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Technical · AM-WD-02 rev D

Cabin wiring scheme

How the AutoMate unit intercepts circuits, and the contactor schedule for both cabin types. For installation by a qualified electrician, tested to BS 7671.

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The arrangement

How the AutoMate unit intercepts and monitors circuits in a welfare cabin distribution board The incoming supply feeds the cabin distribution board. The AutoMate unit takes its own supply from a dedicated 6 amp MCB and contains four 25 amp double-pole contactors, each with a pre-fitted current transformer, CT1 to CT4. Both poles of a contactor control identical appliances in the same cabin and are never split across two rooms. Which circuit sits on which contactor depends on the cabin type. In a standard cabin the climate appliance, the water boiler, the sockets and the lights. In a drying room the heaters, the dehumidifiers, the fans and the sockets. Which physical contactor carries which load is set at commissioning. Separately and never switched: critical always-on circuits including Wi-Fi and data comms, showers and life-safety, plus every other circuit in the board, each carrying its own additional CT. So every circuit is monitored even where it is not controlled. Only line conductors are intercepted; neutrals and earths are never switched and remain in the board unchanged. Incoming supply Cabin distribution board SWITCHED · THE AUTOMATE UNIT 4 × 25A double-pole contactors Both poles control identical appliances in the same cabin, never across two rooms. Own supply from a dedicated 6A MCB. CT1 to CT4 Which circuits are controlled Standard cabin: Heater or AC · Water boiler · Sockets · Lights Drying room: Heaters · Dehumidifiers · Fans · Sockets MONITORED ONLY · NEVER SWITCHED Critical always-on circuits Wi-Fi · data comms · showers · life-safety · anything you designate CT Every other circuit in the board One additional CT per circuit. CT Every circuit in the board is CT-monitored, including the ones we never switch. Only line conductors are switched. Neutrals and earths are never switched.

The AutoMate unit is wall-mounted, similar in size to a domestic consumer unit, and sits alongside the customer’s existing distribution board. It takes its own supply from a dedicated 6A MCB, 230V single-phase, live and neutral plus earth.

Inside are four 25A double-pole contactors wired to the controller’s relay card, and CT inputs for circuit monitoring. The wireless mesh links units between cabins; it is not used for control within a cabin.

Interception works like this: the MCB is fed from the bus bar as normal. The circuit cable is disconnected from the MCB and extended into the AutoMate unit, and a new cable from the contactor terminates back in the MCB. Power then flows bus bar → MCB → contactor → load.

Only line conductors are intercepted. Circuit neutrals and earths are never switched and remain in the distribution board, unchanged.

Sheet 1: standard cabin

Offices, canteens and general welfare cabins.

Typical circuit schedule, standard cabin. Ratings are typical rather than prescriptive, and the contactor column is the arrangement drawing AM-WD-02 rev D shows, not a fixed pinout. See the note below the table.
MCBCircuitContactor (typical)Controlled
6AAutoMate supply—— (feeds the unit)
20AHeater or AC unitContactor 1, 25A d-pControlled
16AWater boilerContactor 2, 25A d-pControlled
20ASocketsContactor 3, 25A d-pControlled
6ALightsContactor 4, 25A d-pControlled
16AWi-Fi / comms— CT onlyMonitor-only, CT
32AShower— CT onlyMonitor-only, CT

“Heater or AC unit” means exactly that, not both. A standard cabin has one climate appliance on that circuit. Where a cabin has both a heater and air conditioning, they become separately labelled circuits, “Heater 1” and “AC 1”, on separate contactors. They never share one.

The contactor numbers above are a typical arrangement, not a pinout. They are what drawing AM-WD-02 rev D shows, and they are what most cabins end up with, useful when you are planning a board. But which physical contactor carries which load is confirmed at commissioning for that cabin, so label by circuit, never by contactor number, and read the unit’s own internal labels on site. Gaia pre-labels the contactors and CTs inside every unit before it ships.

