Replace 240v Plug On Heater

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.
 
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.
 
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!!!:chunky:
 
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.



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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.
 
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
 
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!
 
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.
 
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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