Safe maximum amperage for 20A circuit?

[danielevan]

Hey all --

I've got one 20A circuit, and want to run about 18.2A through it (2x1000W @ 110V). This is new wiring.

Is that safe? I've heard you shouldn't exceed 80% of the circuit's amperage (i.e. 16A for a 20A circuit).

Thanks!

 

[smoknreefrs]

you should not exceed 80% the allowable amps of the conductor used....

for example with 12 AWG wire size the maximum allowed amps is 22-25 amps...

and the max for 10 AWG is 30 amps

i say you would be fine

 

[danielevan]

It's 12 AWG wiring.

Good, looks like 2000W is pretty much the upper limit for 20A.

 

[brian3]

If that is lighting don't just add up the bulb wattage to get the total. The ballast consumes power as well, some are more efficient than others. Typically the hotter it gets, the more power it consumes. Electronic ones are more efficient. The best way is to actually measure the current.

 

[scylam]

Re: Safe maximum amperage for 20A circuit?

<a href=showthread.php?s=&postid=6680237#post6680237 target=_blank>Originally posted</a> by danielevan
Hey all --

I've got one 20A circuit, and want to run about 18.2A through it (2x1000W @ 110V). This is new wiring.

Is that safe? I've heard you shouldn't exceed 80% of the circuit's amperage (i.e. 16A for a 20A circuit).

Thanks!

BE CAREFUL!!!
how do you come out of 18.2A? notice that the starting current of all inductive loads (typically magnatic ballasts, sub. pumps, AC motor in the chiller...) can be as high as 6 to 8 times higher then the norminal current for a period of 8 to 10 seconds.

this short period of time could trip your breaker

 

[danielevan]

Thanks for the note --

If the danger I'm facing is having the breaker trip, then I can live with that.

If the danger is something greater (e.g. fire), then I can't live with that. Breakers are designed to prevent this, no?

 

[scylam]

<a href=showthread.php?s=&postid=6686600#post6686600 target=_blank>Originally posted</a> by danielevan
Thanks for the note --

If the danger I'm facing is having the breaker trip, then I can live with that.

If the danger is something greater (e.g. fire), then I can't live with that. Breakers are designed to prevent this, no?

yes, circuit breakers (ccb) are design to protect conductors (wires) + equipment from 1) overload, 2)short circuit. both can cause fire hazard.
you can't afford to trip your ccb for the reef tank believe me, 'cos you won't alway home! mind to tell me the details of your load type so that may be i can help u out for a better solution / advises?

 

[danielevan]

Right, I'm laying plans, and want to have two circuits for the reef.

A good strategy, no?

 

[scylam]

yeah, i think sharing the burden is a good idea. most electrical distribution boxes allow installation of spare ccb, since both ccb's are for aquarium usage, u'd make sure the ccb's are all protected by the residual current device (RCD / RCCB) in case of current leakage.
have a safe one....

 

[brian3]

Unfortunately if you have a bad connection in a junction box or the like it will heat up and possibly cause a fire even before the breaker trips. Breakers help but are not a guarantee.