# Sub Panel



## Chipy (Apr 20, 2011)

I would like some advice from some LJ'S good at wiring.Any advice would be appreciated.My shop is in the garage and so is my electrical panel.I am running out of room in the main breaker box and would like to add a sub panel.I am thinking 100 amps and 8 position sub panel.In this sub panel i would like to have two 30 amp double pole 240 volt breakers and two extra spaces for 110 volt 15 amp breakers.Off this sub panel







the only two things running at the same time will be a table saw(3hp 240volt single phase and dust collector(2hp 110volt single phase)Please look at my diagram to see if this set up will work.


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## lew (Feb 13, 2008)

Better check with a local electrician about whether this is a "legal" code upgrade. This may put too much of a load on the wiring that feeds the original panel box. It may also void your homeowners insurance.

Just my 2¢


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## hairy (Sep 23, 2008)

The thing I see that I would want more info on is replacing a 30 amp breaker with a 100 amp breaker. The box might be rated for 30, but not 100. You are replacing a 30 amp circuit with a 100 amp circuit. The box might not be able to carry a load that size. I am NOT an electrician, that's why I would find out more before doing it.

I realize it won't always carry a 100 amp load.

My garage has 100 amp service. I have 2 circuits

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220 volt, 20 amp, 3 circuits
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 110 volt, 20 amp, and 6 circuits @ 110 volt 15 amp. The 20 amp 110 volt circuits each have 4 double outlet boxes, for power tools. The 15 amp circuits are lighting only.

My breakers add up to 180 amps. Everything doesn't run at the same time.


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## helluvawreck (Jul 21, 2010)

I would not touch this question with a 10 foot pole. I've done a fair amount of wiring but I always consulted with an electrician and/or worked under his supervision. The reason that I do this is because I have worked in industrial maintenance for over 30 years and I know how dangerous electricity is. If the current goes across your heart it takes a very small amount of current to kill someone. I have also seen how fast a fire is created by an electrical malfunction. It's very important to consult, or work with, a good electrician and to also have the job inspected. If you don't, and you have a fire and it damages your property or harms or kills someone, your insurance company might not pay off. You need to look at the fine print in your policy to see what if anything it says about this. They have ways to determine where and why a fire starts. The main thing that I am sayoing is be careful and take these things into consideration. If you can ever acquire an electrician for a friend do it.


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## crank49 (Apr 7, 2010)

I'm sure someone will tell me that I should not respond with this information, liability and such, but I'll just say, if that was my electric panel I don't see any problem at all with what you are proposing. Replacing a 30 amp breaker with a 100 amp breaker is done all the time. The buss in the main panel has, by design, the capacity to handle any breaker that will fit. In fact I did the exact same thing in my house to run a welder in my garage shop. That was 30 years ago and I haven't burned down the house yet.

Now, I can't say you can do this yourself, because I don't know your ability. I also don't know what the code, permit, insurance, liscensing requirements might be in your situation. I just saying, as an engineer, I don't see a problem with your plan from a design point.

And by the way, that's a very nice drawing. I've had to work with young snots fresh out of school who could not draw that, and I doubt they could read it either.


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## Ken90712 (Sep 2, 2009)

I put an 80 amp sub panel in my garage/shop. My main is 200 amp….I did it all my self with the city inspectors buying it off. When you ck with the city they usually are a big help. I assume your main is 200?


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## DonnyBahama (Jun 21, 2011)

By any chance is your water heater in your garage? Mine is and I recently discovered that there's a 240V circuit with 2×30A legs that was put there in case someone ever decided to replace the gas water heater with an electric one. I'm going to feed a small surface-mount box with this and install 4×15A breakers - one for my dust collector and one for a single-outlet for powering whatever high-power-tool-of-the-moment on one 30A leg, and one breaker for lighting and the other to feed all the standard outlets for low-power draw tools on the other 30A leg. The whole thing will cost me less than $100. (Note: I already have a separate 240V dedicated circuit for my table saw and a specially designed 240V to 2×120V "extension/adapter" cord for use as needed.)


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## helluvawreck (Jul 21, 2010)

*Crank*, I don't have any problem with you or anyone else responding to the question. Personally I will not respond to any question like this - especially if I'm not there in person to see it for myself and even if I am there I will not. Our plant has a 3 ph, 600 v, 4000 amp service and our electrical system is distributed across a 180,000 sq ft building. I have been involved with much of the wiring one way or the other whether done by electricians or not. However, most of the time that I spend on electricity is involved with trouble shooting the control circuits of our machinery and occasionally building a control panel for a special machine that we build in our machine shop. However, even though I might know the answer to a certain electrical question posed on here I will not answer it (and I think that is best). However, I will generally give a statement similar to what I have given here because I do know that electricity is very dangerous - much more dangerous than most people realize. Anyways - no harm done.


