aelectricalman
Senior Member
- Location
- KY
Does anyone in here ever run an insulation resistance (Megger device)test on residential. Is that something that could be benificial in a new home. (From a time versus profit standpoint).
Megger devices
- Thread starter aelectricalman
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BAHTAH
Senior Member
- Location
- United States
Re: Megger devices
With the increasing use of GFCI and ARC-Fault breakers it would not be a bad idea to do a megger test. Typically on a dwelling I will energize the circuits as best I can just to make sure someone didn't drive a nail through a romex somewhere. I have a megger that I do use on feeders especially those run from a service pedestal to the dwelling. In my area we have services where the utility supplies a meter pedestal and we run a feeder 100' or so to he dwelling. I make-up all my receptacle outlets with pig-tails on residential installations so there are only pig-tails for each device, that way when I energize the circuit to check it, all the outlets are energized and on make-up I only have terminations for each device. I don't like using the device as a feed-through, but thats just my way of doing what I think is a better installation. The NEC is a minimum standard.
With the increasing use of GFCI and ARC-Fault breakers it would not be a bad idea to do a megger test. Typically on a dwelling I will energize the circuits as best I can just to make sure someone didn't drive a nail through a romex somewhere. I have a megger that I do use on feeders especially those run from a service pedestal to the dwelling. In my area we have services where the utility supplies a meter pedestal and we run a feeder 100' or so to he dwelling. I make-up all my receptacle outlets with pig-tails on residential installations so there are only pig-tails for each device, that way when I energize the circuit to check it, all the outlets are energized and on make-up I only have terminations for each device. I don't like using the device as a feed-through, but thats just my way of doing what I think is a better installation. The NEC is a minimum standard.
izak
Senior Member
- Location
- Springfield, MO
Re: Megger devices
i think a megger would be a great idea
i think a megger would be a great idea
allenwayne
Senior Member
Re: Megger devices
We did 2,500 homes last year to megger test each one would kill our profit margine why fix what isn`t broke
We did 2,500 homes last year to megger test each one would kill our profit margine why fix what isn`t broke
friebel
Senior Member
- Location
- Pennsville, N.J.
Re: Megger devices
To: aelectricalman and grant,
To answer your question, "does anyone in the residential area do megger test for a new home".
I do not know any electrical contractor that does a megger check on new installations, but I am sure that there may be someone who does.
In the Industrial arena, where I worked for 45 years a megger check was done on all new services, feeders, branch circuits to motors, etc. was done. Then that information was given to the owner of that company for future use.
With all of this said about Megger checks, I am going to ask a question about Megger checks.
QUESTION: When checking feeders, branch circuits to motors, what is a good reading, and what reading would you want to take the equipment out of service for possible repairs or drying out of equipment?
I have the answer to the above question, but I will be interested in the opinion of the readers.
To: aelectricalman and grant,
To answer your question, "does anyone in the residential area do megger test for a new home".
I do not know any electrical contractor that does a megger check on new installations, but I am sure that there may be someone who does.
In the Industrial arena, where I worked for 45 years a megger check was done on all new services, feeders, branch circuits to motors, etc. was done. Then that information was given to the owner of that company for future use.
With all of this said about Megger checks, I am going to ask a question about Megger checks.
QUESTION: When checking feeders, branch circuits to motors, what is a good reading, and what reading would you want to take the equipment out of service for possible repairs or drying out of equipment?
I have the answer to the above question, but I will be interested in the opinion of the readers.
Re: Megger devices
I'm not sure if we are talking about the same thing or not but it sounds like it. We call it a high pot test or dielectric strength test. I work at a modular plant and we are required to do it on all of our houses 1080v@1 sec or 900v@1 min. As far as profits are concerned I think that this process would increase profits helping to prevent call backs . We also do a operational and polarity check on all circuits. Think about it one bad connections or pinched wire after the job is complete and owner is living in there home could lead to bad reccomendations and loss of profits to to service call backs. Any questions or comments would be appreciated.
