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R.C.D. tripping and earthing concerns.

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Evnin' All,

                  I have had a hard day and my brain is in meltdown so please excuse nonsense and silliness.


I installed a new socket in a house today. TT earthing presumably. New A.B.C. overhead supply. Nearest D.N.O. P.M.E. pole earth rod about 15 metres away from the house. When I tested the R.C.D. it worked on the test button, but the switch seemed a bit graunchy. It would not trip off on 30mA test, but did trip off on the 5X R.C.D. test at a socket. I replaced the R.C.D. The same thing happened. No trip on 30mA test setting, but it did trip off on the 5X setting.


An earth fault loop test at a socket showed a reading of 185 Ohms.


A  length of 6.0mm2 green and yellow cable was found in the front yard but the electrode is not inspectable as it is covered by block paving is old. It may have rotted away. With the main switch off the resistance from N. to the earth bar in the consumer unit is about 180 Ohms. 


The consumer unit is a 10 way unit with just one 30mA R.C.D.


I converted the earthing to P.M.E. and then nuisance tripping was seen. I intend to install an all R.C.B.O. board tomorrow.


Sometimes a fridge when turned on will trip the R.C.D., other times it is a freezer, then the kettle. But the appliances test o.k. with an insulation resistance test. Once or twice the tungsten lighting circuits tripped off the R.C.D.


I assume that the addition of individual leakage current is responsible for the R.C.D. tripping, but there is no logic to which individual appliances/circuits seem to cause it. Two suspected rings test o.k. for insulation resistance.


The house owner reported that the gas fitter received a shock when doing something under the AGA. The main gas bond was loose at its clamp. I have replaced the earth clamp.


Any thoughts please?


EDIT. P.S. I have a Voltage tester that will trip off a 30mA R.C.D. if connected to the outgoing R.C.D. L. and E. at the same time. When this was connected to the original R.C.D's LIVE INCOMING terminal and the E. bar the R.C.D. tripped off. Did this raise the Voltage on the C.P.C.s sufficiently to trip off the RC.D?


Z.


Parents
  • 0
    Well I split my shorts today in the loft running a new 10.0mm2 bonding cable. I had to move a dismantled old wardrobe to run the cable. The run was for the gas service. The water did not need a main bonding cable as it was run in a blue poly pipe. The copper gas pipe had a 16mm2 copper cable connected to it outside at ground level that I discovered. The cable ran into the soil, but was not seen in the house. It reminded me of the pipe earthing often seen on oil pipes at storage tanks in people's gardens around here. Anyway the gas supply pipe is properly bonded to B.S. 7671 requirements. The house owner thinks that the local t.v. engineer had previously installed the old consumer unit. That may account for the cable to the earth rod bring in fine flexible green and yellow cable rather that the common seven strand stuff that we use today. Also in the old consumer unit all the neutrals were not in the correct order relative to the lines.


    The N. to C.P.C. short was located  behind a wall light. The fixing screw into the wall had damaged the soft heat resisting insulation of the blue neutral wire behind the mounting plate. Now repaired.


    All R.C.B.O.s were tested and operated swiftly and correctly.


    I was well fed with tea and sandwiches, and the lady thought that I had undercharged her.


    Her son will replace all of the old R080 reflector lamps with L.E.D. versions. Some upstairs were covered over in the loft and ventilation was zero. A fire risk.


    Bye,


    Z.






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  • 0
    Well I split my shorts today in the loft running a new 10.0mm2 bonding cable. I had to move a dismantled old wardrobe to run the cable. The run was for the gas service. The water did not need a main bonding cable as it was run in a blue poly pipe. The copper gas pipe had a 16mm2 copper cable connected to it outside at ground level that I discovered. The cable ran into the soil, but was not seen in the house. It reminded me of the pipe earthing often seen on oil pipes at storage tanks in people's gardens around here. Anyway the gas supply pipe is properly bonded to B.S. 7671 requirements. The house owner thinks that the local t.v. engineer had previously installed the old consumer unit. That may account for the cable to the earth rod bring in fine flexible green and yellow cable rather that the common seven strand stuff that we use today. Also in the old consumer unit all the neutrals were not in the correct order relative to the lines.


    The N. to C.P.C. short was located  behind a wall light. The fixing screw into the wall had damaged the soft heat resisting insulation of the blue neutral wire behind the mounting plate. Now repaired.


    All R.C.B.O.s were tested and operated swiftly and correctly.


    I was well fed with tea and sandwiches, and the lady thought that I had undercharged her.


    Her son will replace all of the old R080 reflector lamps with L.E.D. versions. Some upstairs were covered over in the loft and ventilation was zero. A fire risk.


    Bye,


    Z.






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