Electrical installation · data and telecoms · Cambridgeshire
First fixtofinal test
MYKIN LIMITED is an electrical installation company working out of Cambridgeshire. The work is organised the way the trade already runs: cable in while the walls are open, accessories on once the finish is down, then dead tests, live tests and a written set of results at the end.
Data and telecoms cabling is pulled on the same pass as the power. Software work and the sourcing of accessories sit alongside both, and those four activities are all this company claims.
Cutaway One floor, two rooms, the near walls dropped to half a metre. Scroll and the stage under the cursor lights on the drawing.
00Before the first cable
Nothing is pulled until the route is agreed
The first visit is a walk-round of the shell with a tape and a pencil. Positions get marked on the structure itself, because a position argued over on a drawing is still an argument once the plaster is on. What matters at this point is the supply arrangement, where the main earthing terminal and bonding will land, which walls are structural and will not take a chase, and which parts of the work are notifiable.
If domestic work is notifiable under Part P of the Building Regulations, that is said before anything is cut, along with the route to a certificate through building control.
- Supplythe arrangement on site and the position of the main earthing terminal
- Bondingto the incoming water and gas, and to structural steel where there is any
- Heightsaccessory heights taken from the finished floor level, never from the slab
- Circuitswhat is wanted on its own way, and what is likely to be added later
- Noticewhether the work is notifiable, and who gives the notice
01First fix
Cable in while the walls are still open
First fix is the stage that cannot be revisited cheaply. Everything that ends up buried goes in now: cable, capping, back boxes, conduit where wanted, and the drops for data outlets. Cable is kept in the permitted zones or given mechanical protection, holes through joists are drilled on the neutral axis and grommeted, and runs are held clear of flues and hot pipes. Tails are left long enough to be terminated twice, because the first termination is not always the last one.
Both ends of every cable are marked before it disappears, and each run is photographed against something that fixes its position, so a drill can go into a wall later without a guess. More on the first fix page.
- Markedevery cable identified at both ends before the plasterboard goes on
- Boxesset to the finished wall line rather than to the blockwork behind it
- Grommetsin every metal edge a conductor has to cross
- Photosof each run, taken against a stud centre or a door opening
- Positionthe consumer unit located, with tails and bonding already in place
02Second fix
Accessories on, terminated, pulled up to the line
Second fix waits for the plaster to dry and for the decorator to finish, because an accessory fitted before the painting gets painted. Conductors are identified, the circuit protective conductor is sleeved where it needs to be, terminations are made to the figure the accessory manufacturer gives rather than to feel, and screws are pulled up square so the face sits flat.
The consumer unit is populated at this stage and the circuits are landed on their devices, but nothing is energised to prove a point. A circuit that had a screwdriver in it that afternoon has not been tested yet, and the order matters more than the hour it would save. Detail on the second fix page.
- Identifyconductors identified and the cpc sleeved
- Torqueterminations made to the accessory's own figure
- Facesflush and square, with no painted edges
- Dataoutlets punched down and the patch positions labelled
- Deaddevices fitted, everything still isolated
03Energise and test
Dead tests first, then live, then the results in writing
Testing follows a sequence, and the sequence exists because a fault found while the installation is dead cannot hurt anybody. Continuity of protective conductors, continuity of any ring final, insulation resistance and polarity are all proved with the installation isolated. Only then is it energised, and the live tests follow.
Readings are written down as they are taken. The client is given the certification the work calls for, the results that go with it, and a plain account of anything found that was already there before the work started. Where domestic work is notifiable, the certificate comes through the local authority's building control: this company holds no self-certification scheme membership, and says so at the start rather than implying otherwise at the end.
- Isolate, and prove dead
- Continuity of protective conductors and bonding
- Continuity of ring final conductors
- Insulation resistance
- Polarity, dead
- Energise
- Earth fault loop impedance, and prospective fault current
- Operating times of every residual current device
- Functional checks, then the written results
VdVolt drop over a run
What a long run does to 230 V
Volt drop is the part of a design that a tape measure settles. Cable has resistance, resistance costs volts, and a run that is comfortable at eight metres can be outside the usual figures at thirty-five. The arithmetic is standard: tabulated millivolts per amp per metre, times the design current, times the route length, divided by a thousand, read against 230 V. Three per cent is the figure normally applied to lighting and five per cent to everything else.
What comes out below is a sketch done on the spot, not a design. Grouping, ambient temperature and the supply ahead of the consumer unit all move the answer, and the installation designer makes the final call under BS 7671.
| Conductor | mV/A/m | 3% at 10 A | 5% at 20 A |
|---|---|---|---|
| 1.0 mm² | 44 | 15.7 | 13.1 |
| 1.5 mm² | 29 | 23.8 | 19.8 |
| 2.5 mm² | 18 | 38.3 | 31.9 |
| 4.0 mm² | 11 | 62.7 | 52.3 |
| 6.0 mm² | 7.3 | 94.5 | 78.8 |
| 10 mm² | 4.4 | 156.8 | 130.7 |
| 16 mm² | 2.8 | 246.4 | 205.4 |
+Alongside the power
Data, telecoms and the small software side
Four activities sit on this company's filing and they are not a menu, because they overlap on the same jobs. Data and telecoms cabling is pulled on the same first fix as the power, in its own containment and segregated from it, terminated to outlets at one end and to patch positions at the other, and labelled at both. On a small building that is often a handful of outlets and one patch position in a cupboard. The discipline is the same either way.
The software side is small and deliberately so: the tools this company uses to keep track of its own work, and short pieces of work for clients who want a form, a calculation or one internal page rather than a product. The fourth activity is sourcing: ordering accessories, cable and components on a client's own account where that is simpler than three suppliers and three deliveries.
§The particulars
Registered particulars, and what to send
MYKIN LIMITED is a private company limited by shares, registered in England and Wales. The office below is an address for correspondence and the statutory filings; the work itself happens on site.
To put a job to this company, write to the address below and say what the building is, what stage it has reached, and whether a drawing or a layout exists already. If the walls are still open, say that first — it is the cheapest moment at which to be asked. There is no form on this page and no number to ring, because email keeps the detail in one place, which is where detail is useful.
- Registered name
- MYKIN LIMITED
- Company number
- 17429295
- D-U-N-S
- 235116770
- Jurisdiction
- England and Wales
- Registered office
- 5 Villa Road, Northstowe, Cambridge, England, CB24 1BU
- Written to
- projects@mykin.digital