AMPs and breaker panel questions
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My electrical service is 3 wire and I have two 100 amp main breakers so is my service considered 100 amp?
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Assuming it’s 100 amp service can I replace my very small and crowded 100 amp breaker panel with a higher rated panel, lets say 200 amp, but use 100 amp main breakers? I’m guessing this is no no but worth asking.
Replies
NO NO
Is this a double 100 amp breaker in one panel or two seperate panels with 100 amp breakers? If it is a double you have a 100 amp service.If you replace it should be done by an electrician.A elec permit is required and the local power company will have to, more than likely have to change the drop to your house. The new service will have to meet new elec codes.
His question (as I read it) was, could he upgrade the panel WITHOUT upgrading the service, so long as the 100A main breaker size was maintained.This shouldn't require installation of a drop.
About two years ago I installed a new main out on an owner owned pole, it contains two 100 amp breakers in it and also includes the meter. Power can be killed at the meter. <!----><!---->
The panel (subpanel) I want to replace contains the branch circuit breakers for the home. This panel also has two 100 amp main breakers in it. The branch circuits are just crammed in this poorly designed panel so working on the electrical is a major PITA. <!---->
I guess I just need to find well designed 100 amp panel. The reason I asked about the 200amp panel is because the ones I've seen are well laid out with plenty of wire room inside. <!---->
Thanks for your help.<!---->
-John<!---->
In general, you should be able to upgrade the panel to a larger one, so long as the main breakers are kept the same size.
However, I believe that there are some rules about the minimum size service you must have for a given number of breaker slots, just to discourage overloading. So if you up-sized too much you could end up in technical violation, even though it would be perfectly safe.
Yes that is 100 amp service.
And yes you can put in a an new pannel with more breaker spaces.
And as long as the main breakers are 100 amps then you can use a any panel that is rated 100 amps or MORE.
But you might want to look at this article and worksheet and see if a 100 amps are enough.
http://www.taunton.com/finehomebuilding/pages/bh0019.asp
Great book, thanks for the link, I actually have the book and used it in planning my branch circuits safe and conservative. <!----><!---->
So if I install a 200 amp subpanel it will physically accept 100 amp main breakers?
The 100 amp breakers on the subpanel I guess are optional but I like being able to kill the power at the subpanel saving me from having to go to the main. Installing a 200amp subpanel now would also save me from upgrading the subpanel again if I were to upgrade my service to 200 amps in the future. <!---->
Okay this is sounding good.
> So if I install a 200 amp subpanel it will physically accept 100 amp
> main breakers? That's something you should check before you buy -- the theoretical ability to replace the breakers with 100A ones, the actual availability of said 100A breakers, and their cost.
I did not catch that this was a sub-panel (and in fact when back and you did not "throw it").If this is for shop space (or partially) that guide won't work for calcualting loading.Assuming a single person shop you need to look at the largest combingation of equipment that you are running at any one time. And use the nameplate data and not the breaker size.Typically this might be a table saw, dust collecter, air filters, lights, and HVAC.Typically such a shop only needs about 50-60 amps. But I always suggest getting a 10 or 150 amp panel just becuse most of those that are under 100 amps are very limited in the number of slots.And there is nothing wrong with putting a 100 amp breaker in a 200 amp panel. Just make sure that it fits, which I suspect that in most cases it will.
Bill,<!----><!---->
No shop just a house. Two stories, one floor was already renovated now moving to the second floor. Sorry if my initial post confused anyone. <!---->
Thanks for all the valuable information, I'll try to remember to post back here on my success in installing the 100 amp breakers to the larger subpanel. <!---->
Typically such a shop only needs about 50-60 amps. But I always suggest getting a 10 or 150 amp panel just becuse most of those that are under 100 amps are very limited in the number of slots.
That's very good advice. My shop is fed with a 60A feeder to a smallish subpanel, but I'm going to need to replace the panel soon. Big 240V tools take up two breaker slots each.
