Testing 110v system

[tigerpaul]

There are a few workshops where I'm based which have permanently hard wired 110v sockets fed off a fixed transformer. Its puzzling me how to obtain a loop impedance result on a centre tapped 110v system?
Any ideas?
I use a normal megger mft 1502.

 

[Adam]

I thought it is live - earth as with any loop impedance test. Your tester should test at 55 volts.

Obviously your maximum values are obtained from a different table, which I don't know off the top of my head.

 

[johnboy6083]

i woul;d like to know this too! apparenmtly a special 110v tester can be used, but ive never seen one.

 

[tigerpaul]

I have not tried it yet, but I thought my tester will only work at 230v to earth. Maybe I'm wrong I don't know.

 

[Adam]

I have done loop readings on 110 volt sockets, and thinking about it, it was with an MFT 1502. When you turn your tester to loop, it will display <55v I'm sure.

However, it is not possible to test RCD's on 110 volt systems as the MFT 1502, I believe, needs 110 volts or more.

I know that thereis no need for RCD protection on 110 volt systems, but the installation I was on had one for some reason.

 

[johnboy6083]

ill try it tommorow to see if it works. i use a megger 1552 at work, and a fluke 1653 for my own work.

 

[Strima]

The 1502 does start to measure at 55 volts. I would check my 1552 but it's in the garage with the batteries out and I can't be bothered... :lol:

 

[Adam]

The 1502 does start to measure at 55 volts. I would check my 1552 but it's in the garage with the batteries out and I can't be bothered... :lol:

I'll save you the trouble, as it is probably cold and wet outside, lol.

The 1552 is the same as the 1502 with additional features: http://isswww.co.uk/datasheets/MFT_SERIES_DS_en_V10.pdf

 

[Strima]

I'll save you the trouble, as it is probably cold and wet outside, lol.

The 1552 is the same as the 1502 with additional features: http://isswww.co.uk/datasheets/MFT_SERIES_DS_en_V10.pdf

Work gave me the 1502, I really miss the RCD auto-test function... :lol:

 

[Adam]

Work gave me the 1502, I really miss the RCD auto-test function... :lol:

My employer also issues mostly 1502's, and has hundreds of them. I have not had the privilege of using the auto RCD yet, but I know some of the lads have had the 1552's or newer models. We get our testers swapped every 12 months for calibration.

 

[Knobhead]

What ever you use you will need TWO readings with 110V centre tapped. L1 > E L2 > E

 

[Steve Richards]

I have done loop readings on 110 volt sockets, and thinking about it, it was with an MFT 1502. When you turn your tester to loop, it will display <55v I'm sure.

However, it is not possible to test RCD's on 110 volt systems as the MFT 1502, I believe, needs 110 volts or more.

I know that thereis no need for RCD protection on 110 volt systems, but the installation I was on had one for some reason.

Adam

If you cannot comply with table 41.6 which is for a reduced low voltage system (110V) then as per regulation 411.8.3 you can use an RCD for fault protection by automatic disconnection of the supply.

If by your post this is related

 

[drew35]

Your meter should have a settings menu where you can change between 240v, 60v, or 55v. On my Metrel you hold the screen brightness button whilst pressing any navigation key.

 

[johnboy6083]

The megger 1552 tests 110V supplies (at 55V to centre tap) fine. I tried it yesterday with no problems.