Lockable main switch at switchboard connection - 4777.1 2005

Post Reply
JamieP
Posts: 170
Joined: Tue Apr 14, 2020 11:08 am
Has thanked: 26 times
Been thanked: 8 times

Lockable main switch at switchboard connection - 4777.1 2005

Post by JamieP »

Screenshot_20201017-091911_Drive.jpg
The switchboard we connect the inverter or PCE to must have a main switch that is lockable

How can we comply with this when we connect to a distribution board that is not the main switchboard and doesn't contain a main switch?

Do we simply add a single isolating switch or use the isolating switch for the board if one? Or do we make sure that the main switch on the MSB is lockable?

Or does this technically make connections to a DB non-compliant unless they have a main switch (outbuilding clause for example when treated as own installation)?
User avatar
gregmcc
Site Admin
Posts: 103
Joined: Sun Apr 12, 2020 4:45 pm
Has thanked: 5 times
Been thanked: 34 times

Re: Lockable main switch at switchboard connection - 4777.1 2005

Post by gregmcc »

the way I read it, is the switch between the output of the inverter and the switchboard it connects to, the switch doesn't have to be in the switchboard, it could be beside, above or below, or at the inverter.
User avatar
DougP
Posts: 139
Joined: Sun Apr 12, 2020 10:11 pm
Answers: 2
Has thanked: 8 times
Been thanked: 20 times

Re: Lockable main switch at switchboard connection - 4777.1 2005

Post by DougP »

Isn't that referring to the solar supply main switch? So it's just a CB rated appropriately for the inverter?
JamieP
Posts: 170
Joined: Tue Apr 14, 2020 11:08 am
Has thanked: 26 times
Been thanked: 8 times

Re: Lockable main switch at switchboard connection - 4777.1 2005

Post by JamieP »

Interesting, I always thought it meant the normal supply main switch

Not the solar supply

To me it reads the first sentence there is about the normal supply then the rest is about the solar supply
pluto
Posts: 14
Joined: Tue Apr 14, 2020 9:22 am
Has thanked: 0
Been thanked: 4 times

Re: Lockable main switch at switchboard connection - 4777.1 2005

Post by pluto »

The main reason for the lockable switch on the input/output of PV grid connect inverter is due to TWO supplies to the switchboard; one is the mains supply and the other from the inverter when in export mode.

When AS 4777.1:2005 was being drafted, and I was one of the NZ representatives on the drafting committee, the NZ Electricity Authority, who regulate revenue metering provisioning in NZ which also means it is NOT part of AS/NZS 3000 and AS 4777.1:2005, required that the mains supply into an electrical installation have one revenue meter to show how much enery was purchased from the energy supplier and a second revenue meter to show how much energy was exported from the PV grid connect inverter to the energy supplier.

As revenue metering is excluded from AS/NZS 3000 and ESR 2010, due to it being under control of the NZ Electricity Authority as/nzs 3000 and AS 4777.1 has very little detail in respect of revenue metering.

When AS 4777.1:2005 was being drafted, the intent was to assume that all PV inverter connections would be to the main switchboard only and never to a distribution switchboard.

Recent advances in revenue metering and recent issues of AS/NAZS 4777.1 have enable some differnet revenue metering approachs to be used.

Remember that ESR 2010 only cites the 2005 edition of AS 4777.1.
JamieP
Posts: 170
Joined: Tue Apr 14, 2020 11:08 am
Has thanked: 26 times
Been thanked: 8 times

Re: Lockable main switch at switchboard connection - 4777.1 2005

Post by JamieP »

Thank you for the input

But it didn't answer wether the highlighted statement above applied to the solar or normal supply main switch

I understand the solar supply main switch must be lockable but what I need to know is if I connect to an old main switchboard, do I need to upgrade the normal supply main switch to a lockable one if it's not already? Because that's how I read that clause
pluto
Posts: 14
Joined: Tue Apr 14, 2020 9:22 am
Has thanked: 0
Been thanked: 4 times

Re: Lockable main switch at switchboard connection - 4777.1 2005

Post by pluto »

I would not consider that the existing main isolating switch mounted on the main switchboard in the mains incoming supply supply would need to be changed to make it a lockable isolating switch.

The main reason for a lockable switch on the grid connect inverter supply is to enable if back feeding into the distributors network was to occur, the lines campany have a method of turning off the backfeed from the inverter and then fitting an padlock (or similar lockoff device) to prevent the re-connection of the inverter export without their approval following repair.

This backfeed is unlikely from an electrical installation which has no supply generating devices.

In the case when a standby generating set the changeover device should, and must, be able to prevent the connection of the generating set output to the incoming mains connection from electricity distributors network.
AlecK
Posts: 263
Joined: Thu Apr 16, 2020 11:24 am
Answers: 1
Has thanked: 1 time
Been thanked: 87 times

Re: Lockable main switch at switchboard connection - 4777.1 2005

Post by AlecK »

That's a subclause.
It's part of the higher-level clause 5.3; which is about the ac connection of inverter output to a switchboard of the installation.
So has to be read in that context.
Ie it is talking about the main switch that isolates the incoming supply from the inverter to the installation.

That's the one that's required by para 2 of 2.3.3.1 of "3000" for every incoming supply.

BTW, the word "lockable" is just a waste of letters; as every "main switch" has to qualify as in isolating switch.
2.3.2.2 requires all isolating switches to have provision for securing in the open position;
so it goes without saying that it has to be lockable (as well s all the other required characteristics)
Post Reply