# Replace 240v Plug On Heater



## middle.road (Nov 23, 2015)

Weekend estate sale score! Let there be heat! Heck of a deal ($30) on a $200+ heater. 
Doesn't appear to have seen much use. Then again it may not even work. I couldn't find
a receptacle at the sale to test it. I've never come across this type of plug with this layout.
My plan this afternoon is to swap it with a dryer cord or perhaps a twist plug.
The existing cord is 12ga.
As usual I'm looking for advice, and double checking when doing electrical tasks.


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## JimDawson (Nov 23, 2015)

That's a standard 30 Amp, 250 V plug.  The receptacle should be available at Home Depot or Lowes.  You could change it out with another plug type if needed.  That looks like a heavy duty heater.


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## wawoodman (Nov 23, 2015)

It looks like a 15 amp/220 v. The big box stores should have a matching receptacle. Assuming you have the correct wiring and breaker to the box, just swap the receptacle.

http://www.nooutage.com/nema_configurations.htm

EDIT: Just saw Jim Dawson's post. The overall size of the plug will tell you if it's the 15 or the 30 amp. But it looks like Jim is correct, not me!


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## middle.road (Nov 23, 2015)

Just got back from the Big Blue Box.
I grabbed this and it's 30A. 
Now then, the existing cord currently on it is 12ga. 
So it's a 5600w/4200w @ 240/208v Heater - isn't that around 25 Amps?
Now I'm scratching my head... 
I'm going to go dig through my tub and see what I might have in 10ga. size
Heater is a TPI #HF686TC


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## jim18655 (Nov 23, 2015)

Does it have a UL sticker? That could answer some of your questions. The insulation type in the cord will determine the current carrying capacity of the cord.


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## turnitupper (Nov 23, 2015)

jim18655 said:


> Does it have a UL sticker? That could answer some of your questions. The insulation type in the cord will determine the current carrying capacity of the cord.


Could you please explain that statement?
John.


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## jim18655 (Nov 23, 2015)

The UL (Underwriter's Laboratory) tests equipment to determine if it's safe to use as manufactured. Cheap equipment without the UL sticker may not meet all safety requirements and codes. The 12 gauge cord may be OK on the heater because of its length and the insulation type used in the cord. Check an electrical code book wire chart and there are different current ratings for number of conductors, and temperature ratings of the insulation. In the US #12 copper is rated at 20 amps for type TW, 60C to 30 amps at 90C for THHN insulation (usually limited to a 20 amp breaker).


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## middle.road (Nov 23, 2015)

wawoodman said:


> It looks like....
> http://www.nooutage.com/nema_configurations.htm


I just saved that image and dumped it to the printer. It's going to go into a plastic sleeve and I'm going to hang it on the wall.

Thanks!


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## middle.road (Nov 23, 2015)

Info off of cord:
*(UL) C(UL) E136065-F SJTW   CSA LL96415 FT2*

But man that Plug looks huge compared to the cord.


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## JimDawson (Nov 23, 2015)

If I remember correctly (and I have not double checked this), I think on intermittent devices with a short cord, UL rules allow a smaller cord than normal NEC requirements.  Current carrying capacity is also partly a function of the number of strands in each conductor.  So more strands, the more current carrying capacity, this is because electrons only flow on the outside of the conductor, thus is a function of surface area.  So the more strands in a given gauge, the more surface area.  For instance a welding cable will carry a lot more current than a similar sized length of THHN because of the number of strands.  And welding is also intermittent duty.


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## jim18655 (Nov 23, 2015)

If it's a #12 AWG cord the NEC rates it at 25 amps for two current carrying conductors. I just connected a welder with the same plug on a #12 cord.


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## middle.road (Nov 23, 2015)

Thanks as always guys! I appreciate the input and the double-check so that I don't make a mistake.
I started to dig through my spare cords and cables but's it's a tad cold here tonight and I wimped out.
I'm thinking I've got several dryer style (3) prong cables and a couple of receptacles. 
Else the other better idea that I have is that I have several 'twist plugs' and some 10ga - I think. I may do it up that way.
Going to try tomorrow when it's suppose to be warmer...
Once I get this puppy running it's going to be a heck of a lot safer than the propane heater that I've been using.


