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101 posts

Master Geek


# 260152 13-Nov-2019 13:00
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Hi,

 

Looking for some advise from any Sparkies or people in the know here.

 

Yes - I know, fuse boxes are for registered people only, etc, however I am just looking for information. Assume I am not touching or modifying anything please.

 

So we have a beach house which dates back to the 1940's or so.

 

Inside the house is a classic hard board 'door' with the ceramic fuses and main switch on it.

 

Inside the garage which is a separate building located say 15m from the house, is a small main switch with 2 ceramic fuses inside, one for lighting and one for power points.

 

The cable going from the house to the garage is marked on the plans (old hand drawing), and looks to be 4mm TPS 2C+E cable at a guess, its larger than the 2.5mm for the power points.

 

Inside the house behind the hardboard door, its a bit of a birds nest. However there is a single Earth Bar which also has the Neutrals on it. MAN link of sorts I guess.

 

The cable running to the garage is on a 20A fuse, which I am guessing is well under sized for what it could be, but is fine for its current application. It can clearly be seen the Earth and Neutral for this cable to the garage are on the same Bar, ie they are joined together.

 

Inside the garage inside the main switch out there, are 2 little bars, one for Earth and one for Neutral. These also are linked together. Again the cable coming from the house can clearly be seen that the Earth and Neutral are connected together via this MAN link between the 2 little bars.

 

My question is, is this typical?

 

I understand the concept of if there is a neutral fault or earth fault to phase, and how the power needs to get back to the circuit breaker neutral to trip it etc. But is it strange to have the Earth and Neutral connected together in both locations? From what I have read on this forum, and others, is it is very case-by-case. I do not believe there is any earth stake located at the garage, but there is one on the house obviously. The Earth is going down the TPS cable only.

 

We are looking to convert the garage into a sleepout, as the family is growing and there is not enough room for longer stays. While doing this, I would like to stay up to code and have RCD's installed. I will get someone to come and do this work in the fuse boxes, but I am just wanting information before I do anything. Will there be any issues with the RCD setup if the MAN links are present in both locations?

 

With the 20A fuse in the house which then powers the cable to the shed, it would seem to me a good idea to have a main switch in the shed, then an RCD, which then feeds to next circuit breakers for power points and lighting.

 

Eventually it would be nice to have the house fuse box tidied up, and an RCD added there. Again, will the dual MAN links in both locations cause problems here?

 

The Sparky who does this work will just get on and sort it im sure, but for my own knowledge it would be great to know if how it is is OK for the current setup, and if how it is will also be OK when RCD's are added.

 

Thanks and sorry for the long post.


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101 posts

Master Geek


  # 2352806 13-Nov-2019 15:13
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Bah - Should have read 'MEN' not 'MAN' above.


4243 posts

Uber Geek


  # 2352813 13-Nov-2019 15:37
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I'm pretty sure you cannot get plug in RCD units for old ceramic fuse bases,

 

They will likely have to install a box with a modern common busbar rail...

 

You could just look at protecting each socket  in the garage with a new RCD enable outlet, but probably best to get it done right and replace the old fusebox...


 
 
 
 




101 posts

Master Geek


  # 2352839 13-Nov-2019 16:32
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wellygary:

 

I'm pretty sure you cannot get plug in RCD units for old ceramic fuse bases,

 

They will likely have to install a box with a modern common busbar rail...

 

You could just look at protecting each socket  in the garage with a new RCD enable outlet, but probably best to get it done right and replace the old fusebox...

 

 

 

 

Yes, 100%, the plug on ones are only MCB's, the RCD's have Neutral too.

 

When/if the RCD's get installed we will have the whole box upgraded to the busbar rail / DIN rail type etc.

 

Thanks

 

 

 

My main question really was around the MEN links between Earth and Neutral in both locations, and if the Garage really shouldn't have the MEN link present, given its earth is via the TPS cable to the house main switchboard.

 

Hopefully someone will be able to point this out.

 

 


497 posts

Ultimate Geek


  # 2352877 13-Nov-2019 18:24
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My main question really was around the MEN links between Earth and Neutral in both locations, and if the Garage really shouldn't have the MEN link present, given its earth is via the TPS cable to the house main switchboard.

 

Hopefully someone will be able to point this out.

 

 

The MEN Links will cause an issue. But the sparky should alter this to suit.

 

If he was to install and RCBO to feed the shed, he would then need to remove the MEN link for sure.

 

The MEN link at the Main DB Must remain intact and the RCD's will be fed Downstream from The main MEN link.

 

The only time the Garage needs the MEN link is if there is an independent earth pin at the garage.


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  # 2352880 13-Nov-2019 18:56
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  # 2352882 13-Nov-2019 19:00
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My sparky told me that because of some change in the rules I will probably have to put a seperate earth peg in on the outbuildings when (if?) I get around to upgrading the supply here. At the moment there is no MEN link in either the garage or the shed, and they go to the appropriate bars in the house board, not both to the same one. No idea if that is all legit or not as there have been many dodgey things uncovered here with the old 80s/90s wiring, but the solar installers were happy enough with the replacement board in the garage that I had done.





