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Posted By Topic: MEN Links downstream of Step Down Transformer

Feb 13 2020 11:09


We have an installation that requires a 3 phase step down transformer (400V to 208V, dyn11) to run some US equipment.

Do we need an MEN link in the downstream (208V) switchboard as there is no neutral connection from the MSB to the secondary side of the TX?

Thanks in advance.
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Feb 13 2020 15:31

That sounds like a "Part 1 solution" to me; so just follow the certified design that's required by ESR 59 for any installation that doesn't fully comply with Part 2 of "3000".

Whatever you do, it won't be an "MEN link" as such; because that's part of the "MEN" system of supply to the installation, connecting between the distribution PEN conductor and installation earthing system and so holding the PEN close to zero volts.

Feb 13 2020 16:56

effectively it's an isolating transformer so I would say no N-E link on the 208V side of the transformer.

Keep in mind this is an appliance, lots of appliances have transformers in them and no N-E link

Feb 13 2020 17:27

Look in NZS 6114 it covers the case of installations at voltages other 230/400 V; also covers 50 Hz or 60 Hz.

Feb 14 2020 08:17

Thanks for the replies, much appreciated.