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

I learned about this limit as soon as installing baseboard heaters. I understand that I'm restricted to 3840 watts on a 240 Volt 20 Amp circuit due to the fact that 240 V x 20 A x 80% = 3840 Watt yet I'm wondering why I have to use 80% that the preferably 4800 Watts. Is that "just in case"?

Also, I've review on the net (so it need to be true) the I deserve to swap the 20 amp fuse because that a 30 amp fuse through 12 gauge wiring to rise permissible wattage but that doesn't sound right. Mine understanding, after analysis more, is the doing this would exceed the ampacity the the wire. I recognize the wire coming the end of the fuse crate is 10 gauge however somewhere along the way, after ~ a thermostat, it transforms to 12.

You are watching: How many watts 20 amp 240v

Can who clear the up for me? I'm in Canada, if the matters.

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level 1
· 6y · edited 6y

Supply
CEC 8-104 (6) where a unify switch or circuit breaker is significant for consistent operation in ~ 80% the the ampere rating the its overcurrent devices, the consistent load as established from the calculated load shall no exceed (a) 80% that the rating of the circuit where the ampacity the the conductors is based upon Column 2, 3, or 4 the Table 2 or 4;

The factor you can't put the full wattage ~ above is due to the fact that our breakers are just designed to manage 80% of the load continuously.

As for your conductor size you would need number 10's if you set up a 30 Amp breaker but again friend would should derate by 80%

CEC 14-104 (2) other than as listed for through Subrule (1)(c), the rating that overcurrent defense shall no exceed (a) 15 A for No. 14 AWG copper conductors; (b) 20 A because that No. 12 AWG copper conductors; (c) 30 A for No. 10 AWG copper conductors;

EDIT: check out my reply for fixed resistance heat......It's been a while due to the fact that code class

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level 2
· 6y
Journeyman

^ This is the appropriate answer.

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level 2
Op · 6y

Thank you for the explanation. Ns understand.

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

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

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level 1
· 6y
Spend the extra money to acquire 10 gauge wire. The potential headaches and troubles that may happen from conserving a tiny amount that money isn't precious it. How many far away room your heaters from her breaker? additionally since he's in canada shouldn't the OP walk ahead v 10 gauge due to the fact that they might run fairly regularly?

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level 2
Op · 6y

It seems favor the gauge of the wire varies relying on its location. From the box to the very first thermostat is 12 yet after some of the thermostats, I've noticed it's 14 gauge romex come the heater.

In Montreal, Canada, heaters can run native Mid-September to Mid-May.

See more: Is It A Sin To Wear A Rosary ? Wearing The Rosary As A Necklace

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