed, do three things, 1) Up your coverage. 2) Lower your deductibles. 3) If your shop is attached to your home, move your wife and kids to a motel until the heating season is over. No need for unnecessary loss of life.