I installed a new split load consumer unit once in a house many years ago. The new consumer unit had two R.C.D.s. After installation everything was fine....UNTIL the central heating programmer called for heat later in the day when I had left and tripped off an R.C.D. 


I returned the next day to troubleshoot. The customers were not happy and blamed me for the problem despite me saying the the new consumer unit was more sensitive than the old fuse box, and was likely to detect latent faults. I found the problem, a borrowed neutral for the gas central heating system or a crossed over neutral in the consumer unit, I can't quite remember, but I did rectify the fault.


Would I have discovered the problem before installing the new consumer unit? Probably not unless I had spent most of the day previously and carried out a thorough E.I.C.R. inspection and testing.


There may be latent faults that only come to light after the new consumer unit is installed, like a split immersion heater element sheath in a copper cylinder....that works on a non R.C.D.d circuit with a fuse wire, but trips off the new R.C.D. after the new R.C.D.s are installed. Or a faulty appliance that only shows a fault during a particular part of a cycle, like a washing machine. Or something on a time switch. These latent faults are easy to miss and difficult to locate.


Always insert a get out of jail clause in your estimates. Extra work will be charged for. Or you will end up rewiring the whole house for free when the customer says "It worked o.k. before you came and fiddled."


Explain everything to the customers very clearly before you jump in with both feet. Some will be understanding if things go wrong, others will try to screw you. It is impossible to identify which type your customer is until the bad event. Some sweet dear little old ladies can be demons, and old boys very demanding.


Z.

I installed a new split load consumer unit once in a house many years ago. The new consumer unit had two R.C.D.s. After installation everything was fine....UNTIL the central heating programmer called for heat later in the day when I had left and tripped off an R.C.D. 


I returned the next day to troubleshoot. The customers were not happy and blamed me for the problem despite me saying the the new consumer unit was more sensitive than the old fuse box, and was likely to detect latent faults. I found the problem, a borrowed neutral for the gas central heating system or a crossed over neutral in the consumer unit, I can't quite remember, but I did rectify the fault.


Would I have discovered the problem before installing the new consumer unit? Probably not unless I had spent most of the day previously and carried out a thorough E.I.C.R. inspection and testing.


There may be latent faults that only come to light after the new consumer unit is installed, like a split immersion heater element sheath in a copper cylinder....that works on a non R.C.D.d circuit with a fuse wire, but trips off the new R.C.D. after the new R.C.D.s are installed. Or a faulty appliance that only shows a fault during a particular part of a cycle, like a washing machine. Or something on a time switch. These latent faults are easy to miss and difficult to locate.


Always insert a get out of jail clause in your estimates. Extra work will be charged for. Or you will end up rewiring the whole house for free when the customer says "It worked o.k. before you came and fiddled."


Explain everything to the customers very clearly before you jump in with both feet. Some will be understanding if things go wrong, others will try to screw you. It is impossible to identify which type your customer is until the bad event. Some sweet dear little old ladies can be demons, and old boys very demanding.


Z.