From rLab


A project to cover the electrical works in the Main Room refit.

Clear the west wall, install a plywood skin, then install four work stations with power and data.

Objectives :

  • Replace the existing West Wall mounted sockets with sockets in dado trunking on the new wall.
  • Move the circuit feed onto the kitchen distribution board
  • Maintain power for the heat pump
  • Integrate power and controls for the extractor fan
  • Provide capacity for the 3d-printer stand at a future date
  • Install new data wiring

Current State[edit]

The existing sockets are connected to a 32A ring main, wired back to the Main Board. This includes the metal-clad sockets on the wall itself as well as the floorbox.

The extractor fan is connected via a switch-fused connection unit, which then feeds a separate speed controller and out to the fan itself. Verified that this is fused at 5A, and the fan is fed by a 5 core 0.75mm flex from the controller.

A 20A circuit from DB2A connects to an isolator for the heat pump.

Planned Work[edit]

  • Test the circuit is not feeding the Server Rack in the cupboard.
  • Identify cable route from ceiling into back of new plywood wall
  • Arrange temporary power for the Design PC's and 3d printers. Need 8 sockets. 2 x 4-gang leads from Electronics benches ?
  • Disconnect the existing sockets and data cabling, and remove back to the Main Board.
  • Disconnect and remove the extractor fan wiring. Install extra cable to the fan to allow for fitting behind the plywood wall and into the dado trunking
  • Pull through new 4mm T&E cable between the Kitchen Board and the Main Room for the new ring circuit.
  • Pull through 8 x data cables for new network sockets in dado trunking.
  • Install new dado trunking, and fit sockets and data points.
  • Install fused spur boxes ready for 3D printer stand and member's display PC.
  • Install fused spur for the projector.

Photos and Drawings[edit]


  • Schneider CA3W dado trunking - 3m length, x 3
  • Schneider CAI3W inside angle, x 2
  • Schneider CAX3W outside angle, x 2
  • Schneider CLB32W 25mm double gang box, x 14
  • Schneider CLB31W 25mm single gang box, x 6
  • Schneider CLB51W 50mm single gang box. Option for deeper accessories
  • Schneider CLB52W 50mm double gang box. Option for deeper accessories
  • MK Logic Plus double gang sockets, x 14
  • Double outlet Cat6 data points, x 4
  • 4mm T&E cable
  • 2.5mm conduit cable
  • Cat6 data cable and RJ45 plugs
  • Metal plasterboard fixings and P-Clips


  • First fix materials bought or confirmed already on site.
  • Examined the extractor fan control unit to determine the cabling out to the fan itself.
  • Installed 2 x surface pattress boxes in kitchen ceiling for the 3D printer spur and the kitchen display spur.
  • Examined the boxwork around the roof beam against the west wall.
    • Confirmed this is plasterboard and has enough room for a cable access route.
    • Will require fire-retardant foam to seal the cable access holes after fitting is complete.
  • Design PC's network re-connected via temporary cable to North Wall trunking.
  • 3 x 4-way extension leads prepared for temporary power to the PC's during the works.
  • Single trailing socket prepared for the ceiling-mounted projector.
  • Heat pump - first quote advises we will need an external isolator for a 6kW load.
    • This translates to a 32A radial circuit with a 4-pole IP67 isolator.
    • Cable run will be ~15m inside the building, plus ???m of SWA through the wall and outside to the isolator.
    • Inside run will require either 6mm 70C cable or 4mm 90C cable for current rating.
    • Isolator needs to be fitted at a suitable height to deter 'casual tampering'
    • Works Needed :
      • Sort out balancing on L3 phase (see below)
      • Install 6mm 6491X conduit cable in box trunking to spare exit point adjacent West Wall
      • Use flexible conduit to bridge to a new metal junction box on West Wall.
      • Fit 4mm 3-core SWA from junction box, through wall and into IP67 rated isolator
  • Traced feed for DB2A onto the L3 phase.
    • This is the same phase as the downstairs workshop sockets and bandsaw
    • Need to re-balance this before fitting a new 32A circuit for the heat pumps
    • Sequence :
      • Remove upstairs ring main from Main Board 6L2
      • Move DB1A from Main Board 6L3 to 6L2
      • Fit 32A MCB to Main Board 3L1 for new circuit