Search the forum,

Discuss Change a old garage fuse board / Earthing question... pic s attached in the Australia area at ElectriciansForums.net

S

srl-8

Hey,

I am looking to change a very old fuse box in my garage. I have attached pics for you all.
I am on route to becomeing a Domestic installer, and hoped i could get some more good advice if poss.

This old fuse box, is supplied from the main house Cu. It is on a 32A breaker. The Main Cu is protected by RCD.

The supply enters the garage from below ground in what looks like armoured cable. (see pic). I would like to change this to a small modern 3 or 4 way Cu, obiously with RCD. I will run a new radial & lighting circuit from the new Cu.

Question, I cannot identify a incomming earth ? All I can see is the Live and Neutral from the end of the Armoured Cable. Is this normal? The old metal box is earthed to a old copper pipe.. but cannot see a route back to the house main earth block?

What are my options here? Am I right to assume I either run a 10mm earth all the way from the garage back to the house Cu, Or install a earthing rod more local to the garage supply ?

I am still learning, so all advice or sugestions very welcome.

ps: Providing I am not running any large or abnormal loads from the garage, this supply from the house (on a 32a MCB) is suitable. I would only ever be plugging in the odd power tool, or running 2 light bulbs.. etc

Thanks!!


:stooge_curly:
 

Attachments

  • Garage DB.jpg
    101.8 KB · Views: 134
  • Garage Db1.jpg
    227.3 KB · Views: 118
  • Garage DB2.jpg
    64.9 KB · Views: 112
The original install could be using the armour for the earthing, check the CU in the house for a connection between armour and earth or maybe earthing via the copper pipe which is non compliant. If that pipe is unused you could get rid of it completely or you will need to bond it either to the house CU with 10mm or TT the garage board and then you could bond it to that. Thats a budget constraint, how far is the garage from the house?
 
The garage is detached and is approx 25 meters from the main house DB .

So If i prove that the armor is used as the earth, does that mean i would connect the steal armor wires to the earth block in the new garage Cu ?

Failing that, is a earth rod for the garage Cu acceptable ?

Cheers
 
you need to get Zdb at the garage CU with that lead to the pipe disconnected.( assuming the SWA armour is used.). no need for RCD in garage unless you feed the SWA independently of the house RCD. As you will be using a plastic CU, you will need to fit a banjo to the SWA gland and lug a fly lead off to your earth terminal.
 
The earthing looks to be TN-C-S.

If i cannot proove that the SWA is connected to earth, is it best practice to use throw in a earthing rod for the garage cu.
 
Either through the rcd at the house board or rcd at the garage not both as you want discrimination: you could run it of a breaker at the house supply and rcd it at the garage board. this way if it trips you dont have to go all the way back to the house to reset it and dont forget if something in the garage trips the rcd in the house board.....you will lose all circuits fed through that rcd......
 
or R1+R2, with the SWA dissed. and L/armour shorted at 1 end.
 
Thanks guys,

So to confirm, The Main house DB is RCD protected. So you are saying that there is no need to fit a RCD cu at the garage end?

If I can prove the earth is attached to the house MET via the armor, then I just use a banjo glad and fly lead as mentioned above and connect to the Garage MET.

If no earth returns to the house , then a earth rod would be suitable...

Sound ok ??
 
The earthing looks to be TN-C-S.

If i cannot proove that the SWA is connected to earth, is it best practice to use throw in a earthing rod for the garage cu.

The armour must be connected to earth at the house end whether it's the earthing or not to provide protection.

My preference for remote buildings is a TT system but you would have to ensure that the armour and gland are inaccessible in the garage, I do this by using a PVC gland and cleating the cable tightly underneath it.
 
Thanks guys,

So to confirm, The Main house DB is RCD protected. So you are saying that there is no need to fit a RCD cu at the garage end?

If I can prove the earth is attached to the house MET via the armor, then I just use a banjo glad and fly lead as mentioned above and connect to the Garage MET.

