Transposing Live Wires and Earth Wires

It all depends on how or if the portable generator is earthed.

Either way correct the fault immediately.

This highlights a pet peeve for me. I have never understood why a portable or vehicle mounted generator is permitted to serve as the grounding electrode for systems supplied by the generator.

Without a bonding jumper between the neutral and the generator frame there is no return path to open the O.C. device under ground fault conditions. Hence the frame can be energized and potentially lethal.

The code only states that the frame is not required to be grounded. The only reason I can figure out they wrote it this way is if you do bond the neutral to the frame it is a separately derived system. If someone were to wire this unit into a premise wiring system then the grounded conductor would be grounded at two points instead of only at the service. This could lead to circulating currents as well as related metal enclosures and conduit acting as current carrying conductors.

It seems to me that the above situation could be dealt with by putting a tag on the unit specifying that the bonding jumper must be lifted before hooking up to premise wiring. That way the example of the tradesman injured when the generator frame cut through the extension cord would not have happened.

Hi All,

This is a theme that has been tackled in a previous thread.

I don't agree with DKing1. Bonding one side of the output to the generator frame will not cause an external ground fault to trip the over-current device.

Look at the situation where the extension lead gets a nick or an abrasion in the "Live" insulation and that breach of the insulation is in a puddle on a building site. This is a very typical situation. If the generator frame and "neutral" are bonded then that leak to the "live" wire will actually make the frame live. It will not make the oc device to trip unless the generator frame has a low resistance path to earth.

The output of the generator set should be treated as the output of an isolation transformer. You can touch either live conductors without getting a shock (better not to touch it however). Once there is some earth leakage anywhere in the system then effectively there exists a live and a neutral. Now there exists a shock risk. The safest mode is for the output have an ELCB (GFI) so that it actually needs two faults to allow an unsafe condition.

I find it strange that ELCBs are not mandatory on portable generator sets.

Kind Regards

Chas

Ai) No.

Aii) Yes, if it is not "double insulated" (manufacturer's label will have a square within a square). Energising one that is not will result in a dangerous situation.

Aiii) No. The equipment will operate safely regardless.

Qs) Why, if <...the live and earth wires inside the extension socket are transposed...>, is a piece of equipment with a known safety-critical fault being energised, why does no-one appear to care, why did it not get picked up at its periodical safety inspection ("PATesting"), as a requirement of the workplace, and why would anyone of a sane disposition want to work there?