I'm not sure if we are talking about the same thing or not but it sounds like it. We call it a high pot test or dielectric strength test. I work at a modular plant and we are required to do it on all of our houses 1080v@1 sec or 900v@1 min. As far as profits are concerned I think that this process would increase profits helping to prevent call backs . We also do a operational and polarity check on all circuits. Think about it one bad connections or pinched wire after the job is complete and owner is living in there home could lead to bad reccomendations and loss of profits to to service call backs. Any questions or comments would be appreciated.
aelectricalman
Senior Member
- Location
- KY
Re: Megger devices
No, but with the age of AFCI's and GFCI's I don't think it would be a bad idea. I would venture to say that it would eliminate most of the nuisence tripping previously blamed for poor AFCI designs.
How long does it take to performa Megger Test?
[ January 30, 2005, 12:03 PM: Message edited by: aelectricalman ]
No, but with the age of AFCI's and GFCI's I don't think it would be a bad idea. I would venture to say that it would eliminate most of the nuisence tripping previously blamed for poor AFCI designs.
How long does it take to performa Megger Test?
[ January 30, 2005, 12:03 PM: Message edited by: aelectricalman ]
Re: Megger devices
High pot testers produce AC voltage, meggers DC. Either will show a breakdown, but some standards and manufacturers specify which test and at what voltage. I have to perform megger testing on ABS-American Bureau of Shipping vessels every 5 yrs. They specify min. resistance for equipt. as:
rated v/(kva/100) + 1000, which can be pretty low. I like to see at least 1M.
High pot testers produce AC voltage, meggers DC. Either will show a breakdown, but some standards and manufacturers specify which test and at what voltage. I have to perform megger testing on ABS-American Bureau of Shipping vessels every 5 yrs. They specify min. resistance for equipt. as:
rated v/(kva/100) + 1000, which can be pretty low. I like to see at least 1M.
friebel
Senior Member
- Location
- Pennsville, N.J.
Re: Megger devices
Ok, I have asked the question about "what is a good reading and a bad reading with a megger"?
Before I give you my answer let me talk about the difference between a hypot tester versus a megger test.
First a hypot test will put high levels of AC voltage on the equipment that you are checking and sometimes you will overstressed the winding of a motor or destroy the insulation of the wire.
They call in the industry a hypot test can be a destructive test.
Now a megger will put levels of DC voltage on the equipment that you are checking.
I am quoting out of a book from the AVO company, formerly the Biddle Megger Company.
Page 20 of their book "A Stitch in Time" The Complete Guide to Electrical Insulation Testing
Featuring the Megger Insulation Testers.
Equipment of up to 100 volts, a DC Test Voltage should be between 100 and 250 volts.
Equipment of up to 440 to 550 volts, a DC Test Voltage should be between 500 and 1000 volts.
Equipment of 2400 volts, a DC Test Voltage should be between 1000 to 2500 volts or higher.
Equipment of 4160 volts, a DC Test Voltage should be between 1000 to 5000 volts.
I am now quoting out of the same book on page 14 the "One Megohm Rule". For many years maintenance professionals have used the one-megohm rule to establish the allowable lower limit for insulation resistance. The rule may be stated.
Insulation resistance should be approximately one megohm for each 1000 volts of operating voltage, with a minimum value of one megohm.
For example: a motor rated at 2400 volts should have a minimum insulation resistance of 2.4 megohms.
After this lengthy message, there is a lot to learn about insulation testing.
Ok, I have asked the question about "what is a good reading and a bad reading with a megger"?
Before I give you my answer let me talk about the difference between a hypot tester versus a megger test.
First a hypot test will put high levels of AC voltage on the equipment that you are checking and sometimes you will overstressed the winding of a motor or destroy the insulation of the wire.
They call in the industry a hypot test can be a destructive test.
Now a megger will put levels of DC voltage on the equipment that you are checking.
I am quoting out of a book from the AVO company, formerly the Biddle Megger Company.
