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Thread: Automatic change over panel

  1. #1
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    Automatic change over panel

    I have a small challenge...

    The house has a 60 amp single phase supply.

    A 6.50kva diesel single phase viper generator with an automatic change over panel. (220 VAC rated at 24 amps)

    The right way to do this would be to install a 60 changeover panel with mechanical interlock ...that would just be too easy ... i need at least a small challenge.

    The customer had the setup installed at his previous house ... which was also 60 amps ... but indicated that it worked fine with just the 6.5 kva changeove panel connected to the house ... lucky for him nothing went wrong.

    My thoughts ... to fit a 60 amp contactor in a seperate housing (no space in the changeover panel) and still use the changeover panel as supplied to work with the generator.

    When eskom power is on ... the 60 amp contactor is energised at the top of the contactor ... feeding power to the house ... 2 wires from the top of the contactor will feed into changeover panel to the terminals which would be use for "input".

    When load shedding starts (as indicated in the new schedule sent out last week) the power will switch off drop out the 60 amp contactor.

    The generator will start and feed power from the changeover panel output ... to the bottom of the 60 amp contactor through a 20 amp D curve breaker mounted same enclosure as the 60 amp contactor.

    I am sure it will work ... my only concern ... if the contactor shorts closed ... but also consider that the ATS which has a mechanical interlock ...will engage as soon as the eskom power is switched on ...which will isolate the generator.

    What do you think ... bad idea or you have a better solution.

    Going through my store room i found a spare 3 phase 63 amp automatic changever switch ... i might just use that instead.

    I have come across this issue on more than one occassion thats why i thought i would put it out there.
    Comments are based on opinion...not always facts....that's why people use an alias.

  2. #2
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    Anyone have a connection diagram for a dragon power ATS

    Jiangsu Dragon power cc ltd

    Criterion GB?T1404.11
    AC-33B

    I need to test the ATS

    the control terminals.

    AL AN BL BN AO BO N
    Comments are based on opinion...not always facts....that's why people use an alias.

  3. #3
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    I think it will be safe.


    The power from the meter to the top of the 60 amp contactor (16 mm wires)

    A live from the top of the contactor to a 6 amp single pole breaker ... to the coil

    and to the top of the N/O contact on the 60 amp contactor(1.5 mm wire)

    from the bottom of the N/O to the input of the ATS terminals.

    A neutral from the top of the contactor directly to the contactor coil (1.5 mm wire)

    Inside the ATS panel:

    The output from the input contactor in the ATS panel to be disconnected from the ATS output bridge (to prevent feed back on the 4 mm wire)

    The generator will connect to the generator terminals in the ATS panel.

    the output terminals of the ATS panel will have a 4 mm wire feeding back to a 20 D curve breaker (or maybe a double pole breaker to isolate both live and neutral if it trips) ... from there back to the the bottom of the 60 amp contactor.

    Ther mechanical interlock will preventing power feeding back to the bottom of the 60 amp contactor if the mains power is on.

    So why go to all this trouble ... it saves having to install a 60 mechanically interlocked contactor ... it saves having to run cabling to the DB and separting all the circuits in the DB

    The customer wants to switch circuit if the power goes off ... if he doesnt ... the 20 amp breaker will trip and he sits in the dark.

    I beleive a separate DB should be installed and dedicated circuits should be installed for the generator ... but hey if the customers doesnt want it who am i to argue.
    Comments are based on opinion...not always facts....that's why people use an alias.

  4. #4
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    In my opinion the correct way would be to fit a 60 Amp ATS in the system and use it to change over
    The contactor arrangement you are proposing sounds very much like a make sift ATS and the fact that the contactor is operating the ATS , by sounds of things , does not make the ATS an ATS but just a contactor

    The mains and generator supply is being switched by a single contactor and I see it falling foul of 7.12.2.5

    7.12.2.5 Where an alternative supply is provided to an installation or part of
    an installation as a switched alternative to the main supply, the change-over
    switching device shall disconnect the main supply before the alternative
    supply is switched in. The change-over switching device shall be interlocked
    in such a way that the main supply and the alternative supply cannot be
    connected to the installation or part of the installation at the same time.


    I also believe that you cannot take a 14KVA supply and substitute it with a 6,5KVA supply without ensuring that part of the load is isolated from the generator - I read the regulations as not allowing overloading of the generator by design

    7.12.2.4 Where the alternative supply is intended to provide a supply to an
    installation that is not connected to the main supply, or to provide a supply
    as a switched alternative to the main supply, the capacity and operating
    characteristics of the alternative supply shall be such that danger or damage
    to equipment does not arise after the connection or disconnection of any
    intended load as a result of the deviation of the voltage or frequency from the
    standard range. Means shall be provided to automatically disconnect such
    parts of the installation, as may be necessary if the capacity of the
    alternative supply is exceeded
    .


    I don't believe the intention of the regulation is to have a CB that trips if the generator goes into overload .The regulation is there to protect the consumer and is a continuation of 5.3

    5.3 Basic provisions
    5.3.1 Estimated load
    The load of an installation shall be estimated to determine the type and
    capacity of the required electricity supply.
    NOTE 1 Annex C gives an example of estimating the load for residential installations
    but the method is not to be regarded as an exact method.
    NOTE 2 The supplier may have special requirements for large installations and for
    installations that need special consideration


    Consumers are quick to tell us how to do our jobs and then extremely forgetful when something goes wrong - Been there, done it , have a cupboard full of T-shirts.

  5. #5
    Diamond Member Justloadit's Avatar
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    I would suggest adding in a 3 to 10 minute delay on ESKOM power return before change back, to ensure that the incoming power is reliable, and also to prevent the case where the incoming can come in and out a few times, as the HV circuit breakers kick in and out due to line overload.

    You can get one from any electrical wholesaler.
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