Had electronics classes but electrical panels are new to me.

It all was a long time ago I had 2 years of electronics, and now I am trying to evaluate my fiancé's 200 amp service box, to see if she can add a new 20amp circuit dedicated for an outside pool. I realize it will have to be a GFCI (I've done that before) but my main question is how to determine the maximum load available to the panel. I understand that all circuits should be wired to only 80% of the maximum value of its breaker, so should I assume that each circuit breaker in the panel so far is at 80% its value and subtract that from 200amps? Probably not I'm thinking because I have already found 2 circuits that were erroneously wired, one I fixed and one I'm still trying to run down. So I guess what I need is a link to some publication that I can read and learn the ins and outs of Michigan code for circuit panels. Anyone with an idea of where I can find that online?

 

Welcome to the forums.

We can help you with your panel. There are guys here that love to look at pictures and will tell you exactly what you have.

You have a 200A service. That's pretty big. The items that you need to be concerned with are high draw items.... like electric heat, electric cooking, A/C, hot water heater. It is not uncommon for the total breaker amperages to be well over 200A.

Post a picture of your panel here.

http://www.doityourself.com/forum/el...-pictures.html

 

Given the margin built into the NEC sizing rules I doubt you will have a problem. The proper way is called a demand load calculation.

Adding the breaker handles is meaningless as it does not account for diversity of items like!e beast and AC that do not get used at the same time. Also a breaker may only power an alarm clock, not the 15 amps on the handle.

 

This is for continuous loads. (Loads that are expected to be on for more than 3 hours)

Many locations follow the NEC either as a whole, or with some changes. Locations also very on which code cycle they follow. According to this site: LARA - Electrical Permit Information Michigan is on 2008 NEC cycle with amendments. There is also a link for getting a permit.

The NEC is not online but you can buy it. It is fairly spendy, and reads like a lawyer wrote it, so I would suggest to you to get the book "wiring simplified". It is a good, inexpensive read.