BIGRED

I have an insurance job that requires me to meg out the existing circuits in a residence. How would you go about doing this? I don't even have a megger, what do they cost?

BlueBox

If you do a search here you'll find a bunch of good threads.

The Fluke 1507 is a great model that can be found for a good price on eBay.

wildleg

I got one for 5 somethin on fleabay. its a great tool to have, especially after you get used to it.

__________________
As President Roosevelt said: "We have nothing to fear but fear itself. And Chuck Norris. And 滿口胡言. And Grabthar's hammer. And Gort. and 江南 Style. and rotting in the street and Zombies . . . and Wayne Griffen "

RIVETER

I am just throwing this out there. When there is a fire job, is there a specific voltage that you want to apply above 600 volts?

brian john

1000VDC if you send me you email I can send you some forms

__________________
Brian John
Leesburg, VA

RIVETER

Is this form a kind of list of the circuits checked and at what voltage? I am not planning on doing any more. I was just wondering and thought it would be good information to know. And, your PM box isn't working. Or was you talking to Bigred?

micromind

The megger I use 90% of the time is a BK precision 307A. It cost a couple hundred bucks a few years ago.

It's analog, (which I really like) has 250, 500, and 1000 volt ranges, the test button can be locked on for quick readings of multiple conductors, and it has a 0-3 ohm scale too. It uses 8-AA batteries, which last a long time. It's built in to its carrying case, and the leads store there too.

For 600 volt wiring, I've always used 1000 volts. Unless a test time is specified, a few seconds will tell you if there are problems or not.

I've always tested hot to neutral, neutral to ground, and hot to ground. In other words, test every wire in a cable or conduit against every other wire as well as to ground.

The first thing to do is unhook all GFIs, AFIs, smokes, and anything else connected to a circuit. Leave normal receptacles connected, and switches turned on, but loads disconnected. Check with an ohm meter first. If not open, investigate. All circuits must have no loads connected to them.

If you're working in an existing panel that has neutrals and grounds on the same bus, first remove all the neutrals. leave the grounds, and leave the hots on the breakers. turn all breakers off. Clip one lead to the ground bus, and test each hot and each neutral. Now you have to match up neutrals with hots in each cable and test each one hot to neutral.

I don't know what the published minimum readings are, (there are a few guys around here that do though) and you'll have opinions ranging from 1 meg to zillions of megs, but if there's a problem, it'll be obvious.

My megger is likely the second or third most used instrument. I haven't energized a circuit over 50 amps without megging it for many years. Most branch circuits get megged too, if I can. Megging new circuits before you hit the switch can save some nasty surprises.

Rob

76nemo

Your wiring is rated at 600V's. You're not megging any devices, you're megging the insulation of the building wiring itself which is rated at 600V's for power wiring. The point of IR testing is to exceed it's range of insulation to see where at what lavels it will/may break down.

76nemo

Yeah, an "on-spot" test unless otherwise noted.

76nemo

As mentioned, the 1507 is a nice tool. It's nice because it incorporates PI/DAR, not just spot. Don't think you might not ever use it again, you will, trust me. Look around, but if you're going to spend the $, get a tester capable of PI/DAR.

brian john

What's your email I'll send you a post with forms.

__________________
Brian John
Leesburg, VA

Zog

The point of IR testing is to actually measure the resistance of the insulation, you are refering to a dielectric strength test, which is to find the breakdown voltage of the insulation, and uses different equipment and procedures and is generally considered a destructive test.

76nemo

You worded it a little differently, nice.

I have to ask on here so others can learn. With what applications do you consider IR destructive over other methods? If you speak of insulation breakdown over time due to extreme stressing due to test, you are on a different angle than I. I was on the road of doing spot testing in certain circumstances in an application where they maybe only done once or twice in their lifespan. I am not talking of regular intervals and a PM program.

I have tried to stimulate IR against hi-pot discussions in a couple forums and no one bit. I am unsure of where to start. What exactly do you speak of, stating IR was far aggressive/destructive? Compared to what testing what??

MDShunk

Regardless of the insulation's original rating, I really think you're asking for trouble if you Meg aged wiring at more than twice operating voltage. Ie: use 500 Volts for 208 & 240 circuits and 1000 volts for 480 circuits. If you're ignorant to certain realities of old wiring, you can make anything "fail".

__________________
One reason not to give DIY advice:
Catch a man a fish and you can sell it to him.
Teach a man to fish and you’ve ruined a good business opportunity.

Jlarson

I have an AEMC 1045 that has done well it's going on 5 or so years I think. It is a fluke quality instrument, actually it looks just like a fluke with the yellow and gray colors it's got going on. Its got a timer back light, two ohm meter ranges 20 ohm and 400k ohm, and 250, 500, and 1000 volt settings. I think it also has a threshold setting that will alarm if the readings go lower than the set point but I never used it. Only bad thing is it is $600-$700 new.

Don't get a cheap one you will use it more than once, one of the best uses I found for one in the resi. is finding GFCI issues. Great example I had a GFCI start tripping randomly in my house awhile back. Even with every load disconnected. I finally ended up looking at a cabinet that was mounted right above a downstream outlet in my garage. I meged from the outlet to evey screw head and found one that had hit the NM, I might still be looking if it weren't for the megger.

480sparky

Would not it still be 600v insulation to begin with?

__________________
In winter, why do we try to keep the house as warm as it was in summer when we complained about the heat?

76nemo

Marc has an excellent point which I missed due to being off topic with the OP. As far as testing insulation stressed due to extreme heat/fire,...the insulation rating is moot behind thee idea of the testing itself.

MDShunk

I don't know. My crystal ball is in the shop. My point is, don't concern yourself in the least with the original insulation rating. Meg at twice the circuits actual operating voltage.

__________________
One reason not to give DIY advice:
Catch a man a fish and you can sell it to him.
Teach a man to fish and you’ve ruined a good business opportunity.

76nemo

You lose me there Marc.

MDShunk

If you have a 208 circuit operating on wire with million volt rated insulation, would you Meg it at a million volts? He'll no. Twice actual operating voltage is plenty. In this example, 500 volts is plenty.

__________________
One reason not to give DIY advice:
Catch a man a fish and you can sell it to him.
Teach a man to fish and you’ve ruined a good business opportunity.