Megger rule of thumb

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SmithBuilt said:
What voltage are you testing at.

For 208 volts?

For 480 volts?


And do you use the same criteria for both voltages? I see Brian stated his 480 volt cirteria. What would it be for 208 volt system or would it be the same since the wire is rated for 600v?
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It dosent matter what the operating voltage is, what matterrs is the voltage rating. 600V rated insulation should be tested at 1000V or more, lower voltage ratings tested at 500V.
 
acrwc10 said:
My mistake , I meant page 45. The formulas you are referring to are for NEW cable, I took the OP as asking about an installed cable. If you have a new cable I would expect "infinity" if you had 1megohm on a new cable I don't think I would go pulling it in.
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There is no such thing as infinity.

Yes the formulas from your reference are for new cable, the specs I posted are from the NETA MTS for existing cable.

Cables should new tested before and most importantly after they are pulled.
 
zog said:
There is no such thing as infinity.

Yes the formulas from your reference are for new cable, the specs I posted are from the NETA MTS for existing cable.

Cables should new tested before and most importantly after they are pulled.
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You just want to bust my chops on this don't you? You know when I say infinity I am talking about a reading higher then the scale on the meter or as Pierre said "pegged".
 
acrwc10 said:
You just want to bust my chops on this don't you? You know when I say infinity I am talking about a reading higher then the scale on the meter or as Pierre said "pegged".
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Sorry, pet peeve of mine. Problem is that could mean >100M or >50T or anything in between, I have had problems in the past when I was told something was "Pegged" or "Infinity". turns out thier megger only went up to 500M, when the min spec for this equipment was 50G.

So yes, I am busting your chops, sorry.
 
Infinity is full scale reading of the particular meter you are using.

1,000 megohm, inexpensive meters.
2,000 megohm better.
4,000 megaohms Most Fluke's I have seen.
Newer meters in the teraohms
You show me infinity and I'll show you a meter to prove you infinity has a value.

My reports NEVER say infinity, I say full scale of meter and the value.
 
brian john said:
Infinity is full scale reading of the particular meter you are using.
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I just got a more rugged one for basic daily go/no-go testing, and it only goes to 200 megohm. Good for day to day stuff for me.

R1M-B%20Megohmmeter.jpg
 
electricalperson said:
if your meggering installed wiring and its under 1 megaohm check for connected loads. if there is no loads connected you have a problem and dont turn it on
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well from what i understand the load was still connected. It was a motor(pump) . So your saying we should go to the pecker head and disconnect the wireing there and then test the wire??

What would be a normal reading with the load still attached?? How would one megger (reading) a motor windings to be sure it was ok??
 
iwire said:
Why are you doing those tests?

Does NY require it?

Never seen a EI with any type of meter .... ever.
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If you were to notice my bio at the bottom of the page, I wear two hats.
Inspector sometimes and instructor other times.
There are many times an EC or other will need to perform a megger test - for whatever reason. Some will call me and I give them some choices.
Such as, I will teach them in a classroom setting; I will come to the jobsite and teach them; I will perform the test and teach them; and sometimes they are not interested in learning and just call to have the test performed.

At that point, I am not the inspector, I am the instructor - that is my favorite job title by the way. :grin:
 
I am not sure what to call the insurance, other than my insurance broker has provided me with insurance for that part of my business. Finding a carrier was not easy, at least that is what he said.
It is not too bad, as I do not have any employees...really.;)
 
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