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How to wire up an inverter

First some important safety information!

Inverters produce 240V AC, just like household sockets, which is more than enough to kill you. It is vital to install them with care and treat them with respect. The inverters we sell are designed to power one appliance connected directly to the outlet socket only.

If you wish to connect your inverter to any kind of 240V distribution system, it must be properly designed and constructed, earthed, protected by an RCD (residual current device - cuts off the power in the event of a fault) and preferably installed by a qualified electrician. Please note that it is illegal to do your own 240V wiring in any permanent building in the UK.

Step 1: Choose a good place

First, choose where to install your inverter. It should be as close to your batteries as possible, and in a dry, well ventilated area. And unless you install a relay (see below) you will need easy access to the on switch! Most inverters have mounting holes allowing you to screw them directly to a wall or surface. When choosing a spot, ensure you can still access the DC terminals, socket, switch and fuses.

Step 2: Connect to the battery

Using the cables supplied, connect the inverter to the battery. It is fine to shorten the cables, but if they are too short you should replace them with a cable that is thicker as well as longer.

Step 3: Earth the inverter

If your inverter has an earthing point, connect this to a suitable earth with heavy gauge wire, preferably 2.5 square mm. On a steel-hulled boat, a suitable earth is any substantial bolt or stud on the hull/engine that is close to but not touching the point where the DC negative meets the hull/engine. On land, you should use a proper earth stake driven into the ground, available from any electrical supply store.

Earthing is important as if the inverter is not earthed then neither are your appliances, and a fault in the appliance could make the whole thing live.

Step 4: Plug in a test appliance

Plug an appliance into the inverter's AC outlet, respecting the inverter's maximum power rating, and switch on the inverter. The power light should come on and you may hear a fan running. Finally, switch on your appliance and hey presto, 240V electricity!

Extra help or information

  • Some inverters, like our Victron sine inverters have an automatic standby mode but others will need to be turned off when not in use to avoid wasting electricity.
  • You may find it inconvenient to get to the inverter to switch it on and off all the time. A solution is to fit a relay in the positive (red) DC cable. This will allow you fit a small remote switch in a convenient place some distance away from the inverter itself. Any small switch can be used, a domestic light switch would be fine.
  • When buying your relay, ensure the relay can handle the large current that your inverter may draw; a 1000W inverter may draw 80 amps so a substantial relay is required. Our Durite 100A split charge relay is ideal.
  • Mount the relay in a convenient spot near the inverter. Detach the positive (red) DC cable from the battery and cut it near the relay. Connect the two cut ends to the two large terminals on the relay, usually labelled '87' and '30'.
  • Now connect a thin black cable between the small relay terminal marked '85' and any convenient negative connection (eg. the inverter's negative terminal).
  • Finally, use thin red wires to connect your remote switch between the battery positive terminal and the small relay terminal labelled '86'.
  • Reconnect the battery, and turn on the inverter. If all goes well, you will now be able to control the inverter with the remote switch.

- Do you need an inverter for your off-grid application? Click here for our list of sine wave inverters -


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