Planning for new shop - electrical question

[Lou Ferrarini]

As I posted earlier, in a few weeks we are moving to a new house where I will have a basement shop. The first thing I will have to do is run a sub panel. My present shop has a 60 amp sub which has been sufficient. Since it is in a detached garage that was 100 feet from the house, I used heavy gage direct burried underground aluminum wiring to feed the sub.

Now the question. In my new garage the sub panel will be about 20 feet from the main panel. What is the proper AWG for 60 amps, using copper wiring. Also, would you use a breaker panel or a lug panel?

[Bernhard Lampert]

#4 AWG should do it.

As for the inside, I would use a 'regular' load center with 30 spaces. May be overkill, but makes wiring neat and easy without cramming wires and allows for future expansion. Make sure you get a panel with a separate ground and separate neutral. Ground and neutral only get connected at the main load center (Siemens makes a good one with a removable bridge from gound to neutral).

BUT, since you are in the enviable position to have an entire building, I would feed the sub panel with a 100A..for future expansion (AC, etc).

Congrats on the new wokshop!

Bernhard

[Lou Ferrarini]

#4 AWG should do it.

As for the inside, I would use a 'regular' load center with 30 spaces. May be overkill, but makes wiring neat and easy without cramming wires and allows for future expansion. Make sure you get a panel with a separate ground and separate neutral. Ground and neutral only get connected at the main load center (Siemens makes a good one with a removable bridge from gound to neutral).

BUT, since you are in the enviable position to have an entire building, I would feed the sub panel with a 100A..for future expansion (AC, etc).

Congrats on the new wokshop!

Bernhard

Thanks.

What is the max amps for #4? I thought I read somewhere it was 70 amps?

[David G Baker]

Depends on whether you are using copper or aluminum and the length of the run. Somewhere in the neighborhood of 70 amps.
I have a 200 foot run of #2 aluminum to my out buildings and figure that a 70 amp load is all I would feel comfortable with. I doubt that I would ever have a load any way near that unless I was running my welder, the air conditioner was on and my compressor started all at the same time.

[Brian O'Shea]

You should be looking for the minimum allowable diameter and go as much bigger as your wallet will allow! As mentioned earlier, future expansion is always a possibility. The 4 AWG will carry 60 Amps safely, the other consideration is that is the very rare ocassion that one would pull the entire 60 Amps on a continous basis. Code dictates that the "feed" suite the panel size so plan accordingly. Just remember you can NOT go wrong with bigger wire feeding a panel! If you look into a reel or roll of "single" conductor cable it is much less expensive than say # 4-2. The single cable roll (all of the same color) can be "legally" color coded with colored tape or paints for wiring identification. Most home centers carry 50', 75', 100' reels etc. which offer a great savings over the multi conductor cable. It is also much easier to work with!
Regards,
Brian

[Ray Knight]

some local codes &/or best practice limit the amps to a subpanel to some percentage, usually 1/2 of the original panel. I am facing the same issue. I have 200A to the house, 50A to the garage, and want to run a 50A subpanel for the ww shop addition. Codes are based on all or most of circuits being safe to use simultaneously. I am not personally worried, because I won't be running my welder, my grinders, my lift, my air compressor in the auto shop all at the same time I run a bandsaw, dc, and table saw. Fortunately I had hugely overspec'd the feed to the garage, so all I need to do is switch out the 50A feed breaker to 100A, then put in my new 50A subpanel, the wires are all big enough. RK

[Brandon Shew]

#6 AWG will safely handle a 60 AMP panel. If you run # 4 you could go to 80 AMPs. You could probably also get by w/ a #8 for the neutral and ground if you run a #6 wire. If you run #4 then you can use # 6 for the neutral and ground.

[glenn bradley]

I ran #6 but only about 4 feet. It is rated at 60amps per the manufacturer. I have a 125amp lug panel but use a 50amp breaker in the main to feed the lug panel. I wanted a master kill switch but the cost to benefit factor wasn't there for me. Do yourself a favor and run at least some of the lights directly off the main. That way if the panel should blow, you're not in the dark. All my lights are off the main with all tools and shop outlets of the sub.

[Von Bickley]

Lou,

You will be O.K. with a 6/3 with ground (copper).:)

[Greg Peterson]

I have a 60 amp, 12 space main lug load center for my 240 shop equipment. Shop outlets, lighting and heater are on the service panel, which is about six feet to the right of the sub panel.


I could have gone with a larger panel, but it would have not have fit where the smaller panel is now, and the cost of bigger wire and the longer run (twenty feet or more) just didn't add up for me. If I need more than six 240 circuits, then chances are pretty good I will have won the lottery.

[Chris Friesen]

What is the proper AWG for 60 amps, using copper wiring. Also, would you use a breaker panel or a lug panel?

Normally that would be #6. I went with a 125A breaker panel "kit" because it was cheaper than a smaller lug panel and separate breakers.

As others have mentioned, make sure you do a load calculation to ensure that your main service can handle the draw. You don't want to be tripping main breakers....

