New power distribution board question for any sparkies out there

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davecla

61 posts

Master Geek

#280106 26-Nov-2020 18:12

I'm wanting to upgrade my old style power distribution box (plug in ceramic type) for a flash new modern one.

I've got a couple of questions that I wanted to get straight in my head before the sparkie comes to visit, hoping someone can answer.

I'm going with a combination distribution + meter type board. The meter side will need a sealable main disconnection switch just like on the old board today.

Will the meter section of the board require it's own main switch? I can't see why it would but wanted to check.

I've got two sub main circuits, one is a big 63A fuse link, runs off to a pool shed with a heatpump etc. What would this be replaced with? I cant see any MCB's rated that high, seems 40A is the biggest.

The second submain goes to a shed, its connected via a 20A fuse, I guess this just becomes a 20A MCB ??

One last question, the brochure for the combo box the sparkie recommended says the meter section can go at the top or at the bottom, but sparkie said meters to top. Is this just preference or code? Meters at bottom would mean door would open a better way around (its not reversible)

I know I can ask my sparkie all this when he turns up, but hoping to have a few clues first.

cheers

dave

andrewNZ

2487 posts

Uber Geek
Inactive user

#2611326 26-Nov-2020 18:20

Houses aren't my field, but:

I'd expect only one main switch

MCB's definitely come 63A

Not sure about the meters, I think it's preference, but there could be more to it (height to the main switch, cable entry location etc)

gregmcc

2147 posts

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#2611327 26-Nov-2020 18:30

I'm going with a combination distribution + meter type board. The meter side will need a sealable main disconnection switch just like on the old board today.

Will the meter section of the board require it's own main switch? I can't see why it would but wanted to check.

Generally no main switch is required before the meter, but it's good practice to have one.

That is a BIG submain for a house, get your electrician to check what size it should be, I would guess it should be 20A or 25A, It depends on the brand, 50A, 63A, 80A are available. If your electrician is using a domestic grade range of MCB's the higher current ones may not be available.

Be careful as the standard network fuse size is 63A

The second submain goes to a shed, its connected via a 20A fuse, I guess this just becomes a 20A MCB ??

YES

No specific "code" that specifies meter top or bottom, although there may be a "Rule" that your power network/metering company wants.

Ideally the meter at the top is the most common, do you have a 3 phase supply or single phase?

JeremyNzl

359 posts

Ultimate Geek

#2611328 26-Nov-2020 18:31

Pretty sure the Main Switch needs to be less than 2m off the floor. Meters at the bottom may put the main switch above this height.

Alot of older houses mine inc had the switchboards mounted very high.

SomeoneSomewhere

1804 posts

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Lifetime subscriber

#2611336 26-Nov-2020 18:51

We normally put the meter at the bottom - it means all the cables can enter through the top and not go past the meter window, plus if you have limited cable length they're more likely to reach.

Correct, main switch must be below 2m. Place it in the lowest row of breakers and this will usually not be a problem.

I would recommend a sealing kit for a DIN rail switch if your power company requires the main switch terminals to be sealed. Main switch > Meter > Loads. Using a surface-mount switch is impractical as usually domestic boards have a meter window, so you can't actually reach into the meter compartment and flip it, so you need another one on the DIN rail anyway.

Always get a bigger board than you think you will need. If you're looking at the three-row 45-way Trical ones, they are very very tight between the rows, especially if you have a 63A submain and some three-phase.

It may be worth considering a main switchboard + meterboard just for the big stuff, and then a sub-board to handle everything else immediately next to it.

davecla

61 posts

Master Geek

#2611345 26-Nov-2020 19:03

Thanks for all the replies

two phases coming in

Yes its the 45-way Trical board that I was going with, Sparkie seemed to prefer that one over the wider plasticy ones.

I didn't think about the fixed window not giving access to a surface mounted switch - duh!

Thanks again,

dave

SomeoneSomewhere

1804 posts

Uber Geek

Lifetime subscriber

#2611362 26-Nov-2020 19:50

Most of the plastic ones are just a pain.

Yeah, those are *very* tight between the rows of breakers and from the breakers to the N/E bars. It's the same body as the 30-way version with an extra row squeezed in.

It looks like they now do an 'EZMP10-604', which is a four-row taller version. I suspect it will still be tight and there are often earth/neutral bar issues with these larger narrow domestic boards.

They also now do 'Jumbo' boards, which look to be wider. A 'JEZMP8-482' or 'JEZMP10-723' might also be worth looking into - these should hopefully include significantly more earth/neutral space. Pricing appears to be competitive.

Vynco's new VM series boards are also available in a 51-way size similar to the EZMP8-453.

I should have a look at the VM boards; one of the wholesalers near me had one on display. Removing & reinstalling the cover on the Trical boards is truly truly awful.

Catalogues for reference:

https://www.trical.co.nz/wp-content/uploads/2020/07/Trical-Product-Price-Guide-2020.pdf

https://www.vynco.co.nz/application/files/6215/9813/8739/PUB0117_VM_Series_Brochure_A4_4pp_Aug20_v6_WEB.pdf

mclean

581 posts

Ultimate Geek

Subscriber

#2611584 27-Nov-2020 09:59

In many older houses the enclosure is big and deep enough that you can leave the existing metering in place, remove the old distribution components and simply install a new surface-mount consumer unit within the enclosure. Can be a lot less cost/stuffing around.