Required or obliged to megger

noon9elec

Member
I have yet to see it in the NEC, but does it say any where that it is necessary to megger or doe an insulation resistance test on existing knob/tube, MC, NM cables. A simple panel change in an older building is turning into a mini nightmare now that an Engineer is involved. The Engineer is saying that "meggering" is not only required, but that a moral obligation should be employed. I don't know, I thought it was a typical panel change. I can't control what circuits are doing down stream. any thoughts? Thank you
 

ActionDave

Moderator
Staff member
It's neither a requirement or a moral obligation. If you don't know what's on all the circuits you risk doing more harm than good.
 

Coppersmith

Senior Member
It's neither a requirement or a moral obligation.
Absolutely agree. You are only required to do what you contracted to do and no more. If they want additional work performed, give them a proposal to perform that work or refer it to another vendor.

If you don't know what's on all the circuits you risk doing more harm than good.
Here I'm going to disagree. If all the circuits were operational before you began to do the panel change, then they should be operational afterwards as well. By operational I mean that the breaker held closed. You have no knowledge or obligation to know what's going on with those circuits after they leave the panel beyond properly filling in the index.

In my opinion, if you see a violation in the panel, you have an obligation to correct it. This would include putting a smaller breaker on a circuit if it is oversized for the wire. (But never a larger breaker on an oversized wire since you don't know the downstream wire sizes and equipment needs). If you happen to see a violation outside of the panel (e.g. crawling through the attic), you have an obligation to notify the owner. Then you can (if you want) ask if they want it corrected (at extra cost). You have no obligation to fix it without compensation, however I personally would leave that circuit off if it presented an imminent danger.
 

K8MHZ

Senior Member
Absolutely agree. You are only required to do what you contracted to do and no more. If they want additional work performed, give them a proposal to perform that work or refer it to another vendor.



Here I'm going to disagree. If all the circuits were operational before you began to do the panel change, then they should be operational afterwards as well. By operational I mean that the breaker held closed. You have no knowledge or obligation to know what's going on with those circuits after they leave the panel beyond properly filling in the index.

In my opinion, if you see a violation in the panel, you have an obligation to correct it. This would include putting a smaller breaker on a circuit if it is oversized for the wire. (But never a larger breaker on an oversized wire since you don't know the downstream wire sizes and equipment needs). If you happen to see a violation outside of the panel (e.g. crawling through the attic), you have an obligation to notify the owner. Then you can (if you want) ask if they want it corrected (at extra cost). You have no obligation to fix it without compensation, however I personally would leave that circuit off if it presented an imminent danger.
I took it that Dave meant that megging the circuits could do more harm than good, and I agree with him.
 

GoldDigger

Moderator
Staff member
I took it that Dave meant that megging the circuits could do more harm than good, and I agree with him.
As one example, suppose that there was a doorbell transformer attached to one of the K&T runs. If you do not know it is there or cannot find it to disconnect it, a megger could break down the insulation on the primary and even energize and damage the doorbell wiring on the secondary.
 

sameguy

Senior Member
What if you don't have morals?
Have him show you in the bid docs. where a megger was brought up.
+1 to potential damage down stream, in the GC, Owner, Contractor, meeting bring this up and if it isn't in the bid it is extra; lay any damage on the pro who brought it up in writing.
If this ends in court you better have your paperwork in order, start now if you didn't keep track before.
 

noon9elec

Member
thanks for input

thanks for input

Thanks for the input. this is a sticky situation where multiple electrical contractors are working in the same building. and fingers are being pointed as to who is responsible for a poorly installed MC splice that failed. While meggering is a great tool and resource, there is no way to encompass this task on a typical remodel job. yes/no Statistically, how many sole proprietor electricians utilize a insulation resistance meter on a daily basis? Thanks for your time
 

ptonsparky

Senior Member
Thanks for the input. this is a sticky situation where multiple electrical contractors are working in the same building. and fingers are being pointed as to who is responsible for a poorly installed MC splice that failed. While meggering is a great tool and resource, there is no way to encompass this task on a typical remodel job. yes/no Statistically, how many sole proprietor electricians utilize a insulation resistance meter on a daily basis? Thanks for your time
We have three electricians, if you include me, and three meggers. Not a daily basis use but available.

A meg test would not have found your failed splice prior to failing and maybe not even after.
 

ActionDave

Moderator
Staff member
.... Statistically, how many sole proprietor electricians utilize a insulation resistance meter on a daily basis? Thanks for your time
Well you just heard one report from NE. If you count me and my boss you've probably covered 85% of your target group.
 

Strathead

Senior Member
Meggering knob and tube has a good potential to be ineffective. Air is a pretty good insulator, so the wires could be bare and not have any indication of a problem on a megger.
 

jap

Senior Member
Meggering knob and tube has a good potential to be ineffective. Air is a pretty good insulator, so the wires could be bare and not have any indication of a problem on a megger.
That could be the case for any conductor that may be meggered, not just knob and tube, and it will catch a problem depending on the conditions surrounding those open conductor.


JAP>
 

jap

Senior Member
The poster indicated a failed MC connection.

If there was some event that caused a fault when the circuit was energized there may be a chance that the megger could have caught a problem that a simple ohms reading on a multi meter wouldn't have.

JAP>
 

kwired

Electron manager
The poster indicated a failed MC connection.

If there was some event that caused a fault when the circuit was energized there may be a chance that the megger could have caught a problem that a simple ohms reading on a multi meter wouldn't have.

JAP>
if the failure results in a ground fault, maybe, if failure just results in open circuit condition megging isn't going to predict such failure.
 

jap

Senior Member
if the failure results in a ground fault, maybe, if failure just results in open circuit condition megging isn't going to predict such failure.
I doubt if something simply failed to operate because of a loose connection there'd be much finger pointing going on wouldn't you agree?

JAP>
 

ptonsparky

Senior Member
I doubt if something simply failed to operate because of a loose connection there'd be much finger pointing going on wouldn't you agree?

JAP>
Conjecture. We don’t know.

Megging prior to melt down will not help. If the is no fault to detect, then there is no fault.
 
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