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## Ulma Doctor (Nov 23, 2015)

nice score on the heater!that thing's gonna put out some BTU's
it looks like it could double as an electric arc furnace!!!


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## atunguyd (Nov 24, 2015)

JimDawson said:


> Current carrying capacity is also partly a function of the number of strands in each conductor.  So more strands, the more current carrying capacity, this is because electrons only flow on the outside of the conductor, thus is a function of surface area.



This is not entirely correct, while the skin effect is real, at the frequencies that our power is distributed, it only comes into play at very large loads (read that as only for line distribution). 

At 60 hz the skin depth of copper is around 10mm, so if your wire diameter is under this it makes no difference if you use strands that are 1mm diameter of one conductor that is 5mm diameter. 

I think the strands in most tools are there to make the wire more flexible and have little to do with skin effect. 

Consider this : the wiring used to wire up houses typically only has a few strands (8 to 10), if skin effect were a issue this would also have many fine stands like we use in say an extension cord. 

When you get to the point where you are distributing serious power and need conductors greater than 10mm diameter then skin effect will be a factor in choosing stranded conductors. 



Sent from my SM-N920C using Tapatalk


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## turnitupper (Nov 24, 2015)

jim18655 said:


> The UL (Underwriter's Laboratory) tests equipment to determine if it's safe to use as manufactured. Cheap equipment without the UL sticker may not meet all safety requirements and codes. The 12 gauge cord may be OK on the heater because of its length and the insulation type used in the cord. Check an electrical code book wire chart and there are different current ratings for number of conductors, and temperature ratings of the insulation. In the US #12 copper is rated at 20 amps for type TW, 60C to 30 amps at 90C for THHN insulation (usually limited to a 20 amp breaker).


Thanks for that Jim. I have just checked most of the equipment in the house and while many have UL markings on them, none have UL marked cords except for an old treadmill motor. The others have various other testing laboratory markings on them. Maybe it is that in Australia we have different voltage/plug configurations to that of the US but if the plug/cord is not UL stamped, would that not make the UL sticker on the appliance void. Just thinking .
John.


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## jim18655 (Nov 24, 2015)

UL tests the equipment as a whole, as built.


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## David S (Nov 24, 2015)

The maximum current of your heater at 240 vac is 23.3 amps.  The sjtw 12 awg power supply cord is rated for 25 amps.  It looks like the plug is moulded onto the cable and not a separate UL recognized component so it doesn't have to be marked.

For flexible cordset above 25 amps, eg 30 amps would require a 10 awg cable, similar to what I have for my 30 amp shore power cable for the RV.

If your heater is approved by UL and there is not evidence that the powersupply cord has been replaced, I would say you are good to go.

David


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## 4GSR (Nov 24, 2015)

Once you fire up the heater, check how hot the short cord gets.  Touch it with the back of your hand or a infra red thermometer.  If it's too hot to touch, replace the cord with heavier wire.  If warm, should be fine.  Make sure nothing is set on top of the wire and keep an eye on it often!


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## coolidge (Nov 24, 2015)

jim18655 said:


> Does it have a UL sticker? That could answer some of your questions. The insulation type in the cord will determine the current carrying capacity of the cord.



No it will not. The insulation will determine the voltage capacity, typically for stuff like the you have 300 volt and 600 volt. The gauge and length of the conductor will determine the current capacity. Its not uncommon to find short power cords that are a gauge smaller than what you would think should be the proper gauge for a given current draw, cord length matters.


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## jim18655 (Nov 24, 2015)

Temperature rating of the insulation also determines current carrying capacity. Higher temp rating allows more current before the insulation melts and shorts. Check the ampacity charts in the NEC. Higher temperature rating equals higher ampacity.


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## middle.road (Nov 25, 2015)

4gsr said:


> Once you fire up the heater, check how hot the short cord gets.  Touch it with the back of your hand or a infra red thermometer.  If it's too hot to touch, replace the cord with heavier wire.  If warm, should be fine.  Make sure nothing is set on top of the wire and keep an eye on it often!


Most definitely!

