Testing equipment grounding conductor

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spsnyder

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How would you test the grounding integrity of an existing bus duct enclosure used as the EGC? The duct is ~200 ft long and does not have a separate EGC. It is rusting in some locations so we want to quantify the conditions. Is there a standard for the testing of egcs? Thank you.
 
spsnyder said:
How would you test the grounding integrity of an existing bus duct enclosure used as the EGC? The duct is ~200 ft long and does not have a separate EGC. It is rusting in some locations so we want to quantify the conditions. Is there a standard for the testing of egcs? Thank you.
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Not sure you really can.

Some minor surface rust is not going to matter any.
 
You can utilize a ductor/micro-ohm meter, DLRO/Digital Low Resistance Ohm Meter.

BUT if you have rust on a busway I'd be more worried about the integrity of the bus insulation. Number one problem with busway, moisture followed by massive arcing ground faults.
 
brian john said:
You can utilize a ductor/micro-ohm meter, DLRO/Digital Low Resistance Ohm Meter.

BUT if you have rust on a busway I'd be more worried about the integrity of the bus insulation. Number one problem with busway, moisture followed by massive arcing ground faults.
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Will the reading really mean anything? It uses a rather low current compared with GF level currents, and while a high resistance means there is a problem, a low resistance does not mean there is no problem.
 
Production testing of circuit breakers that I am famililar with 1200A-3000A uses a ductor or micro-ohm meter. It circulates 100A for the reading. This is much less than the 63KA short circuit amps it is guaranteed to interrupt.
 
SG-1 said:
Production testing of circuit breakers that I am familiar with 1200A-3000A uses a ductor or micro-ohm meter. It circulates 100A for the reading. This is much less than the 63KA short circuit amps it is guaranteed to interrupt.
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And the 100 amps is less that the 3000-30,000 amps a circuit breaker is exposed to, but it gives us a reading for reference. With the DLRO you would take comparison reading along the length of the busway and across each coupling.

Will the megger readings mean anything, YES it means if you know what you are doing you will minimize the risk turning the busway into scrap.

I have NEVER had a busway I tested blow up, I have been on countless jobs were the busway was energized without testing. I was there to install temporary and discern what caused the busway to fault.

Usually water and/or bad installs.

The number one blow up we see is busway, followed by bolted pressure switches and EGC fished into energized switchboards with the other end connected.
 
Thank you very much Brian et al. I am looking into borrowing a DLRO from a different group. If I am unable to borrow the meter, is there ANY value in the following test.

1. Measure the resistance of a 200' wire (~no. 12)

2. Run a 200' wire the length of the wireway. Connect one end of wire to the buss duct.

3. Measure resistance of curcuit with multimeter.

4. Back out wire resistance.

If the resistance is high we know we have a problem. If it is low, we haven't learned much.

What do you think? Thanks again.
 
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