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You are 100% correct. I still cannot understand why alternators ( portable or standby ) do not come with a built in RCD device.
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It's not that simple to modufy a vov unit to work on an installation. If you connect the line which is not going to the circuit breaker to earth, you are basically shorting out half of the stator coil and the unit will not even run for 20min before the stator burns out. One needs to disconnect the centre tap of the stator from the frame before connecting the one line to the frame as you suggested and this is an almost impossible task.Comment
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if i may ask, why with a load connected. If you measure at the gennie plug, NO LOAD, L to E and N to E -- you get +- 110V L-E and +- 110V N-E ?
..also, someone mentioned VOV gennies not legal......why are they selling it and why are there millions connected to the db boxes via a change over switch?
a lot of my cocs i have signed and issued was for the single phase CHANGEOVER SWITCH and DB wiring splitting .....i have no control on which SP gennie the client plugs into the plug that leads to the SP change over switch after i leave.Comment
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Eish !Comment
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My brother, that's a portable vov genny and shouldn't be connected to the installation.
The earth leakage and other protection aint gonna work.Comment
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sorry i dont understand Derlyn.............please note I am trying to find out about the tests you mentioned. (with respect)
and. no it is not a portable VOV gennie, IF it is a portable V-0 gennie, no centre tap, i am asking what stops the owner of the house plugging in another vov gennie once you issued your coc and left the building.....
eish.
never mindLast edited by ACEsterhuizen; 22-Sep-23, 04:30 AM.Comment
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It is advisable to take voltage measurements on any genny with a light load connected to check if it's VOV or not.
Many gennies that are not vov will still give strange voltage readings if measured on no load. This is due to the high impedance of most multimeters.
Incandescent lamps work well and I use my test box as in photo attached. Plug it in and if both lamps light up, it's VOV for sure. If only the left side lamp lights up, you good to go.
You are correct that you cannot be held responsible for anything plugged in by the client after you leave site, however, it's a good idea to first check the genny that the client intends connecting BEFORE doing the installation. If I find it's a VOV, I explain to the client why I will not be doing the installation and also show them the relevant regulation.
I usually plug in my test box in front of the client and they do understand that it's in their own interest not to just plug in anything. On many occasion I have had clients requesting that I accompany them to the genny sales house to make sure that the genny they are purchasing is suitable for purpose.
Peace out, Brother.
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thank you sir. it was all i asked.
i will build your 2 light system, but smaller. with a reasonable load.
and thanks again, for understanding, that a customer can change a gennie at any time, without the coc signatory knowing it, and how that "makes a coc not worth the paper it's written on", is an irresponsible, rash and injudicious statement to say the least and is demeaning to the profession, it boggles the mind. If that vov gennie is plugged out, the coc is "worth it" again, if it is plugged back in, the " coc is "not worth the paper" again....
sorry to have bothered. have a great day.Last edited by ACEsterhuizen; 22-Sep-23, 05:38 AM.Comment
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Best you can do is to also put a sticker on saying no to VoV and pictures pictures pictures of it all. : )
Sent from my CPH2197 using TapatalkComment
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Perhaps a cost issue, but note that at a technical level there will be earth point requirements that are far from guaranteed to be in place. Without an earth spike (of appropriate quality) or a connection to the main earth point, is the RCD going to pass an earth leakage fault test at the point of consumption?Participation is voluntary.
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Good morning Dave.
Happy long weekend to you.
We've actually been through this discussion before regarding earth leakage relays. This name is deceptive. I will, for instance, get an earth leakage to trip without 1mA flowing to earth.
It is a residual current relay which measures the current through the live and neutral conductors and trips if there is a difference in these 2 currents of equal to or more than the sensitivity of the relay. It does not know if that current is flowing to earth or not.
It doesn't measure current to earth. It does not know how much current is flowing to earth. All it knows is how much current is flowing in the live and neutral and they must be the same.Comment
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Thinking of this V0V...
What if you had to take the output line and Neautral and then combine that Neautral to the Earth cable of the output cable which is going to the DB as well as sink a rod in the ground with doing a fall of potential test to make sure it is low ohms.
So basically the earth of the Genny output is not in play and then the earth and Neautral is bonded to earth
Sent from my CPH2197 using TapatalkComment
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Dangerous. The body/frame of the genny will not be earthed.
The only option with a vov is to disconnect that centre tap and then bridge the neutral and earth like we do with inverters.Comment
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The first thing to consider is that if there is no return path, there will be no "fault" current. (One of the basic principles of a safety supply).
The second thing to consider is as follows:
There is a supply side and a load side to an RCD.
The return path for a fault on the load side has to be via the supply side of the RCD for the RCD to trip.
If the fault point and return are both on the load side, the RCD will not trip as there is no difference in current at the points in the circuit it is measuring to sense a difference in current.Participation is voluntary.
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I agree 100%, Dave.Comment
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