3 phase delta sub panel

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NYIHockey5

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I am installing a 200a, 3 phase delta sub panel in a computer server room 110 feet from the main service. I am not familiar with 3 phase delta installations, so I don?t know what size conductors I should be installing. Any help would be greatly appreciated
 
NYIHockey5 said:
I am installing a 200a, 3 phase delta sub panel in a computer server room 110 feet from the main service. I am not familiar with 3 phase delta installations, so I don?t know what size conductors I should be installing. Any help would be greatly appreciated
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Treat this the same as you would any other 3-phase 3-wire load (i.e. a motor or a transformer). The only semi-unique thing about this panel, from other panel installations, is that you would not pull a neutral conductor.

What is the source of your delta supply, a transformer? Are you including ground fault detection and alarming?
 
The only semi-unique thing about this panel, from other panel installations, is that you would not pull a neutral conductor.
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How did you determine that?


I asume that since it is going in a server room, the equipment load would be mostly 120V.

If thats the case, no need for the three phase.



Three phase Delta, as I know it, has 120V to ground on A and C phases, 208v to ground on B phase and 240V between any two.

I'd run a single phase panel to a server room if it had no 3 phase equipment.
 
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If you need 120 volts, you need a neutral. A four wire feeder. A three phase delta feeder will only provide you with the nominal voltage supplied by the transformer.
I'm not an IT guy, but I would have to belive the equipment in this room is single phase.
If you cannot find a wye secondary you will need to install another transformer.
Whats the voltage? Caution, you may have a high leg. Measure to be sure.
 
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220/221 said:
How did you determine that?
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The OP said 3-phase delta. No mention was made of voltage levels. I did ask for information on the source of the delta supply.

I asume that since it is going in a server room, the equipment load would be mostly 120V.
If thats the case, no need for the three phase.
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You can assume anything you want, though it would be helpful if you stayed with the OP.

Three phase Delta, as I know it, has 120V to ground on A and C phases, 208v to ground on B phase and 240V between any two.
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Then you lead a sheltered life. I was in a small facility just last Wed which had two utility meters next to each other, one for 120/240 single phase and the other 240V delta-grounded B phase.

I'd run a single phase panel to a server room if it had no 3 phase equipment.
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Again the OP asked specifically for 3 phase.
 
In my years of dealing with IT equipment, I've seen very few pieces of 3-phase IT equipment that didn't have a neutral connection and all of those were connected to a 120/208v wye-connected supply. (Perhaps some old mainframe disk drives were delta, don't know.) I have seen lots of 208v and 120/208 Y-connected stuff, but never delta. I'm also ignoring HVAC here.

If it were me, I'd be asking the engineer/designer lots of questions about delta v. wye connections. Even the Honking Big Servers these days are 120/208.
 
220/221 said:
Three phase Delta, as I know it, has 120V to ground on A and C phases, 208v to ground on B phase and 240V between any two.
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You're describing a high-leg Delta, which is definitely not the only kind.
 
With respect to the o.p., lately, iv'e been installing nothing but 250 volt rated power supplies without any neutral. Mostly they have been 30 amp and recently one was 3 phase 50 amp.

Rick
 
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220/221 is correct it is 120/208/120 volts. As far as the customer has told me all of the equiptment is to be 120 volts. However he has allready purchased the 3 phase panel and whats it hooked up that way for future considerations.
 
NYIHockey5 said:
220/221 is correct it is 120/208/120 volts. As far as the customer has told me all of the equiptment is to be 120 volts. However he has allready purchased the 3 phase panel and whats it hooked up that way for future considerations.
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I am still a little confused. First you said you had 240V available, then you say something is 120/208, and finally you say everything is 120V.

I would agree, that the 240V delta supply, in your OP. is going to be difficult to use with this equipment. Even a center tapped delta will only provide 240/120 3PH 4W, not the 208/120 your equipment needs. It sounds like you really need to have a 208Y/120 source 3PH 4W and feed your panel with a 3-hots and 1-neutral.
 
NYIHockey5 said:
220/221 is correct it is 120/208/120 volts. As far as the customer has told me all of the equiptment is to be 120 volts. However he has allready purchased the 3 phase panel and whats it hooked up that way for future considerations.
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Some day he will wish he had not, just remember this DO NOT USE B PHASE.
 
