heater: 16.7 amps times 1.25 = is #12 awg ok?

Stevenfyeager said:
Infratech 4000 w 240v heater has 16.7 amp rating. 16.7 X 1.25 = 20.9 amps which is too high for Cu # 12 Romex, correct ?
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Correct. Article 424 states that it would be considered a continuous load. Also article 424 is not listed in 240.4(G) as being exempted from the small conductor requirements in 240.4(D) (if it was you could use something like MC instead of NM).

That said, I can't tell you how many times I have called 4,000 watts of electric heat "close enough" to be on a 20 amp circuit 😇
 
electrofelon said:
Correct. Article 424 states that it would be considered a continuous load. Also article 424 is not listed in 240.4(G) as being exempted from the small conductor requirements in 240.4(D) (if it was you could use something like MC instead of NM).

That said, I can't tell you how many times I have called 4,000 watts of electric heat "close enough" to be on a 20 amp circuit 😇
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In the ampacity table, I could use individual conductors like #12 THWN in pvc (good for 25 amps) instead of Romex, correct ?
 
Did you calculate the amps or is that value on the nameplate? The amps may be calculated at 250 volts on the factory nameplate, and not the typical 240. If it was designed for 4000 watts at 250v, the actual amps will be less at 240 volts and it would have calculated to 16 amps at 250V.

Is there a volt rating on the nameplate?
 
Stevenfyeager said:
Infratech 4000 w 240v heater has 16.7 amp rating. 16.7 X 1.25 = 20.9 amps which is too high for Cu # 12 Romex, correct ?
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Is too much for even THHN/THWN as the small conductor rule still limits 12 AWG to 20 amps.

Reality is a 20 amp breaker likely never trips.
 
suemarkp said:
Did you calculate the amps or is that value on the nameplate? The amps may be calculated at 250 volts on the factory nameplate, and not the typical 240. If it was designed for 4000 watts at 250v, the actual amps will be less at 240 volts and it would have calculated to 16 amps at 250V.

Is there a volt rating on the nameplate?
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A watt is a watt no matter the voltage, If these are the WD-40 Infratech heaters you need #10awg. I have installed several of them, They get too hot for some people if they are too close the the heater, I used to separate the 3 elements and switch them separately. Unless you have the control panel that allows "dimming" of the heaters. Also its a good idea to put them on some kind of timer so they don't stay on for extended time.
 
infinity said:
As Suemark asked if the heater is actually labeled for 4000 watts at 250 volts it will have a lower output and therefore less current at 240 volts.
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thinking back, I had ten of them hooked up and on, at 240v they pulled 100 amps. That would be 16.66 amps each.
this was 15 years ago so I'm not sure it was exactly 100 amps but I think it was.
 
Thank you all. You have advised using #10, and I will do that. Interior decorator wants just switches, no control panel. Another question: if 1.25 times the 16.7 is 21 amps, I'll need to use a 30 amp switch, correct ? She is buying decor switches from an Infratech dealer, which I bet are only 15 or 20 amp. I'll find out. My supply house only has 30 amp toggle style switches. And also, can I run one hot wire directly to each heater and the other hot wire through the switch ? Thank you.
 
LarryFine said:
Yes, if you can find a four-pole handle-tie. (You mean one 2p switch for both heaters, right?)
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LarryFine said:
The interior decorator shows an Infratech link of four switches for the four heaters. They are decor style switches. I’m wondering if they’re rated for only 15- 20 A. I have enough information now to rough in the wiring for the heaters. At this point she says the products will be delivered in about a week. I’ll look at the switches then.
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Stevenfyeager said:
Thank you all. You have advised using #10, and I will do that. Interior decorator wants just switches, no control panel. Another question: if 1.25 times the 16.7 is 21 amps, I'll need to use a 30 amp switch, correct ? She is buying decor switches from an Infratech dealer, which I bet are only 15 or 20 amp. I'll find out. My supply house only has 30 amp toggle style switches. And also, can I run one hot wire directly to each heater and the other hot wire through the switch ? Thank you.
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You could use one of those decorator switches to control a relay which controls the heater if you can't come up with one with proper rating.
 
Can you legally use a single pole switch to control a heater? I know many line voltage thermostats do just that, but can that extend to a wall switch? And if so, could you use the poles of a double pole switch in parallel for increased current handling? I have seen 20 amp double pole decora switches, but not 30 amp.
 
CoolWill said:
Can you legally use a single pole switch to control a heater? I know many line voltage thermostats do just that, but can that extend to a wall switch? And if so, could you use the poles of a double pole switch in parallel for increased current handling? I have seen 20 amp double pole decora switches, but not 30 amp.
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They can handle their rated amps for resistance loads. Inductive loads is where you may need to pay attention to additional ratings
 
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