If no earth returns to the house , then a earth rod would be suitable...

Sound ok ??

sounds good to me. best practice would be to have the RCD at the garage end so as a fault in the garage will not affect the house installation. this , however would mean feeding the SWA independent of the house RCD, as you don't want 2 RCDs on the same circuit. either one or both will trip in the event of a fault.
 
The earthing looks to be TN-C-S.

If i cannot proove that the SWA is connected to earth, is it best practice to use throw in a earthing rod for the garage cu.


You don't seem too sure what the earthing arrangement is in your house, ...As your still training, ...Be ''SURE'' what arrangement you have, before you start any work on your garage!!!

A. TN-S Earthing normally taken directly from the DNO cables armoring/lead sheath into the MET.

B. TNC-S earthing normally derived from DNOs neutral conductor at the cut out box, then into the MET.

C. TT earthing normally via a a separate earth conductor directly into the MET. (often disappearing without trace, and often with no earth rod pit in the garden)
 
Last edited by a moderator:
I have noticed the gas meter is actually only 2 meters from the new proposed installation. The gas has the 10mm cpc running back to the main MET in the house. Is it alright to connect to this from my new garage board earth.

I think this is, as I have identified a path back to the main earth block...?
 
spinlondon is agreeing with malcolm, methinks.
 
You will have to confirm that the 10mm bonding conductor to the gas will be capable of carrying the fault currents of a combined Bonding/CPC conductor.

But you have what looks like a perfectly good SWA there, so as posted either do an R2 on the SWA armour or an R1+R2 and see what you have.
 
i'd be inclined to rely on the armour for your main earthing and use the 10mm as an additional parallel main earth.
 
No I am disagreeing with Malcolm.
There is no reason why a conductor cannot both be a CPC and a bonding conductor.
I would personaly rather use the armour as a CPC for the SWA, as that is what it is intended for.
However there is nothing preventing the use of a supplementary conductor, such as the gas bond.
I note from the pictures, that there is a copper pipe whith an earth connection.
What is this pipe for, and is it suitable to be used as a conductor?
 
The old pipe is a disused/empty copper water pipe, that enters back into the main house. I would imagine, this is bonded at some point and also would offer a path back to to MET. ?? I can see that this was used as a bond at some point in the past.

??
 
It appears you have a number of options, use the armour, use the gas bond (if the SWA conductors are 10mm²), use the old water pipe, or a combination of the three.
As there are extraneous-conductive-parts that are bonded back to the house MET, making the garage TT is not really an option.
 
agreed. better than dissociating the garage from the house, as the zone is already extended by the 10mm cable and the disused water pipe.
 
Last edited:
The fact that the old water pipe, the gas and the SWA are all earthed/bonded, would suggest that the equipotential zone is already extended, and judging from the pictures, has been for some time.
Attempting to isolate and separate the zone would IMHO be a nightmare.
 
It looks like the live and neutral are about 2.5mm coming through the amor cable. what did you mean by..

"use the gas bond (if the SWA conductors are 10mm²), " ?
 
you can't have undersized earthing and/or bonding conductors, but i've never known an installation not to comply with oversized ones.
 
Hi,

I just wrote a thread concerning this problem. The earth from the house should never be run to the garage. Lets assume that during digging you accidently went through the SWA cable. You would receive a severe shock because you are actually in contact with the earth and providing a lovely path to earth. The garage should always be earthed using the TT arrangement consisting of earth rods. So 2 wires from house to garage is correct, with the earth supplied from earth rods. Building sites use equipment supplied by sepearted supplies ( a transformer) where no earth is used for safety. Hope this helps.

