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Thread: 230 volt generator with a V-O-V earth connection

  1. #21
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    Would a loop impedance test on the generator not be easier? If the earth and neutral is done right, no danger light will appear on the tester?

  2. #22
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    As far as Iíve seen, the generators that has build in plugs are V0V and those with the termination box are the correct once with provision made for the earth and neutral to be bridged at the termination box of the generator. Just plug in a loop impedance tester. It will say whether its safe or not

  3. #23
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    I have done tests on many brands of these smaller generators, by breaching out the neutral to the earth, on all of them the conversion from v-o-v to o-v-o was safe and successful. I have not tried this on Honda EU generators and not sure if it will work, how ever there is a Honda EU available that is o-v-o, just you will have to import it as Honda SA refuses to do so.
    Brands tested include Honda EP6500CSX, SDMO, Ryobi and a few Chinese brands.

    All you need to do is attach a wire (size dependant on the size of the generator) from the earth point on the generator to the neutral wire from the alternator. This is why it is essential that ALL generators have an earth spike attached to them.

    This entire v-o-v and o-v-o mess is one the reasons electricians should not be allowed to install generators, this should be left to certified generator technicians. This is just one of many safety measures required for the installation of a generator that electricians tend to ignore. (please note that I do not claim all electricians are guilty but most are)

    Other very dangerous issues I often come across are
    Too little air flow for cooling
    incorrect exhaust installation resulting is possible co2 poisoning
    Generators installed using plugs (SAN clearly states that if connected to the DB the generator must be hard wired)
    Incorrect breakers, there must be one for the mains, one for the generator and one for the load.
    No bund wall round the generator to contain 110% of all fluids in the generator (As per environmental act)
    No fire fuse link to shut of the generator in case of fire (not yet legally required but the responsible thing to do and very cheap)
    The exhaust is not protected from accidental contact
    DBs fed from the generator do not have signage nor do they have emergency stops connected to the generator, or visible indicators to indicate if mains or generator power is being supplied.

  4. #24
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    Quote Originally Posted by Greg View Post
    AndyD

    I am an electrical contractor. This whole generator thing is one big disaster. I would go as far as to say that 99% of electrical contractors don't know generators inside out.

    I have spoken to countless contractors and let me tell you the one is as confused as the next. Even the council inspectors are confused. You ask them a question and they simply reply with a word for word quote from S.A.N.S 10142.

    The regulations should be written in plain english. If they say V-O-V gen sets may not be connected then tell me why?

    Most of the big diesel gen sets are installed at the boundary boxes and the main supply cable run via the auto change over switch.


    If V-O-V is one method of wiring the alternator then what are the other methods and what do they mean? How does one tell if it is V-O-V? Is the only way to actually check if the centre tap on winding is earthed? Is this actually possible short of taking the whole alternator to pieces. Is there a more simple method?

    I contacted Honda SA regarding my unit and they do not know what type it is. (Honda EP6500CXS 220 Volt)
    Greg all HONDA generators supplied in SA are v-o-v
    Simple test to see if it v-o-v or o-v-o is to measure between neutral and earth
    v-o-v = 115 VAC
    o-v-o = 0 VAC

    The reason they may not be installed is because they have 115VAC on the neutral, breakers tend only to break the live, thus some one working on the building while the generator is running can be electrocuted if they touch the neutral even if the breaker is off.

  5. #25
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    Quote Originally Posted by JacquesPN View Post
    I have done tests on many brands of these smaller generators, by breaching out the neutral to the earth, on all of them the conversion from v-o-v to o-v-o was safe and successful. I have not tried this on Honda EU generators and not sure if it will work, how ever there is a Honda EU available that is o-v-o, just you will have to import it as Honda SA refuses to do so.
    Brands tested include Honda EP6500CSX, SDMO, Ryobi and a few Chinese brands.

    All you need to do is attach a wire (size dependant on the size of the generator) from the earth point on the generator to the neutral wire from the alternator.
    Hi Jacques

    Bridging out the centre tap earth and neutral wire is not good enough on it's own as you are basically bridging out half of the alternator's winding. Alternators dont last too long if one does this. The secret is to also disconnect the earth wire from the centre tap on the alternator. The problem doing that, however, will make the guarantee null and void. It should be done by the supplier prior to delivery.

    I have long stopped doing domestic alternator installations because of the unavailability of standby units that are not VOV wound.


    If you approach any dealer that specializes in supplying alternators and ask them to explain the difference between a portable unit and a standby unit, the chances are close to zero that you will get a satisfactory answer.

    Until such time that suppliers are forced to differentiate between portable and standby units, I'm afraid there will be no end to this problem.

    Cheers and peace out ... Derek.


    Edited 28/7/2020 at 16.32

    This is not meant to be an advertisement but one of the very few units that test out ok for connecting to an installation is a 7,5 kVA Grip generator supplied by Gentech Industries. The unit in the attached photo's was bought from Builders Expess in East London.
    L-N 230V
    L-E 230V
    N-E 0V

    Click image for larger version. 

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    Last edited by Derlyn; 28-Jul-20 at 04:41 PM.

  6. #26
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    Quote Originally Posted by JacquesPN View Post
    This entire v-o-v and o-v-o mess is one the reasons electricians should not be allowed to install generators, this should be left to certified generator technicians. This is just one of many safety measures required for the installation of a generator that electricians tend to ignore. (please note that I do not claim all electricians are guilty but most are)
    What qualification do "certified generator technician" have ? I would asume a electrical certificate, a installation electrician certificate and a generator installer certificate?

    I dont believe the problem is with the installation electrician, i believe the problem is with the generator suppliers. Conning people into buying stuff which is not authourised for the application, like telling customers that the plug top to plug top is a quick safe connecting solution.

    I am busy dealing with this exact problem today, the "certified generator technician" is telling one of my customers that the best solution to his problem is to thow away the ATS and to replace it with a manual transfer switch at the DB. This will solve the problem of using a 5 kva genrator to try run his whole house. I have told my customer that so long as the "certified generator installer" can issue a "valid COC" for the 32 amp manual transfer switch connected from his meter to his main switch and the 5 kva generator , i dont see why not
    Comments are based on opinion...not always facts....that's why people use an alias.

  7. #27
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    Quote Originally Posted by Derlyn View Post
    Bridging out the centre tap earth and neutral wire is not good enough on it's own as you are basically bridging out half of the alternator's winding..
    I'm not sure that is what Jacques is saying exactly. One question to be answered here is how many generators actually have a centre tap to earth on the windings?
    Is the v-o-v readings one gets on most of these "portable" generators using digital voltmeters simply because the generator is set up as a safety supply and the "neutral" is floating?

    Agreed if there is a centre tap to earth and one bridges out the neutral terminal to earth, there are going to be problems. And pretty quickly I would think...

  8. #28
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    I have a supplier in Brits that disconnects the earth for me thus removing the 140+- Voltage between earth to neutral and i just bridge it where i do the termination. He says it won't damage the generator and warranty stays in place

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