We received the following information from Michael Rush of Selectronic in Bayswater, Victoria. Safety is very important when dealing with 240 volt so it is a good idea to take onboard Michael's comments. You can contact him at mrush@selectronic.com.au.

Use of ELCB protection devices on Selectronic inverters in portable situations

Introduction
The purpose of this report is to consider the use of Earth Leakage Circuit breaker (ELCB) protection devices with an inverter when used in a portable situation. We will investigate the type of ELCB which may be used, their usefulness and limitations.

Background
A Selectronic inverter takes power from a DC source, normally a battery, and converts it to AC power (normally 240V) suitable for running standard mains operated appliances. The output is just as hazardous as mains power therefore the same precautions should be taken when operating appliances from an inverter as you would from a normal mains outlet.

It is important that you read and understand the user manual that came with the inverter and follow the safety recommendations when using the inverter. If you have any questions after reading the user manual, please contact Selectronic and we will always be happy to assist.

When using the inverter, never operate any faulty appliances, and if in doubt have the appliance checked by a qualified person. Also never operate any appliance in a hazardous situation and always follow the appliance manufacturer’s recommendations when operating any appliance from an inverter.

Using ELCB's in a portable situation
A portable situation is defined as connecting the inverter to the battery supply and using the inverter via the front power point. In this situation it is assumed the inverter is not connected to an earth stake, and that the output has not been connected MEN (earth and neutral connected together). When used in this configuration, the output is ‘floating’ above earth and any ELCB connected between the inverter and the appliance will not trip in the event of a fault within the appliance. This is because there is no return path for the ‘fault’ current and therefore the ELCB does not detect any imbalance in the load current. Likewise if there are more than one faulty appliance connected to the inverter via an ELCB, then the ELCB would still not trip. This is because any fault currents would flow between the appliances via their earth connection after the ELCB. Therefore the ELCB would again see a balanced current as no fault current would bypass the ELCB.

In a portable situation, the ELCB would only trip in the event of a fault between the live terminals and case within the inverter together with a fault between the live terminals and case within the appliance (assuming the appliance is earthed and not double insulated). These faults would need to be such to cause sufficient fault current to flow though the earth connection between the inverter and the appliance before the ELCB would trip.

When an ELCB is required to be used with an inverter in a portable situation, only an external plug in type or external inline type should be connected to the inverter. Under no circumstances should the GPO (power point) on the front of the inverter be removed or replaced with an ELCB type GPO.

Conclusion
The use of an ELCB with an inverter in a portable situation does offer the user a greater level of protection than not using one, however it should be noted that the ELCB will normally not trip in the event of an appliance fault. It is therefore important to ensure the appliances and the inverter are regularly checked for safety.