| HorneTD 2005-06-17, 11:31 pm |
| AutoTracer wrote:
quote:
> I need to either replace my distribution box or add sub panel so that I can
> use arcfault breakers. (my current panel does not have these available). I
> am trying to decide if 100A is enough (and I won't need to change the
> entrance conductors) or if I should upgrade to 200A for future upgrades.
>
> In particular, I have done the load calculation per NEC 220 and come up with
> 75A. I want to reserve enough extra current for a future spa. When doing a
> load calculation can I use all 100A rated on the panel or is there a
> derating factor I must use? How high in the load calc can one go before a
> larger service panel is indicated?
>
>
Add the hot tubs load to the calculation. If it comes out less than one
hundred amperes fine. If it comes out more than you will need a heavy
up for the hot tub and you might as well do it now as not rather than
wire your new circuits twice.
One trick that may save you some money is to install the sub panel,
fitted with a main breaker, now and supply both panels from new service
entrance conductors later. You will avoid the cost of completely
rewiring the existing panel's circuits into the new service equipment.
The end result is not as elegant because you would end up with two
panels each of which would have main breakers. This takes advantage of
a rule that permits the service to consist of up to six disconnecting
means. In order to take advantage of that the existing equipment has to
be in reasonably good condition and there has to be enough room for both
panels including the required work and step back space in front of them.
If the existing panel does not have a single main breaker but has
space for six mains instead you cannot use that technique. If the
existing panel only has space for five or fewer main breakers you are
good to go.
--
Tom Horne
Well we aren't no thin blue heroes and yet we aren't no blackguards to.
We're just working men and woman most remarkable like you.
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