unused 208V leg on commercial bldg.

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Hi all, new to the forum, but getting a lot of good info on a lot of really diverse topics. Thanks to all in advance. My problem is this: I am working on wiring a church that used to be a barroom, and the bar used 120/208 service. There is 120 line to ground each leg on 1 and 2, and 208 to ground on 3. leg to leg there is 240 on all. I do not have any equipment that is going to use the 208, only 120/240. Will it affect the system (meter, transformer, etc.) to simply remove the fuse on the 208 leg and not use it? I can't see where it would hurt, but have never run into this before.I would greatly appreciate any help on this issue. The rest of the work is straightforward commercial installation of lights and power, including package A/C's. Just want to verify my thinking. I'm trying to avoid having to replace the entire service. Thanks again!
 

480sparky

Senior Member
Location
Iowegia
Sounds like a 'high-leg' delta system. Is the one leg with the odd voltage marked with orange? If so, that's what you have.

There's no need to remove the fuse. In fact, I doubt you could do that because there's more than likely some 2-pole breakers that utilize that 'high leg" of the system. Removing the fuse would disconnect on phase of the power to those circuits.

Changing the service would not make a difference. Your Poco would have to change their transformers.
 
Thanks for the quick response. The 208 leg is not marked at all. Also, I am replacing the panel, and will be rewiring some of the existing in-use devices, so the use of that leg should not be an issue. Just wanted to be sure it wouldn't adversely effect the incoming side of the system. Going tomorrow to look at the building again and do a little demo on the old stuff, so will get a better look then. Thanks again!
 

wireman71

Senior Member
So, I"m curious could you put in a new panel and not utilize the high leg. IE: Put in a single phase panel. Tape heat shrink off the high leg? Would that be code legal? I have no idea where even to look.
 

wireman71

Senior Member
Course what I'd recomend is putting in a 3 phase panel then feeding a single phase panel if more breaker spaces were needed.
 

benaround

Senior Member
Location
Arizona
Wireman71,

It's common practice to supply a single phase 120/240 panel off of this type

of service, IMO it is a good idea to do so.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
If you have a three phase supply why would you want to only utilize single phase? The three phase system is already in place, just install a three phase panel, mark the high leg with the appropriate marking and leave it for the future.
 
Hey guys,

Thanks for the ideas, but it looks like this job may be a bust anyway. The guy who wants the work done is a car salesman/preacher, and he has been jerking me around. Wasted about 4 hours of my and my partner's time this morning because he wasn't at the building when he told me he would be. He also won't answer my calls or return messages, but will answer if I blcok my phone no. when I call!!! Needless to say, I'm a little "put off" by all this, to put it mildly.
Anyway, the only thing he is using now that is 240 is a couple of large window units. The place is an old barroom, which used beer boxes, ice machines, etc. All he needs is light, 110 outlets and a few new package units. Should all be straight 120/240 service, so I don't need the 208.
If I ever do manage to do this job, I plan to just use a single phase panel to save money, as he has no plans to ever expand the current building. He does plan to add a new building behind this one in the future, but that will be ground up construction.
Thanks again for all the resonse. I will keep checking the forum for new ideas/discussions now that I know about it. Ya'll have been a lot of help already.

Mike.
 

Harold-eng

Member
Location
Tampa, FL
Convert it to 120Y/208

Convert it to 120Y/208

Be careful on your load calculations for a hi-leg service. A and C carry all of the 120V loads, then the single phase and three phase 240V load is added to that. I.e. your load is not evenly distributed on the three phases and you can overload a delta hi-leg service if not careful.

If in the future you want or need 208V (which allows even distribution of your 120V loads), you can have the POCO convert the 240 delta hi-leg to 120Y/208. A hi-leg service typically uses two transformers, called an "open delta" of different size. The POCO can replace the transformers on the pole so they use 3 instead of two (must be all same size) and reconnect them in a wye configuration. I have done this when converting an old lightly loaded building, like a warehouse, to another use, like a retail shop. The increase in load (revenue to POCO) may justify the POCO to make the change at no cost.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
mwysinger said:
Will it affect the system (meter, transformer, etc.) to simply remove the fuse on the 208 leg and not use it?
Makes perfect sense, and that's exactly what I'd do. Keep in mind that you can place any line-to-line 240v loads that do not use the neutral between the high leg and either 120v leg.

480sparky said:
There's no need to remove the fuse. In fact, I doubt you could do that because there's more than likely some 2-pole breakers that utilize that 'high leg" of the system. Removing the fuse would disconnect on phase of the power to those circuits.
Exactly what I meant. If you end up near the service's ampacity on 120/240v, and have line-to-line-only loads. keep the high leg available for future use. Stopping it at the disco fuse is a perfect way to do that.

wireman71 said:
Course what I'd recomend is putting in a 3 phase panel then feeding a single phase panel if more breaker spaces were needed.
There's no reason to spend the extra money for new 3-phase equipment if the high leg serves no purpose. A separate smaller 3-ph panel can always be added later.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Minuteman said:
I think that it is odd that there isn't a 3 pole breaker in that panel, like for an A/C unit.
That brings up my example to this scenario. I recently did an old brick 2-story completely-gutted building that was being converted into a downstairs commercial space and two upstairs apartments.

