Is Voltage Drop A Concern

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ritelec

ritelec

Senior Member
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Jersey
hi all.
there is a large new building about 800 foot long 100 foot wide. High bay. cut into 18 tenant spaces. Large garage doors , future offices, warehouse,production,...parking and pole lighting. you get it.

this building is at the end of a large industrial park.
that large industrial park has many services at 480 volt.

this new building is going to be fed from a set utility transformer to a 1600amp disconnect feeding a 20 circuit breaker meter bank. 2 inch pvc goes from bank to each tenant space for a 200 amp 3 phase 4 wire panel.

the new system is going to be a 120/208 volt 3 phase 4 wire.

as I've almost filled 2- 200amp 3 phase panels for one large tenant with 120 volt florescent lights 208 volt high bays,3 -50 amp roof units. 60 amp mixers.
 
800*100 = 8,000 total sq. ft. / 18 tenants = < 450 sq. ft. per tenant is the units are equally divided.

If you divide 1600 by 8, you get 200-amps per unit at 100% usage by everyone (not likely to happen).

Gut-check says 200-amps should be fine for a 450 sq. ft. tenant space (especially being separately metered). If you do load calculations, you may find putting some 300-amp services in a couple of units would be fine.
 
The meter bank is on the wall. not wired yet and transformer isn't on sight yet.and i just kinda walked into this.
I've mentioned my concern about voltage drop. I think it should have been at the 280/277 but the 120/208 volt equipment was cheaper. I think there;s going to be a problem with voltage.
 
ritelec said:
utilty pulls to the transformer. i pull transformer to dicsonect for meters
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If the utility has a voltage drop problem, you will only be able to do something about it after you can prove the problem.

By sizing the conductors between the transformer and meter by the NEC, your voltage has a better chance of being maintained. If you calculations indicate you need a larger wire, do you have the option of providing it (getting paid of course)?
 
80,000 sq ft is an ok size building. But 800' long..... I hope the service isn't at the end. Even in the middle it's a long run to the end bays. I wouldn't think for that size service entrance conductors your VD from the transformer to the main could be that much ( I didn't see this length). I would be more concerned with being limited to 2" conduits and a good size load.

Take a spreadsheet and list the lenghts of the feeder conduits. As you get the build-out drawings, enter the loads. Check your VD and make sure your wire is sized properly. You can also assume some loads prior, and check out what the VD might be based on your assumptions. A little leg work now, may answer some of your questions. Make sure the owner puts the lighter loads on the end(s) and he can save some more money!

Just My Thoughts.

R
 
I dont know if i am little late on this one but why not have two transformer one at " 1/3 " way of each end so you have better loading and less voltage drop as well because 800 feet is pretty long leg to bring some of the conductors unless you bring in 480 then transformed it down at Load centre .

I know few strip mall done this way they bring in 480Y/277 in and have dual voltage running in some area especally with larger tentents which they will have pretty good number of lumiaires so it will add up pretty fast there.

Merci , Marc
 
hardworkingstiff said:
800*100 = 8,000 total sq. ft. / 18 tenants = < 450 sq. ft. per tenant is the units are equally divided.
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You're a little off on your math. 800*100=80,000


I agree that a building this size should be supplied with a voltage system higher than 208Y/120. Why isn't the building supplied with 277/480?
 
You say you just kind of walked into this, does that mean the job itself? If so, you might want to find out what happened to the guy that started it, and why he is not there. There are going to be problems with what you are describing, and unless the owner is going to let you make things right, it may not be worth it. I would venture to guess that there is not an engineer involved, and it was a design build by the Contractor.

1600A @ 208V is only 576KVA. Divided into 20 panels for 18 spaces (I assume 2 house panels) only leaves 80A per panel. Who came up with 200A panels? How does anybody think you are going to serve 18 tenants with 80A each.

You need to have 2 separate electrical meter banks. Split the building in half, then put each meter bank in the middle of each half. This puts the farthest load only about 200 feet away. That will make the VD pretty manageable. Each feed should be 1600A, which will give you 160A per 200A panel. (80% loaded). The utility will probably place two 500KVA transformers, but don't worry about what they give you, just tell them you need 2 x 1600A services. They always run their transformers small because of load diversity. That should get you back on track.

From a liability position, be cautious, because if you take over someone else's work, you may then become liable for it as well. Also, if the previous Contractor was fired, or walked, the General Contractor will probably be charging him for whatever it takes to finish the job. So don't be shy about doing what it takes to do the job right.
 
kingpb said:
From a liability position, be cautious, because if you take over someone else's work, you may then become liable for it as well. Also, if the previous Contractor was fired, or walked, the General Contractor will probably be charging him for whatever it takes to finish the job. So don't be shy about doing what it takes to do the job right.
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I think that before one is to take this type of attitude, one should find out what happened to the original EC if there was one. We do not need to go about bashing our fellow ECs in this world we work in. Friendly competition and a sense of fellowship should be fostered. If the EC is a creep...it is a different story.
 
I stated standard contractual stuff. Where was anybody bashed? No names were mentioned, nor were there any accusations made. BTW: I am an engineer, not an EC.

Are you trying to say EC's don't get fired, or decide to walk away from jobs?
 
I think...what we have here is...failure...to communicate. :)

Pierre, I think you might have misread the post. I just read KingPB's post, and I'm hard-pressed to see any bashing involved. In fact, in the past I've had a bit of an adversarial stance with KingPB on a few occasions, but I would have to say this is one of his best posts, to be fair. ;)
 
kingpb said:
Are you trying to say EC's don't get fired, or decide to walk away from jobs?
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I was involved with a 1st time GC about 5 years ago. He kept adding nickel and dime stuff and I sent him a change order. I had already roughed in the slab, when he got huffy about the change orders. We both agreed it would be best if he paid me for what I did and we parted ways.

He was glad to get rid of me and I was glad to be away from him.
 
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