Why is a 240 Volt 20 Amp circuit limited to 3840 watts (20 A x 240 V x 80%) as soon as it can be 4800 watt (20 A x 240 V)?

I learned around this limit once installing baseboard heaters. I recognize that I'm limited to 3840 watt on a 240 Volt 20 Amp circuit since 240 V x 20 A x 80% = 3840 Watt however I'm wondering why I need to use 80% of the maximum 4800 Watts. Is it "just in case"?

Also, I've review on the web (so it need to be true) the I deserve to swap the 20 amp fuse because that a 30 amp fuse with 12 gauge wiring to increase permissible wattage however that doesn't sound right. My understanding, after reading more, is the doing this would certainly exceed the ampacity that the wire. I understand the cable coming out of the fuse box is 10 gauge however somewhere follow me the way, after a thermostat, it alters to 12.

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Can someone clear that up for me? I'm in Canada, if that matters.

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· 6y · edited 6y

Supply
CEC 8-104 (6) wherein a unify switch or circuit breaker is significant for continuous operation in ~ 80% that the ampere rating the its overcurrent devices, the constant load as figured out from the calculated pack shall no exceed (a) 80% of the rating that the circuit whereby the ampacity of the conductors is based on Column 2, 3, or 4 of Table 2 or 4;

The factor you can't placed the complete wattage top top is since our breakers are only designed to handle 80% the the fill continuously.

As for her conductor dimension you would need number 10's if you installed a 30 Amp breaker however again friend would should derate by 80%

CEC 14-104 (2) other than as provided for by Subrule (1)(c), the rating the overcurrent defense shall not exceed (a) 15 A because that No. 14 AWG copper conductors; (b) 20 A for No. 12 AWG copper conductors; (c) 30 A for No. 10 AWG copper conductors;

EDIT: read my answer for resolved resistance heat......It's been a while because code class

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· 6y
Journeyman

^ This is the appropriate answer.

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Op · 6y

Thank you because that the explanation. I understand.

So the 80% is due to the fact that of the style of the breaker, not because the wire can't take care of the load.

Is the 80% firm or does going to 4000 watt on a circuit restricted to 3840 watt OK?

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level 1
· 6y
Spend the extra money to acquire 10 gauge wire. The potential headaches and also troubles the may take place from conserving a tiny amount of money isn't precious it. How numerous far away are your heaters from her breaker? likewise since he's in canada shouldn't the OP go ahead through 10 gauge because they may run quite regularly?

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Op · 6y

It seems like the gauge that the wire varies depending upon its location. From package to the first thermostat is 12 yet after few of the thermostats, I've noticed it's 14 gauge romex to the heater.

In Montreal, Canada, heaters deserve to run indigenous Mid-September come Mid-May.

See more: How Much Is A 1963 Silver Quarter Worth, 1963 Quarter Value

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