Metal cased consumer unit or distribution board.
This type of consumer unit is more suited to an industrial installation, yet for some reason was installed in a domestic property.
The exterior is made from substantial sheet steel, with a steel door over the devices.
This one has a 63A RCD incomer and six MCBs of various ratings.
The grey case is of significant depth and height, far larger than most other similar units available at the time.
The front panel is secured with four screws, one in each corner. These have some corrosion due to the damp enviromnent this was installed in.
The MG logo on the top centre is a stick-on label.
The back shows the three fixing points, and several round holes fitted with rubber grommets where wiring entered.
Merlin Gerin Cat No. AMG 9
Type Tested to BS5485 : Part 12 and 13 : 1979
Incoming capacity 100A 50Hz 240/415V
Stafford Park 4, Telford, Salop
The main switch is a 30mA RCD, an arrangement no longer permitted as a single fault on any of the circuits would result in the whole installation being disconnected.
The six MCBs have clearly been rearranged at some point, as the labelling underneath makes little sense, and three of the labels have been completely blacked out with marker pen.
MG CEE27 current operated earth leakage CB
each month press test button T. the circuit breaker must trip.
63A 240V 0.03A EMG 630302
The French words 'test mensuel' are moulded into the plastic underneath the square white test button. (test monthly).
Inside, there is a substantial amount of space for wiring - far more than on most other fuseboxes or consumer units.
Incoming supply connected to the bottom terminals of the RCD (left side). Circuit wiring connected to the neutral bar (left side), earth bar (right side) and the bottom terminal of the individual MCBs.
From left to right, the installed devices are:
4 module 63A 30mA RCD
32A MCB
32A MCB
20A MCB
20A MCB
15A MCB
5A MCB
Unlike most other designs, the busbar is located at the top of the devices, with circuit wiring connected at the bottom.
The neutral from the RCD connects directly to the neutral terminal bat to the left, with the line extending across the top of the MCB positions.
Connections between the busbar and devices is made via a small forked metal piece.
In these photos, part of the plastic busbar covering has been removed to show the interior.
The MCBs are C45 series, single pole, 240/415V, breaking capacity M3 (3000A), BS3871
The metal fork which connects to the busbar is a separate item, and can easily be removed.
The RCD uses the same forked metal tabs to connect to the busbar.
Although this has space for 4 incoming and 4 outgoing terminals, only two terminals are used on this model.