First you said you had 240V available, then you say something is 120/208, and finally you say everything is 120V.
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Now I think I am getting what you have. When you said 120/208/120, did you mean: Van=120, Vbn=208, and Vcn=120V? The proper term for this system is 240/120 [delta]: I like to add "3-phase 4-wire" and others add "center tapped delta".

For these systems my preference is to use a single phase panel for the 120V loads and a separate panel (without a neutral) for the three phase loads.

It is very easy to mis-interpret the slang in our industry. Context is very important.
 
:cool:

Make sure the panel has enough space. You can olny use 14 out of 20 spaces.

Mark the heck out of it if it's going in a server room. I write "Caution: 3 Phase Delta syatem. "C" phase is 200V to ground" and write 200V on every B phase blank.

I purposely refer to it as 200V instead of 208 to limit confusion with a 120/208 3 phase Wye system. For some reason, around here, I usually see something like 197 on the hi leg. Don't ask me how it works though. I'm a mechanic and don't quite comprehend everything.
 
RUWired said:
With respect to the o.p., lately, iv'e been installing nothing but 250 volt rated power supplies without any neutral. Mostly they have been 30 amp and recently one was 3 phase 50 amp.

Rick
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That is a good way to avoid harmonics.

As far as the OP 120/240 4 wire. Nasty combination with IT equipment I would recommend a 240 to 208 Y step down XFMR. If you are loading all the IT equipment onto A-C phase and nothing on B phase you are going to have an imbalanced load, and that is a code violation on it's own.
 
220/221 said:
:cool: I purposely refer to it as 200V instead of 208 to limit confusion with a 120/208 3 phase Wye system. For some reason, around here, I usually see something like 197 on the hi leg. Don't ask me how it works though. I'm a mechanic and don't quite comprehend everything.
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The topic of center-tapped delta systems seems to be discussed on a monthly basis. This may be nothing more than a pet peeve of mine, but most of the discussions appear to have inconsistent methods of describing this system.

The 240/120 3PH 4W delta system produces a nominal 208V to ground/neutral conductor from the high leg. To call it anything else adds confusion and misinformation as well as violates the NEC: 100-I (definitions of Voltage and Voltage, Nominal) and 110.4. Actual measured voltages will always vary based on the normal +/- tolerances of the POCO as well as from voltage drop in the circuit.

In the US we have many voltage systems available to us. Most of them are based on multiples of 120V and many include a 1.732 factor. Because of this it is very easy to mistake one system for another, which is why I try to include (but am not always successful) the number of phases and wires in my descriptions.
 
jim dungar said:
The topic of center-tapped delta systems seems to be discussed on a monthly basis. This may be nothing more than a pet peeve of mine, but most of the discussions appear to have inconsistent methods of describing this system.

The 240/120 3PH 4W delta system produces a nominal 208V to ground/neutral conductor from the high leg. To call it anything else adds confusion and misinformation as well as violates the NEC: 100-I (definitions of Voltage and Voltage, Nominal) and 110.4. Actual measured voltages will always vary based on the normal +/- tolerances of the POCO as well as from voltage drop in the circuit.

In the US we have many voltage systems available to us. Most of them are based on multiples of 120V and many include a 1.732 factor. Because of this it is very easy to mistake one system for another, which is why I try to include (but am not always successful) the number of phases and wires in my descriptions.
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Do you feel better now ? :smile: I think the lack of information is the problem 75% of the time if not more, and that is in all situations not just in the post's here.


I am feel the imbalance caused by using only 2 of the 3 phases is a big issue with this installation if they do not correct the system to a 120/208 Y. (just for you Jim) that is a 120 volt to ground on all 3 phase's and 208 volt phase to phase 4 wire system.:smile:
 
acrwc10 said:
I am feel the imbalance caused by using only 2 of the 3 phases is a big issue with this installation if they do not correct the system to a 120/208 Y. (just for you Jim) that is a 120 volt to ground on all 3 phase's and 208 volt phase to phase 4 wire system.:smile:
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I believe that is a 208Y/120 system.:grin:
 
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