New service to home shop opinions

docdesigns · Aug 24, 2016

I am installing a new underground separate service into my home shop and have a question about the service entrance sizing of the neutral. It would be common place here to run a 3 wire aluminum direct burial cable consisting of 2-4/0 hots and 1-2/0 neutral for a 200 amp 240 volt service single phase. The main loads will be a 3 phase convertor running one 7.5hp CNC VMC and one 7.5hp CNC lathe.

I am wondering if running a full size neutral and using a triplex type direct burial 4/0 cable would be of benefit instead of the downsized neutral? The cost between the two is very little.

This distance is 225 feet from the utility pole with the transformer to the meter socket and main panel.

Thanks for any help.

cg285 · Aug 24, 2016

bigger is always better with wire size. i just recently ran 225ft 3-4/0 alum burial cable for my 200@ 240v underground service. i saw no reason to cheap out on the nuetral

Bill D · Aug 24, 2016

The important distance is the run from the meter to the shop panel. No need to up the neutral unless you expect to have huge 120 volt loads running all at the same time. Except for lighting, vent fans,hand tools I doubt if you will have any need for more then 10-15 amps of 120 volt service. Just make sure any ac is 240 volt and any machine tool over say 2 hp is 240 and the smaller neutral will be fine.
If you feel the need to increase wire size up the load lines rather then the neutral. Depending on inspectors you can buy cable and breakers/panels from craigs list. I bought a loaded breaker panel from Ebay ten years ago for about $100 delivered. The panel alone was over $100 back then. I ran #2 wire (craigs list find)since it was cheaper then #4 from the store.
I think it is a good idea to use the same make of panel as you already have. Assuming it is a good brand. That way you can swap breakers around as needs changes and also for testing.
As long as you have a trench open drop in some pvc conduits for later use for tv. phone, alarm or whatever gets invented in a few years.
Bil lD.

CountryBoy19 · Aug 24, 2016

Bill D said:
The important distance is the run from the meter to the shop panel. No need to up the neutral unless you expect to have huge 120 volt loads running all at the same time. Except for lighting, vent fans,hand tools I doubt if you will have any need for more then 10-15 amps of 120 volt service. Just make sure any ac is 240 volt and any machine tool over say 2 hp is 240 and the smaller neutral will be fine.

This ^^^
The reason the neutral is smaller is because it is accounting for 240 V loads and proper leg balancing. Even if you have large 120V loads, if they are balanced across both legs and run at the same time there will be very little current running on the neutral wire, most current is flowing on the 2 hot legs. For true 240 loads all the current is on the hot legs.

gadget73 · Aug 24, 2016

What they said, neutral is for unbalanced 120v. With a phase coverter as your primary load, you're probably only really going to use 120v for lighting, controls, etc.

Big +1 on laying an extra pipe for future wiring needs too. You may never use it, but you'll cuss if you decide you want to add something and have to trench all that open again. PVC conduit is pretty cheap.

JRIowa · Aug 24, 2016

Bill D said:
No need to up the neutral unless you expect to have huge 120 volt loads running all at the same time

Probably won't pass code. It's been a while now, but all 220 VAC single phase require neutral and ground per NEC. IOW, 4 wire for all 220 connections.

Do you HAVE to do it? Nope! No unless you never intend on selling it. Then you'll have to fix it or the buyer won't be able to get insurance. I can guarantee you that it will be cheaper to put it in now than later.
JR

Bill D · Aug 24, 2016

I did not mean no neutral. Of course you have to have a neutral wire. It just can be a little smaller, per code, then the two hots. I believe the ground can also be smaller, check code on that one.
Bill D.

Monarchist · Aug 24, 2016

docdesigns said:
I am installing a new underground separate service into my home shop and have a question about the service entrance sizing of the neutral. It would be common place here to run a 3 wire aluminum direct burial cable consisting of 2-4/0 hots and 1-2/0 neutral for a 200 amp 240 volt service single phase. The main loads will be a 3 phase convertor running one 7.5hp CNC VMC and one 7.5hp CNC lathe.

I am wondering if running a full size neutral and using a triplex type direct burial 4/0 cable would be of benefit instead of the downsized neutral? The cost between the two is very little.

This distance is 225 feet from the utility pole with the transformer to the meter socket and main panel.

Thanks for any help.

Single-phase already covered.

Future-proofing?

You find a 'deal' on the wire, you MIGHT want to make that run readily convertible to 3-P, 5-wire Wye, OR Delta... and per code for it.

OTOH, anything TOO DAMNED overbuilt is the same as burying RECEIPTS for MONEY you cannot really recover.

Risking the need to trench again in five or fifteen years for an upgrade that may NEVER happen could be cheaper.

KISS

Go one-size up per code for the run and its various parameters. The small extra cost comes back over mebbe 20 years off the 'lectric meter from reduced Ohmic loss.

More than one-size up, diminishing returns. Not usually any further payback you can still measure.

Bill

JRIowa · Aug 24, 2016

Neutral must be same size as "hot" wires. I don't remember calcs for ground, but it is reduced.]
JR

gadget73 · Aug 24, 2016

Honestly I'd go with the normal single phase wiring of appropriate size, plus a good size conduit for future expansion. If you ever run proper 3 phase, you can drag it through the pipe when that time comes. Conduit is cheaper than a bunch of extra fat gauge copper wire.

gbent · Aug 24, 2016

Ground must be as large as the largest single current carrying conductor.

