Hello to everyone,
It took some time before i could get back to the mission.
Since the last time i posted, ive left the downstairs ring switched off and locked off, with normal safe isolation practices in place.
Purchased a Fluke 125 Clamp Meter, and have been using it to track current flow through the main earth bonding to the MCU. Their is current flowing along the main earth bond of of at least 500mA when i have checked, and it fluctuates, increasing as the evening moves in to peak usage for the grid. The main earth bond increased 0.53A to 1.44A when i had the main power off, with the live at 0.02A and the neutral at 0.02A. The micro tesla readings for the cables as bunch leaving the electricity cupboard was 4.8uT, seems high for a house with no power.
I also performed a test as i noticed strange readings a previous evening of 2.9A running through the main Earth bond, with the same cleaner running and lights and maybe a computer. This time i powered down the house, using only the cooker socket, switched on a 1200w Dyson cleaner.
The E = 1.77A, L=5.56A, and the N=5.47A, using the clamp meter.
I also had the Dyson running through a wattage meter, and recorded these results close to the same time
Voltage 237V AC, 5.05A, 50Hz.
I checked the downstairs ring main, and did a number of tests.
I disconnected the ends of r1, rn and r2 from the MCU, and measured from ends of each loop.
r1 loop = 0.53 R
rn loop = 0.43 R
r2 loop = 0.73 R Thinner earth wire (0.43 R x 1.67) = 0.72 R
I then disconnected the furthest socket in the ring, and confirmed loop a and loop b, and tested with a long lead end to end. Values don't include resistance of the leads.
r1-a = 0.34 R end to end rn-a = 0.27 R end to end r2-a = 0.46 R
r1-b = 0.18 R end to end rn-b = 0.16 R end to end r2-b = 0.28 R
The loop b has less sockets than loop a, in fact it would seem most of the load of the downstairs ring main, with the added spurs.
Next i reconnected the end socket, and performed a resistance check between line and neutral, with a connection block connecting the r1-a to rn-b, and r1-b to rn-a.
The calculated expected resistance for line to neutral was (r1 + rn)/4 = (0.53 R + 0.43 R)/4 = 0.24 R.
The calculated expected resistance for line to earth was (r1 + r2)/4 = (0.53 R + 0.73 R)/4 = 0.32 R
Socket 1 r1 + rn = 0.28 R r1 + r2 = 0.33 R
Socket 2 r1 + rn = 0.22 R r1 + r2 = 0.30 R
Socket 3 r1 + rn = 0.24 R r1 + r2 = 0.33 R
Socket 4 r1 + rn = 0.23 R r1 + r2 = 0.30 R
Socket 5 r1 + rn = 0.24 R r1 + r2 = 0.32 R
Socket 6 r1 + rn = 0.24 R r1 + r2 = 0.30 R
Socket 7 r1 + rn = 0.22 R r1 + r2 = 0.37 R
Ive only opened socket 5 so far, thats where i split the ring. I originally thought it was the mid point, but when i traced the sockets order, i quickly realised they wired all the kitchen sockets in series on the same side of the ring. I will proceed to open and check all the wiring of the sockets, and replace some of them likely.
I then rewired the ring to the MCU, and tested the insulation at 500v, which was a fail.
L1 to L2 = 0.06M R
L1 to L3 = 0.05M R
L2 to L3 = 0.04M R
I suspect there is an RCD socket in the shed, so im going to remove tomorrow and perform another insulation test, but the insulation test should have been at least >1M ohms. Ive also discovered the plumber installed the central heating pipes over the mains cables in the celling, some of the cables are resting on a radiator pipe, and have been for nearly 12 years.
Updated 18/11/2015 11:06
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I disconnected the shed RCD Socket, and the insulation results were:
L1 to L2 = 1.22 M ohms ( the value went up to between 8M and 10M, then dropped back to 1.22 M, so something might not be right i suspect)
L1 to L3 = 192 M ohms (Values kept climbing while holding test button, maybe because other devices connected on other breakers, dimmer switches and computers)
L2 to L3 = 200 M ohms (Values kept climbing while holding test button, maybe because other devices connected on other breakers, dimmer switches and computers)
I started investigating socket 1 in the kitchen, and discovered the wires are so tight, i can not even remove the socket from the pipe boxing. Then i looked above the cupboard above socket1, and discovered the kitchen fitter had not run a spur from socket1, but cut straight in to the ring and added another socket. The main wire colours are visible coming out of the back box, so he must have struggled. It might also be why the wires are so tight on the socket below.
The kitchen was fitted by a respectable kitchen fitters company 15 years ago.
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Forgive me if my electrical terminology is a bit off.
What do you guys think?
Yours gratefully.