Adding a Three Phase Service

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physis

physis

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I'm working with a "master electrician" who thinks you can get three phase from a transformer connected to single phase. I was finally able to convince him that you can't, at least without extra fancy, expencive and unnecissary stuff.

My experience is mostly residential and small commercial and I've never done a new three phase service. So here're my questions:

[1] Am I gonna have a problem leaving the existing single phase service and be able to add a three phase next to it? I'd just ask the power company but strangely, it's not that simple for me. I'm still trying to convince the "master electrician" that he needs to do this.

[2] What can I expect the drop voltage to be?

[3]I need 240v. or 208v. for the only peice of equipment that needs to be powered at this point. Am I going to need a transformer and if I will should I use a 208v. Y if I'll need to power the existing single phase from the new three phase?
 
physis said:
I'm working with a "master electrician" who thinks you can get three phase from a transformer connected to single phase. I was finally able to convince him that you can't, at least without extra fancy, expencive and unnecissary stuff.

My experience is mostly residential and small commercial and I've never done a new three phase service. So here're my questions:

[1] Am I gonna have a problem leaving the existing single phase service and be able to add a three phase next to it? I'd just ask the power company but strangely, it's not that simple for me. I'm still trying to convince the "master electrician" that he needs to do this.

[2] What can I expect the drop voltage to be?

[3]I need 240v. or 208v. for the only peice of equipment that needs to be powered at this point. Am I going to need a transformer and if I will should I use a 208v. Y if I'll need to power the existing single phase from the new three phase?
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You are not working with a MASTER and rules here dont permit me to say what he is
What makes you think you need 3 phase to get 208 for i piece of equipment ? is it 3 phase or simply 208
 
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Jim W in Tampa said:
You are not working with a MASTER and rules here dont permit me to say what he is
What makes you think you need 3 phase to get 208 for i piece of equipment ? is it 3 phase or simply 208
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Well, he has a masters card, but I agree with you.

The equipment needs 208 or 240 three phase, period.

I'm thinking about 208 because I beleive a 208 three phase Y also gives me 120v. But I'm a little out of practice and I don't have a lot of three phase experience.
 
physis said:
Well, he has a masters card, but I agree with you.

The equipment needs 208 or 240 three phase, period.

I'm thinking about 208 because I beleive a 208 three phase Y also gives me 120v. But I'm a little out of practice and I don't have a lot of three phase experience.
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You need to contact the poco fast. Wanting and getting 3 phase are not the same
 
Jim W in Tampa said:
You need to contact the poco fast. Wanting and getting 3 phase are not the same
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I know this, It's killing me that it hasn't been done yet, stupid master electricians. :grin:

Edit: There really isn't a concern about three phase being availabe, it's a rather industrial neiborhood.
 
Not bad. I've pretty much made peace with the antagonist in this thread - Now, looking back at everything that's transpired, I'm glad it has happened, it's grown me a little more. With that in mind, consider it "Chicken Soup for the Soul" for your problem with your boss. ;)
 
If you only need 3 phase for one piece of equipment I would suggest going with 240/120 Delta. The poco (I?m guessing PG&E) can add a small transformer along side the existing single phase transformer to obtain the 3rd phase. You can then install a new 3 phase service and feed your existing service off it along with installing a new 3 phase circuit for the equipment. If the existing transformer feeds other customer you save the cost of installing a dedicated transformer just for your building. If you do go 3 phase wye what effect will it have on any existing 240 volt equipment in the building? I'm not sure if the poco or AHJ will let you keep the existing 120/240 service and add a 3 phase service with the same voltage.

How big is the equipment? Could you use a rotary phase convertor or a VFD?
 
curt swartz said:
If you only need 3 phase for one piece of equipment I would suggest going with 240/120 Delta. The poco (I’m guessing PG&E) can add a small transformer along side the existing single phase transformer to obtain the 3rd phase. You can then install a new 3 phase service and feed your existing service off it along with installing a new 3 phase circuit for the equipment. If the existing transformer feeds other customer you save the cost of installing a dedicated transformer just for your building. If you do go 3 phase wye what effect will it have on any existing 240 volt equipment in the building? I'm not sure if the poco or AHJ will let you keep the existing 120/240 service and add a 3 phase service with the same voltage.

How big is the equipment? Could you use a rotary phase convertor or a VFD?
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It's interesting stuff Curt and I've actually thought about the rotary phase converter but I don't consider it to be a satisfactory solution.

The equipment only needs 40 amps. But this guy's just starting out, he's just moved in to this place and I have little doubt his three phase demand is going to increase relatively soon.

Edit: in responce to your linked question George, I've fired employers like that. Let me ask you this, would you hang out with a guy like that or bring him to social affairs? If your answer's yes then fine, but if it's no, then why would you work or him?

