Sort This One Out

[seajayess]

Ok last Saturday we had to install a new supply to a large freezer in a food processing factory, so 10mm 5 core SWA from a Sub board to control panel all tested out fine and left isolated for refrigeration engineers to finish of their installation.

Got called back today as LED's on panel were glowing although panel was still isolated. After 2 hours trying to find out why ended up with only 1 explanation, that due to the amount of currents in the factory there was some current traveling up the Neutral enough to light LED's.

But while testing the SWA with the cable completely removed from C/U and freezer panel so just a piece of SWA with nothing connected to it you could get 238 volts between it and the supply line conductors and nothing to Neutral or Earth so why is there a potential difference.

How is this possible when there is no connection to anything ?

To me it is somehow connected to Earth, but how. We did an insulation resistance test on it and there is no connection to anything in the building.

Hope this makes sense CJS

 

[The Godfather]

What is the incoming supply type?

Don

 

[Jono Pashley]

inductance off another circuit? ?:|

 

[seajayess]

3 Phase PME and at the mains there is on average 700 Amps per Phase but the cable was not connected to anything. And it cant be induced as the voltage is not on the cable as I said no voltage between cable and N or Earth it is like the cable is at 0 voltage CJS

 

[The Godfather]

3 Phase PME and at the mains there is on average 700 Amps per Phase but the cable was not connected to anything. And it cant be induced as the voltage is not on the cable as I said no voltage between cable and N or Earth it is like the cable is at 0 voltage CJS

Daft question, but what electronics (if any) exist in the unit?

Don

 

[seajayess]

The cable was not connected to anything, used a volt meter one probe on any phase the other probe on the SWA that wasn't connected to anything so should be no potential difference even removed it from the glands so even the steel wire wasn't connected and as I said meter read 238 volts CJS

 

[batty]

Is the cable running near other cables?

 

[The Godfather]

The cable was not connected to anything, used a volt meter one probe on any phase the other probe on the SWA that wasn't connected to anything so should be no potential difference even removed it from the glands so even the steel wire wasn't connected and as I said meter read 238 volts CJS

So if your wiring was tested OK, then the Refrigeration Engineers come in and you now have a a fault?

The Godfather

 

[The Godfather]

Is the cable running near other cables?

But isn't 238V rather high for any mutual conductance?

The Godfather

 

[Evans Electric]

Its wierd CJ , but inductance is the only answer. I presume it will not power a light bulb. Are there any non SWA cables in the same run ?

There is a post of mine about 70mm meter tails interfering with a PC monitor screen through a solid concrete block wall, it was because I had run them seperate on the tray instead of bunching them . After reclipping them tight together the inductance was reduced to a few inches.

 

[seajayess]

I don't think there is a fault, I just wanted someone to tell me why this was happening , its like its getting an earth inductance , is something to do with the building be steel framed , the other sparky I was with has been a sparky for 25 years and he cant explain it, just thought somebody on here may be able to CJS.

 

[batty]

But isn't 238V rather high for any mutual conductance?The Godfather

Sounds rather high but I had over 90v on a circuit the other day after connecting cpc to bar there was no volts but the wiring is a bit dodgy on the job.

Batty

 

[The Godfather]

Sounds rather high but I had over 90v on a circuit the other day after connecting cpc to bar there was no volts but the wiring is a bit dodgy on the job.Batty

My Boys tell me they wouldn't expect much over 150V at worst and typically around 100V.

The Godfather

 

[The Godfather]

As I've already stated, perhaps the wiring connected after the OP's installation needs to be verified.

Don & His Boys

 

[seajayess]

Its wierd CJ , but inductance is the only answer. I presume it will not power a light bulb. Are there any non SWA cables in the same run ? There is a post of mine about 70mm meter tails interfering with a PC monitor screen through a solid concrete block wall, it was because I had run them seperate on the tray instead of bunching them . After reclipping them tight together the inductance was reduced to a few inches.

No you dont seem to understand there wasn't 238 volts to earth from the SWA there was 238 volts between the SWA and the live line conductors, but the SWA wasn't connected to anything just like a piece of cable lying through the building CJS

 

[Evans Electric]

Its wierd CJ, but if its not connected, then its induced. I can't think of anything else. TBH

 

[seajayess]

But how can Earth be induced ? CJS

 

[The Godfather]

But how can Earth be induced ? CJS

It's not, there has to be a fault.

The Godfather

 

[seajayess]

No there is no fault I have checked the cable by test and I have visually inspected the whole length of the cable, its got to be some science factor to do with electricity I to cant work it out CJS

 

[The Godfather]

No there is no fault I have checked the cable by test and I have visually inspected the whole length of the cable, its got to be some science factor to do with electricity I to cant work it out CJS

OK CJS, it is Friday night and some of the more experienced members have yet to see this thread, so be patient.

(As I'm just as intrigued)

regards

The Godfather