Converting building from single phase to three phase... what is needed ? (photo)

Power company will run 3 phase wiring to building at reasonable cost but main breakers must be changed...and, what else ? Building is commercial flexspace with nine spaces, thus the "house" meter and nine seperate meter boxes.

Each meter has 4 poles..would those be left as is ? Would the 120 volt single phase be dealt with via transformers for each metered space, and if so, where...inside or outside ? And FWIW, although there are nine potential spaces, in reality..so far it's more like seven spaces...as one company owns two spaces as one unit and so do I....the remainder are empty shells unsold as yet.

In the photo, I believe the two boxes on the right side have to do with the irrigation system electrical. Also, isn't it sort of lame to have all that stuff just tacked on the wall outside like that ? I mean, anyone could come along, unscrew a panel, flip the main and shut down the power for every business in the building seems to me.

Outside meters are common, actually the norm for most powercos. many will only allow inside meters in certain circumstances, such as high rise buildings with inside transformer vaults, etc.

As for the requirements.....

meter boxes may need to be changed.... quite likely that the breaker boxes may need to be changed, as they probably do not have provision for 3 buses.

The meter is the business of the powerco. They have a requirement, which probably is available from them as a handbook, for services. They will require a certain form of meter box for each type of service, which your electrician needs to install for them. They then put in the meter to establish/initiate service.

So, the answer to your question is that the powerco and your electrical contractor are the folks to give you a good answer, compliant with local codes. Powerco generally won't initiate service without the facility having been brought up to code for that type service, evidenced by the local inspector having signed it off.

Each meter base has 4 jaws?

You may be keep some of the existing bases if 120/208 single phase is OK for the remainder of the 9 units and you choose a 208/120 3ph wye service... If you choose something different the sky is the limit on cost.

Each meter has 4 poles

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Sounds like single phase 240-120, 2 jaws "in", 2 jaws "out".

What flavor of three phase do you want?

What flavors do they offer?

What flavors you definitely don't want?

What flavors you can tolerate?

If they gave you "four wire" three phase (which may be obsolete), you would get:

120/240 (which implies nothing changes for the others.)

240 three phase, (two transformers on the pole, perhaps, not three), and that would be (perhaps in addition to the existing panel you have, in your space. I have been told up to 800kva (hey, that's what the local utility guy said....)

And yes, our members that are real electrical engineers may take issue with what I just said.

Keep in mind that the NEC has (in the past) limited services to a maximum of six, and that may apply to you, or may not......


Remember, my advice is at no cost to you.....

The single phase service should be left alone and a new 3 phase meter socket and CT panel installed as well as a 3 phase distribution panel. The items that need three pahse will be run off the new stuff leaving the single phase alone. it is too costly to redo all your single pahse just because you may need to run a few 3 phase devices. They way the transformers on the pole will work is as follows. the utility could choose to build a 120/240v 3 transformer bank for light and power that wil feed both service entrances but they likely will not. they will probably leave your single phase alone and install a 2 transformer 3 phase bank on an adjacent pole this can be done on the same pole too. We call these an open delta three phase bank and they work well when light three phase loads are present. the single phase meter you have is not compatable with three phase power. I am a lineman for duke energy and I do these upgrades all the time. There is alot more detail to what I have given but if you have more specific questions you can email me.

I have never had any dealing with real 3 phase power, but I was told that a building may not have both a single and three phase entry. Hence the use of a single phase transformer for lighting etc. circuits Is this a local code thing or an insurance company requirement or a myth? Two of my neighbors run extension cords to their farm shops to bring in single phase.
Rob

Are you going to have three phase to all spaces or just some? 460 or 208? Most of the building that I have built in this area have inside electrical rooms or separate attached area for electrical. keeps the riff raft out. Access boxes are provided for power co and fire Dept. For the most part everthing gets changed except for the single phase stuff you are keeping...

robvds said:

I have never had any dealing with real 3 phase power, but I was told that a building may not have both a single and three phase entry. Hence the use of a single phase transformer for lighting etc. circuits Is this a local code thing or an insurance company requirement or a myth? Two of my neighbors run extension cords to their farm shops to bring in single phase.
Rob

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Local handbook for the powerco calls out single and 3phase as different, and allows separate drops for them if of different frequencies, voltages, or phase count. That said, most buildings I have been in simply derive the 120 out of a transformer if they are 480. Obviously it doesn't apply if 208 3 phase is brought in.

I don't know if the powerco here would rather drop 208 separately, or combine. Separate is easier as an upgrade, if the 3 phase is goingf to separate areas and loads. But I have seen buildings converted over to 208 and re-wired.

Around here all 3 phase is 600volt
Rob

My shop has two drops coming in and two meters, one for single phase and one for 3-phase. (In Louisville, KY.)

I would certainly try to add 3 phase rather than convert the building to three phase. Then the only additional wiring is to run the three phase where you need it.

We went from single to 3 phase..... 120-0-120 to 208 3ph.

The local powerco (not the one I quoted, the town actually has an independent powerco) redid our drop to 3 phase, and put our single phase on 2 legs of it.

The panel was upgraded, some of the 3 phase goes thru it. As I understand it, the panel had provision for a 3rd bus, so that was fairly easy, it got added.

It must be said that our original drop was from 2 of the three transformers that still exist out on the pole...... so essentially what happened was they added a 4th wire, and we changed our panel to accept it, plus we added a 3 phase main breaker and single wire connectors for the equipment testing area.