Wiring a Smart-UPS RT 5000 to a distribution panel to supply 120v to the room

[Anonymous user]

We have an office that has a Smart-UPS 5000 (SURT5000XL) with a step down isolation transformer (SURT003) feeding a distribution panel. The panel then supplies 120v to the outlets in the room. I came across this office because we were having major problems with our equipment each time there was a power disturbance. We found that the electrican was not using the step down transformer to feed the panel so there was not a proper neutral. We are now using the the isolation transformer inline and using the L14-30 output on it to connect it to the panel.

A new electrician was used to put the transformer inline but after the last one I wanted to double check his work.

1. Should the neutral bus on the panel should be floating or if it can be bonded with the panel?

2. Does the attached diagram show how the system should be installed?

Thank you,

David

[BillP · Accepted solution]

Hi mrabe,

I hope this can help you out.

In response to your second question.  As per NEC rules, it is illegal to use a plug-in and then wire that up to a panel.   With regards to your first question - when using a 4-wire transformer output, you would treat it the same as utility power.  Neutral and Ground can be bonded in the panel if that is how the panel is designed.  You must use the Neutral from the transformer in the panel.  The AP9628 is best, but it only gives you a single leg of 120v.  If you only need 120v loads/output, it will work fine.  If you truly need a 4-wire hardwire output, the proper transformer would be the APTF10kW01.  Keep in mind that the APTF10kW01 is a 10kVA unit, if you will be using this on your 5kVA you will only be limited to 5kVA on the transformer.

The other (better) option would be to just use a spiltphase 5kVA unit with a hardwire kit, SURTD5000RMXLP3U with the SURT018.

[Anonymous user]

Thanks Jon, exactly the information I needed.

[BillP]

You're welcome, glad to help.