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Reduced tariff contactor control.

wessex
Further to a previous post and single phase storage heaters being spread over a three phase supply.

The utility company have provided three phase metering which controls a 100A single phase contactor provide by them and is supplied from one of the line phases being controlled by a switch neutral from the metering unit.

The main post metering supply has a four pole isolator provided. The relay feed is taken from before the isolator and has no isolation after having being switch by the contactor. I,m looking to control two indpendantly DB mounted contactors each having a four pole main switch.

My issue is a matter of isolation within the DB as effectively a separate switched supply, controlling the DB contactor would not be isolated by the DB mainswitch. Also would an independent neutral have to be taken to the contactor or could the neutral with the db used. Borrowed neutral comes to mind. Perhaps the addition of an aux contact mounted to the main switch would be a solution.

Your thought please.
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    Thanks for the replies. Point taken about the aux contact providing adequate isolation. Equally if I have a contactor box providing the potential free contacts I'll effectively have three supplies in the same enclosure.

    I was trying to recreate the original set up in as much originaly each three phase supply was protected by a 30A switched fuse, so I was using a four pole MCB as the DB main switch and switching the neutral, but I could run the control feed through the fourth contact and run the neutral directly to the neutral bar.

    The company providing the replacement meter were only able to provide a single pole contactor.
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  • 0
    Thanks for the replies. Point taken about the aux contact providing adequate isolation. Equally if I have a contactor box providing the potential free contacts I'll effectively have three supplies in the same enclosure.

    I was trying to recreate the original set up in as much originaly each three phase supply was protected by a 30A switched fuse, so I was using a four pole MCB as the DB main switch and switching the neutral, but I could run the control feed through the fourth contact and run the neutral directly to the neutral bar.

    The company providing the replacement meter were only able to provide a single pole contactor.
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