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## helluvawreck (Jul 21, 2010)

However, I will say that I see one thing in the drawing that I would personally question in my own mind. I'm pretty sure that what I'm talking about would not be done that way here in our county. That's one of the problems; different cities, counties, and states can differ on certain details across the country. Anyways, everyone must make their own judgements about things like this. I think it's best to just ask a local electrician in your local area. Actually, in our Lowe's there is a retired electrician that runs the electrical department and he hasn't been retired all that long. He seems to be very knowledgeable about house wiring and is also very friendly. That isn't a guarantee that his answer will be correct.


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## dkirtley (Mar 11, 2010)

Adding a 100 amp sub panel like that is no problem in itself. The wiring you show looks about right. The problem is that you don't give enough information to know if the main feed circuit is sufficient to add that big of a circuit. Without knowing what the local standards are, it is not possible to say.

The things that you have to consider are not just the running loads. You have start up loads as well. We also don't know what is on the other circuits. It makes a difference. Especially with a lot of the sensitive electronics we have in our houses now.

I have worked as a licensed journeyman electrician many years ago and I would still call in a pro for that big of a change to the service. If for no other reason than to not have anything that homeowner's insurance company could point fingers at. I just wrote a $350 check to an electrician the other day to do some work , part of which I could have done myself. It just isn't worth it.


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## crank49 (Apr 7, 2010)

*Helluvawreck*, I assume no offense meant and certainly none taken. I think we all try to help our fellow LJs whenever we think we can. I've just been jumped on before for giving electrical advice so I was trying to qualify things up front. By the way I started out as a maintenance electrician in 1972 and still work as a sparky from time to time, usually installing machines I design and build now.


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## helluvawreck (Jul 21, 2010)

No, *Crank*; absolutely no offense meant to you and none taken by me. I've just seen a couple of fires over the years occur in some of the plants I've worked in - none of them big fires. Recently there was an accident a couple of counties over where an HVAC man was electrocuted in an attic and his co worker was severly injured. It was a big deal case. The accident happened when he stepped on a wire that was fastened to the top of a rafter with a wiring staple - something as simple as that. Not only is the HVAC company being sued so is the homeowner. The homeowner had just purchased the house and was simply having HVAC work done on the house by a licensed company. The wire should probably not have been run across the top of the rafter and the wire staple was probably driven in a little too tightly. He stepped directly on top of the staple. It was just a fluke accident. I may be overly cautious - I don't know. Also, insurance companies are a little less lenient than they use to be. Anyways - I enjoyed talking to you.


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## DonnyBahama (Jun 21, 2011)

That is SO messed up that the homeowner is being sued over that. What was he supposed to do? Go up in the attic and inspect every little thing before allowing the HVAC contractor up there?! Having just purchased the house, I can't understand how the homeowner can/should have any culpability. Litigation in this country is SO out of hand!!! Utterly ridiculous.


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## Grandpa (Jan 28, 2011)

I think they have to sue the homeowner in order to sue his insurance company. I am certainly now lawyer but I think that is what they do. 
On the drawing above this should work IF the main panel has the capacity for this load. If it is already filled with larger circuit breaker then there could be a problem. This should be listed on the panel data. 
On the safety issue…..there I was asked by a family member if there was a possibility of not being able to resusitate someone if they were shocked at the right time. I said sounds unlikely to me but I am no doctor so I will ask since I go to Sunday School with 3 doctors. Well, the next week I asked the first one that showed up and sure enough he said if you get even a small shock at the correct time you will probably no be brought back. The heart works on electrical discharges if I understand it correctly. He told me if the shock came just after your system discharged its impuls then you would be in troble. Talk about trying to time a shock…. I am not a doctor so that is the way I remember it. I know we have some doctors on here.


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## TopamaxSurvivor (May 2, 2008)

Assuming you have a 200 amp main panel you should be fine. The only issue I see with your drawing is the ground needs to be separate from the neutral in the sub panel. All bonding takes place in the main service and is separate through out the rest of the system. The neutral is insulted from the panel. Do not install the bonding screw. You will probably have to get an equipment grounding kit and add it to the panel.


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## Grandpa (Jan 28, 2011)

Good point and exactly correct.


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## helluvawreck (Jul 21, 2010)

*Donny*, don't get me started on lawyers and big government but s**t happens.


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## DonnyBahama (Jun 21, 2011)

What was that joke about a thousand lawyers at the bottom of the ocean?


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## TopamaxSurvivor (May 2, 2008)

Good start! ;-))


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## Chipy (Apr 20, 2011)

Hey I got a lawyer friend next door I will just get him to hook up my sub panel problem solved just kidding!


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