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Thread: Generator starts while the main power is on

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    Generator starts while the main power is on

    Hi every one Iím n newbie and this is my first post and I hope that I can also provide some info while Iím here.
    Sorry to start with a problem and hope that someone can help, Iíve connected our companies main power to a generator.
    The main power comes from the municipality (3 phase) runs throw the generator then feeds back to another circuit breaker on the DB that feeds the building.
    This all works well and all the power is on in the building but when I connect the battery of the generator then the generator starts while the main power is still on.
    This is wrong obviously because I want to connect the generators battery and then I want to switch the main power off and then the generator should start.
    Do I need a change over switch or am I missing something the folks removed it from there old offices and we installed the generator at the new office and they set it worked fine and there were no change over switch.

    Its got a panel with a DKG 105 DATAKOM on it with now wiring diagram.

    Help would be much appreciated

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    Site Caretaker Dave A's Avatar
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    Welcome to TFSA

    This might help. I see there's an installation manual and users manual to download...
    The trouble with opportunity is it normally comes dressed up as work.

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    jvan66 (04-Oct-11)

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    Diamond Member AndyD's Avatar
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    It does sound like an AMF panel wiring or program issue. Are you a qualified electrician?

    The changeover is effected by 2 x interlocked contactors rather than a switch as such. The contactors are controlled by the outputs from the AMF panel along with the starter motor. This isn't the kind of wiring you should attempt if you're unsure of these types of systems. At best you might lose a generator winding and an eybrow or two, at worst.....well yeah.
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    jvan66 (04-Oct-11)

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    Hi many thanks for the feed back , yes I am a qualified electrician but my problem is there is no wiring diagram I wanted to swop the two contactors wires around but decided not to fiddle with I then went to the company where the genie was build but they cant provide me with a diagram so Iím a bit stuck. Thanks for the link Dave I will try to work of that and I will see if it is wired the same. Attach is a pic of the panel.

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    Gold Member Sparks's Avatar
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    Open the panel and sketch the circuitry you see it. As you follow the wires, you will see where the fault lies. The quickest way will be to trace backwards from the starter. It's contactor must not get power while there is Escom power. To be on the safe side I suggest you remove the wires from the starter and connect a lamp to them so as to safeguard your Genny from starting up while there is Escom power.

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    Iíve made a sketch already but the thing is the genny work fine at the old place and it was just disconnected on the db and brought to the new place so every thing should still be the same. I havened had a chance to go throw the manual of the DKG 105 datakom and I have no experience with these devices yet so I donít know if any thing should be programmed thatís to say if there is programming involved just may be the problem is with the DKG 105 datakom.

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    Hi all, Iíve made a little break through with my genny problem. Eskom power runs throw the jenny and feeds back to the DB and when I drop the eskom power the genny starts which is success ( with some of youís help thanks for that) but always the but now when I switch the eskom power back on then the genny continues to operate.

    "The manual states the following
    The genset continues to operate after AC mains are reestablished
    The genset continues to operate after AC mains are reestablished
    Widen the AC voltage limits. The hysteresis value for the AC voltages is 10 volts.
    When the AC mains fail, the lower limit is raised and the upper limit is reduced by the hysteresis value to prevent a new load
    transfer after the load is transferred to the mains.

    Iíve played around with the upper and lower limits on the DKG 105 Datakom but the genny keeps on running.
    So close but jet so far I would appreciate If any one out there have any ideas regarding this error

    Many Thanks

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    Diamond Member Justloadit's Avatar
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    Usually gennies run for 15 to 20 minutes after a mains returns. There could be a timer
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    Diamond Member AndyD's Avatar
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    Many back-up gensets are configured to treat low voltage episodes (brown-outs as the Americans call it) as power fail. You can set the voltage where the generator will kick in. In SA the nominal supply voltage is 220v, the generator should kick in if it drops below say 200v. If the Eskom supply voltage increases to 215volts for example the generator should then shut down again. The difference between the voltage the generator kicks in and the voltage it kicks out at is the hysteresis or differential. This can also be set on most AMF controls. Sometimes you can also set a time delay so the Eskom voltage would need to be 215volts for a preset time before the generator shuts down and Eskom power is reapplied.

    Confused?? You will be soon... :-) There's often a miriad of settings you need to apply to the AMF controller, I would try find a local supplier or agent to help you out.
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    I believe in a change-over. Basic and seldom lets you down.

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