208v Question

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  #1  
Old 02-01-14, 12:52 PM
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208v Question

Hi. I am a computer repairman that has specific power needs. I just secured my first commercial office space and I have an agreement with the landlord to either get a 208V 30A outlet installed or a 240V 30A. When I went into the breaker room on my floor, I found 2 separate boxes. 1 controls office outlets. The other one is 3phase/4wire delta and controls high power items like heaters. I've included a link to 15+ pictures of everything in the breaker room on my floor at the bottom of this post. Ok, so, mainly I need 6000-7000W of continuous power because I'm going to have a PDU hooked into the 208V or 240V outlet and then 8-10 computers(not servers) running off of that PDU at once for stress testing. What would my best option be with this building to achieve that? I'm guessing 208V/30A line out of the 3phase/4wire delta that's powering the heat? What if he doesn't allow me to make modifications on that, then what would my best option be?

Information that may or may not be relevant:
The building was built in the late 1800s but seems to have updated power.
It has 6 floors(I'm on the 5th), approximately 5 offices per floor and around 70% occupancy(may or may not be relevant for power load?)

Link to 15+ pictures of breaker room:
imgur: the simple image sharer
(click the numbers above the picture to see the other pictures)
 
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  #2  
Old 02-01-14, 01:15 PM
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What would my best option be with this building to achieve that? I'm guessing 208V/30A line out of the 3phase/4wire delta that's powering the heat? What if he doesn't allow me to make modifications on that, then what would my best option be?
You cannot get a 208 volt line out of a 120/240 volt 3-phase 4-wire panel. Without seeing the Square D panel with the cover removed, I am guessing just from the panel schedule it is 120/240 volt single phase panel. You can get a 230 volt line from either panel with a 2 pole breaker, but I'd leave it up to a qualified electrician.


Oooops I meant 240 volt
 

Last edited by CasualJoe; 02-01-14 at 01:42 PM.
  #3  
Old 02-01-14, 01:27 PM
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There won't be 208vac available at that building. That's an old "red" leg service with two utility transformers. Also called poor mans three phase service.

Like Joe said..... you can get 240vac with a two pole breaker.
 
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Old 02-01-14, 03:03 PM
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How certain are you guys that I can't get 208 out of it? 240/30A would be my best option then?
 
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Old 02-01-14, 03:29 PM
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Almost all equipment that is rated 208 will work just fine on 240 volts, but you should check yours. If you really require 208 you can add a buck/boost transformer to buck the voltage down 32 volts to give you 208. You did not say if you needed 3 phase for your PDU, but if you do, then you will need 2 buck/boost transformers.

That label on that panel is likely wrong. The building likely has a high leg delta 3 phase 4 wire system. This still uses three transformers but the voltage from B phase to ground is 208, not 240. This is not the 208 you want though. The system that PJ was referring to is a open delta:

[ATTACH=CONFIG]25935[/ATTACH]

They should be able to get a 240 volt 30 amp circuit for you from either panel, if there is space available, but that is not your concern.

Just as a note, in commercial buildings, most states require electrical work to be done by licensed electrical contractors.
 
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Old 02-01-14, 03:31 PM
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How certain are you guys that I can't get 208 out of it?
Unless you're planning to request that a transformer be installed, 100%. Why would you want to when you have perfectly good 240V power right in front of you?

240/30A would be my best option then?
Yes. Only = best.
 
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Old 02-01-14, 03:36 PM
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Great posts. Thanks. My power supplies say they automatically adjust voltage from 120-240. With a 240 volt 30 amp outlet, would I be able to run 6000W continuous without messing other things up on the same panel? I really don't want to get in bad with the LL. Also, yeah, my landlord requires that they be licensed and insured.
 
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Old 02-01-14, 03:51 PM
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My power supplies say they automatically adjust voltage from 120-240
You will be fine with 240 then. The landlord said he will provide you a 240v 30 amp circuit so he knows what is going on.

Your 6000w is not continuous. That is likely what the PDU is rated for. If you have the PDU on and there is nothing plugged into it the load will likely be quite small. At full load 6000w @ 240v = 25 amps. Its the same as putting a 1000 watt power supply in a computer, but only putting in bare bones parts. That power supply will be putting out only 250 watts.
 
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Old 02-01-14, 05:46 PM
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Also, yeah, my landlord requires that they be licensed and insured.
Considering the appearance of some of the work around the panels in your pictures, I cannot imagine your landlord being too concerned with anything except a cheap price.
 
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Old 02-01-14, 07:14 PM
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Considering the appearance of some of the work around the panels in your pictures, I cannot imagine your landlord being too concerned with anything except a cheap price.
LOL! I agree, Joe.

Cryptoo, is the landlord a new owner of this property? Or did he or she suddenly get a new enthusiasm for doing things properly because the area is showing signs of becoming more valuable?

It's heartening, either way, to see this level of investment in a property in the Motor City right now. I hope that continues and grows.
 
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Old 02-01-14, 10:32 PM
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It will be more or less continuous 6000w for when I am stress testing these particular rigs. I am building litecoin miners for people, which will have 2-3 7990 graphics cards on each board(1 7990=450w) and they will be running at 100% capacity.

As for the owner, I guess he has owned the building about 10 years and owned multiple commercial buildings but has sold all but a couple.

As for the work being shoddy, I don't know. In the contract I signed, it stipulates that all work done must be by someone who is licensed and insured/bonded in the state of Michigan. I can't speak for the others, but I don't want a law suit or a murder charge if someone dies in a fire I started by being negligent.
 
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Old 02-02-14, 06:04 AM
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I don't want a law suit or a murder charge if someone dies in a fire I started by being negligent
You are not doing the work so you have no liability.
 
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Old 02-02-14, 06:36 AM
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Two hundred eight volt equipment must be rated for 240 volts (or rated for a range of voltage that spans 208) in order to use on "220", "230", or 240 volts. Subjecting equipment to overvoltage is not good. Going the other way, running 240 volt only equipment on 208 volts, is more forgiving although this should be limited to resistance heating equipment including hair dryers, and manually fed tools where you are careful not to press them to their limits.

You can construct your own power strip (portable subpanel if it has breakers for its receptacles) to plug into a 120/240 volt or 240 volt only receptacle.

You should not find the 208 volts of a high leg 240 volt 3 phase delta system at any receptacle except measurable between a hot and ground at a 3 phase receptacle but you are not permitted to wire up equipment or portable subpanels to use ground as a return..
 
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Old 02-02-14, 11:40 AM
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Given a 7KW load , I calculate a line current of 16 amps which is 80% of 20 amps . Presuming there will be a 3-phase Feeder to a sub-panel with 2-pole breakers for load distribution , I suggest 30 amp Feeder conductors.
 
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