doing my head in.

[telectrix]

situ is a park homes prefab for sale. i have been tasked with doing an EICR. wylex 3036 board with a later added 30mA up front RCD. Ze = 0.3. Zs readings at cooker outlet 0.32. lights 0.47. RFC sockets all read between 687 and 720 ohms. cpcs are intact and connections checked. tested the Zs on both sides of the RCD to eliminate bogus readings there. 1553 aborted RCD test showing >50V. obvious conclusion is a floating earth, but no visible signs of a fault. going back tomorrow with wander lead to check some R2 readings. just to eliminate test faults, got home and plugged 1553 into a socket. 0.47 ohms on hi current. 0.47 ohms on no trip. any ideas?

 

[wildgoose]

I'd be tempted to split the rfc where you think the halfway point is, and then measure the resistance of the 6 legs back to the board with your wander lead. Then see if there's any unexpected values or cross connection.
I know it sounds simple but going back to basics has helped me out many times when I can't understand what's happening?


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[Dave OCD]

Are you certain there isn't a socket or FCU on the ring that you may have missed Tel ? It sounds like nothing more than a loose connection somewhere to me ? [Unless there's a dodgy junction box or similar underneath ?]

 

[telectrix]

going back tomorrow with a wander lead. get the r1, r2, rN readings, then wander the R2 to a socket. 1 socket is only about 4ft. from the CU. so that. a starter.

 

[ipf]

All continuities OK, tel?

 

[telectrix]

All continuities OK, tel?

going to test them tomorrow. had not got wander lead today and was a bit rushed as we have the kitchen fitters in today .

 

[ipf]

Sorry, just noticed previous post. If it's affecting all sockets, thus both ring legs, it seems the problem is close to the circuit origin.
Float on, I say.

 

[telectrix]

update. went back dead tests all OK. r1, r2, rN, R1+R2 , all well as expected. reconnected in CU and did a hi-current test at CU with L-E shorted at approx mid-point. Zs then came in at 1.5 ohms. considering the Zdb was 0.8 ohms, not a bad reading.