I understand this thread has already gotten most of the answers you need but nobody mentioned looking at the feeder wires that go to the panel. Look and see what gauge they are and you will have your answer as to how many amps you can have maximum for the main circuit breaker. I forget (its been almost half a year since I installed my panel) but I used 2/0 gauge which I think is good for up to 125 amps. Since I have 100 amp main breaker I am playing it safe. If you have big enough wires which you never know then maybe you can go up to 150 amps, you know? Alright I am outta this thread :)
Oh yeah, I was refinishing wood floors in a home and noticed their main panel. The cover was off since they were painting and I noticed that the feeder wires were 1/0 or 2/0 gauge, too small for the 200 amp main breaker the panel was sporting. I told the HO (he just bought this house and hadn't yet fully moved in) about this and he said the guy he bought the house from did a lot of his own work and did the panel or so he thought. I was a bit worried, yanno? Ya gotta keep up with stuff like that.
Handyman, painter, wood floor refinisher, property maintenance in Tulsa, OK
if they are 2/0 copper, they are OK
I had a similar complaint about my 100amp panel being way too small. It had about 16 spaces. I intend to upgrade my service to 200amps, and bought a Cutler-Hammer CH series 200amp panel. I was redoing my kitchen and needed a few extra slots. Until I upgrade the service I put the 100amp main in it. The catch is, a Cutler-Hammer 100amp main is completely different. My old Square D 100amp main was similar to the CH 200 and I was able to make it work. So, do make sure that you check the fit before buying anything. Also, be aware that the cost of an individual main breaker costs almost as much as a complete panel with the main in it.
Okay here is where I’m at.
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Wire service to the house is at least 2/0 copper but I’m thinking it could be 1/0. It’s been a couple of years since I installed it. I do remember it was like wrestling with 3 big snakes all at once. I’ll double check this.
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I purchased a Cutler Hammer and as Sandalboy mentioned the cutler hammer 200amp panel has a completely different 100amp main breaker then the 200amp main breaker.
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The guy at the electrical store told me to just put in a 100amp main breaker on the cutler hammer panels distribution lugs and energize the panel that way. I thought this would work at first but then realized that it’s physically impossible to fit my main feed wires into the 100amp main breakers. The wire is way to big.
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At this point I can see two options:
Remove the 200amp main breaker in the new subpanel and hook my main feed wires directly to the lugs.
Leave the 200amp breaker in the subpanel and connect my feed wires to it as it was designed. As I see it, this would just pass any overload through the 200amp breaker to the main panel’s 100amp breakers. I don’t see how leaving the 200amp main breaker in the subpanel is any different then hooking directly to the lugs since my main panel will handle any overload. Please correct me if I’m wrong here.
Simple - leave the 200A breaker in the panel the way it is.
Since this is a subpanel, the wires feeding the panel are protected by the 100A 2-pole breaker at the pole. The Main 2-pole breaker in the panel serves as a convenient disconnect switch, but not much more: it doesn't matter what its rated at, as long as it's at least 100A.
If I understand correctly that while this is a "sub-panel" by wiring it is the "main panel" for the house by function. That it is the first distribution point within the house.I don't know if the code requires it or not, but I would certainly want a "main disconnect" within the house. That is the place that most people would go to if there was a problem to disconnect the power.And I am not a pro so I don't know all of the twist and turns of the code. AFAIK you can use the 200 amp breaker as long as the feeder wires can't be overloaded if they are protected by appropraitely sized breaker at the main disconnect.However, I think that I would put a label on the panel or at least stick a note inside of it explaining this. So that some time in the future someone does not thing that there is enough power for say a heat pump or hot tub.
Barry and Bill,<!----><!---->
Thanks for your input. <!---->
At this point I plan to leave the 200amp subpanel with its main breaker intact. As you both mentioned, the 200amp breaker will simply act as a convenient in-house main disconnect at this time.
I'll also be sure to post a note inside the panel clearly explaining the configuration, you know, just in case I get hit by a Mack truck before I'm able to upgrade to 200amp service. <!---->
-John<!---->
Edited 4/18/2005 2:44 pm ET by john m