[r_marcinko]

Thanks in advance for any assistance. A couple of questions to follow, but I will try to give background to what I'm dealing with first.

I bought a shop that came with 3-phase power. All of my equipment is single phase, so I had service switched to single phase. I had an electrician install a safety switch and new single phase panels for all of my equipment. Everything worked out great.

Now to my question/confusion. After making the hookup of my new panels/equipment, the electrician tied the new single phase service into the original 3-phase entrance wiring and fed the existing 3-phase panel that way. Here's a picture of that:

Here's a picture of the pre-existing 3-phase panel that is now powered by single phase:

This three phase panel originally used to power several 3-phase circuits for the prior owner. I don't use any of these circuits right now, except for one that appears to feed anoter pre-existing panel that is single phase. Here's a picture of that panel:

This panel has circuits for lighting and outlets throughout shop.


So, I'm assuming I can clear out the 3-phase panel of all of those 3-phase circuits and start using it for single phase circuits. I am comfortable around single phase panels/circuits, but have never dealt with a 3-phase panel or breaker. How do I go about wiring a single phase circuit inside of this 3-phase panel that is now supplied with single phase power?

 

[joed]

Every third slot in the three phase panels will be dead. If you continue use them you will to determine which slots those are and put blank overs over them or blank breakers that do nothing.
It looks like he only used the red and black phases. Anything connected to the orange phase will not function.

 

[carmusic]

why did you change for single phase?, 3 phase system is ok for single phase equipment!

 

[MrElectricianTV]

why did you change for single phase?, 3 phase system is ok for single phase equipment!

Guessing by the orange leg, he had a delta service with no neutral. He could have installed a transformer for 120/240 single phase.

 

[r_marcinko]

I'm what electric company describes as "large power". Although my equipment could run on 3 phase, it's not ideal because it is all resistance loads. I was upgraded to the largest single phase pole transformer available. I have two 800amp safety switches, each have two 500mcm copper for each hot.

This three phase panel basically only handles my lights right now. is there a special type of breaker needed?

 

[beenthere]

Sounds like some big kilns.

 

[mpoulton]

Guessing by the orange leg, he had a delta service with no neutral. He could have installed a transformer for 120/240 single phase.

The original 3-phase panel had a neutral bar, with a neutral conductor from the main disconnect. The phases were marked black, red, and orange. Based on that, it was pretty clearly a high-leg delta service (120/240V 3 phase). There's no reason he couldn't have run his equipment on that service. Changing to single-phase-only was entirely unnecessary and makes the shop less valuable for literally no reason. Anything he could run on his new service could have been handled by the old service, perhaps with a transformer upgrade if necessary.

 

[mpoulton]

I'm what electric company describes as "large power". Although my equipment could run on 3 phase, it's not ideal because it is all resistance loads. I was upgraded to the largest single phase pole transformer available. I have two 800amp safety switches, each have two 500mcm copper for each hot.

This three phase panel basically only handles my lights right now. is there a special type of breaker needed?

Why did you ditch the 3-phase??? This just doesn't make any sense. You could have kept your 3ph service and just upgraded the main transformer in the bank to handle your heavy loads. The kind of service you had is not intended to handle mostly symmetrical heavy 3ph loads. It's meant for users who have mostly 1ph loads, plus some additional 3ph needs that are smaller. It seems to make very little sense to intentionally delete the ability to use 3ph equipment later on if you wanted to.

 

[micromind]

I don't mean any offense here, but only a fool would change a 3Ø service to single phase. And only a total hack electrician would do it.

That being said, a 3Ø panel has a bus extension (the part the brakes lands on) for each phase, then it repeats. Starting from the top and working downward, it's phase A, then phase B then C then A then B then C and so on.

When a 3Ø panel is supplied with single phase, one of the phases will be dead. Find out which one is dead and don't put breakers on those bus extensions. It'll be every 3rd one.

 

[r_marcinko]

Appreciate the thoughts. Believe me, i woulda liked to keep the three phase because there was a perfectly good 3 phase 10 ton air conditioner that is a brick now. But that was literally the only piece of 3 phase equipment that I will ever need. The existing 3 phase infrastructure, from the power company transformer all the way down way woefully inadequate. This was all told to me from power company engineers and electrician...so I converted. I'm happy with that decision because I'm used to the single phase equipment and it works very well. I'd just like to understand how I can use this old 3 phase panel to power a couple new circuits in the future.

