3 phase service

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bth0mas20

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Im will be installing a 120/208 3 phase service in a machine shop. Their is already a single phase 240v service that the man is using a phase converter for his 3 phase needs. He is getting more 3 ph equipment so will need a service to meet the demand.

can I mount a disc swith on the other side of the block wall from the meter? Does it have to be fused? Then come out of the disc sw and feed the existing 3 ph panel that is 40 ft away and presently being fed by the phase converter.

Or do I need to just mount the 3 ph main bkr panel and re wire the branch circuits 40ft back to new panel by meter.

Also their is concrete outside of the wall that the meter will be mounted on.
My next question is about grounding the service. What is the easiest way to ground this new service? Can I use the existing single ph ground or do I need to bust up concrete? What are my options? Any help would be apprecieated.
Thanks.
 
bth0mas20 said:
can I mount a disc swith on the other side of the block wall from the meter? Does it have to be fused? Then come out of the disc sw and feed the existing 3 ph panel that is 40 ft away and presently being fed by the phase converter.
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Yes, yes, and that would work.

Or do I need to just mount the 3 ph main bkr panel and re wire the branch circuits 40ft back to new panel by meter.
Click to expand...
That also could be done.

My next question is about grounding the service. What is the easiest way to ground this new service? Can I use the existing single ph ground or do I need to bust up concrete? What are my options?
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The GEC must be unbroken between the main disco and 'the' electrode. Jumpers may be used between electrodes, but may only be downsized to #6 for the portion connecting only an earth electrode, such as a driven rod.

With a main disco back-to-back with the meter, whether a separate disco or the main of a panel, that's where the neutral bond and electrode connections must all be made. I'd have to see your present install to advise further.
 
So are you planning to have a single phase service as well as a 3phase????

The grounding won't be any different than single phase.
 
Call the power company engineer to make sure the 3 phase is available.
Or if they are going to charge to bring it to you.
The disconnects have to be "grouped"
 
He plans to keep his single phase service and add the 3 ph next to it.
Is their a problem with that. I will refernce 230 and look some more.

How would you drive groundrods if theirs only concrete their.
Drill holes and chip up or protect it in ridgid along the top of concrete till reaches dirt. It not a high traffic area.

Also the service company is comming out their to evaluate the install. They claim the business next door has 3 ph that they can come from. Im currently waiting to hear If they can do it and what voltage it will be at. Hopefully 208 because of his equipment being rated at 240.
 
Also can you clarify how to group these disconnects. Ive never had a job like this yet and im learning alot so far..Thanks for all the help so far.
 
I think with both single and triphase service most poco will discorurage haveing both on them something like 120/240v 1? and 208Y/120 3? system on the same premise they will ask the owner of that place once you get 3 ? installed then you have to get rid of single phase drop so they can use one meter for all of it unless you got two complety diffrent voltage system that diffrent matter.

My POCO will ask the customer to go with three phase much as they can and kick the single phase drop out of the spot.

Merci,Marc
 
bth0mas20 said:
Also can you clarify how to group these disconnects. Ive never had a job like this yet and im learning alot so far..Thanks for all the help so far.
Click to expand...

As I understood it you have a meter outside with the main directly inside, back to back. No disconnect outside.
If your existing three phase panel is 40 ft. away you will be required to install a disconnect before it enters the building. Then the other, the existing 120 v disconnect would have to be outside, too.

I did one almost exactly like your doing. I called the AHJ (Inspector). He volinteered to come out and take a look before I started. If something looks reasonable and safe, they might work with you. They did me.
I ended up not setting a meter base. The poco put CT's on it and the meter was on the pole. Still had to have the fused disconnect.
 
I would set up a site meeting with POCO and AHJ. If you are not guaranteed the job I would work out a consultation fee with the owner and tell him your scope of work is dependent on the requirements of the POCO and AHJ. Everything up to the service point is strictly governed by POCO, and everything after that is NEC- regardless of what the AHJ might think. Having AHJ there might save you some headache
Bill
 
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