Page 20 of their book "A Stitch in Time" The Complete Guide to Electrical Insulation Testing
Featuring the Megger Insulation Testers.
Equipment of up to 100 volts, a DC Test Voltage should be between 100 and 250 volts.
Equipment of up to 440 to 550 volts, a DC Test Voltage should be between 500 and 1000 volts.
Equipment of 2400 volts, a DC Test Voltage should be between 1000 to 2500 volts or higher.
Equipment of 4160 volts, a DC Test Voltage should be between 1000 to 5000 volts.
I am now quoting out of the same book on page 14 the "One Megohm Rule". For many years maintenance professionals have used the one-megohm rule to establish the allowable lower limit for insulation resistance. The rule may be stated.
Insulation resistance should be approximately one megohm for each 1000 volts of operating voltage, with a minimum value of one megohm.
For example: a motor rated at 2400 volts should have a minimum insulation resistance of 2.4 megohms.
After this lengthy message, there is a lot to learn about insulation testing.
izak
Senior Member
- Location
- Springfield, MO
Re: Megger devices
the megger tests i have seen performed rarely take longer then ten minutes, and that was with ALL the proper officials standing around, checking thier watches and logging ALL the results..
the megger tests i have seen performed rarely take longer then ten minutes, and that was with ALL the proper officials standing around, checking thier watches and logging ALL the results..
allenwayne
Senior Member
Re: Megger devices
Is that 10 min/tested wire? If it is multiply that by what .................... Last spring we had a builders model home get struck by lightning and caused a small fire that was quickly put out.The fire dept. called in the building inspectors that quickly pulled the C.O.
The electrical inspector required that the entire home was to be megger tested,we had to unhook all fixtures, appliances,open all splices.
Testing was done and unsatisfactory tested wires replaced.Then results were sent to inspector reinspection and reinstatment of the C.O. Total bill from us to builder was around $1,200.00 minus the $295.00 for replacement of wires that failed the test.The only way to use a megger in a home is to test each and every wire individually that would be a killer on profit margin
Is that 10 min/tested wire? If it is multiply that by what .................... Last spring we had a builders model home get struck by lightning and caused a small fire that was quickly put out.The fire dept. called in the building inspectors that quickly pulled the C.O.
The electrical inspector required that the entire home was to be megger tested,we had to unhook all fixtures, appliances,open all splices.
Testing was done and unsatisfactory tested wires replaced.Then results were sent to inspector reinspection and reinstatment of the C.O. Total bill from us to builder was around $1,200.00 minus the $295.00 for replacement of wires that failed the test.The only way to use a megger in a home is to test each and every wire individually that would be a killer on profit margin
Re: Megger devices
thanks for the clarification between hi-pot and megger. THere is also dc type hi-pot test available now. When you perform a high pot test with a ac tester there shouldn't be any equipment hooked up to the lines. All you should have are your switches receps (minus gfci)you can have lights wired also as long as there is no bulbs installed. I don't know about Hi-pot destroying insulation of wire if it is done right. The voltages and test times are straight out of the NEC. Not to mention that modular plants have been doing this test for years. A note on the DC type tester, with a DC type tester you can have everything in the house hooked up and run the test, but I don't reccomend it, cuase it gives you to many false shorts.
thanks for the clarification between hi-pot and megger. THere is also dc type hi-pot test available now. When you perform a high pot test with a ac tester there shouldn't be any equipment hooked up to the lines. All you should have are your switches receps (minus gfci)you can have lights wired also as long as there is no bulbs installed. I don't know about Hi-pot destroying insulation of wire if it is done right. The voltages and test times are straight out of the NEC. Not to mention that modular plants have been doing this test for years. A note on the DC type tester, with a DC type tester you can have everything in the house hooked up and run the test, but I don't reccomend it, cuase it gives you to many false shorts.
aelectricalman
Senior Member
- Location
- KY
Re: Megger devices
Thank you all for contributing.
Thank you all for contributing.
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