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Old 06-08-2010, 08:23 PM   #1
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I have a question regarding adding a subpanel. Current main breaker is a 225 amp Cutler-Hammer which feeds an already existing 125 amp subpanel located next to main panel. The existing subpanel is fed with 2 60 amp breakers from the main panel. These two panels service the house.

I have a 400 square foot separate rec room building which will have a small kitchen, small window a/c, half bath, water heater, normal outlets, lights for a 400 square foot room, etc. The building is 50 ft away from the main panels and is totally detached.

What is the best way to get electricity to this building? Can I add another subpanel coming from the main panel in this detached building fed by 2 60 amp breakers? Or is there a better way?

I just discovered this site today, so thanks for any help.

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Old 06-08-2010, 08:32 PM   #2
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You have a 225a breaker as a disconnect ?
Or as a main breaker in a panel ?

Then a 125a sub panel being fed with a 60a 240v breaker ?

Detached building will require grounding rods
Small kitchen - with an electric stove ?
Microwave ? what will be in the kitchen ?
What is the rating on the WH, most are 30a 240v
That would be 1/2 of a 60a sub

Where are you located ?

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Old 06-08-2010, 10:01 PM   #3
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Sorry, the main panel is 225 amp. The subpanel is 125 amp and is fed from the main panel with 2 60 amp breakers.

Little building will not have electric stove--only microwave, small hot water heater, small window a/c, outlets for TV, lamps, etc. If subpanel is the way to go, then the line will be run from main panel in the house underground to the subpanel in the building. I don't know if adding another 60 amp breaker in the main panel to feed the new sub will overload my main panel. The usage on the new building will be fairly light, but with a microwave, small refrig, small a/c etc, it will add up quickly.

I am in Louisiana.

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Old 06-08-2010, 10:22 PM   #4
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What kind of heat?
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Old 06-08-2010, 10:25 PM   #5
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If the 125a panel is fed with a 60a breaker then it is only a 60a sub

Sub-panel is the only way to go with the electric load you will have
But, what you need to do is add up the Load to determine what size sub
Most likely a 60a 240v sub will be enough

But an AC can take up some juice, water heater more
It can add up pretty quickly

With a 225a Main panel you have quite a bit of pwer
Adding another sub should not be a problem
But what heavy electric use items do you have in the house ?
AC, stove, dryer, WH etc

I have quite a bit of electric devices & a 200a main & still have plenty of juice left
If you don't have a huge electric bill that is usually also a good indicator
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Old 06-08-2010, 11:03 PM   #6
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Hey, thanks for the info. Main house has pretty heavy usage. Two a/c units, electric stove, cooktop, microwave, dryer, around 3,800 square feet. But have never had any problems with power. I am trying to calculate the total pull on the main breaker, but I agree that another 60 amp breaker shouldn't overload anything.

Added building will have propane fireplace for heat-(already installed)

Thanks again. This is a great site!
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Old 06-09-2010, 06:29 PM   #7
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Quote:
If the 125a panel is fed with a 60a breaker then it is only a 60a sub
Dave, breakers that are fed in parallel will give you twice that amperage. Two 15's ON THE SAME PHASE feeding one device will give you 30. I wouldn't do it for permanent installations, but I have for temporary welders and the like. If I read the OP correctly, he has two 60's feeding that panel.
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Old 06-09-2010, 06:34 PM   #8
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Dave, breakers that are fed in parallel will give you twice that amperage. Two 15's ON THE SAME PHASE feeding one device will give you 30. I wouldn't do it for permanent installations, but I have for temporary welders and the like.
I'm thinking its a 60a 240v breaker
So its 120a @120v
But if you exceed 60a on either leg it will trip

Maybe someone is feeding 2 hots via (2) 60a 120v breakers
But I wouldn't call it a 120a panel
And I would never recommend to anyone to setup a sub that way

All depends upon exact setup
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Old 06-09-2010, 06:56 PM   #9
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I think thinks are getting a little sidetracked with terms. Isn't a sub-panel fed by 2 breakers? Yes, they are tied together and only 60 amps at 240V is available but in reality, there are two breakers feeding the sub-panel. His second sub will be no different than the first sub.
Don't main lug panels have a max amp listed on the tag?
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Old 06-09-2010, 09:54 PM   #10
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Yes, both panels, main and current sub have a max amp on the tag. 225 for the main and 125 for the sub. There are TWO 60 amp breakers feeding the current subpanel. Does that give total of 60 amps for each leg in the sub?

By the way, this is the way the house was orginally wired. There are 12 breakers in the current sub, none exceeding 20 amps. Load on these breakers are not even close to 20 amps, however. One breaker for example is a 20 amp breaker dedicated to a half bath that has only 2 lights and one outlet.

Just trying to determine if putting in the sub in the detached building is the safe and correct way to do it. If there is a better way, I am certainly open to any ideas.

THANKS for all the posts!
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Old 06-09-2010, 10:18 PM   #11
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Sub panel is the way to go
Yes, you end up with 60a on each pole/leg

Some 240v beakers have 2 handles tied together



Some only have 1 handle that trips both poles



And some people may use (2) single breakers to create a 240v circuit
But they are supposed to have a handle tie on the handles

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Old 06-09-2010, 11:30 PM   #12
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Quote:
Originally Posted by rirudd View Post
Yes, both panels, main and current sub have a max amp on the tag. 225 for the main and 125 for the sub. There are TWO 60 amp breakers feeding the current subpanel. Does that give total of 60 amps for each leg in the sub?
Just so you understand this, I think it was already posted, you have 60 amps available at 240 volts or 120 amp at 120 volts. That's 60 amps on each leg to neutral. Your total available power (P=IXE) 14.4 kilowatts
Quote:
By the way, this is the way the house was orginally wired. There are 12 breakers in the current sub, none exceeding 20 amps. Load on these breakers are not even close to 20 amps, however. One breaker for example is a 20 amp breaker dedicated to a half bath that has only 2 lights and one outlet.
Breakers are chosen to protect the wiring. Even though you normally only have a couple things plugged in, there is nothing to prevent the plugging in of other stuff. The breaker makes sure the wire doesn't overheat.
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Old 06-09-2010, 11:34 PM   #13
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Quote:
Originally Posted by a7ecorsair View Post
Breakers are chosen to protect the wiring. Even though you normally only have a couple things plugged in, there is nothing to prevent the plugging in of other stuff. The breaker makes sure the wire doesn't overheat.
Even with only one thing plugged in, if there was a ground fault or an arc between hot and neutral, these would pull the full 20A and trip the breaker.
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Old 06-10-2010, 12:36 AM   #14
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Hey, thanks for the post and pics. My existing sub has the two 60 amps handles tied together creating the 240 volt. New sub will have the same. I am forging ahead with the additional subpanel.

I am really glad I found this site. Thanks again!
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Old 06-10-2010, 12:36 AM   #15
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Quote:
Originally Posted by Scuba_Dave View Post
I'm thinking its a 60a 240v breaker
So its 120a @120v
But if you exceed 60a on either leg it will trip

Maybe someone is feeding 2 hots via (2) 60a 120v breakers
But I wouldn't call it a 120a panel
And I would never recommend to anyone to setup a sub that way

All depends upon exact setup

It read like he was saying there were two breakers. I see it was a two pole OP was describing. My mistake. And no, for God's sake I wouldn't recommend anyone do it the way I described.

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