DC LV Battery Power Supply for Motorhome

ebee:

 

broadgage:

Contrary to a widely held belief, an RCD still gives some protection on systems with no CPC or on systems with neither of the supply wires earthed. (as with many inverters and small generators)

Most dangerous electric shocks are a result of current passing through the body from a live conductor to the general mass of earth or to articles connected thereto. Any current through the body of the victim is not returning to the source via the other circuit conductor, and would therefore operate an RCD regardless of what if any earthing arrangements exist. 

"systems with neither of the supply wires earthed" Have I misunderstood that bit? Yes without a cpc you`d still get an RCD to work for earth fault protection but if neither of the supply wires were earth referenced the RCD would not trip on earth fault, there would be no earth path therefore no danger , example bathroom shaver socket or isolating transformer

 

Small portable generators and some inverters, and some overseas mains supplies have neither wire connected to earth. An RCD still gives some protection in such circumstances for reasons already given.

Consider what happens if a person inadvertently touches one wire.

The installation might be so well insulated from earth that no significant current can pass through the victim, and no dangerous shock can be received. In that case the RCD has served no purpose, but done no harm.

No consider the alternative situation in which one side of the supply is inadvertently earthed, perhaps by cumulative leakage currents, or by a pre-existing earth fault. In this case a dangerous current could pass through the victim, perhaps with fatal results. A working RCD will trip and avoid this danger. A most wise precaution.

ebee:

 

broadgage:

Contrary to a widely held belief, an RCD still gives some protection on systems with no CPC or on systems with neither of the supply wires earthed. (as with many inverters and small generators)

Most dangerous electric shocks are a result of current passing through the body from a live conductor to the general mass of earth or to articles connected thereto. Any current through the body of the victim is not returning to the source via the other circuit conductor, and would therefore operate an RCD regardless of what if any earthing arrangements exist. 

"systems with neither of the supply wires earthed" Have I misunderstood that bit? Yes without a cpc you`d still get an RCD to work for earth fault protection but if neither of the supply wires were earth referenced the RCD would not trip on earth fault, there would be no earth path therefore no danger , example bathroom shaver socket or isolating transformer

 

Small portable generators and some inverters, and some overseas mains supplies have neither wire connected to earth. An RCD still gives some protection in such circumstances for reasons already given.

Consider what happens if a person inadvertently touches one wire.

The installation might be so well insulated from earth that no significant current can pass through the victim, and no dangerous shock can be received. In that case the RCD has served no purpose, but done no harm.

No consider the alternative situation in which one side of the supply is inadvertently earthed, perhaps by cumulative leakage currents, or by a pre-existing earth fault. In this case a dangerous current could pass through the victim, perhaps with fatal results. A working RCD will trip and avoid this danger. A most wise precaution.