Service GFI Testing

[mikeames]

What is the best way, if there is a best way to test 4KA Service GFI without pushing the test button or tripping it out? Is there a maintenance proceedure that should be done regularly? Ie look at the coil....Is there a reliable tets that will tell you if the unit is bad???

 

[roger]

Re: Service GFI Testing

Mike this is a thousand dollar question. (or more) I honestly don't know of any way to test it as a unit without tripping it using the button or putting a true ground fault across it. Then after the test, (this has been brought up before) was this trip the final trip.

Roger

 

[brian john]

Re: Service GFI Testing

Mike:

On new services and as part of maintenance we test GF systems for current pick up at all factory presets for current. The second test is a timed opening of the switch, this test is performed at 150% of the GF relay current setting (hopefully obtained from a coordination study) and the operation of the switch is timed utilizing a function of the test set. Additionally we ducter/microhm/DLRO the power contacts for contact resistance and lastly the service is meggered (watch for controls during this test), line to load with the switch opened, pole to pole and pole to ground with the switch closed and the neutral/grounded conductor disconnect link is removed and the load neutral is meggered to the line neutral.

If there are additional features such as Low voltage relays, phase loss relays or Blown Fuse Trip these features are also tested for proper operation (pick up drop out ect).

 

[roger]

Re: Service GFI Testing

Brian, this is the kicker,

The second test is a timed opening of the switch, this test is performed at 150% of the GF relay current setting (hopefully obtained from a coordination study)

This still means opening the switch in a test.

The coordination study would not be necessary on a new service if designed for a new building.

P.S. I'm not trying to be argumentitive.

Roger

[ July 29, 2003, 07:09 PM: Message edited by: roger ]

 

[brian john]

Re: Service GFI Testing

Roger:

On tripping out the switch this test can be performed with the shunt trip disconnected if the shunt trip leads are available (this can and is dangerous as the switch is open exposing live bus) or some circuit breakers secondary injection test sets are available that have a NO TRIP feature but of course these test sets only work on selected circuit breakers.

In our area switchboards come from the factory with the setting at minimum for current and time (usually 100 or 200 amps and Instantaneous or .1 seconds). The Design engineer or his designated representative is responsible for supplying the GF settings. Though in practice this is seldom provided.

 

[roger]

Re: Service GFI Testing

Brian, I am aware of the test proceedures and being able to see the relay function with the shunt coil disconnected, hence the reason I pointed out in my first post the term "unit".

Like you, we are usually furnished the settings from the designer and manufacturer. In no way would we randomly pick these numbers, and we even have a PE in our office.

Roger

 

[brian john]

Re: Service GFI Testing

Roger:

We're asked all the time where would we set the GF relay, our answer is where your engineer wants it set. We do work with a frim that specializes in coordination studies we recommend utilizing them or any PE of their choice. Too much liability here.

 

[roger]

Re: Service GFI Testing

Brian, I'm always involved with manufacturers in coordination studies (SQ D & CH). This usually works pretty well but I can't say how unbiased it is.

Roger

 

[mikeames]

Re: Service GFI Testing

As always thank you it was good to hear the input. We came to the same conclusions.