elec. power to a garden shed

ondro · Jul 10, 2017

Hello,
I have following scenario, 20A circuit breaker in the CU. 3 x 2.5 SWA cable feed to a garden shed CU. In the shed CU I have 0.69 ohm on the income cable. On the shed are two 16A radial circuits of socket outlet. When I do Ze on the sockets , I get 2.9 ohms.
The radial circuits have 2.5mm2 flat cable no longer than 5m from the shed CU.
Any idea why is the reading so high please?

telectrix · Jul 10, 2017

is there a RCD in shed? this could cause a high reading if using no-trip EFLE test. try doing the test this way to eliminate the possibility. ( use the hi-current 2 lead test ).

[ElectriciansForums.net] elec. power to a garden shed

Pete999 · Jul 10, 2017

ondro said:
Hello,
I have following scenario, 20A circuit breaker in the CU. 3 x 2.5 SWA cable feed to a garden shed CU. In the shed CU I have 0.69 ohm on the income cable. On the shed are two 16A radial circuits of socket outlet. When I do Ze on the sockets , I get 2.9 ohms.
The radial circuits have 2.5mm2 flat cable no longer than 5m from the shed CU.
Any idea why is the reading so high please?

What do you mean "I have 0.69 ohms on the income cable, and Ze at the sockets"???????

telectrix · Jul 10, 2017

confusion with Zdb and Zs methinks, poor terminology by OP.

Pete999 · Jul 10, 2017

telectrix said:
confusion with Zdb and Zs methinks, poor terminology by OP.

Could be another reason though, but I'm to much of a gentleman

ondro · Jul 10, 2017

Pete999 said:
What do you mean "I have 0.69 ohms on the income cable, and Ze at the sockets"???????

I did Ze test in the shed CU. The result is 0.69 ohm. Then I have connected two radial circuits and did Zs test in the socket outlets. The result is 2.9 ohms

ondro · Jul 10, 2017

Pete999 said:
Could be another reason though, but I'm to much of a gentleman

Yes I may have poor terminology. Can you tel me what does mean Zdb please?

Pete999 · Jul 10, 2017

ondro said:
Yes I may have poor terminology. Can you tel me what does mean Zdb please?

The Ze at the CU in the garage reffered to as Zdb

Pete999 · Jul 10, 2017

ondro said:
I did Ze test in the shed CU. The result is 0.69 ohm. Then I have connected two radial circuits and did Zs test in the socket outlets. The result is 2.9 ohms

What is the R1+R2 of the Radial circuit??

ondro · Jul 10, 2017

Pete999 said:
The Ze at the CU in the garage reffered to as Zdb

OK. Thanks. So Zdb is 0.69 ohms and Zs is 2.9 ohm.
Yes an RCD is on the place.

Pete999 · Jul 10, 2017

ondro said:
OK. Thanks. So Zdb is 0.69 ohms and Zs is 2.9 ohm.
Yes an RCD is on the place.

No rcd in the house then? R1+R2??

telectrix · Jul 10, 2017

ondro said:
OK. Thanks. So Zdb is 0.69 ohms and Zs is 2.9 ohm.
Yes an RCD is on the place.

then i refer you to post #2. just remember to remove the L-E short before energising.

ondro · Jul 10, 2017

Pete999 said:
No rcd in the house then? R1+R2??

An RCD is also in the house

Pete999 · Jul 10, 2017

ondro said:
An RCD is also in the house

Not good practice to have 2 RCDs in series

telectrix · Jul 10, 2017

maybe it's irish... to be sure, to be sure.

ondro · Jul 10, 2017

Pete999 said:
Not good practice to have 2 RCDs in series

can have two RCDs influence to high reading of Zs please?

Strima · Jul 10, 2017

What's the R1+R2 of the circuits?

Pete999 · Jul 10, 2017

ondro said:
can have two RCDs influence to high reading of Zs please?

Eh????

buzzlightyear · Jul 10, 2017

ondro said:
can have two RCDs influence to high reading of Zs please?

are you for real!

Pete999 · Jul 10, 2017

buzzlightyear said:
are you for real!

Don't think so Buzz

buzzlightyear · Jul 10, 2017

I'm trying to get my head round this one .

Pete999 · Jul 10, 2017

buzzlightyear said:
I'm trying to get my head round this one .

Not me mate I gave up at post 17 or thereabouts.

buzzlightyear · Jul 10, 2017

any body down their in the smokes (London) pop in to see what the op doing

Midwest · Jul 10, 2017

Pete999 said:
Eh????

Think OP is asking if two RCD's in series, be the cause of his high Zs

westward10 · Jul 10, 2017

Not under fault conditions but with the Mickey Mouse soft test of a loop tester you may get inaccurate results.

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