Hi, I have 100 amp panelwith 8 unused spaces, running typical fridge, maybe 3 space heaters( 12.5 amps peak winter ), micro-wave, toster, TV computer, 120 washing machine.

I'm thinking of installing a 100 amp 6-8 space subpanel 200 ft away, but probably only need 60 80 amps at most.

So my question is regarding how to determine maxime number of amps to be drawn through my 100 amp panel. I know I can add togther total of all my amps and see if they total more than 100, though they may not all be used at same time.

Can I put a 100 amp 2-pole breaker in a 100 amp panel?

r6

First, adding the amps in the panelboard is futile. You need a load study to see what the calculated load is and if you have the required amperage for your upgrade.

Next 200', will require a voltage drop calculation (not required by the NEC)

In answer to your immediate question, no you cannot use a 100 amp breaker inside of a 100 amp load center. You need to find out what is the largest size breaker that the manufacturer of the load center will allow.

Lastly, because you are feeding a multioutlet secondary panelboard, you are limited to no larger than a 80% load at the secondary panelboard.

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donf.. "First, adding the amps in the panelboard is futile. You need a load study to see what the calculated load is and if you have the required amperage for your upgrade."

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Donf, there is 7 free spaces in the 100 amp panel, and if each were 15 amp, then , in theory if they each of those circuits draw 12.5 amp at same time that would be 87 amps and at most, I would use a 80 amp 2-pole breaker.

I redid total amp at cabin and only came to 42.5-amps( see bottom of this post ) total so probably 60 amp 2-pole is plenty big enough.

[QUOTE]
Next 200', will require a voltage drop calculation (not required by the NEC)[/QUOTE

Yeah I already planning on 7.6 voltage drop and yes I know that is more than recommened 5% drop

[QUOTE]In answer to your immediate question, no you cannot use a 100 amp breaker inside of a 100 amp load center. You need to find out what is the largest size breaker that the manufacturer of the load center will allow.[/QUOTE

Ok, that is what I thought, just looking for confirmation of that.

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Lastly, because you are feeding a multioutlet secondary panelboard, you are limited to no larger than a 80% load at the secondary panelboard.

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I suppose the mean if 100 amp main then cannot use larger the 80 amp 2-pole breaker to subpanel since 18 amps is 80% of 100 amp panel.

Thx, for confirmation and verification mychaning day by day plan. :--). Below is assessment for this 12 x 16 single room cabin 190 ft away from main panel
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15-amps larger window air conditioner
.. substitute 12.5 amps for space heater in winter…

3.5-amps tiny fridge

4-amps lights though outdoor lights draw 1.5 amps, so may 5 amps total

11-amps coffee maker though ours is only 8 – 9.3 amps

9-amps for 3 computers

H,mm that is only 42.5 amps so in theory we could get by with the 70 amp panel but the problem is it only has 2 spaces,

so we go with 100 amp panel cause it has 6 or 8 spaces, and that way we can run separate 20 amp circuits too two different walls of cabin in case you don’t want to use the same recepatcle for heater in winter that AC uses in summer.



r6