Megging after rough in

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On one of my last projects the GC's crew came back in after me for a list of small modifications to framing, kitchen, etc.. They managed to cause not one but two dead shorts to my wires.
 
Hope they paid for the repair. I did a custom house where the owner was a gadget nut and fought with the GC. Job took an entire year because of them disagreeing and GC would stop work several times. After I roughed in 15 NM runs in 4 car garage with huge attic owner decided he wanted a set of pull down steps in garage to get to his ten pinball machines in the attic so I had to move all if the cables, Originally installed straight set of steps leading up to second floor but changed that to custom made quarter turn steps, moved the laundry chute three tines making me move wires three times. With all of that the bright sparky working with me suggested that we strip the ends of every white,red,& black wires and tie ones in the over 150 receptacles we installed then make sure we had 120 volt power at end of every receptacle, luminare, exhaust fans etc. Good thing we did. Forgot to refeed the middle of receptacle run that was moved a few times 8 months earlier.
 
Jim Reizner said:
Residential plumbers do not pressure test residential water systems - they just turn the water on and check for leaks.
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??? Obviously you do not do plumbing around here. Virginia Residential Code requires a 100 psi water pressure test to pass rough in inspection. This is way before the well is hooked up to the house or city/county water system is connected to the house.

DWV is tested (except in winter where freezing is an issue then air is used) with a 10 foot standpipe to pressurize piping underground and in some jurisdictions the completed rough in DWV is filled to the water runs out of the roof vents to check for leaks. Other jurisdictions it is filled to the highest fixture.

Also gas plumbing is tested to 15 psi before any connections are made to the supply side.
 
Little Bill said:
All the plumbers pressure test their plumbing with compressed air
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Not all. Around here they use a hydraulic ram device to pressurize the potable water pipes with 100 psi water. Why? Ever see a joint come apart with 100 psi air behind it for power? No wonder they use compressed air to do work, that's a lot of horsepower. If a joint fails with100 psi water, you get a pop and a leak, as compressed water contains little power (ability to do work).

But in freezing weather, water does not work well, have to be quick and drain before temp falls to 32.

https://www.amazon.com/VEVOR-Hydrostatic-Hydraulic-Container-Irrigation/dp/B072MZFC5Q is an example.
 
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Little Bill said:
I've done several new construction residential, and also helped others do the same. All the plumbers pressure test their plumbing with compressed air.They leave a gauge on it for several days and check for leaks. Some use water, but most use air. I think most just use water for the drains. Maybe your area doesn't, but it's required here by building inspectors.
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They'll do that up until they have their first catastrophic joint failure. Then they'll use water with a hand pump to boost the pressure.
 
electrofelon said:
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.
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Have been on residential jobs where the plumber & plumbing inspector only cared about leaks in drain & waste lines. Years ago they would cap off these lines and fill 3 or 4" vent pipe sticking thru roof and fill it with water. Inspector would use chalk to mark level. If line was still at water level 24 hours later it passed. Big commercial jobs plumbers always pressure tested water supply lines & waste ,drain & vent lines. Never meggered wires in residential work. Have a Simpson megger that puts out up to 5,000 bolts DC. would be afraid of even using 250 volts to megger 120 volt residential circuits with all of the dimmers, smart switches, combination receptacle USB charger etc.
 
garbo said:
Have been on residential jobs where the plumber & plumbing inspector only cared about leaks in drain & waste lines. Years ago they would cap off these lines and fill 3 or 4" vent pipe sticking thru roof and fill it with water. Inspector would use chalk to mark level. If line was still at water level 24 hours later it passed. Big commercial jobs plumbers always pressure tested water supply lines & waste ,drain & vent lines. Never meggered wires in residential work. Have a Simpson megger that puts out up to 5,000 bolts DC. would be afraid of even using 250 volts to megger 120 volt residential circuits with all of the dimmers, smart switches, combination receptacle USB charger etc.
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There would be no devices on rough. Even if you meg a circuit with devices, you always disconnect the devices before doing so. Switches might be the only thing I would leave. But you would have to close the switches for the current to pass through.
 
jaggedben said:
Okay guys, neutral-to-ground faults at receptacle boxes that are not downstream of a GFCI device. After the boxes are made up with the receptacles. How do you test for that when everything is made up? AFCI doesn't catch it.
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A continuity test at the panel from ground to neutral...if it beeps, then the neutral is touching a ground somewhere

Sent from my Pixel 7 using Tapatalk
 
electrofelon said:
I think it would find an event that could result in a series arc, like a nail thru the wire. Then there are parallel arcs neutral - neutral bonds, and neutral ground bonds.

Sometimes I just have little thought experiments imaging what aliens would think of they analyzed the way we do things, having no preconceived notions. Given Romex, staples, idiot installers, nails, seems like perhaps a no brainer?

No one addressed the rumor that this is done commonly/universally in other parts of the world. Does anybody know?
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Nail through a wire isn't going to be too common of a find after rough in unless they are still doing some construction after you started rough in.
Maybe most common thing that may come up is siding being installed during or after your rough in. One the next common things but will be well after rough in is cabinet mounting screws or other post drywall activities penetrating a cable.

I once had a 10-3 cable to a dryer that wasn't even concealed yet had a short circuit/ground fault within the cable. Was installed through exposed framing in ceiling of a basement and never had any finish installed over it. Never found any obvious damage on cable exterior. Did not have a megger back then, but did have a high resistance reading between conductors with nothing connected - had to be bad run of cable from factory. Rest of a 250 foot coil had similar reading - my supplier did replace it.

I see others already mentioned this - didn't read through all the replies:oops:
 
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electrofelon said:
An afci will indeed trip on a N-G bond in the branch circuit
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If it is a type that has any level of GFP in it. May not trip until there is a load though.

The ones that do not require neutral to run to the AFCI - I don't see them being able to detect low level ground fault current at all.
 
wwhitney said:
I don't believe that "having a neutral terminal on the breaker" = "performs some GF detection and will trip on a N-G fault". I recall one brand of single pole AFCIs advertising that you can use them on an MWBC, and just to land the neutral on one of the two units, doesn't matter which.

Cheers, Wayne
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Those obviously do not have GFP circuitry in them or would trip any time there is a load on them that isn't also returning to the output neutral terminal of the same device.
 
ptonsparky said:
Using 4" screws to hang kitchen cabinets seems to increase that chance.
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I learned long time ago never run cables horizontally inside walls where cabinets are to be hung, especially in the upper and lower zone of the typical cabinet finished height where mounting screws are more likely to be.
 
In most areas the plumbers put a stopper in the drain line in the last cleanout in the house and then fill the vents with water to the top of the vents. Gas is always pressure tested.

I had a shorted circuit one time in a new house. Drove a staple in to tight, I guess. House was all sheet rocked. Luckily, I found it 15 feet from the panel in the unfinished basement.
 
Once the rock is in your all done anyway if there is a problem and they are the most likely trade to cause it..

I would say Ohming after rough would help tell you the wiring is ok would be a good idea.
 
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