high ohms at sockets

A1Electrical · 16 Nov 2010

evenin' all...
just been to a house after a washing machine engineer told the owner that she had 460 ohms at her kitchen sockets. radial circuit.
tested with megger, and got readings of between 21.5 and 4.8k ohms!
tester ok, recently calibrated etc.
ran a trip sequence and tripped out at 49.5ms at 1x but flashes the '>50v'
touch voltage warning at 5x so stops. Ran a ramp test which tripped at 27ma. During continuity tests at socket, if i turned on the cooker hood, the readings dropped to 21 ohms. if i put the lights and the fan on, it dropped to 9.9 ohms.
thinking maybe a L-N fault somwhere but have to go back tomorrow as people were on the way out to 'dinner'. will run full range of tests then
Any other ideas greatly appreciated

Regards

londonboy · 16 Nov 2010

What was the earthing type, TT?

Did you get a Ze while you were there?

A1Electrical · 17 Nov 2010

earthing type is tt. didnt have time to get Ze. the owner cancelled today as they were down in cornwall and got flooded in so will try again when they call.

bernardgreen · 17 Nov 2010

A1Electrical said:
During continuity tests at socket, if i turned on the cooker hood, the readings dropped to 21 ohms. if i put the lights and the fan on, it dropped to 9.9 ohms.

I would suspect that the hood was connected between Live and Earth so maybe the earth and neutral have been swapped somewhere between kitchen and CU.

Spark123 · 17 Nov 2010

Start with the basics, Ze and R1+R2 for the circuit.

onlyfitidealboilers · 18 Nov 2010

baffled

Spark123 · 18 Nov 2010

Sorry, it was electrical speak - I hope A1Electrical will understand.

Basically what I am saying is make sure the earthing to the property is up to spec (AKA Ze or external earth fault loop impedance).
Then check the circuit itself is sound by checking the resistance of the live and earth path (AKA R1+R2)

ban-all-sheds · 18 Nov 2010

onlyfitidealboilers said:
baffled

http://www.tlc-direct.co.uk/Book/5.3.1.htm

http://www.tlc-direct.co.uk/Book/8.1.1.htm

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high ohms at sockets

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