What does not move is the priority order. Loads are taken in order: heaters, air conditioning, dehumidifiers, water boiler, sockets, lights, and which physical contactor carries which load is set at commissioning for that cabin. If a cabin has more controllable loads than contactors, lights come out first and then sockets; water boilers and dehumidifiers are never the ones dropped, and the decision goes to a Gaia engineer rather than being made automatically.

Critical always-on circuits are monitor-only. Wi-Fi, comms and showers give no saving from switching, so they are measured with a CT and never interrupted. Life-safety circuits are treated the same way, always.

Sheet 2: drying room

Drying room cabins. Air conditioning is rarely fitted.

Typical circuit schedule, drying room. CTs are pre-installed on all four circuits. The contactor column is the arrangement drawing AM-WD-02 rev D shows, not a fixed pinout.
MCBCircuitContactor (typical)Controlled
6AAutoMate supply—— (feeds the unit)
16AHeatersContactor 1, 25A d-pControlled
16ADehumidifiersContactor 2, 25A d-pControlled
6AFansContactor 3, 25A d-pControlled
20ASocketsContactor 4, 25A d-pControlled

Drying rooms rarely have additional circuits, and air conditioning is rarely fitted. Any extra circuit is CT-monitored.

This schedule is also the answer to why a drying room costs more to run than a site office: three high-load circuits, all live at once, in a room nobody switches off on a Friday.

Other ways to start

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Installation notes

  1. The AutoMate unit contains 4 × 25A double-pole contactors. Its dedicated 6A supply needs live and neutral (and earth) run from the distribution board into the unit.
  2. Circuit interception: the MCB is fed from the bus bar as normal. The circuit cable is disconnected from the MCB and extended into the AutoMate unit, and a new cable from the contactor terminates back in the MCB. Power then flows bus bar → MCB → contactor → load.
  3. Extension cables must match the size of that circuit’s existing cable, typically 2.5mm². Circuits routed through a contactor must be on a breaker of 25A or less.
  4. Both poles of a contactor must control identical appliances in the same cabin, never split a contactor across two rooms, even for the same type of load.
  5. Pre-fitted CT clamps on the controlled circuits handle up to 20A. If the load through one contactor exceeds 20A, tell Gaia and upgraded CT clamps will be supplied.
  6. Critical always-on circuits, Wi-Fi and comms, showers, life-safety, are monitor-only and never switched. Circuit neutrals are never switched; only line conductors are intercepted.
  7. Contactors are wired to the controller’s relay card; the mesh only links units between cabins. All work by a qualified electrician, tested to BS 7671.
Schematic, sheet 1 of 2, standard cabin. The cabin distribution board on the left carries a main switch and RCD, then MCBs: 6A AutoMate supply, 20A heater or AC unit, 16A water boiler, 20A sockets, 6A lights, 16A Wi-Fi and comms, 32A shower. The four controlled circuits run across to the AutoMate unit on the right, each through its own 25A double-pole contactor, contactor 1 heater or AC, 2 water boiler, 3 sockets, 4 lights, and back out to the load. The Wi-Fi and shower circuits are CT-monitored only and are never switched. A controller and PSU sits above the contactors, fed by the dedicated 6A supply, with the relay card driving the contactors and a mesh link to other cabins.
Sheet 1 of 2, standard cabin. Drawing AM-WD-02 rev D, July 2026. Not to scale. Every label, rating and note in this drawing is written out in full on this page.
Schematic, sheet 2 of 2, drying room cabin. Same arrangement as sheet 1, with the distribution board carrying a 6A AutoMate supply, 16A heaters, 16A dehumidifiers, 6A fans and 20A sockets. All four load circuits are controlled, each through its own 25A double-pole contactor, contactor 1 heaters, 2 dehumidifiers, 3 fans, 4 sockets, and CTs are pre-installed on all four. Air conditioning is rarely fitted to a drying room.
Sheet 2 of 2, drying room. Drawing AM-WD-02 rev D, July 2026. Not to scale.

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Drawing reference AM-WD-02 rev D, sheets 1 and 2, July 2026. Not to scale. For installation by a qualified electrician.