Mate of mine lives in a beautiful historic 3 storey house. Over the last couple of years I have done a fair bit of work there. Installed a kitchen, and recently 2 bathrooms.
On the 3rd floor there are 2 large bedrooms unoccupied and a bathroom. The bath had mixer taps and he asked me if I would fit one of those power shower units to give a bit more oomph to the gravity fed water system. I explained that RCD protection would be required as the house is supplied by 2 x Wylex CU's with BS3036 type fuses.
No problem was his reply let's replace both boards with 2 new boards with RCD's and mcb's. Have to admit because of the tail/cable positions it was a much easier job to put in the 2 new CU's without having to extend any cables.
Because of the nature of RCD's I extensively tested the circuits before proceeding with the replacement of the CU's. On IR tests all circuits were showing >199MOhms except 1 circuit that was reading 4.21 Mohms. Now I know it is within the limit but it seemed curious to me so I suggested this circuit be retested 6 months down the line to see if any further degradation had occurred.
So I proceeded to install the 2 new boards, filled in the certs and said I would return next week to install the power shower.
I returned next week and commenced the power shower. A heavenly job as I was allocated an empty bedroom to store tools and materials because its a long way up them stairs. Plugged the radio in and started work. Put an FCU outside the bathroom (luckily the ring ran right across the landing. Ripped down the lathe and plaster wall at the head of the bath , put in the plumbing and electrical feed. Boarded up.
Whilst I'm working the radio cuts out. Test the lights, they've gone to. Run downstairs to find the RCD tripped. Do an IR on the new cable..it's fine. Turn the RCD on and do a loop test..all fine. Now I'm stumped.
Any way over the next few days the RCD keeps tripping. Sometimes 10 minutes between trips sometimes a few hours. I point out to my mate we seem to have a problem with the RCD that protects the upper floor power/lights and the stairwell/ outside lights. Luckily for me the first 2 floors are unaffected so my mate is not inconvenienced.
Next day I ask him did it trip during the previous evening..he says no. Go back to work on the upper floor and the same frequency of tripping occurs yet again. I'm beginning to tear out my hair now. My radio is the only appliance plugged so I unplug it. Still the RCD keeps tripping.
Next thing I do is turn off all the circuits bar 1 (hoping its a L to E fault). Now pattern emerges so I'm unable to narrow down the faulty circuit. I'm fast coming to the conclusion its a N/E fault.
This pattern keeps re-occurring...many trips during the day but only the occasional 1 during the evening.
Anyway, finish the shower, test and commission. Ask my mate to keep a log of any RCD trips and keep me updated. No telephone calls for a long time. Then out of the blue comes a weekend of many trips. I go back and on a hunch decide to retest the RCD.
Eureka!!!! the damn thing is tripping on the half test. Take out the defective RCD, quick trip to TLC, get replacement and reinstall. Retest and the RCD is doing what is says on the can. I am relieved.
A few more weeks pass and I get a telephone call...the damn thing is tripping again. The situation is made worsen by the fact they have a house guest on the the 3rd floor. I go round and Ireally don't know what to suggest..I'm clutching at straws. I look inside some power sockets and they are caked with dust so I'm wondering if this could be the problem. Also the sockets are 20 years old so maybe a bit of current is tracking to earth.
My mate says he will replace the sockets. But that lighting circuit is still troubling me. 4.21 Mohms on the IR test. Will it mean lifting up his beautifully polished or painted floorboards? Will it mean chasing out the walls and replaing cables? This is a house that is all uptogether so I'm nervous about suggesting this course of action.
few days later I get a call the problem has been solved by the house guest, and I'm invited round. My mate takes me into the bathroom and calls the young female house guest. He turns on the lights and says to the young girl....'Show him your trick'..............
Any ideas lads? I'll post photos shortly
On the 3rd floor there are 2 large bedrooms unoccupied and a bathroom. The bath had mixer taps and he asked me if I would fit one of those power shower units to give a bit more oomph to the gravity fed water system. I explained that RCD protection would be required as the house is supplied by 2 x Wylex CU's with BS3036 type fuses.
No problem was his reply let's replace both boards with 2 new boards with RCD's and mcb's. Have to admit because of the tail/cable positions it was a much easier job to put in the 2 new CU's without having to extend any cables.
Because of the nature of RCD's I extensively tested the circuits before proceeding with the replacement of the CU's. On IR tests all circuits were showing >199MOhms except 1 circuit that was reading 4.21 Mohms. Now I know it is within the limit but it seemed curious to me so I suggested this circuit be retested 6 months down the line to see if any further degradation had occurred.
So I proceeded to install the 2 new boards, filled in the certs and said I would return next week to install the power shower.
I returned next week and commenced the power shower. A heavenly job as I was allocated an empty bedroom to store tools and materials because its a long way up them stairs. Plugged the radio in and started work. Put an FCU outside the bathroom (luckily the ring ran right across the landing. Ripped down the lathe and plaster wall at the head of the bath , put in the plumbing and electrical feed. Boarded up.
Whilst I'm working the radio cuts out. Test the lights, they've gone to. Run downstairs to find the RCD tripped. Do an IR on the new cable..it's fine. Turn the RCD on and do a loop test..all fine. Now I'm stumped.
Any way over the next few days the RCD keeps tripping. Sometimes 10 minutes between trips sometimes a few hours. I point out to my mate we seem to have a problem with the RCD that protects the upper floor power/lights and the stairwell/ outside lights. Luckily for me the first 2 floors are unaffected so my mate is not inconvenienced.
Next day I ask him did it trip during the previous evening..he says no. Go back to work on the upper floor and the same frequency of tripping occurs yet again. I'm beginning to tear out my hair now. My radio is the only appliance plugged so I unplug it. Still the RCD keeps tripping.
Next thing I do is turn off all the circuits bar 1 (hoping its a L to E fault). Now pattern emerges so I'm unable to narrow down the faulty circuit. I'm fast coming to the conclusion its a N/E fault.
This pattern keeps re-occurring...many trips during the day but only the occasional 1 during the evening.
Anyway, finish the shower, test and commission. Ask my mate to keep a log of any RCD trips and keep me updated. No telephone calls for a long time. Then out of the blue comes a weekend of many trips. I go back and on a hunch decide to retest the RCD.
Eureka!!!! the damn thing is tripping on the half test. Take out the defective RCD, quick trip to TLC, get replacement and reinstall. Retest and the RCD is doing what is says on the can. I am relieved.
A few more weeks pass and I get a telephone call...the damn thing is tripping again. The situation is made worsen by the fact they have a house guest on the the 3rd floor. I go round and Ireally don't know what to suggest..I'm clutching at straws. I look inside some power sockets and they are caked with dust so I'm wondering if this could be the problem. Also the sockets are 20 years old so maybe a bit of current is tracking to earth.
My mate says he will replace the sockets. But that lighting circuit is still troubling me. 4.21 Mohms on the IR test. Will it mean lifting up his beautifully polished or painted floorboards? Will it mean chasing out the walls and replaing cables? This is a house that is all uptogether so I'm nervous about suggesting this course of action.
few days later I get a call the problem has been solved by the house guest, and I'm invited round. My mate takes me into the bathroom and calls the young female house guest. He turns on the lights and says to the young girl....'Show him your trick'..............
Any ideas lads? I'll post photos shortly