Monarchist · Aug 24, 2016

gadget73 said:
Honestly I'd go with the normal single phase wiring of appropriate size, plus a good size conduit for future expansion. If you ever run proper 3 phase, you can drag it through the pipe when that time comes. Conduit is cheaper than a bunch of extra fat gauge copper wire.

An employer some forty-odd years ago figured that way. Then, as the biz grew, one hot summer they went dark and found they had melted the power feed jacketing and part of the wire itself right into the conduit walls.

Serious trenching op cross the carpark followed, and at a 'combat speed', what with their HQ AND second-largest retail showroom hard-down.

Bill

Rock6.3 · Aug 24, 2016

Monarchist said:
An employer some forty-odd years ago figured that way. Then, as the biz grew, one hot summer they went dark and found they had melted the power feed jacketing and part of the wire itself right into the conduit walls.

Serious trenching op cross the carpark followed, and at a 'combat speed', what with their HQ AND second-largest retail showroom hard-down.

Bill

I'm not sure what you are attempting to convey here. Are you saying that direct bury cable without the conduit would have prevented the outage?

Monarchist · Aug 24, 2016

Rock6.3 said:
I'm not sure what you are attempting to convey here. Are you saying that direct bury cable without the conduit would have prevented the outage?

No Fine Way! Conduit is righteous!

Only saying that you have to pay just as much attention to slowly creeping growth as purposely planned major additions.

Their overload "sneaked up on them". It was a sustained one, not just a peak.

That should not have happened, even if all they did was pay basic attention to the electricity bill

Bill

brooksie · Aug 25, 2016

This is a sub-panel, I think code requires 4 wire connection with ground and neutral separated. Local code might let you put ground rod at breaker panel for separate ground.

Pete Deal · Aug 25, 2016

Here the run between the utility pole and the meter socket is owned and controlled by the utility company. Ours is a branch of First Energy and yours may be too since they seem to control half the country. They have guidelines on their site on their standards for new services. The way it is done here is that the owner puts the conduit in the ground (3" for 200a) and they pull and terminate their wire. This is not a sub panel since the run between the pole and the meter socket is the first run so all they run are 2 hots and a neutral. One thing that is not clear is this your house or a separate building? Here they won't run two services to the same building. One suggestion that I did on my shop is to install a meter/disconnect instead of just a standard meter socket. This makes doing major stuff in your panel a little nicer since you can shut if off if you want.

Monarchist · Aug 25, 2016

Pete Deal said:
. One suggestion that I did on my shop is to install a meter/disconnect instead of just a standard meter socket. This makes doing major stuff in your panel a little nicer since you can shut if off if you want.

+1, Amen, MORE than "a little" nicer, and write THAT on the wall!

Wouldn't want to have to handle installing a (several..) new panel(s) "hot", now, would we?

DAMHIKT.

Bill

cg285 · Aug 25, 2016

Pete Deal said:
Here the run between the utility pole and the meter socket is owned and controlled by the utility company. Ours is a branch of First Energy and yours may be too since they seem to control half the country. They have guidelines on their site on their standards for new services. The way it is done here is that the owner puts the conduit in the ground (3" for 200a) and they pull and terminate their wire. This is not a sub panel since the run between the pole and the meter socket is the first run so all they run are 2 hots and a neutral. One thing that is not clear is this your house or a separate building? Here they won't run two services to the same building.

same here but in my case the second building (shop) was all up to me. power company connected their end and put the meter in.
also one county i lived in, osceola (the taxation county), it was you dig the 3' hole and lay conduit, inspection, fill to 18" and lay flag tape, inspection. 60miles away: do what you want, no inspections - although 2' direct burial is normal

SteveF · Aug 25, 2016

gadget73 said:
What they said, neutral is for unbalanced 120v. With a phase coverter as your primary load, you're probably only really going to use 120v for lighting, controls, etc.

Yes, but this is why we have the NEC and electrical inspections. Because every once in a while someone puts in lights, a 120v shop vacuum system, plugs in a 120v table saw, plugs in a 120v heater and, by sheer luck, all happen to be on the same leg and because it was done according to the NEC, it doesn't overheat the neutral and melt the service feed.

Doc - If you are pulling a full 200 amps, your voltage drop is 4.1% which is good according to the NEC MINIMUM, 3% is the NEC Recommended, so I personally would bump up the cable size.

Steve

JST · Aug 25, 2016

The meter is where your stuff really starts, but check with the utility about your requirements. Here, the overhead drop is theirs, we are responsible for everything from the weatherhead onwards.

But for buried, we are responsible for all of it out to their designated connection point, which may not be right at the pole.

Conduit is best, and not the minimum possible size, either. Keeps you from having to dig it up the whole way later.

Yes, GROUNDS can be smaller, but not neutral.

The whole wire size deal is a joke, actually. YOU have to put in 200 amp service, and run heavy cable. Then the powerco has you sharing a 15kVA transformer, with 8ga wire dropped to your meter........ You still have to comply, though. They MIGHT put in a more capable source.........

New service to home shop opinions

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