SRT5kXLT as backup for well pump

[Anonymous user]

Hi Everyone,

I have an SRT5KXLT which i would like to use as an emergency backup for a 220v well pump.  The well pump is rated at 1.1kw.  it will be direct wired to a manual transfer switch - essentially taking the place of a generator.  I'm basically using the UPS as an inverter and battery bank.  I have a few questions and I'm looking for help and feedback. Appreciate any advice in advance!

The UPS has input wiring of L1, L2, and Neutral/ground.  I know that neutral is bonded to ground at my main panel.  

1) Should the input wiring be L1, L2, and neutral or L1, L2, and ground?  (I believe it should be neutral but would like confirmation)

2) The output on the UPS is three prongs.  is it also L1, L2, and neutral?  

3) My transfer switch is connected to the main panel with 220V, including neutral and ground.  When i switch to UPS supplied power, and the UPS didn't provide a ground, then i am now using the main panel ground but with UPS supplied L1, L2, and neutral.  Is this an issue? should I be grounding the UPS chassis ground screws to my main panel ground?

Thanks,

Michael

[BillP]

Hi Michael,

The input and output of this UPS is L1, L2, Ground. There is no neutral. It will default to 208v and can be configured to 240v, but not to 220v. If you are in the US, you likely have 240v and not 220v as you indicated. One thing to note - when this UPS is on battery it will output 208v (or 240V) when you measure from L1 to L2, but it will not be 2 balanced legs of 120v as you might expect. While on battery this unbalanced ouput could be 120v on one leg and 88v on the other, or any other combination that adds up to 208v (or 240v) from L1 to L2. The UPS is designed with IT environments in mind and not motor loads. You may want to consult with your pump vendor to ensure that this won't be an issue.

If you require a balanced output you would need an isolation/stepdown transformer on the output of the UPS.

I would suggest the SRT5KTF:

http://www.apc.com/shop/tt/en/products/APC-Smart-UPS-SRT-5kVA-Tower-Isolation-Step-Down-Transformer/...

Thanks

Liam

[Anonymous user · Accepted solution]

thanks Liam.  I am mostly concerned about the unbalanced output impact on the motor.  (apparently unbalanced voltages can lead to windings overheating)

If I use the APC isolation transformer will that ensure balanced output on the 240v transformer output?  i.e. could I take the 240v output from the SURT003 L14-30R connector, run it to a panel and split it into two separate 120v circuits.?