high zs readings on site cabin

[Farmelectrics]

carried out dead testing on new site accommodation,all dead tests were fine however, when I conducted live testing I got high zs redings on lighting circuit 22 ohms, fused spur for heater 21 ohms so I thought maybe its a tt system but when I tested sockets I got a reading of 0.69 ohms ze at cabin db was 22 ohms so why the lower reading for the sockets

 

[westward10]

So what is the earthing system.

 

[Farmelectrics]

if I'm honest not sure was told it was a tns but need to confirm on Monday weve only landed a site hut on site and was asked to provide a test cert for the cabin

 

[Farmelectrics]

confused why the ring main is a lot lower than the other circuts hence me asking for advice

 

[Nigel]

Personally when testing the first live tests I do is Ze and PFC.

No point carrying on if those are iffy.

 

[Farmelectrics]

agree Essex i did do the ze and pscc pfc first that's were i got the 22 ohm reading from the lighting circuit was similar as was the spur at this stage i wasn't concerned as i presumed it must be a tt system but when i carried out a zs on ring main i got 0.69 and am simply asking why

 

[westward10]

Did you retest the lighting circuit once you got a reduced Zs on the ring final circuit.

 

[Nigel]

agree Essex i did do the ze and pscc pfc first that's were i got the 22 ohm reading from the lighting circuit was similar as was the spur at this stage i wasn't concerned as i presumed it must be a tt system but when i carried out a zs on ring main i got 0.69 and am simply asking why

Where did you test the Ze? It should have been clear what the earthing arrangement is it that point.

 

[buzzlightyear]

confused why the ring main is a lot lower than the other circuts hence me asking for advice

radial ?

 

[Risteard]

carried out dead testing on new site accommodation,all dead tests were fine however, when I conducted live testing I got high zs redings on lighting circuit 22 ohms, fused spur for heater 21 ohms so I thought maybe its a tt system but when I tested sockets I got a reading of 0.69 ohms ze at cabin db was 22 ohms so why the lower reading for the sockets

Neutral/Earth fault on sockets.

 

[Farmelectrics]

there are no faults on sockets dead tests were all ok I took a zs at the site cabin sorry not a ze now I know the cabins are protected by a commando socket / rcd so the readings are actually ok ie 1667 ohms but its the zs of 0.69 that had me scratching my head will retest on Monday but was looking for ideas on the matter thanks in advance

 

[westward10]

It is possible the external impedance of the cabin dramatically changed between tests. You need to work back to the source and confirm the earthing system before you continue.

 

[telectrix]

just wondering if an operator error took a reading L-N instead of L-E?????

 

[westward10]

just wondering if an operator error took a reading L-N instead of L-E?????

He would have plugged into the socket so I think not.

 

[Dillb]

He would have plugged into the socket so I think not.

My Metrel tester allows me to carry out either a Zs or Zn test. So could be operator error.

 

[MFS Electrical]

And so will a megger mft 1720 & 1721 if you put the wrong connector in the wrong hole and are using the 2 hi setting

 

[DPG]

Any update on this one?