[Rob Russell]

#6 AWG will safely handle a 60 AMP panel. If you run # 4 you could go to 80 AMPs. You could probably also get by w/ a #8 for the neutral and ground if you run a #6 wire. If you run #4 then you can use # 6 for the neutral and ground.
It is not allowable to downsize the "neutral" conductor. That is a current-carrying conductor (CCC) and must be the same size as the "hot" conductors. The Equipment Grounding Conductor (EGC) can be smaller than the CCCs. For example, assuming copper conductors, per Table 250.11, up to a 60-amp circuit can use a #10 EGC and a 100-amp circuit can use a #8 EGC.

Rob

[Tom Veatch]

It is not allowable to downsize the "neutral" conductor. That is a current-carrying conductor (CCC) and must be the same size as the "hot" conductors. ...

I seem to recall from somewhere that the neutral conductor could be downsized under some conditions. Perhaps when the load is predominately 240v?

Not intending to contradict what you said, just trying to clear up possible confusion in my rememberer. IIRC, when I expanded the shop and upsized the electrical service several years ago, we pulled 2 #2 for the hot leads, and 1 #4 for the neutral. All but a couple of the circuits in the shop are 240v. Perhaps that makes the difference. And, of course, the code changes from year to year.

[Josiah Bartlett]

I seem to recall from somewhere that the neutral conductor could be downsized under some conditions. Perhaps when the load is predominately 240v?

Not intending to contradict what you said, just trying to clear up possible confusion in my rememberer. IIRC, when I expanded the shop and upsized the electrical service several years ago, we pulled 2 #2 for the hot leads, and 1 #4 for the neutral. All but a couple of the circuits in the shop are 240v. Perhaps that makes the difference. And, of course, the code changes from year to year.

Having recently had to replace a burnt out neutral in an otherwise perfectly good installation, I would not do this. I ended up replacing the neutral with the same size wires as the hot, and it was a royal pain to pull all that wire.

[Ray Knight]

I know that sounds silly. As many as you have machines and a few extra, right. But once the dry wall is up, I don't want to go back. I am currently putting 120 receptacles about every 6 ft, close to the floor, and every 4 ft, just above where the bench/counters will be. I am putting 220 where I think the saw and DC will be, and adding an extra 220 recept in each corner, and one in the ceiling where the TS will be. Does that seem about right. And while we are talking, how do most of you handle the power cord to the saw, just run it on the floor, put it in a floor mounted cable guard. I have seen it buried in the concrete, but don't want to cut the concrete now, not sure where I will keep the table saw. any thing except overhead or in the concrete seems to invite tripping and get in the way of sweeping. Appreciate experience, thanks Ray Knight

[Rob Russell]

I seem to recall from somewhere that the neutral conductor could be downsized under some conditions. Perhaps when the load is predominately 240v?

Not intending to contradict what you said, just trying to clear up possible confusion in my rememberer. IIRC, when I expanded the shop and upsized the electrical service several years ago, we pulled 2 #2 for the hot leads, and 1 #4 for the neutral. All but a couple of the circuits in the shop are 240v. Perhaps that makes the difference. And, of course, the code changes from year to year.

There are situations where the neutral conductor sizing requirements can vary. One example would be 3-phase wiring where 120v loads are sharing the neutral. IIRC, there are cases where the neutral has to be larger than the CCCs but that's getting way beyond what any of us would do in a residential shop.

When you rewired, your inspector could have allowed a "downsized" neutral for some smaller 120v loads if most of the load was 240v.

Remember that the AHJ (Authority Having Jurisdiction) is the final word on what is and isn't allowable. We tend to refer to the National Electric Code as the definitive electrical code, but it's really just a guideline. What is the code for a specific locality is an electrical code as they have adoped it. Many states use the NEC as a base and then modify it. Some areas don't even start with the NEC. So - if your inspector said the downsized neutral was OK - for you it's OK. My AHJ wouldn't allow it.

[Mike Henderson]

This is not a code comment - it's just a theory comment.

In most situations, a smaller neutral will work fine. Let me explain with some examples.

Suppose you use a 50 amp sub panel and wire only 120 volt outlets and you spread the outlets over both hot legs. If you pull 25 amps on outlets that are connected to one leg and no load on the other leg, the neutral will be carrying 25 amps. If you pull 25 amps on both legs, the neutral will be carrying zero current (ignoring power factor considerations).

If you have only 240 volt appliances, the current on the neutral will be zero.

So, in a most likely situation, the current in the neutral will be quite a bit less than the current in the hot legs.

But there is a chance that you'll pull all 50 amps on one hot leg (this would be 120 volt circuits) and that would overload the neutral if you used smaller wired for it.

So follow the code - just in case.

Mike

[Rob Russell]

Mke,

I agree with your theory. Remember that the electrical code is based on preventing fires, so it's going to take the route of most protection.

Rob

[Mike Henderson]

Mke,

I agree with your theory. Remember that the electrical code is based on preventing fires, so it's going to take the route of most protection.

Rob
I absolutely agree!! Code and the inspector are there to help/save you.

Mike