ISOLATED GROUND PANEL

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Elect_Engr

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While analysing a set of Electrical drawings(for a nursing home) from US, we found that all computer receptacles(quad)have been provided with an isolated ground wire.These IG circuits are taken to 20A MCBs in a Common panel in the building.It is not clear as to why a breaker should be provided in the ground line.
It was also noticed that a load of 800 to 1000 VA is considered for these circuits.

We are not sure whether this is a mistake or there is some reason behind it.

It would be much helpful if someone out there in the forum can throw more light on this.

Thanks,
 
Re: ISOLATED GROUND PANEL

How did you arrive at the idea that there was a circuit breaker in the ground wire (equipment grounding conductor or grounded conductor?)
 
Re: ISOLATED GROUND PANEL

Well, there is a Panel schedule( Panel 'CP', 120/208 V, 3 Ph, 4 wire, 100 Amp main breaker ) indicating 20 Amp 1 ph breakers(#12 wires in 3/4" conduit) to each IG circuit.Apart from this, separate circuits are also provided from another panel for each of these circuits.

I understand that ,the circuit home runs are coming from one panel and an isolated ground wire from a different panel is taken to each circuit.But why the breaker? And how this isolated ground is derived? Will there be a separate grounding transformer for that purpose?

Thanks in advance for any clarifications..
 
Re: ISOLATED GROUND PANEL

Isolated grounds are just that, ground wires carried back to a sub-panel or even a main panel with out any connections in between. There is no breaker on the ground wire, only the HOT conductor feeding the circuit. If the plans show different, there is a mistake. Ask your local AHJ and they will tell you the same.
 
Re: ISOLATED GROUND PANEL

You mentioned "Quad" outlets. Could it be that the designer wants one normal power and one computer power isolated-ground duplex receptacle at each location? That would explain the separate runs from the two panels and the two panels with what seems to be identical loads.

Best thing is to talk to the designer or engineer an find out what is needed.
 
Re: ISOLATED GROUND PANEL

I have found that in health care facilities that a panel that is labeled CP normally means critical power which means that if normal power is lost you will still have power from this panel. my guess is you have both critical and normal power at each of the quads but that is just a guess without being able to see the actual prints or installation
 
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