Small UPS with PLC Panel

[junglepig]

We are considering the following installation:

A 20 A branch circuit from a lighting panel provides 120 VAC to a PLC control Panel. After passing through a 15A breaker and surge suppressor, the 120 VAC comes out of the panel via metal conduit, and feeds a GFCI outlet on a wall near the panel.
From this outlet, we feed a maintenance/bypass switch, which allows a load to be fed either from the utility power (wall outlet), or a UPS. The load side of the switch is then run back into the panel to supply UPS backed 120 V power to the PLC and associated I/O circuits.
The UPS is of the always online, double conversion type.

What special considerations should be given to grounding and safety of such a system?
Any obvious problems?

Is this a good approach to providing clean UPS power?
Thanks!

 

[dereckbc]

Re: Small UPS with PLC Panel

For a UPS this size there is no special requirements for the grounding, it is not SDS. Just run a EGC in the conduit. Unless required, I would dump the GFCI, just asking for a problem. Other than that there is not much you can do to improve it since you are using dual conversion UPS other than maybe increase the battery capacity or parallel redundant configuration.

[ April 07, 2004, 05:18 PM: Message edited by: dereckbc ]

 

[waltppiva]

Re: Small UPS with PLC Panel

Sounds like you're installing a small UPS. The UPS probably does not have an isolation transformer in it, so it would not be a seperately derived source, as Derick stated. With this, you would normally just pull a ground in with your phase conductors and terminate the ground to the cabinet/equipment ground. The installation manual for the UPS should give you the instructions and any special considerations that may be particular to this brand of unit.

Walt Magill
Service Mgr
Precise Power, Inc.