 

[joed]

Like has already been said, You just need to skip every third space in the panel as it will be dead. You can even use the old three pole breakers and just use the two live terminals. That way the dead phase space will also be filled.

 

[mm11]

This is a commercial building- not a DIY situation at all

 

[AllanJ]

Did you say that you had to upgrade the (3 phase) service because it was too small, and in the process you chose single phase for the new, larger, service?

Now, are all the lines and wires and circuits marked with orange dead with the rest of the wiring live?

 

[r_marcinko]

Yes, the existing 3 phase service was too small to handle my requirements. I already owned all of the single phase gear that was necessary to complete installation once power company switched out to larger single phase transformer. It was a decision based on $, time and convenience.

Not sure I understand your second question. Yes the pre-existing 3 phase gear remains and is now supplied by single pahse and orange leg is missing.

 

[MrElectricianTV]

The original 3-phase panel had a neutral bar, with a neutral conductor from the main disconnect. The phases were marked black, red, and orange. Based on that, it was pretty clearly a high-leg delta service (120/240V 3 phase). There's no reason he couldn't have run his equipment on that service. Changing to single-phase-only was entirely unnecessary and makes the shop less valuable for literally no reason. Anything he could run on his new service could have been handled by the old service, perhaps with a transformer upgrade if necessary.

PSE&G in New Jersey does not permit a neutral conductor to be installed in a panel with delta power. I always had to install a separate single phase panel for the single phase loads. This sometimes became a problem when a piece of 3 phase equipment needed a neutral conductor as well, usually for an internal 120 volt control circuit.

I saw many delta panels in California with a neutral conductor. I also met a number of electricians who had no idea why they had high voltage to ground on one leg.

 

[mpoulton]

PSE&G in New Jersey does not permit a neutral conductor to be installed in a panel with delta power. I always had to install a separate single phase panel for the single phase loads. This sometimes became a problem when a piece of 3 phase equipment needed a neutral conductor as well, usually for an internal 120 volt control circuit.

I saw many delta panels in California with a neutral conductor. I also met a number of electricians who had no idea why they had high voltage to ground on one leg.

So you had to use a main disconnect, then feed separate panels for 3ph loads and 120V loads? That is very odd.

 

[MrElectricianTV]

So you had to use a main disconnect, then feed separate panels for 3ph loads and 120V loads? That is very odd.

No. I would install a trough and tap off the mains to feed each panel. One panel would get 3 hot legs only, the other would get two hot legs and a neutral.

3 power companies in NJ and only one has this restriction.

 

[TimPa]

Yes, the existing 3 phase service was too small to handle my requirements. I already owned all of the single phase gear that was necessary to complete installation once power company switched out to larger single phase transformer. It was a decision based on $, time and convenience.

Not sure I understand your second question. Yes the pre-existing 3 phase gear remains and is now supplied by single pahse and orange leg is missing.

just curious, did they pull new larger wires to supply the power to the existing 3 phase disconnect and subsequent distribution panel. from what I can tell, they look the same.

 

[TimPa]

PSE&G in New Jersey does not permit a neutral conductor to be installed in a panel with delta power. I always had to install a separate single phase panel for the single phase loads. This sometimes became a problem when a piece of 3 phase equipment needed a neutral conductor as well, usually for an internal 120 volt control circuit.

I saw many delta panels in California with a neutral conductor. I also met a number of electricians who had no idea why they had high voltage to ground on one leg.

if they would have been better served with a wye system, can that be achieved at the pole transformer, then run a neutral into the building? or does it have to be re-wired to wye farther back the transformer line? thanks

 

[MrElectricianTV]

if they would have been better served with a wye system, can that be achieved at the pole transformer, then run a neutral into the building? or does it have to be re-wired to wye farther back the transformer line? thanks

I suppose that the power company can do whatever they want. However from discussions that I have had in the past with power company reps, they don't make major changes for customers unless it is economically feasible for them. When you fill out an application for a commercial service change they want a load schedule included. If the biggest load is only a 10 ton air conditioner, they are not likely to make a change. However if a small factory is moving in with lots of equipment that will run 24 hours a day the power company will see a return and a profit on the investment that they made.

It sounds as though the OP to this thread had enough equipment that made it worthwhile for the power company to make the changes.