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Looking at running a sub panel to feed some lights and receps. The main panel is 100 amps what size breaker can I use for the sub panel itself ??? I'd like to run a 50 amp breaker to feed the sub.:biker:

Thanks
 

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Looking at running a sub panel to feed some lights and receps. The main panel is 100 amps what size breaker can I use for the sub panel itself ??? I'd like to run a 50 amp breaker to feed the sub.:biker:

Thanks
Am I to understand your main breaker box inside your house is a 100 amp service? Let me get this part out of the way before I advise.
 

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Mississippi Cajun
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What is your total load on the main box?
 

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Done
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Sub's should be no more than half of your main. That being, I got away with running a 60 amp sub off my 100 amp main. Ground and neutral bars should NOT be bonded in the sub.
 

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Poser Member # 99
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If your main panel is only 100 amps you can run a sub panel with a 50 amp breaker this is bad news

Add up the numbers on the breakers in your panel and subtract that amount from a 100. That's what is left for capacity in that box. that's it if you try to add a 50 amp breaker for a sub panel that has 80 amps used you will burn your house down

I hope you have more than a 100 amp main panel if not.
Don't do it.
Get a licensed Electrician to look at your service and have him tell you what you can and can't do
 

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If your main panel is only 100 amps you can run a sub panel with a 50 amp breaker this is bad news

Add up the numbers on the breakers in your panel and subtract that amount from a 100. That's what is left for capacity in that box and that's it if you try to add a 50 amp breaker for a sub panel that has 80 amps used you will burn your house down

I hope you have more than a 100 amp main panel
Um, your assuming your drawing 100% of each circuit all the time. I installed 2 sub's. One 50 amp and one 25 amp. My service is 100 amp. My install passed code inspection. If your concerned check your amp draw with a large load on your panel. It also helps to have your load balanced on both legs.
 

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Banned
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How old is this service??? I've not seen a 100 amp service installed around here, 200 amp is standard and 250 amp is not unusual . :)
 

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Poser Member # 99
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I have a 200 amp Service and I've been known to put some heavy loads on it but Just cause you have it don't mean you cant overload it . I've seen a couple of places burnt up with some one adding sub panels and then overloading every thing and then poof

Oh I'm going to run a welder Oh I need a compressor running oh some heat . maybe some lights . oh the beer fridge . don't forget the tunes . now I need to drill a hole ooppps. I over loaded the sub panel . I didn't know the wife was cooking on the electric stove . The dryers running, lights are on ,the heats running the frig is open in the house. The TV's on . and I'm on the computer and so is the wife and kids poof the house is black never say it can't happen because it can and doe's more then people will admit

Just saying better to be safe then Sorry
 

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Agreed.
Now I have a 100 amp service. I run a large compressor, garage heater, central air conditioner, drill press, small welder, 2 computers, electric stove, electric hoist, plus all the other amenities of a normal house. As long as everything is properly wired, grounded and protected by circuit breakers that are sized for the load and conductors, I sleep easy.
 

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Poser Member # 99
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I would hate to see someone do the wrong thing.


They were saying that 6 people lost there lives. Because there Christmas tree that was more then 60 day old being in there home caught on fire and burned down a multimillion dollar home down and these people lost there lives the lights shorted out and caught the tree on fire home was Built on 2005 . It's been on MSN this week .
 

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I saw that. How horrible. I am confident in my ability. The OP should contact a licensed electrician to be sure. I have taken factory maintenance classes and have worked with licensed sparkys for a long time.
I also think you do need to be careful when asking for advice from unknowns on the internet.
 

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Life long rider
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There is nothing in the electrical code that dictates the maximum size sub panel allowed. You can technically install a 100 amp sub panel on a 100 amp main panel. What is more important as far as safety and compliance goes is that your wire is sized appropriately for the breaker size and that your wiring method, whether if its the appropriate cable type or conduit and thhn wire is properly sized and terminated.

As far as capacity goes , being that your main breaker is 100 amps your bus bar should also be rated to carry 100 amps. No matter how many sub panels or individual breakers you put down stream you won't be able to pull more than 100 amps total before the main trips off.

Adding up all the breakers does not address the total capacity , in your case 100 amps. In most electrical services if you add up the total number of amps for all of the breakers you will almost always exceed the total amperage of the service. Contrary to popular belief if you install a 50 amp breaker and use the appropriate size wire on a panel that has already 80 amps used you will not burn your house down. However if both the main panel load and the sub panel load exceed 100 amps you will trip the main breaker.

