Question re: Portable Gensets & ELD safety switches


Folks,
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
isnt earthed.
Does this sound right?
If this is correct, is there any way to get an ELD to work on a portable
genset?
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.
Cheers,
Rod.......Out Back
Reply to
Rod Out Back
Loading thread data ...
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 too.)
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.
Reply to
budgie
Use mains supply and piss off the genny its a safety hazard
for
the
genset
conductor
When
(hopefully)
active
protection. ( If
threshold
core.
if you
bird on
output is
will
I
connect
building
Reply to
FruitLoop
for
the
genset
You want a proper residual current device so that anything not coming back tot he gen trips the breaker.
Cheers.
Ken
Reply to
Ken Taylor
"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.
.......... Phil
Reply to
Phil Allison
please explain how to do that when the nearest power outlet is 3k away ?
Reply to
Miss Jadzax
FFS, just use modern DI tools and all ya will need to worry about is lightening and the tax man!
--
Regards ......... Rheilly Phoull
Reply to
Rheilly Phoull
"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 ?
........ Phil
Reply to
Phil Allison
Why do you think it is mandatory to have RCDs fitted to all outlets on building sites? Perhaps tradesman all use ancient power tools? Reasoning like yours is beyond stupid.
Reply to
Fred At Home
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.
Reply to
Fred At Home
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.
Reply to
Mark Harriss
You can see why he's a fruitloop ...
Reply to
budgie
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 not help.
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.
Reply to
The Real Andy
Its simple really , wire or maybe green generated electricity
Reply to
FruitLoop
Hi Rod, 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 best protection.
Reply to
APR
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 or wiring.
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).
Commentary: 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.
Reply to
David, not to be confused with
"David, not to be confused with the other Davids."
David,
Many thanks for a most useful reply. This is what I was trying to find out.
Cheers,
Rod.......Out Back
Reply to
Rod Out Back
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.
Wotta wanker...
Cheers,
Rod.......Out Back
Reply to
Rod Out Back
"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.
........ Phil
Reply to
Phil Allison
"Phil Allison"
** Typo alert:
.......... Phil
Reply to
Phil Allison

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