Went through my two boxes of twist-lok type plugs and receptacles. That was a learning experience.
I've been picking them up at sales and such when I see them for a buck or two.
With chart in hand I sorted them and found out that I've got a boatload of L5-125V's, very few matching
receptacles, and nothing I can put to use without buying a receptacle.
I am attempting (without spending a lot of $$$$) to redo the circuit that powers the 14x40 lathe.
Then just unplug the heater when using the lathe and vice-versa.
I didn't count on scoring a 240V heater when I re-did the wiring back in September.

And then, and then, a buddy called and told me I could come and get his old 2-ton heat pump that he 
just upgraded on his garage/shop. 
Now I've got to look at seriously upgrading and re-doing the feed into the house.
Funny thing on that, the electrical utility can't tell me how many amps I have coming into the house.
I'm not trusting of the 200A panel down in the basement.
In hindsight I should have had the the main re-done before we moved in...
Time to start doing some calculations.


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## mksj (Nov 26, 2015)

Not sure what the end result of your initial question is. If it is go with the factory cord and plug, then the answer is there is no reason to change it out. The unit draws 5600W at 240V which works out to 23.3A.  If you look at the Ampacity for most 2 conductor (UL Approved) electrical cords they indicate 12G wire with 2 conductors is fine for up to loads of 25A. Since the more common household sockets are usually 15A, 20A, 30A and 50A in various voltages and wire configurations, this unit uses a 6-30P plug and a 6-30R receptacle. Although the plug/socket have a 30A rating the wire would not be drawing the full current.

Your other machinery may have different ratings and plug configurations, such as twist-lock. I do not like the situation where you have to unplug and plug different cords when switching equipment your using regularly. So options would be to tap off the current 240V electrical box and add a separate electrical box/receptacle for the heater. About $20-30 if you do it your self.  This would allow you to switch on the heater when not using other machinery on the same circuit.  If you plan on running the heater together with machinery, then you may need to add a separate electrical line back to your electrical panel  box with its own breaker. Many Houses have a 200/225A service, but it is highly unlikely that you will draw anything close to this unless everything in your house is electric and turned on. I use a 100A sub panel in the garage with separate breakers for sockets and equipment.


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## Bill C. (Nov 26, 2015)

middle.road said:


> Most definitely!
> 
> Went through my two boxes of twist-lok type plugs and receptacles. That was a learning experience.
> I've been picking them up at sales and such when I see them for a buck or two.
> ...



---------------------------
That is strange they can't put a powered chart reader to give you/them a 24 hour power readout. I think that is a clamp meter that reads the current passing through a coil that snaps closed around one of the power cables.  We had one for our RV to check the amount of current it was drawing.  

Good luck with your project.


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## Bill C. (Nov 26, 2015)

You be careful with those twist locks.  When my Dad and I worked for GE they used those plugs on standard extension cords.  One day Dad brought home several new or slightly used pairs of male and female ends.  He said the company declared them a trip hazard since if someone got their foot under the cord it wouldn't pull apart. But you see them in almost every drive-through restaurant hanging from the ceilings where they should be off the floor.


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## Wobbles (Dec 8, 2015)

4gsr said:


> Once you fire up the heater, check how hot the short cord gets.  Touch it with the back of your hand or a infra red thermometer.  If it's too hot to touch, replace the cord with heavier wire.  If warm, should be fine.  Make sure nothing is set on top of the wire and keep an eye on it often!



Or... If that seems like too much, I have the ability to thoroughly test that heater for you at no charge. You can forward the heater to me and I'll return the unit to you the minute testing is completed. Should be about next May.


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## middle.road (Dec 8, 2015)

And it works! Left the plug, mounted the receptacle up close to the ceiling and ran 10ga to it.
Cord did not get warm at all (so far). Ran it for about thirty minutes yesterday morning and
it took the chill off. Need to rig a proper mount for it.
Will have to be careful so as not to impact the electric bill too much.
Beats the devil out of the propane dragon... Nice not to have open flame in the shop!

@Wobbles : Is Cornelia pretty temperate like up here?


