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

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

    anyone know what one of these generators look like...

    also not a trick question...

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    FACT:

    all ryobi mobile generators have a V-O-V earth connection (centre tap on winding which is earthed) and there fore cannot be connected to a fixed installation.

    Note : Such a generator may only be used as a free standing unit to provide power to specific appliances.

    i havent checked any others makes but i would strongly advise that you contact the supplier of your generator.

    i need to connect a generator to a fixed electrical installation so if anyone knows of a generator which doesnt have this type of connection...please let me know.

    i am looking for a 5.5 kva unit

    i think i have just put the can opener into the big can with lots of worms...

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    just to give you an idea how big this problem is....i personally have been involved in at least 30 installation where this type of generator has been installed in domestic and small bussiness applications...

    where a manual changeover switch with a small ammeter has been installed and connected to the main DB.

    so far not one generator company i have contacted can supply me with a small unit not V-O-V.

    in fact the one company i spoke to has sold literally 1000s not 100s of these units which have been used to connect to fixed electrical installations.

    now here is a thought...the generator cannot be connected to the electrical installtion like the bigger units...it is plugged in...so your house is a big appliance....i had to laugh as i was typing this but it is a thought...in this day and age anything is possible.

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    there is a solution...i dont have time right now to post but will do it later today after my dentist appointment...i am sure i will be feeling in the mood once all my teeth have been removed.

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    Site Caretaker Dave A's Avatar
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    Quote Originally Posted by murdock View Post
    there is a solution...
    Disconnect the center tap?
    The trouble with opportunity is it normally comes dressed up as work.

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    Diamond Member AndyD's Avatar
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    The problem is that you're using a site / mobile generator as a back-up generator. The small generators might be marketed as a domestic/small business back-up solution but they were not designed to do this. The reason they're V-O-V configured coils is to reduce the risk of fatal shocks when they're used in high risk applications like building site work. The supply voltage they deliver is 220v L-N but both neutral and live supply conductors are at 110v wrt earth. The theory is you're less likely to go toes-up from a 110v shoch than a 220v one.
    There's also going to be issues with any premises that contains equipment that utilises earth referenced serial comms where the max permissible N-E voltage is 1.5v. This is sometimes found in EPOS systems for example. There's also a chance you'll destroy surge and noise suppressors that may be installed in the DB.
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    100 % correct andy....and very important the new cbi e/l units dont operate because of the voltage.

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    Hi Guys I am new here.

    So to understand this correctly the V-O-V earth connection is done to limit the voltage from live to earth and neutral to earth as mentioned to avoid injury in the event of a short to earth on site.

    I have a Honda EP6500CXS portable generator at home. I installed it with a manual change over switch on my plug and light circuits. When the generator runs and I test the plugs with a plug tester the tester shows no earth. The plug tester does also not trip the earth leakage, nor does the test button on the E/leakage work.

    I then fitted a bridge piece between the earth and neutral on the alternator. This got all of the above working correctly. This set up has run for 80 hrs like this over the past 2 years.

    With my neutral to earth bridge piece in place if I run the generator and test the following I get

    L to E 223 Volts, N to E 0 Volts.

    With my bridge piece removed I get

    L to E 147 Volts, N to E 67 Volts.

    So is my theory correct that to check if the generator has a V-O-V earth run the unit with nothing connected. Measure between the Neutral and earth. If you get a big reading as above it is V-O-V earthed. If you get a reading of 0 Volts or 1 Volt the unit is not V-O-V earthed.

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    Diamond Member AndyD's Avatar
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    So is my theory correct that to check if the generator has a V-O-V earth run the unit with nothing connected. Measure between the Neutral and earth. If you get a big reading as above it is V-O-V earthed. If you get a reading of 0 Volts or 1 Volt the unit is not V-O-V earthed.
    Not necessarily. With a generator that's not V-0-V (single winding) the neutral may still be floating in relation to earth so you might still see a voltage N-E.

    If your generator is V-O-V and you earth the neutral with a spike in the ground, then if the centre point of the windings isn't earthed you could develope 110v on the chassis of any appliances you are running. Result = Dead person.

    If your generator is V-O-V and you earth the centre point and the neutral you effectively short one of the windings. Result = skittish person with no eyebrows after large flash/bang.

    Generators are lethal if they're connected incorrectly. There's a whole section of legislation written specially for them....and with good reason. Every installation is different, you also need to know where to isolate your council supply and you also need to know what earthing system your premises has. I would strongly suggest you get a competent electrician with generator experience to test your setup and at least advise you the correct way to connect. His hour labour charge is well worth the safety of you and your family.
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    Site Caretaker Dave A's Avatar
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    Quote Originally Posted by AndyD View Post
    If your generator is V-O-V and you earth the centre point and the neutral you effectively short one of the windings. Result = skittish person with no eyebrows after large flash/bang.
    A thought occured reading your scenario - shouldn't a V-O-V generator have overcurrent protection on both the live and the neutral then?
    The trouble with opportunity is it normally comes dressed up as work.

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