A question I've come across recently:
We have a portable genset (Honda 5kva) which we use around the property for
working on fences etc, where we need 240V. We have one of those orange
4-outlet ELD safety switches, which I bought with the idea it would cut the
power if someone was stupid enough to cut the power cord.
However, it has been pointed out to me the ELD wont trip because the genset
Does this sound right?
If this is correct, is there any way to get an ELD to work on a portable
Should I simply keep the ELD outlet for the shed?
I already have ELD's fitted to all the buildings as it is, so it would
really be only handy for the 4 outlets...
Any info appreciated.
Short answer: yes.
Yes. It must have an earth connection. Earth it.
These devices work on a core balance system. Current in the active conductor
balances the return current in the neutral when there is no ground fault. When
you make yourself part of the circuit, providing a connection to (hopefully)
ground, the current through you = the difference between current in the active
and neutral conductors. If this is sufficient it will trip the protection. ( If
it is below the trip threshold, in principle it is below the harm threshold
So the question is whether you present a circuit that will unbalance the core.
You will if you grab the phase (active) and the machine frame. You won't if you
grab the phase and sit there isolated from the rest of the system like a bird on
a wire. The good news is that as long as your contact with the set's output is
downstream of the sensing core, any situation in which you will get a zap will
cause an imbalance.
Leaving the set floating provides one form of protection, although not one I
would rely on in all circumstances.
And an earth leakage system won't save you from frying if you happen to connect
yourself between phase and neutral.
I've seen contractors bang in an earth stake on the gensets on no-mains building
sites. I've also seen lots that don't.
"Rod Out Back" ** If an ELCB does not trip because the generator frame is not earthed -
then a person in contact with either AC wire is not getting a shock.
If a person manages to be contact with both AC wires - they will get a
shock, but an ELCB will not help them anyhow.
"Rheilly Phoull" ** That is a VERY dangerous myth.
Are not the business ends of electric drills and saws etc made from metal ?
Can you not touch them ?
What if they become live through contact with a cable ?
You have been mislead. If the genset had no path to earth then you would
never get zapped unless you:
1. ... came into direct contact with the genset.
2. ... were the link between active and neutral.
Obvioulsy an RCD will work on a genset so make sure you use it.
BTW an RCD is useless in scenario no 2 above.
Reminds me of the time I was helping a Telecom Liney splice a massive
co-ax cable, I had my back turned to him and heard the alternator bog
down and almost die. As I turned around I saw him flopping about the
cable pit and then the alternator stalled.
He'd dropped the hot air gun into knee deep salt water at the
bottom of the cable pit and nearly fried himself as there was enough of
an earth return to the gen set frame sitting on the wet salt pan surface
to pass a current via the DOUBLE INSULATED hot air gun.
In this situation, provided there is enough current flowing through
the earth lead (from the description i am guessing there is) then an
ELCB would trip.
As Phil said, without any return, an ELCB is useless. For double
insulated tools, unless you are working in a situation where there is
a possible ground path to the genny, then you will not get a shock
unless you touch the active and neutral, in which case an ELCB will
For tools that are not double insulated, then an ELCB may be useful.
That is if there is any possible way for one to be in contact with a
active peice of the tool and an earthed peice of the tool.
My advice, keep the ELCB, it cant hurt.
This issue is covered very extensively by Mines Department requirements for
the use of generators on mine sites. The Mines Department electrical
inspector for your area can provide you with literature that details how the
generator and protection system, including the earth, should be wired for
This is correct.
Yes there is, however, it requires the genset output to be rewired and a good
quality earth (stake, etc) to be attached to the genset frame and the output
earth terminal. If a gen is rewired for RCD use then the RCD must be fitted to
the generator, you cannot 'safely' use one on an extension cord.
The necessary rewiring entails connecting one side of the alternator to the
earth to form an earthed-neutral style circuit. This point, and the other side
of the alternator, are then connected into the supply side of the RCD.
The Australian standard for generators and the wiring rules require the
generator to be wired this way if an RCD is used. If an RCD is not used the
alternator must be left floating unless it is permanently wired into an
installation. It is recommended that small (< 25Kw) portable gensets have the
output floating and not use an RCD, as follows (ref AS2790 cl 6.1.8 and 6.1.9).
6.1.8 Equipotential (earthing) facilities.The
following parts shall be in effective electrical contact
with each other:
(a) The engine frame.
(b) The generator frame.
(c) All external metal enclosing electrical equipment
6.1.9 Connections between main winding(s) and
frame. Connections between main winding(s) and the
frame shall be as follows:
(a) Single-phase winding (without earth-leakage
protection) . The winding shall not be connected
to the frame.
(b) Single-phase winding connected to a current-operated
(core balance) earth-leakage device
complying with AS 3190. The input neutral
terminal of the device shall be connected to the
earth terminal of the device (where that terminal
exists) or to a frame terminal (see Figure 1).
1. It is considered that, in the absence of
earth-leakage protection, a single-phase winding
is safer when isolated from frame. In the event
of a single fault to frame, the situation then
resembles an MEN installation (where one
conductor is earthed).
2. Where a core balance earth-leakage device is
fitted, the connection between winding and frame
is necessary to permit correct operation of the
device. If the device were subsequently removed,
it is likely (and recommended) that the
winding-to-frame connection would be removed.
Dear village idiot,
Actually, it's not very simple at all. Mind telling me how this would work
in the real world? Dont tell me; you're a 'green' contract fencer! I can
see that your fencing rig would be a 40ft semi-trailer, so you can fit the
30-odd feet of 'green' renewable energy equipment...and the 50km of power
cord. What a smart little cookie you are!
Tell me, in what way would a renewable energy power source be so much safer?
I doubt your average vehicle mounted inverter will be earthed to ground
either. As best I can see, the same issue applies.
"Rod Out Back" ** Seems that you still cannot comprehend that if the AC supply is NOT
ground referenced then electric shock hazard becomes close to zero.
It is *BECAUSE* the regular AC supply *IS* ground referenced that ELCBs
are needed to protect human life.
Folk working on construction sites in the UL and Europe have long used
portable isolation transformers to create an "earth free environment " -
way safer than the usual one.