Regards,

Bill
 
The armour of SWA is designed, so that if the cable is penetrated by a metallic object, the armour will provide the earth path.
Why would someone connect the armour to an unreliable high resistance earthing point such as an earth rod, as opposed to a reliable low resistance earthing point such as would be supplied with a TN system.
As for the reference to building site supplies, is the supply to the shed, separated?
 
when i read threads created by domestic installers who havent got a clue about what theyre saying it makes me want to retrain to be something else, what a bummer that the system is allowing these courses be accepted and these cowboys let loose when REAL sparks sit a 4-5 apprenticeship it does my head in! well id like to see them try and get on a building site anyway whoops gutted because your not sparks haha
 
Stansmith, firstly what a stupid responce you have just posted. A domestic installer, (when fully trained/assesed and certified by one of the approved bodies, eicnic, elecsa, napit etc) is more than capable of carring out electrical work within their scope.

If i knew 'everything' i wouldn't be on here asking questions. I am learning, and at no point do i consider myself to compete with fully trained and time served sparks. However, we all (even you at somepoint) has to start somewhere.


Most persons on this site have been extreamly helpfull, and I have learn alot from them. I guess I wont be learning anything useful from you.

Lastly, If i wanted to get a job on a building site, it would be quite easy. I would approach the contractor as an electricans mate, to gain experience and only when I was fully confindent, I would then take on greater responsibilities.

Anyway, sorry that you think people like me are cowboys, nor we dont have a clue. I have to disagree with your opinions.

All the best

S




when i read threads created by domestic installers who havent got a clue about what theyre saying it makes me want to retrain to be something else, what a bummer that the system is allowing these courses be accepted and these cowboys let loose when REAL sparks sit a 4-5 apprenticeship it does my head in! well id like to see them try and get on a building site anyway whoops gutted because your not sparks haha
 
Srl-8 the line through stansmith's name indicates that he has been banned.
It was decided that he was notreally the kind of person we want as a member of the forum.
He may if he want's read your post, but he won't be able to respond.
 
S8 while sometimes the "time served" guy can get a little vocal over this I think what E54 wrote about the Domestic installer, was not the guys themselves but the training centres is spot on and I have to agree.

Unfortunately in today's world the old tried and trusted method of training in now a rarity due to costs etc and sometimes the only way into the industry is through perhaps not perfect training. what is a concern to most "time served guys" is that the DI is actually still learning the basics and making what could be very very serious mistakes due to inexperience.

The time served guy was lucky that even nearing the end of an apprenticeship he would still be under the wing of an experienced electrician, and mistakes that were made were picked up and learnt from, unfortunately the DI does not have this luxury and that is the bottom line really.
 
I agree with your comments malcolm, it is a concern for me aswell, but this is the route that the government have deemed to be acceptable. I personally think the short course does not prepare you anywhere near enough, but it does give you the building blocks to continue.


With the power of the internet, books, and forums like these, there isnt much you cant find out.

I would love to have a experience sparks look over my shoulder for 5 years, but that is just not available to me, or lots of other budding electricans.

We can only but try are best, and fingers crossed.. We reach own goal.
 

Reply to Change a old garage fuse board / Earthing question... pic s attached in the Australia area at ElectriciansForums.net

Similar Threads

Hi, Just a quick sanity check really around rcbo discrimination.. but also RCDs being used as L-E fault protection. Scenario being a garage...
Replies
8
Views
237
I want to make some electrical upgrades to my detached garage. I want to update the subpanel in the detached garage, and I want to add a 240V...
Replies
3
Views
768
Hi fellow sparks, I've just started out on my own so I'm spending a lot of my time trying to find out the correct way of doing things of...
Replies
13
Views
978
I have a detached garage with a 60 AMP subpanel which has lost power. I traced the failure to the wire running under the walkway via conduit...
Replies
3
Views
809
Hi all, I am looking for some advice regarding old rewireable (3036) fuse boards in regards to additions and alterations. I am an electrician and...
Replies
28
Views
4K

OFFICIAL SPONSORS

Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Electrical Goods - Electrical Tools - Brand Names Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc

YOUR Unread Posts

This website was designed, optimised and is hosted by untold.media Operating under the name Untold Media since 2001.
Back
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock