Megging after rough in

[kwired]

As far as plumbers pressure testing, I've seen less of that since pex came into play. Most almost always tested when they ran copper lines and did tend to find a leak now and then. PEX seems to never leak unless maybe it was pretty cold when installed, then a heat gun tends to fix it. They often don't have many concealed fittings compared to copper tubing either .

 

[hillbilly1]

I worked with one plumber many years ago, he used cpvc. He would always miss gluing one fitting, and I was usually there when he turned on the water. One high end house, I had water running out of the can lights in the basement, another the line blew off the water heater while I was standing there talking to him! LOL!

 

[kwired]

Was on project probably 2016 or 17 where we were installing VRF heat pump system throughout a school. The HVAC guys were pressure testing their lines with nitrogen, which IIRC were testing at maybe 400 PSI? I know they could easily get at least 800 straight from the nitrogen tank. They mostly had pro press fittings they utilized. Had about 80-100 PSI in the system when a fitting that didn't get crimped finally let loose. I wasn't near it at all and it was still loud. Maintenance guy for the school was in fairly immediate vicinity, probably still has PTSD from that.

 

[Dennis Alwon]

I used to buy 1000' reel and I would ohm the nm cable before I installed it because we had found a few rolls that were defective from the factory

 

[jaggedben]

A continuity test at the panel from ground to neutral...if it beeps, then the neutral is touching a ground somewhere

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That doesn't work on existing equipment that's in service without turning off all power and lifting a neutral. Which no one is going to do.

 

[kwired]

That doesn't work on existing equipment that's in service without turning off all power and lifting a neutral. Which no one is going to do.

if not the service panel you lift either neutral or EGC and then test continuity, but you are testing everything leaving that panel and if you do have continuity you will need to disconnect even more things to isolate and find where the cross over is.

 

[macmikeman]

99 times out of 100, any damaged non metallic sheathed cables happened after the rough in, and the only real good megger testing everything would do is if it is witnessed and recorded prior to sheetrock installation. At least that is my experience. By the way, the Navy used to make us megger test rolls of romex before we were allowed to remove them from the locked bonded storage containers for the residential projects I was involved with on , at , Pearl Harbor. Never had any issue till after all the follow on trades got done destroying the integrity of the sheaths and conductors after rough inspections passed. Most times it's due to air powered nail guns and I can't spell the P word for beans...... Other than that there is roto zips with the guards removed to deal with, but that one is a lot easier to track down and repair then the nails that make it thru the nail plates.

 

[letgomywago]

99 times out of 100, any damaged non metallic sheathed cables happened after the rough in, and the only real good megger testing everything would do is if it is witnessed and recorded prior to sheetrock installation. At least that is my experience. By the way, the Navy used to make us megger test rolls of romex before we were allowed to remove them from the locked bonded storage containers for the residential projects I was involved with on , at , Pearl Harbor. Never had any issue till after all the follow on trades got done destroying the integrity of the sheaths and conductors after rough inspections passed. Most times it's due to air powered nail guns and I can't spell the P word for beans...... Other than that there is roto zips with the guards removed to deal with, but that one is a lot easier to track down and repair then the nails that make it thru the nail plates.

Pneumatic

 

[RdmanElect]

That doesn't work on existing equipment that's in service without turning off all power and lifting a neutral. Which no one is going to do.

We are talking about after roughing in

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[jaggedben]

We are talking about after roughing in

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And my question that you quoted explicitly expanded the discussion to after boxes are made up. Sorry for the thread drift.

 

[tortuga]

Does anyone find it kinda odd that we dont do this? Plumbers pressure test their supply and waste lines, why don't we test our circuits? I am thinking primarily with residential. Particularly now with AFCI's it would find inter-neutral bonds and N-G bonds. I heard once this is standard in other parts of the world, is that true? I think if I was charged I would dump all afci's and require megging.

In the manufactured building industry they do a dielectric strength test, its described in 550.17:

(A) Dielectric Strength Test. The wiring of each mobile home
shall be subjected to a 1-minute, 900-volt, dielectric strength test
(with all switches closed) between live parts (including neutral
conductor) and the mobile home ground. Alternatively, the test
shall be permitted to be performed at 1080 volts for 1 second.
This test shall be performed after branch circuits are complete
and after luminaires or appliances are installed.
Exception: Listed luminaires or appliances shall not be
required to withstand the dielectric strength test.

Also RV's in 551.60,

 

[RdmanElect]

And my question that you quoted explicitly expanded the discussion to after boxes are made up. Sorry for the thread drift.

Gotcha, sorry I didn't read the rest of the comments

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[electrofelon]

99 times out of 100, any damaged non metallic sheathed cables happened after the rough in.

I guess I need to revise the proposition in the OP. I am not so worried about the installing electrician damaging his stuff while installing, so yeah, megging immediately after the rough in while no work by other trades has happened, would not likely find problems. I guess I am thinking more of situations where a bunch of stuff happens after rough-in, like siding in particular.

 

[jaggedben]

I guess I need to revise the proposition in the OP. I am not so worried about the installing electrician damaging his stuff while installing, so yeah, megging immediately after the rough in while no work by other trades has happened, would not likely find problems. I guess I am thinking more of situations where a bunch of stuff happens after rough-in, like siding in particular.

Yeah, so it's more like megger before finish, rather than after rough in. Although I suppose if you do both and document then you have the greater ability to point the finger when another trade has done the damage. And for good measure to check your own work, megger each circuit after making up the boxes but before landing the neutral, when making up the panel. I will never say these are bad ideas.

 

[rambojoe]

The confusion and missing key word is, unless all make up, line and load and switch legs are tied after you finish rough in- then maybe. If not, are you gonna meg every cable? Or just the homers?
For resi, its a bit much.

Pass rough inspection and go make more money.

 

[macmikeman]

The thing is , I always double check my wiring after roughing in visually, and then I tone test to make sure i didn't leave anything out . Especially in the lighting. Takes around 1/2 hour. And yes it has saved me from what I feel is disaster more than once..........

 

[garbo]

When NM cable came packed in cardboard boxes until early 1990's I never had any damaged sections. Now with the plastic wrap had the jacket on one roll damaged. Miss the cardboard box because we always thru in stripped pieces of jacket and trash in them. Wonder how many electricians out there ever installed the old cloth covered Romex. At the end of the day your hands would be covered with a tar like substance. During the change over back in late 1960's to ( not sure of the proper term ) thermoplastic jacket supply houses charged 50¢ a box more for the new style.

 

[ptonsparky]

When NM cable came packed in cardboard boxes until early 1990's I never had any damaged sections. Now with the plastic wrap had the jacket on one roll damaged. Miss the cardboard box because we always thru in stripped pieces of jacket and trash in them. Wonder how many electricians out there ever installed the old cloth covered Romex. At the end of the day your hands would be covered with a tar like substance. During the change over back in late 1960's to ( not sure of the proper term ) thermoplastic jacket supply houses charged 50¢ a box more for the new style.

Never worked the cloth covered as new. I must be a newbie.

 

[kwired]

I very seldom make up connections at rough in. Don't even strip sheath off in boxes unless going to use as a temp outlet.

I don't get all those that say their inspectors want to see them made up. If main thing is to see the grounding conductors there is a way around that as well - non contact voltage tester at final inspection will pick up open grounds if there is load on the other conductors - it will be capacitively coupled voltage which is what NCTV's use in there basic operation to begin with.

Even installs with raceways I often will not have conductors pulled yet at rough in inspection time.

Rough in inspection is giving permission to install drywall or other coverings, connections in accessible boxes is still doable at a later time if you want to see them. I don't care and have had occasional inspector pull a cover off to look inside. Most don't tend to do this unless you are new to them and they just want to see what you typically do that first job or two they look at of yours or if there is something suspicious that makes them want to look harder.

 

[Fred B]

The test is when everything is powered and there are no problems. Nothing there says that testing has to be done before power is applied.

-Hal

Common but really doesn't prove anything like an absence of a small insulation damage that would cause larger problem down the road.

More extensive testing usually required in commercial applications that involve a commissioning process.

Around here (if they got a permit) plumbing requires pressure testing.