ups system

[arnettda]

I am installing a 20 kva ups system. Can you give me some code references to read as pertaing to conductor sizing, and any other things I may not be thinking of. I feed it with straight 240 no neutral and then it produces its own neutral in the ups system. It ia all a little new to me. Thanks.

 

[tkb]

The UPS manufacturer will recomend the input and output conductor size and the overcurrent sizes.

You should request the cut sheets from the UPS dealer.

 

[dereckbc]

Agree follow the manufactures minimum cable sizes.

Only code reference you will need to be up on top of is 250.30 that deals with Seperately Derived System. This will be the key to the performance quality of the UPS. The manufacture should also have some requirements for the SDS.

 

[tkb]

If you don't go with the manufacturers recomended sizes it could affect the warrantee on the UPS.
Also make sure you get the factory startup when you purchase the unit.
They will set up the UPS and make any adjustments that may be needed.
Watch out on your quote. Some will qoute 8x5 start up and some will quote 24x7.
If you need to start up the unit on the weekend or at night make sure you have 24x7. (hours x days)

 

[dbuckley]

I feed it with straight 240 no neutral and then it produces its own neutral in the ups system. It ia all a little new to me. Thanks.

Although that is a perfectly valid arrangement, assuming you have 120V loads downstream of the UPS, if the inverter fails then the UPS cannot switch to bypass[*], so the loads will be dropped.

Thus if you want the loads to operate under UPS failure or maintenance conditions, you need to run the neutral to the UPS from the supply. If there are no 120V loads then you dont need a neutral on the output side of the UPS, and all will work as expected.

*: Make sure you configure the UPS that way under these circumstances, as if the UPS does go into bypass then the 120V loads have no neutral reference, and the loads will get damaged.

 

[dereckbc]

Although that is a perfectly valid arrangement, assuming you have 120V loads downstream of the UPS, if the inverter fails then the UPS cannot switch to bypass[*], so the loads will be dropped.

Maybe, maybe not as it depends on the bypass switch type. Static Bypass have transformers built into them to derive a neutral circuit, thus the SDS.

 

[tkb]

Maybe, maybe not as it depends on the bypass switch type. Static Bypass have transformers built into them to derive a neutral circuit, thus the SDS.

If this unit has a wrap around bypass then a neutral will be needed on the input.