1 Phase UPS, 3 phase panel / E-Stop button

[bnewport]

The contractor I work for installs a lot of UPS and generator systems. One UPS we install is a small (typical 12 kVA) name brand single phase unit. The output voltages are:
L1-N 120V L2-L3 208V
L2-N 88V L1-L2 32V
L3-N 120V L1-L3 240V
The output can be configured either 120/208 or 120/240. They specify using a 3 phase panel for the 120/208 single phase configuration. What does the NEC say concerning using a 3 phase panel for this? I don't agree with having 88V on L2 even if the panel is marked as such. Why not use a single phase panel instead?

Also, when does the code require an EPO (E-Stop) button for a UPS? What is considered an information technology room? We usually err on the side of caution, and install one.

Bryan

 

[ron]

Re: 1 Phase UPS, 3 phase panel / E-Stop button

I think there is something wrong with the unit. There shouldn't be 88V L-N.
In any case, an EPO would be required if you need the wiring leniencies permitted by Article 645, and you plan to comply with all requirements of 645.2. If that is not the case, then an EPO is not required.

 

[dereckbc]

Re: 1 Phase UPS, 3 phase panel / E-Stop button

Something is wrong here. All the L-N voltages should be 120, and and all L-L voltages should be 208. They are using a 3-phase panel on the output because the UPS output is configured 3-phase output.

As Ron stated an EPO is only required for 645 compliance. Most data and telephone companies avoid 645 because of the EPO issue (it's a bad thing).

If you can give me the make, and model number I can look up the specs and give you more details.

 

[kiss]

Re: 1 Phase UPS, 3 phase panel / E-Stop button

I have installed a few of these UPS systems,and its wild and unusual of the different voltages depending on the phase to neutral that you connect to. I clearly mark the outside of the panel indicating the voltages on each phase. I also mark on the inside of the panel directory the same. On one install we took out the buss detail to the phases that gave us these wild readings.

 

[steve66]

Re: 1 Phase UPS, 3 phase panel / E-Stop button

My first thought is that you need to measure the voltages with some type of load on the unit. Some electronic power supplies have a minimum load requirement. But this shouldn't apply to a UPS.

I drew out the voltages you mentioned. Then I realized you said this is a single phase unit. I think you are right, it is a single phase unit and should not be connected to a 3 phase panel. Get the instructions for the unit but I bet you will find that you should use:

L1 - N for 120 V single phase loads
L2 - L3 for 208V single phase loads
L1 - L3 for 240V single phase loads

The unit is probably not intended to use more than one of the above at the same time. And again, I agree, this should not be connected to a three phase panel since L2 - N and L1 -L2 would not be valid voltages.

Steve

 

[steve66]

Re: 1 Phase UPS, 3 phase panel / E-Stop button

Also, notice that the 32V between L1 and L2 added to the 208V between L2 and L3 equals the 240V between L1 and L3. This means the voltages are in phase. Not the 120 deg. phase difference you get with a delta or wye connected circuit.

This means that if you connect a load between L1 and neutral, and another load between L2 and neutral, the currents will add together and create a larger current on the neutral.

With a three phase delta or wye, a reduced current would flow on the neutral.

 

[dereckbc]

Re: 1 Phase UPS, 3 phase panel / E-Stop button

This wouldn't by chance be a Powerware 9150 or a APC SYA12K16? The reason I ask is these are the only manufacures I know that offer a 12 KVA UPS with single phase input. Typically at this power range UPS are 208 or 480 3-phase input. That being said the 9150 and SYA12K16 have L1, L2, N, and G input and output, no L3 on input or output.

The outputs match the inputs either 240/120 VAC @ 180 degree phase rotation, or 208/120 VAC @ 120 degree phase rotation.

[ May 12, 2004, 03:06 PM: Message edited by: dereckbc ]

 

[bnewport]

Re: 1 Phase UPS, 3 phase panel / E-Stop button

The unit is a Liebert Nfinity. L1-N or L3-N = 120VAC, L2 - 88VAC, L1-L2=208V Its a goofy way to configure an output... I tried to draw it out, but I couldnt figure it out except for the voltages. (couldnt figure out coil config). I have been told by a rep that it is an autotransformer. For those of you that dont believe they manufacture a unit like this, check out: http://www.liebert.com/assets/products/english/products/netpwrpr/nfinity/60Hz/usersman/acrobat/sl_23950.pdf

go to page 18

Bryan

 

[ron]

Re: 1 Phase UPS, 3 phase panel / E-Stop button

It is a single phase unit. If you use a 3 phase panelboard, one of the phases should remain dead (no terminations). Do not use L2-N voltage, as 88V will be useless and is not designed to provide power.

 

[dereckbc]

Re: 1 Phase UPS, 3 phase panel / E-Stop button

Strange unit. I would use setup # 3 and a single phase panel board.

L1 to Terminal 1
L2 to Terminal 3
N to termianl 4
G to termianl EG
GEC to termianl 5

I agree with Ron if you use a three-phase panel board L3 should not be used.

 

[steve66]

Re: 1 Phase UPS, 3 phase panel / E-Stop button

Apparently this it is OK to connect this to a 3 phase panelboard. See to the note that says to refer to NEC 215.8 and 210.4(D).

They do say you can use the two 120V outputs at a max of 67 amps each. Just remember the neutral current would be 134 amps. This would require a larger neutral wire and a 200A panelboard.

Steve