Central Vacuum Installation

The Electrical supply

The vacuum unit is permanently connected to the mains electricity. All the domestic models can be run from a normal 3 pin, 13 amp socket. Each vacuum unit has an internal transformer which provides 12V to a pair of terminals at the side of the vacuum unit. These are connected to a pair of contacts on the back of each vacuum socket using bell wire or speaker cable (or similar - 2 core cable, 0.7 sq. mm recommended). The cable from the 12 volt terminals connects to each of the sockets in parallel. It can be attached to the pipework using cable ties or tape.

The 12V connections to the sockets should be in parallel, not series - please ring if this is not clear. It is not necessary to run a cable from each socket back to the vacuum unit nor from one socket to the next. The cable from each socket can follow the pipe and two cables can be joined with a connector wherever a run of pipe joins another, so that there is only one pair of wires going back to the vacuum unit. If joining 2 cables together, ensure that the connection is well made with a connector, junction box or solder, as it will probably be inaccessible when then building is complete. Click here to download a wiring diagram

The cable can also be run from socket to socket so that the only connections are made at the sockets. In this case it is likely that extra cable will be required. If more cable is required, use 2 core, 0.75sq mm cable.

Important - Commissioning

When the pipework and wire have been installed, check the continuity of the wiring. At each socket, make sure that the 2 ends of the wire are not touching, & check the circuit by putting an ohmmeter across the 2 ends of the cable at the vacuum unit end. It should be an open circuit.

Now test the wiring to each socket in turn by twisting the 2 ends of the wire together at the socket end. Only test one socket at a time. Check the circuit again at the vacuum unit end - it should be a closed circuit. Separate the 2 ends of the wire at the first socket before testing the second. Repeat for each socket.

The system is normally operated by inserting the (metal) end of a flexible suction hose into the vacuum socket, which completes the 12V circuit & a signal is sent to the vacuum unit, which then starts & will run until the hose is removed from the socket. (There is an option to have a switch in the handle of the flexible hose which allows the vacuum unit to be switched on & off without removing the hose from the socket.)

Note :

If the ‘O’ ring on the back of the vacuum socket is smeared with a little petroleum jelly, it is much easier to fit (or remove if necessary)

Drill out a hole on the back (or side) of the box of the socket fitting & put low voltage cable through for connection to terminals on back of socket.

If in doubt, consult an electrician or ring the help line 01491 836666 for advice. As the sensing circuit is only 12 volts there is no danger if this is incorrectly wired, but the vacuum unit will either not work at all or will be permanently switched on.

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