When updating older systems there are a number of things that will likely cause problems. There may be wiring faults, connections may have become loose or worn, and wiring can degrade leading to problems with the modern switch gear that you are there to install.
Add to this the need to find these faults due to an interrupted power supply that saw the entire home switch off with no answer as to what was causing it. The power supply would often go off around twice a day. Everyday..
The customer made contact after receiving one of my leaflets in the post. The request was simple: I would like to install a vehicle charger but UKPN has told me I need to upgrade my supply.
Sounds simple enough; confirm whether the electrical system is suitable to supply a car charger, and upgrade the bits that are stopping UKPN from swapping out the fuse.
We started by carrying out an assessment of the installation. We wanted to ascertain what was needed and where. The home was quite large and had 2 switchboxes; one in the original part of the home and then a second in the garage converted part of the home added in the early nineties.
The car charger was to be supplied from the second consumer unit; the supply cable was an adequate size, and so it should have been straightforward. However, because the units were old, we were unable to supply the car charger from the current unit, which meant an upgrade was needed.
At the first consumer unit, this had undersized supply cabling which needed upgrading, and there was the problem with the wiring faults that kept tripping the RCD that covered the whole installation.
After I had tested the homes wiring, it was evident that there were numerous faults across the 20+ circuits in the home that would all need to be identified and cleared if the system was to function correctly.
The Sub Board:
I started here as this was the most time sensitive task that the customer required. Whilst I also needed to install a means of isolating the sub main from the main fuse (as it was fed from the fuse via Henley connectors and offered no isolation) the main unit would also need isolating and thus, we opted for a 2-way distribution board to supply both the units whilst offering adequate isolation of the boards independently of the other.
This meant the sub board could be isolated without having to pull main fuses or interfere with any of the equipment owned by the supply companies.
A further complication was that the RCD unit currently installed was only rated at 80A. UKPN were to up the fuse to 100a, Which meant this would need changing also. We installed a Type S time delay RCD main switch to govern the installation, and so this stayed on during an earth fault at any of the final circuits, we protected each final circuit with its own 30mA RCBO.
This allowed us to compartmentalise the earth fault to just that final circuit without it effecting the main RCD that was installed at the main distribution unit.
With the supply to the sub board addressed, it was time to change the sub board. Connected to it were a number of lighting circuits with 2 power circuits that fed that part of the home. The lighting circuits had been bunched onto one protective device, it was discovered that this was likely the case because there were borrowed neutrals on the 2-way switching in the hall.
This meant a rigorous fault find on the lighting circuits to discover where the neutral had been borrowed, and to unpick the confusion around the switching that had been caused by the conduit conversion wiring method, AND, the use of single core cabling to achieve 2way switching. This had led to junction boxes being installed in the ceilings.
With the lighting sorted, the sockets were also showing problems with RCD related faults. Another fault find found damp walls adjacent to a bathroom which had corroded a spur outlet causing the circuit to trip. This was replaced with a new accessory and the damp walls will be repaired in due course.
With the unit now reliably operating, the car charger could be installed.
The main board:
More of the same on this unit. A number of faults including open earth continuity on lighting, borrowed neutrals on the stairs, damp socket outlets near a conservatory wall, and some obsolete cabling that had been left connected.
The borrowed neutral was the most torubling fault here. This is becuase the circuits trip out if the circuits are put on to thier own device. The borrowed neutral was found at the outside coach lantern that was feeding the light fitting on the stairs. A convenient means of wiring, but one that can be very dangerous if the borrowed neutral is not identified.
Some more faults finds to the lighting and some of the socket outlets needing to be disconnected meant that the wiring left connected was suitable enough to be used without fear of the protective devices tripping off.
In all, there was around 5 days of fault find finding and upgrading for this, what could be described as 'a board change'. But this was a special situation as the wiring had been installed quite well, save for the borrowed neutral practices that are quite common in Norfolk.
The work has been very satisfying to correct, unpick, and work through the numerous faults that had been causing such frustration.