Loop Impedance Testing - Strange fault code

[Midwest]

Being doing a domestic bathroom refurb', lighting, altering shower circuit (have a Megger 1730 MFT).

History, property has no RCD protection, but as it was a Hager CU, had contemplating using RCBO's (TN-C-S supply). Before doing any work, I decided to clamp the meter tails, as the property has only 1 x RFC. Did so with tv etc on, fridge freezer running, appliances turned on but not running, lights turned on. Got a reading of above 30mA. Suspecting my cheapo earth leakage clamp meter was at fault (although gave normal readings at my house, previously), got a ex' lead out with exposed earth. TV gave the highest reading of 3mA. Went back and clamped tails again, got reading of 9mA.

Yesterday, altered bathroom lighting, did initial tests, all okay (IR L/N to earth 350). Today, altered existing shower circuit for new shower pump. All tests fine (IR 3 x >999), till I got to Zs. MFT was making audible warning tone (which I had with high touch voltages) and displaying <> PE above indicated voltage. MFT completed Zs test (0.16ohms & 1.24kA) and audible tone returned. Contacted Megger, who suggested Ze test at CU. Ze test completed, but same audible tone (0.12ohms & 1.90kA). Also did PFC/PSC and got similar results with 0.11ohms & 2.14kA. There is a supply transformer across the road.

Megger range me back, never seen fault code before, but suggested it could be touch voltage on circuit, or faulty tester.

Anyone experienced this before?

 

[Wilko]

Sorry to hear the tester is giving you grief. A bit of a worry that Megger can't be definite on what fault code means ... My usual response to cranky test kit is to try a fresh set of batteries

 

[Midwest]

Hmmmm, reading a pdf from Megger, it shows the 'PE' when explaining testing for touch voltages. Going to confirm continuity on bonding.

Electrical test equipment | power station to plug | Megger - https://uk.megger.com/electrical-tester-contractor-edition/march-2016/checking-touch-voltage

 

[Midwest]

Sorry to hear the tester is giving you grief. A bit of a worry that Megger can't be definite on what fault code means ... My usual response to cranky test kit is to try a fresh set of batteries

It uses rechargeable and they are fully charged. Just a bit concerned getting this fault code, doing Ze test, i.e. supply isolated and EC disconnected.

 

[Wilko]

Had a read of doc - next thought - is it possible that little touch pad's surround is grotty ? It wouldn't take much to trigger it to read perhaps.

 

[Zdb]

I didn't think that rechargeable batteries were suitable for use with multifunction testers?

 

[Octopus]

I didn't think that rechargeable batteries were suitable for use with multifunction testers?

Why not?

My Metrel has them fitted and they are changed in situ when the unit is plugged into the mains..............

 

[SparkyChick]

I didn't think that rechargeable batteries were suitable for use with multifunction testers?

My MFT1731 comes supplied with rechargeables... one of it's best features IMHO

 

[Gavin John Hyde]

when was it last calibrated? as it might be worth comparing some known results against the values on the calibration certificate ??? i had an issue with a kt63 sending out funny readings a couple years ago. when i had it calibrated it was out by quite some margin... never found the reason for it.. i could do a PFC/PSCC and the thing would give seemingly random results...

 

[telectrix]

I didn't think that rechargeable batteries were suitable for use with multifunction testers?

the megger 1700 series are OK with them. with earlier MFTs it was recommended not tu use r/c's because of the high s/c/current.

 

[Ian1981]

I've got a megger mft 1552 and says rechargeable batteries aren't to be used.
Only because rechargeables don't get upto the required voltage combined (8 in total) for the tester to work.
New models such as the megger mft 1730 series for example are rechargeable

 

[Midwest]

Had a read of doc - next thought - is it possible that little touch pad's surround is grotty ? It wouldn't take much to trigger it to read perhaps.

Megger did suggest that, pinkies nowhere near it. Did a plug in test at home, noo probs.

when was it last calibrated? as it might be worth comparing some known results against the values on the calibration certificate ??? i had an issue with a kt63 sending out funny readings a couple years ago. when i had it calibrated it was out by quite some margin... never found the reason for it.. i could do a PFC/PSCC and the thing would give seemingly random results...

Don't think its my MFT, although anything is possible. Got a towel rad' to connect up to the RFC tomorrow. Test the bonding, clamp again, see what occurs. MFT was calibrated last August, do monthly tests, and I did a socket Zs test today (on known socket) in my house, no issues.

 

[Midwest]

Update:
Put my 1730 on charge all night (was 3/4 charged yesterday). Zs on socket at home, no issues (i.e. no PE or audible warning tone). Zs on socket in property, no issues. Installed new FCU, before testing did Ze at CU, no issues similar results as yesterday. Confirmed continuity for gas & water bonds. Did initial tests for new FCU, all good.

Before packing up, repeated extraneous checks on pipework in bathroom with local cpc, all good except one piece of copper pipe for shower, connected to water tank via pushfit. Got a fault code ' VOL O-L, which translates to voltage overload during test?

Waiting for call back from Megger. I'm now wondering if the fault lies with the MFT or the rechargeable are past their sell by date?

 

[Midwest]

Call back from Megger, no idea about the conflicting results. The VOL 0-L, is possibly caused by ghost voltages from nearby cables. Rechargeable batteries have a long shelf life, and because of age will not effect test results, only time any battery will, is when they have low voltage and require replacing or recharging.

So haven't a Scooby doo about yesterdays issues

PS MFT's are the work of the devil, and should be banned.

 

[telectrix]

never had a moment's trouble with my 1553.last time it gave a silly reading, refused to carry out a Zs, the earth in the property was floating @ around 140V, due to a loose connection N-E in the service head. rang DNO and was told to fix it myself as they could not attend till next day. this meant cutting seals and pulling fuse to release the cover over the N-E.

 

[Midwest]

never had a moment's trouble with my 1553.last time it gave a silly reading, refused to carry out a Zs, the earth in the property was floating @ around 140V, due to a loose connection N-E in the service head. rang DNO and was told to fix it myself as they could not attend till next day. this meant cutting seals and pulling fuse to release the cover over the N-E.

Hmmm, I was thinking about the service head connection. The property had a CU fitted about 15 years ago, and not very well. But with both tests I did, got good Ze readings. When I go back next week, I might just check it. Cheers

PS was even thinking of contacting DNO, to check their supply, having read here of duff connections, t'other end of their cable?

 

[telectrix]

in the case i mentioned, i tried to get a Ze. MFT said NO. then coughed up 66 ohms, then O/R. all down to the N-E link needing a turn of the screws.

 

[Midwest]

Got acceptable Ze's, but can't explain yesterdays strange codes, so will take a shufty at the connection, and speak to the DNO after that.