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#116105 - 10/07/04 12:54 AM Maximum amps on 200 amp panel
vethead Offline
first timer

Registered: 10/07/04
Posts: 2
I want to build a detached garage and add a 100 amp sub-panel out there. I currently have 200 amp service to the house. The main panel has 30 slots, with 10 of them open. My question is what is the maximum amperage all of the breakers can add up to in a 200 amp service panel. Currently I have about 320 out there now, but that is before I would add the 100 amp breaker for the sub-panel on the detached shop. Can I do it?

#116106 - 10/07/04 01:38 AM Re: Maximum amps on 200 amp panel
frenchelectrican Offline

Registered: 09/18/03
Posts: 671
Loc: Wisconsin and Paris France ...
one sure fire way i always do is check the load what you will be using it normally and the size of the house it do make the diffrence there and i dont have all the details what you provide here and you say 320 amp?? if you say 320 that is indivuals breaker add up total sum but actual current somehow will be less.

you can add subfeed box[s] there is no limit to how many as long it dont go over 42 breaker limit for each subfeed box as long the load demand is below of the main breaker rating

if more question just feel free to ask us

merci, marc
Observer,écouter et Prudence [translated : Look , Listen and work safe ]

#116107 - 10/07/04 08:20 AM Re: Maximum amps on 200 amp panel
JasonB Offline
Sharp -Shooter
Carpal Tunnel

Registered: 04/27/04
Posts: 16697
Loc: Cape Spencer, New Brunswick, C...
Most power companies will also provide you with a usage history for your account. This can be used to determine what your actual maximum load has been historically. It won't be anywhere near 200 amps.

Don't just add up the breakers. That's meaningless. Add up the appliances. Each appliance should list it's current or wattage requirements. If it gives watts, just divide by volts to get amps. A 60 watt, 120v lightbulb draws 60/120=0.5 amps.

Anyhoo, total your loads. The biggest loads are HVAC, water heater, washer/dryer, electric oven/range.

Even if you total more than 200 amps, you'll notice that most of these appliances aren't run at the same time.

At the same time, 100 amps is alot of service for a shop. Whatcha gonna run out there? I'd think 50 or 60 amps would suffice.

Good luck,

er, somethin'....

#116108 - 10/07/04 09:45 AM Re: Maximum amps on 200 amp panel
Arnold Offline
Helpful Electrician

Registered: 07/09/02
Posts: 5000
Loc: United States
In reply to:

what is the maximum amperage all of the breakers can add up to in a 200 amp service panel?

As has already been stated, there is no maximum. It is not uncommon to find that they add up to as much 800 amps.

But power company records are not going to be of much use unless you have a peak usage meter that measures the biggest 15 minutes of usage.

The answer to your question can only come from a "demand load calculation". If you google that term, you can read more about it, and even figure out how to do it if you really want to (although it's not an easy calculation).
_____________________________________________ Start every day off with a smile and get it over with

#116109 - 10/07/04 12:46 PM Re: Maximum amps on 200 amp panel
vethead Offline
first timer

Registered: 10/07/04
Posts: 2
Thanks for all the great info. The local electrical inspector finally called me back, and told me the same thing. Seems like I will be fine with what I want to do. I guess I now need to check into what I really need for a sub-panel out in the shop. Thanks again for the info.


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