Discuss Wierd one in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

C

Cirrus

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Installed 2 new ccts in a house today. Did all dead tests and results were good. Ze was 0.30 ohms on a TT system with 6mm down to spike. Powered up and then did Zs and came out at 0.34 Kilo Ohms on all ccts:eek:
How can this be?????
 
B

beaver74

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  • #2
Installed 2 new ccts in a house today. Did all dead tests and results were good. Ze was 0.30 ohms on a TT system with 6mm down to spike. Powered up and then did Zs and came out at 0.34 Kilo Ohms on all ccts:eek:
How can this be?????
firstly i think you mean Zs (with bonding attached) .30 is very very low for a Ze on a t,t
as for Zs being that high i can only think a loose conection,what are the earth loops at the first piont on each circuit if thay are as high the problem is in the board ie loose earth bar what pfc reading do you get L-N
if it is olso high it point to a loose line conductor
 
C

Cirrus

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  • #3
Sorry - pfc was .030 ohms. Can't be a loose connection as it is over 3 ccts that I tested (maybe more) and 2 were installed by me. I do 15 of these a month and never have issues so I know it ain't a loose connection in either my final ring circuit or cooker circuit.
 
W

wayne

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  • #4
Sorry - pfc was .030 ohms. Can't be a loose connection as it is over 3 ccts that I tested (maybe more) and 2 were installed by me. I do 15 of these a month and never have issues so I know it ain't a loose connection in either my final ring circuit or cooker circuit.
PFC measured in ohms?
 
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C

Cirrus

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  • #5
Oops. Had too many cans Wayne. Pfc was 0.77kA:eek:
 
W

wayne

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  • #6
do you want to restart this thread??
 
C

Cirrus

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  • #7
haha it's all correct now.
Pfc o.77kA
Ze .30 ohms
ZS on all ccts tested around .34kohms
 
P

PAUL M

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  • #8
A Ra of .30 ohms seems very low,i did a TT the other week and i had real problems getting it below 100 ohms,
 
C

Cirrus

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  • #9
I have had low Ze readings for the last few TT systems I have had. This was a 6mm earth and the spike was 7 feet from the baord.
 
P

PAUL M

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  • #10
The only time i have had very low (i mean very very low)readings on my Ze was when the customer had a sub station at the bottom of his garden,dont know why but there you go.i think you need the welsh wizard to unravvle this mystery scooby.
 
F

frank12

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  • #11
The typical Ze on a TT is 21 ohms
 

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