This VFD acronym, what is one of those?

And, this idea of the power company adding another transformer next to the single phase transfrormer secondaries and providing three phase from the configuration, I haven't heard of this being done. It sounds interesting though.

As far as existing equipment in this building, it's super minimal. At most there's a water heater.

PG&E, nope, I've been in Arkansas for a bit more than a year now. My last stage name, Physis 3 I think, used to reflect that but George helped me get my original physis back, I've lost passwords a couple times, and I really haven't had time to update my profile, nor care much either to be honest.
 
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curt swartz said:
If you only need 3 phase for one piece of equipment I would suggest going with 240/120 Delta.
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What is this, 120/240 delta you speak of? I've read your responce but this peice of it sort of slipped by me. I've always considered deltas to be semetrical, otherwise it would be shaped like a sling slot, not a delta (triangle). Sometimes I hate knowing what words mean, it doesn't seem to help.
 
ED's4Wdelta2_(2).JPG

Delta....

Many places that seem like they should have 3 phase - sometimes well - don't. And if they do - maybe not the flavor you need.

Anyway - hate to say it. If you have to ask what a delta is - IMO you should not be putting "Master Electrician" in quotation marks - kinda hypocritical. JMSO

That said - for 40A - it would be more cost effective to buy new equipment, or rewire/swap motors for single phase. Because rarely is 3 phase just right outside the front door - if it were it would have been in the building already.
 
e57 said:
ED's4Wdelta2_(2).JPG

Delta....

Many places that seem like they should have 3 phase - sometimes well - don't. And if they do - maybe not the flavor you need.

Anyway - hate to say it. If you have to ask what a delta is - IMO you should not be putting "Master Electrician" in quotation marks - kinda hypocritical. JMSO

That said - for 40A - it would be more cost effective to buy new equipment, or rewire/swap motors for single phase. Because rarely is 3 phase just right outside the front door - if it were it would have been in the building already.
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I want to thank you very much for the schematic, that's very helpful.

But I hate to say that the rest of your post is rather a joke to me. For instance, I haven't and don't need to ask "what a delta is".

Master electrician is parenthisized because I find it humorous.

And you would scrap $100,000 of equipment because you're incapable of providing 40 silly amps of three phase. thanks for the advice.

And three phase is right out side.
 
I think the open Delta would be an ideal solution.

If you install a Wye, you might not like the reduced performance of the water heater (it might be a water warmer, lol).

You might also get into derating issues on existing circuits with a Wye. 2-hots and a neutral would no longer be 2 CCCs but would become 3 CCCs. If you had a conduit with 6 hots and 3 neutrals, your derating would go from 80% to 70%. With THHN conductors that might not be an issue, but it is something to look for.

The Delta seems to be an ideal solution (oh yea, I already said that).
 
So many posts and yet no answer. :D (Only because no one from your power company has answered)

I agree with that the NEC will allow both services, beyond that your at the merci of the power company.

In my area we have a lot of power companies and each one handles things differently.
 
I've already found out what VFD is but thanks non the less. I've managed to sort a steer these guys into that but now they're overly bent on going with that. The trouble is that the VFD costs about $2000 and the existing single phase panel is only 100 amps. I think it would cost less over all and allow for expansion if we installed an additional three phase panel. These people, or more specificly this "master electrician" still will not contact the power company to get any details on the three phase that's available. At some point I'm going to do that myself but unfortunately it's not gonna matter, the best I can do is sort of sublimanaly guide this guy. Hardly an electrical issue but it is in a very real sense, part the job.

And I do appreciate your guys's input.
 
iwire said:
So many posts and yet no answer. :D (Only because no one from your power company has answered)
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You're exactly right Bob, I'm damn near pulling my hair out because none of these idiots will ask the power company what they can provide.
 
e57 said:
ED's4Wdelta2_(2).JPG
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You are only partly correct.

Your diagram is not a simple DELTA configuration.

It is a very specific delta where one winding is center tapped. The resulting configuration is properly called a 240/120 3-phase 4-wire system, although it goes by many other names including: High leg delta, wild leg delta, center tapped delta.
 
jim dungar said:
You are only partly correct.

Your diagram is not a simple DELTA configuration.

It is a very specific delta where one winding is center tapped. The resulting configuration is properly called a 240/120 3-phase 4-wire system, although it goes by many other names including: High leg delta, wild leg delta, center tapped delta.
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Your point being? Odds are better that there may already be a portion of a service like it there, if there is 3 phase in, and being used in the area. (Say right out front) And as Curt Swartz pointed out - there may already be other equipment in the building for 240v as opposed to 208. So a delta high leg as he mentioned is still suitable for 240 3-wire, as well as four wire.
 
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