Richard rich.ms



101 posts

Master Geek


  # 2352884 13-Nov-2019 19:01
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sparkz25:


My main question really was around the MEN links between Earth and Neutral in both locations, and if the Garage really shouldn't have the MEN link present, given its earth is via the TPS cable to the house main switchboard.


Hopefully someone will be able to point this out.



The MEN Links will cause an issue. But the sparky should alter this to suit.


If he was to install and RCBO to feed the shed, he would then need to remove the MEN link for sure.


The MEN link at the Main DB Must remain intact and the RCD's will be fed Downstream from The main MEN link.


The only time the Garage needs the MEN link is if there is an independent earth pin at the garage.



Perfect thank you.

So hypothetically if the house received a RCD to protect all house things except for the hot water cylinder, and the CB feeding the garage, so the RCD at the house was just for pointpoints and lighting... and then the garage received an RCD protecting its powerpoints and lights, would both MEN links then be ok as is?

It makes sense if the house RCD then also fed the garage then the garage MEN would be a problem. But how about the above?

Thanks

 
 
 
 


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  # 2352897 13-Nov-2019 19:06
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There is some upcoming change (may have happened in NZ now) about _all_ circuits needing to be RCD protected. I was hoping to get my supply and panel upgrade in before that happened but no way its happening till some other major expenses are dealt with, and I dont think I will hit the 5kw limit vector have on solar before the house is reroofed so no urgancy on the supply upgrade for now.

 

But feedback from AU where it is now a requirement is that there are lots more hot water faults happening now that RCDs will trip at the first sign of a failing element rather than keep going for years with massive leakage happening.





Richard rich.ms

497 posts

Ultimate Geek


  # 2352964 13-Nov-2019 20:13
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Perfect thank you.

So hypothetically if the house received a RCD to protect all house things except for the hot water cylinder, and the CB feeding the garage, so the RCD at the house was just for pointpoints and lighting... and then the garage received an RCD protecting its powerpoints and lights, would both MEN links then be ok as is?

It makes sense if the house RCD then also fed the garage then the garage MEN would be a problem. But how about the above?

Thanks

 

 

 

Firstly you need more than one RCD in the house, as the new rule is to be no more than 3 MCB's per RCD.

 

The MEN link should only be in the main DB under today's rules as we no longer install linked boards, so that would mean that you have to remove the MEN link from the sub-board in the Garage.

 

In this image you can see that there is 3 RCD's and 3 MCB's per RCD, you can see the main Earth Bar and also the main Neutral bar underneath the little neutral bars in the highlighted area you can see the Bare MEN link, this must remain as this is the Main DB.

 

You would then Feed the RCD's their own Neutral from the Main Neutral Bar that has the MEN link attached and from the outgoing side of the RCD's you can feed one of the smaller Neutral Bars for your Sub circuits that are fed from that RCD.

 

And in the bottom left of the picture those 3 MCB's that are not RCD protected would e for as you say the Hot water, oven, hobs, and or a Sub board (garage)

 

Here is some information and where the pic is from.

 

http://www.zoneblue.nz/cms/page.php?view=ac-distribution




101 posts

Master Geek


  # 2352965 13-Nov-2019 20:21
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Thanks yes that makes perfect sense.
I oversimplified my house RCD suggestion. Yes multiple would be required as you said.

I think i have all i need now. Thanks very much.



101 posts

Master Geek


  # 2352966 13-Nov-2019 20:30
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dolsen:

 


This isn't a bad overview.


 


https://electricians-success-academy.com/learn/what-is-men-system



Sorry missed your post. Yes i have seen this before. Not a bad overview as you said. :)

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  # 2352994 13-Nov-2019 21:34
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probs need to consider that fuse board containing asbestos.   Some sparkies wont touch them, others will....and likely organize a replacement in a safe manner

 

 

 

 

 

 


510 posts

Ultimate Geek


  # 2352997 13-Nov-2019 21:45
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A sub board containing an earth conductor from the main switch board should NOT have an MEN link. There should ONLY be an MEN link if the outbuilding has it's own earth electrode - not physically run back to another switchboard. As in, if it had an independent earth electrode it should not have an earthing conductor connected to it from the main board. If there is not an earth electrode at the shed, then it must have the earthing conductor (min 4mm depending on mains, 4mm suffices up to 10mm - 1/3rd of largest active conductor or 4mm minimum is the rule) from the main board to the sub board (and NO MEN link in place at the sub board)




101 posts

Master Geek


  # 2353162 14-Nov-2019 10:44
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Goosey:

 

probs need to consider that fuse board containing asbestos.   Some sparkies wont touch them, others will....and likely organize a replacement in a safe manner

 

 

No asbestos, all fine in that regard.




101 posts

Master Geek


  # 2353163 14-Nov-2019 10:45
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snnet:

 

A sub board containing an earth conductor from the main switch board should NOT have an MEN link. There should ONLY be an MEN link if the outbuilding has it's own earth electrode - not physically run back to another switchboard. As in, if it had an independent earth electrode it should not have an earthing conductor connected to it from the main board. If there is not an earth electrode at the shed, then it must have the earthing conductor (min 4mm depending on mains, 4mm suffices up to 10mm - 1/3rd of largest active conductor or 4mm minimum is the rule) from the main board to the sub board (and NO MEN link in place at the sub board)

 

 

Thanks


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