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Posted By Topic: 40 amp. Circuit

Nov 07 2013 01:28

Hi guys. I\'ve got a laminator to wire it draws 40 amps. Peaks at 42 amp. I figured a 50 amp cb would be sufficient 10 mm tps. Single phase . I was contemplating on 63 amp cb but then I would have to go16 mm. But because the main current draw are elements. 50 amp cb would be ample as there\'s no huge start currents. As motors. Have.

Nov 07 2013 09:22

You don\'t give a length of run for this install. 10mm could be installed on a 63 amp breaker over a short distance.

Length of run is one of the critical factors in selecting the correect bale size as vlot drop is related to cable size, load and distance.

Another important consideration if the effect of this extra load on the installation supply.
Is there sufficient capacity in the supply to the installation for another 50 amps of load?
Is the cable feeding the distribution board big enough for another 50 amps of load?
What does ths 50 amps of load do to the balancing of the 3 phase supply if the installation is fed 3 phase?

Nov 08 2013 09:00

Just because it is a resistive load don\'t forget there will still be some inrush current until the element heats up. may have to move from a C curve breaker.
Ron P

Nov 08 2013 23:51

Bit of a thread hi-jack: Ron I think you\'ve helped me figure out why a customer had gone though 2x Clipsal dimmers (another company did the install): first one installed, it lasted a few weeks then blew, client got him back to replace it, and apparently the replacement lasted not much more than two weeks either. Client didn\'t call him back...

Dimmer was rated to 450W incandescent load, client had 400W of incandescent load.
I\'m guessing it was the repeated high inrush current until filaments warmed up that would kill the electronics?

Nov 09 2013 15:15

if the enclosure that holds the dimmer is tight and no ventilation or if there are 2 dimmers installed in the same plate most dimmers say to downrate the load to about 250 to 300 watts. More than likely the dimmer is just getting too hot and damaging the electronics.

Nov 09 2013 22:18

Thanks blair.

Single dimmer plus mech, didn\'t check for ventilation issues but standard flushbox in ~30yr old house.

I\'m guessing with more and more insulation being retrofitted, we will see more issues like this?