The only existing equipment to be re-used was a 120v air handler downstairs and a 3-ph roof-top AC unit, disco/fused at 30a. The existing high-leg open Delta drop now terminates at two weatherheads.

The first supplies a 3-ph 200a meter with two #3/0's and a #4, plus a #1/0 neutral, and then a box, where the two #3/0's are tapped with two #4's. The two tapped #3/0's and the neutral continue into the building and into a 200a 1-ph MB panel via conduit.

The two #4 taps, the unbroken third #4 from the meter (the high-leg), run via a separate conduit into a 125a 3-ph ML 12-sp panel (a la the 6-disco rule) which supplies the RTU only, with a 30a 3-p breaker. There is also a bare #4 for bonding the tap box and the 3-ph enclosure.

The second weatherhead supplies only 120/240v to a dual meter base, and then two 200a discos, and the two apartments' 200a ML panels via a pair of #4/0 al SER's. This is typical 1-ph residential stuff. 230.2(D) allows separate services for different service characteristics.

The point is that you can basically provide a single-phase electrical system from a 3-ph service, by simply dead-ending the high leg where it is no longer required. The main disco is the perfect place if you have no need for it, and it can easily be used later if necessary.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
infinity said:
If you have a three phase supply why would you want to only utilize single phase? The three phase system is already in place, just install a three phase panel, mark the high leg with the appropriate marking and leave it for the future.
In my opinion, it's not worth the money to install an entire 3-ph panel, just to leave the B-phase useless. It's better to add a small 3-ph panel if and when it's needed.

mwysinger said:
Thanks for the ideas, but it looks like this job may be a bust anyway.
That creates a vacuum. :D Oh, well, I might as well finish my thoughts, for future use. :rolleyes:
Anyway, the only thing he is using now that is 240 is a couple of large window units. The place is an old barroom, which used beer boxes, ice machines, etc. All he needs is light, 110 outlets and a few new package units. Should all be straight 120/240 service, so I don't need the 208.
The two 240v units are a perfect example of keeping the high leg available. One could be connected between each 120v leg and the high leg, freeing up a bit more ampacity on the grounded A-C phase (or pair of phases, if you're Rattus :grin:).

Harold-eng said:
A and C carry all of the 120V loads, then the single phase and three phase 240V load is added to that. I.e. your load is not evenly distributed on the three phases and you can overload a delta hi-leg service if not careful.
That typically happens on high-leg Deltas. The high-leg load is often much lower than the rest. In fact, it's common to down-size the high leg to suit its load, such as I did above. Of course, one must engineer all of this.

A hi-leg service typically uses two transformers, called an "open delta" of different size.
This is exactly why the high-leg load is typically less. The high-leg Delta originated as a 3-ph conversion to an existing 1-ph 120.240v service, where the 1-ph loads were established, and the added 3-ph load was small.

After all, how often would someone specify a high-leg open Delta for a new installation?
 

iwire

Moderator
Staff member
Location
Massachusetts
These is no way I could feel good about abandoning the 3rd phase regardless of it's being needed now or not.

I would install a 3 phase panel.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
iwire said:
These is no way I could feel good about abandoning the 3rd phase regardless of it's being needed now or not.

I would install a 3 phase panel.
And what would you power from the B-phase?
 

iwire

Moderator
Staff member
Location
Massachusetts
LarryFine said:
And what would you power from the B-phase?

Apparently nothing today.

But IMO if you already have a 3 phase service at the building it is a short sighted move to install only a single phase panel.

The difference in price to do it now negligible.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
iwire said:
Apparently nothing today.

But IMO if you already have a 3 phase service at the building it is a short sighted move to install only a single phase panel.

The difference in price to do it now negligible.


That was initial thought too. The cost now, when you're installing a new panel, to go from single phase to three phase is nominal. I would think that the building owner who has 3 phase now would want three phase after the job is completed even if it's immediate use is not required.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
From Mark's later comment, I'd keep the system 3 phase even it it cut my profit a bit. Sounds like the perfect DIY owner who will add to the job once Mark is finished. The hi-leg could prove to him why he needs a qaulified electrician :smile:
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
infinity said:
The cost now, when you're installing a new panel, to go from single phase to three phase is nominal. I would think that the building owner who has 3 phase now would want three phase after the job is completed even if it's immediate use is not required.
It's not that 3-phase would be unavailable, it's just that you wouldn't install a more expensive panel, just to not be able to use 1/3 of it. If any 3-phase loads were added later, it would likely be one at a time.

Here's how the cost difference presented itself to me: A C/H 200a 3-ph MB panel was about $325, while the C/H 200a 1-ph panel was about $110, and the C/H 125a 3-ph panel was about $80.

Plus, if a 3-phase load is to be added later, I'd rather be able to charge more than simply plugging in a 3-pole breaker would justify.
 
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