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## middle.road (Dec 10, 2015)

OK, I've figured out how to get a mild winter, just install a heater in your shop.
It's suppose to be 70°F around these parts tomorrow. Let's hope it keeps up....


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## middle.road (Dec 31, 2015)

44° tonight - puddering in the shop and it is comfortable.
Considering the garage/shop has old wooden overhead doors with single pane windows and junkie windows on two walls
it's not too bad.
Cord is a tad warm-ish on the 12ga. segment after running for over 90mins.


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## abrace (Jan 1, 2016)

Just a reminder, because it often gets overlooked by homeowners (and even a lot of electricians) is that the ampacity of the conductors and OCPD for fixed space heaters need to be sized at 125% of load. Since this gets fastened to a wall or ceiling it is considered 'fixed'. Obviously this applies to the conductors between the panel and the receptacle and does not address the power cord, others have covered that.

5600W / 240V * 125 % = 29.2A. The #10 the OP ran for this is more that sufficient for this.

That said, there are a lot of 4000W heaters sold at the big box stores that a lot of people seem to think is OK to run off of 12AWG romex.

4000W / 240V * 125 % = 20.8A. This is .8A above the 20AMP limit for 12AWG and actually requires 10AWG and a 25A breaker.

---Aaron


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## middle.road (Jan 2, 2016)

I may end up changing out the pigtail for a 10GA. I was lucky enough to spend the day in the shop.
It didn't get over 40° here today and I finally figured out where to set the dial to cycle it. 
So it's holding the shop in the low 60's and it was very comfortable this evening. I stuck a 10" fan over
in the cold corner and that's at least stirring it up. The ceiling is well insulated, the walls aren't...
And with the unit now cycling the cord isn't getting warm.
So much better than the propane that I had been running.


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## abrace (Jan 3, 2016)

middle.road said:


> I may end up changing out the pigtail for a 10GA. I was lucky enough to spend the day in the shop.
> It didn't get over 40° here today and I finally figured out where to set the dial to cycle it.
> So it's holding the shop in the low 60's and it was very comfortable this evening. I stuck a 10" fan over
> in the cold corner and that's at least stirring it up. The ceiling is well insulated, the walls aren't...
> ...



Warm appliance cords are fine, hot isn't. A quality cord, such as something made out of SJ wire (SJOOW etc) has insulation rated for 90 degrees of heat, and that is in centigrade. If you can keep your hand on the cable and hold it without it burning you, you are fine.

Keep in mind that this cord is basically hanging out in free air and not trapped in a wall with insulation like romex or MC usually is.

I wouldn't sweat the cord unless it starts getting hot to the touch...a little warm is nothing to worry about.

Stay warm, I have 2 7500W heaters coming for my shop myself.

---Aaron


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## middle.road (Jan 3, 2016)

abrace said:


> .......
> Stay warm, I have 2 7500W heaters coming for my shop myself.
> 
> ---Aaron



(2)! and 7500w?! Lucky Dog. Of course NH winters are not mild....
This puppy kept it @64° until I packed it in last night at around ten and then it was ~32°. My feet were feeling the concrete.
Gotta replace the garage doors. I'd hate to see what a thermal image would show. Might jerry rig a couple of tarps on the inside.


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## abrace (Jan 3, 2016)

middle.road said:


> (2)! and 7500w?! Lucky Dog. Of course NH winters are not mild....
> This puppy kept it @64° until I packed it in last night at around ten and then it was ~32°. My feet were feeling the concrete.
> Gotta replace the garage doors. I'd hate to see what a thermal image would show. Might jerry rig a couple of tarps on the inside.



I like King Electric heaters. I got them for about $400 each, which isn't too bad. Only draw back is that they need #8 wire, and I am doing all MC (metal clad) in the shop, so it is like dealing with a hose. 2 7500W heaters was slightly more than 1 15KW heater, but this way I can run either 1 or both at any given time to match the heat output to the needs, and having 2 helps with heat distribution. These things throw the heat pretty far.

I bought a single 10Kw one for my 2 car garage a few years ago and it was great. Made in the USA. Good product, but they are meant to be hardwired with a wall line voltage (240V) thermostat, so the install is a little more complicated than a cord and plug heater.

---Aaron


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