If you have concerns that you will not have enough capacity to run your new sub panel loads turn on everything that you would normally have on at any given time, amp clamp both your A&B phases to see how many amps you are pulling, chances are they won't be balanced - average the two. Estimate what your new load will be. If those 2 numbers don't exceed 85 amps you will be good to go. The rule of thumb and electrical code state that your electrical service shouldnt exceed 85% of the continuous load. Continuous load is what is run non stop for 3 hours or more.

Think of it this way... How often does anyone truly have every electrical device running full bore all at the same time? If we did us electricians would be millionaires from putting 400 amp services in everyone's houses!!

A good way to save on amperage is to get big load items like welders and compressors set up for 240 volts .. That's 1 reason that ranges and dryers are 240 volts. A 100 amp service is good for 24,000 watts. That's 24,000 watts simultaneously. That, in most cases is good to run a hell of a lot of stuff. Some typical big power eaters are electric baseboard heat, compressor based AC, electric water heaters and ranges. How you divvy up your watts is up to you.

Buckshot is correct: don't bond your neutral and ground in the sub panel..

I hope I didn't go all Sheldon from big bang theory....
 

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Alberta Strong
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There is nothing in the electrical code that dictates the maximum size sub panel allowed. You can technically install a 100 amp sub panel on a 100 amp main panel. What is more important as far as safety and compliance goes is that your wire is sized appropriately for the breaker size and that your wiring method, whether if its the appropriate cable type or conduit and thhn wire is properly sized and terminated.

As far as capacity goes , being that your main breaker is 100 amps your bus bar should also be rated to carry 100 amps. No matter how many sub panels or individual breakers you put down stream you won't be able to pull more than 100 amps total before the main trips off.

Adding up all the breakers does not address the total capacity , in your case 100 amps. In most electrical services if you add up the total number of amps for all of the breakers you will almost always exceed the total amperage of the service. Contrary to popular belief if you install a 50 amp breaker and use the appropriate size wire on a panel that has already 80 amps used you will not burn your house down. However if both the main panel load and the sub panel load exceed 100 amps you will trip the main breaker.

If you have concerns that you will not have enough capacity to run your new sub panel loads turn on everything that you would normally have on at any given time, amp clamp both your A&B phases to see how many amps you are pulling, chances are they won't be balanced - average the two. Estimate what your new load will be. If those 2 numbers don't exceed 85 amps you will be good to go. The rule of thumb and electrical code state that your electrical service shouldnt exceed 85% of the continuous load. Continuous load is what is run non stop for 3 hours or more.

Think of it this way... How often does anyone truly have every electrical device running full bore all at the same time? If we did us electricians would be millionaires from putting 400 amp services in everyone's houses!!

A good way to save on amperage is to get big load items like welders and compressors set up for 240 volts .. That's 1 reason that ranges and dryers are 240 volts. A 100 amp service is good for 24,000 watts. That's 24,000 watts simultaneously. That, in most cases is good to run a hell of a lot of stuff. Some typical big power eaters are electric baseboard heat, compressor based AC, electric water heaters and ranges. How you divvy up your watts is up to you.

Buckshot is correct: don't bond your neutral and ground in the sub panel..

I hope I didn't go all Sheldon from big bang theory....
I second this. :thumbsup
 

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The Extreme Member
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Message sent
 

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Yeah, but you're Canadian. Don't you have different electricity there, kinda like how your dollar isn't really worth a dollar (U.S. that is)?


Sent from Motorcycle.com Free App
We call it a "Loonie", and its worth about 35 cents after taxes :(.

We do have "Medicare" though, which is free provided you live long enough to get an appointment and the "doctor" you eventually get to see is conversant in at least one of our official languages.

"Did I mention its cold as a whore's heart up here" :D.
 

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As to the "point"; I've recently had a garage built with a 100 amp pony panel fed from my 200 A house entrance. The Electrician did mention he could have installed a 200 A pony using more robust wiring if I had wanted it.

IMHO, when it comes to wiring, its prudent to resist the temptation to massage the codes using "do it yourself" skills in order to save a few bux. If your home ever catches fire, for any reason, your insurance company will check the wiring in an attempt to get off the hook.
 

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As long as you get a building permit and it meets building codes after inspection, they have no leg to stand on. There is no law stating the work must be done by a licensed electrician.
 
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