Zs reading on garage CU 1.20ohm?

[electro]

tested a garage to day recored the r1+r2 of the sockets had a reading of 0.40ohm

testing loop test (Zs) got a reading of 1.20ohm

test Ze at the house CU and got a reading of 0.21ohm (tncs)

Ze+ (r1+r2) = 0.61ohm

so why was i reading 1.20ohm on my tester from last socket ?

should i be worryed ?

 

[spinlondon]

Were you using a plug in type tester, or taking the reading from the back of the switch plate?

Sometimes the inner workings of the socket become corroded, espeially if they're not used much.

I generally take the readings from the back of the switch plate, as this allows me to ensure connections are tight, earths are sleeved and to check for corrosion.

 

[electro]

yes i was testing from a plug at socket. should i just add ze+r1 r2 and use as my Zs on cert?

 

[ianmacd]

Where did you test R1+R2 from? Was it the house DB or is there a DB in the garage too?

Was the 1.20ohm consistent across all the sockets (within minor tolerances)?

Ian.

 

[spinlondon]

It's quite permissable to calculate the Zs.

I'd consider checking that there are no loose connections.

 

[electro]

i tested my r1+r2 from garage circits. yes all sockets was the same give her take 1 or 2

 

[spinlondon]

Sounds like it could well be corrosion of the inner workings of the sockets.

The ones with lower readings could be ones that are used more often.

Could try plugging and unplugging the adapter a few times, or dropping the front cover off and taking the readings at the terminals.

 

[electro]

ok cheers. thank u

 

[ianmacd]

What is your Zdb and/or R1+R2 of the distribution circuit?

Ian.

 

[batty]

What meter do you have my fluke 1652 operating temperature goes to -10 don't think its that cold but maybe it could affect results.

Batty

 

[ianmacd]

What meter do you have my fluke 1652 operating temperature goes to -10 don't think its that cold but maybe it could affect results.Batty

Also low batts could be an issue.

 

[batty]

Also low batts could be an issue.

Yes I am a bit low the weather gets me down.

 

[Lurch]

So we're missing .4ohms? Have you added in the cable from the house to garage CU?

R1+R2 of garage sockets

R1+R2 of sub main from house

Ze of house

Should add up to Zs of garage sockets.

 

[spinlondon]

More like 0.6ohms.

 

[Lurch]

More like 0.6ohms.

Around half an ohm!

 

[ianmacd]

Hence me asking for Zdb and R1+R2 of distribution circuit .

 

[Jono Pashley]

Hence me asking for Zdb and R1+R2 of distribution circuit .

Same thoughts, OP makes no mention to the resistance of the submain.