how to wire a contactor 2nc 2no

fca1
fca1 Solar Expert Posts: 124 ✭✭
in Advanced Solar Electric Technical Forum #1
Sorry if this is bit offtopic...

i'm starting to get confused with these contactors thing... explaining...

i want to replace a relay by a contactor so i can use more load on home made kind of ATS...
on the relay its easy i have 2nc and 2no open contacts and a 2common contacts

i connect inverter on NO, grid on NC and the loads on the common, i energize the the coil with the inverter when that makes the inverter primary source of power when inverter is turned off coil looses power and the grid connected to nc contacts pass

its not completely like this one but close...

Attachment not found.

now i have searched a lot of contactors but i can't find the "common" contacts
this is one is an example but all the other that i find are more or less the same...
using this example where are the nc no and common ?
Attachment not found.

i'm confused... the contactor can't be used as relay ?

thanks--
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #2
    Re: how to wire a contactor 2nc 2no
    fca1 wrote: »
    Sorry if this is bit offtopic...

    i'm starting to get confused with these contactors thing... explaining...

    i want to replace a relay by a contactor so i can use more load on home made kind of ATS...
    on the relay its easy i have 2nc and 2no open contacts and a 2common contacts

    i connect inverter on NO, grid on NC and the loads on the common, i energize the the coil with the inverter when that makes the inverter primary source of power when inverter is turned off coil looses power and the grid connected to nc contacts pass

    its not completely like this one but close...

    Attachment not found.

    now i have searched a lot of contactors but i can't find the "common" contacts
    this is one is an example but all the other that i find are more or less the same...
    using this example where are the nc no and common ?
    Attachment not found.

    i'm confused... the contactor can't be used as relay ?

    thanks--

    Well, a "contactor" makes contact on command, rather than ever opening contacts on actuation. So that may be the problem. I see that this contactor has two auxiliary contacts which are each SPDT (with both NO and NC terminals). But those cannot handle the current.
    One way to get the same effect would be to use two separate contactors, each driven from one side of an SPDT switch or relay. But to use those for an ATS function, you would have to be able to insure that one contactor opened before the other closed.

    You will find some listings for "DPDT Contactors"
    but these really are high-current relays. Which is what you want....
    SMA SB 3000, old BP panels.
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #3
    Re: how to wire a contactor 2nc 2no

    Interesting that I just finished hooking up an emergency generator for our local fire department. It has the ability to auto start on grid failure and then transfer all loads from grid to generator.
    The auto transfer of loads is done by operating a small motor (like a timer motor on steroids) that first opens the closed circuit breaker, then closing the other breaker which had been open, using a teeter-totter like lever. This complete system by the way, (diesel generator and control panel) had been used by the Canadian Coast Guard in their light houses to ensure the light house was always in operation, and is designed to run non-stop, (24/7/365) for up to a year, only needing fuel to keep it running. The engine has a large engine-oil tank beneath it and a relatively huge oil filter to allow such extended operations.
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