480 or 208 Service?

[SpookySpook]

Trying to figure out the cheapest method for a local farm I work at. We have 3 structures, 2 of the structures each have a 100A single phase service. We are looking to add a 3 phase 480v 50HP 66A air compressor in the non-serviced structure. Called our utility company and it would be no cost to have them give us 3 phase. The new service is going to the compressor structure which is located 150' from either currently serviced structures in the center. We want to just lose the two single phase drops and just make those subs off the compressor shack. My question is would it be cheaper to get 208/120v service then use a transformer just for the compressor or should I get 480v service and use a transformer to get 208/120 and feed each structure with that or do I keep it 480v and use a 30KVA transformer at each structure. I know its cheaper for wire and such running at a higher voltage.

Thanks!

 

[ActionDave]

The only reason I can see for 480V in this case is motors, if you have enough of them or if you think you will have more of them and the poco will give you 480V three phase at no cost then take it.

 

[electrofelon]

Any reason not to just keep the 2 single phase services and take the new 480? It may not be elegant and you have three monthly service/meter charges instead of one, but considering transformer losses and rework costs, I doubt you will ever make it back.

 

[Fnewman]

Before making a final decision, I would make sure I knew what rate schedule(s) would be applicable. Almost certain a 3 phase 480 v service will be billed differently from the other two. Given overhead costs it would be unusual if having multiple services would be more cost effective, but will depend on your useage patterns.

 

[SpookySpook]

Perhaps you're right then...so the 480v compressor is being used for our haunted house we put on so it will only be used one month. Perhaps we will keep the 2 single phase services and only use the 480v for the compressor. Hell we could have service ended after every season...It's funny how you get fixated on one concept and don't think out of the box. Thanks guys!

 

[ActionDave]

...so the 480v compressor is being used for our haunted house we put on so it will only be used one month.

Well that is an important nugget of information that was left out.

 

[SpookySpook]

Haha surprise! Yea so one of the structures is used throughout the year, the other is used only 4 months of the year and the compressor shack is 1 or 2 months. Now if I got the 480v only for shed, can I come out my meter and go directly into a fused disconnect then into the compressor? We don't plan on using 480v for expansion...the compressor is overkill even for the future, but we got a good deal on it.

 

[SpookySpook]

Let me clarify that, go from my meter to a 200A fused disconnect then into the compressors fused disconnect. I don't need a panel correct? As long as the ground and neutral are only bonded in the 200A disconnect.

 

[MyCleveland]

So you have a building with one item....no maintenance recep or lighting ?

 

[roger]

Let me clarify that, go from my meter to a 200A fused disconnect then into the compressors fused disconnect. I don't need a panel correct? As long as the ground and neutral are only bonded in the 200A disconnect.

You need to consult your boss, this is a little over your experience level at this time.

Roger

 

[Fnewman]

If your 480 v 3 phase billing rate has a demand component, you will set a demand in one month and pay for in all the next 11!

 

[Phil Corso]

Gentlepeople....

Expounding on Fnewman comment... whether it occurs in the 1st 15 (or 30) minutes of the first day of the billing period, or the last 15 (or 30) minutes of the last day of the billing period!

Regards, Phil Corso

 

[kwired]

It is a little surprising they will install the three phase service at no charge. Might want to see what kind of rates you will pay, even with 8 months annually with little to no load. Their infrastructure doesn't pay back very well with that kind of loading pattern. If this were something that ran nearly all day every day it would pay back pretty well.