Hi guys, new member here needing advice on workshop wiring.

[Martin Turner]

Hi guys, new guy here and may need some help with my new home workshop wiring.

I currently work on crane's and straddle carriers so have a mechanical and electrical knowledge on drive's, motors, PLC controls etc.

Also I still have my Gas Safe running and I am still on the Worcester WAI scheme so have a knowledge on heating system and control wiring.

 

[westward10]

Hello Martin feel free to ask away.

 

[Octopus]

Welcome. Get your tin hat ready!

 

[Pete999]

Welcome Martin

 

[Pete999]

What exactly would you like to ask regarding your workshop electrical installation, an idea of the size ans what applications you intend using would be a good starting place, along with what you have already with regards to electrics.

 

[The Ghost]

He did say he may need some help, not that he does. He's probably far too busy wiring it up right now to be bothered with this forum.

 

[Pete999]

He did say he may need some help, not that he does. He's probably far too busy wiring it up right now to be bothered with this forum.

A heads up on progress would be nice.

 

[Martin Turner]

Thanks for the warm welcome guys.

I haven't started yet as today I am on shift at Southampton docks.

Long story short I have a split two way board in our house and the existing 10 mm that did our shower via a 40A MCB was done away with a few years ago but I left it in the loft to feed a future workshop.
The attached work shop it now built down the side of our house and the 10mm is now in there ready to progress with.

The questions:-

1. As this cable is already protected by a 30ma RCD would you just fit a board in the workshop with just a main switch and MCB's?.

2. As above but fit a RCD protected board in the workshop but then you would have two RCD's in parallel?.

3. Remove the 40A MCB from my house board and fit onto the non protected side a 40A RCBO, this would stop the house tripping if the workshop trips.
This would be a harder option though as the previous owners boxed in our consumer unit so you can only open the door at the moment.

In the workshop:-

Lighting
32A ring for sockets
1X 16A socket
1X 32A socket

Thanks in advance.

 

[Pete999]

Wire the 10mm2 onto a non RCD protected CB in the house CU and fit a garage CU in the workshop complete with RCD protection and CBs for circuit protection, this would limit any earth fault tripping to the workshop and alleviate any trips into the house to reset an RCD. In my opinion

 

[Wilko]

Hi Martin and Welcome to the Forum !

 

[westward10]

Wire the 10mm2 onto a non RCD protected CB in the house CU and fit a garage CU in the workshop complete with RCD protection and CBs for circuit protection, this would limit any earth fault tripping to the workshop and alleviate any trips into the house to reset an RCD. In my opinion

Unless the 10.0 requires additional rcd protection.

 

[Martin Turner]

Thanks for the advice, I could do it that way but the 10mm wouldn't be protected between the two boards if it's fed from the non protected side. It would probably be ok though as the only part of the cable you can get at is where it runs across my loft of our house and then through the wall into the workshop.

 

[westward10]

If any part of it is buried in a wall at a depth of less than 50mm and without earthed containment it requires additional rcd protection. If this is not the case and fault protection can be maintained without the use of an rcd then you can omit rcd protection.

 

[Martin Turner]

The original 10mm shower feed goes from the CB, through the wall to the outside and then in black plastic conduit up the wall and then back into my loft space.
Clipped through the loft and then did drop originally into a shower isolation point, this has been disconnected and run into the workshop.

 

[Pete999]

The original 10mm shower feed goes from the CB, through the wall to the outside and then in black plastic conduit up the wall and then back into my loft space.
Clipped through the loft and then did drop originally into a shower isolation point, this has been disconnected and run into the workshop.

Any joint between CU in the house and the workshop?

 

[adamgaskin]

without seeing what condition the 10mm cable is in and wether any of it is showing on it's journey outside I would go with the harder option there and remove the mcb, fit a RCBO on the original board and then just use mcb's on the board in the workshop bearing in mind this work would be notifiable under part p and you would need an eic.

 

[Pete999]

without seeing what condition the 10mm cable is in and wether any of it is showing on it's journey outside I would go with the harder option there and remove the mcb, fit a RCBO on the original board and then just use mcb's on the board in the workshop bearing in mind this work would be notifiable under part p and you would need an eic.

Which ever way you did it.

 

[adamgaskin]

Yes sorry, I meant notifiable and needing certification either way

 

[Pete999]

Yes sorry, I meant notifiable and needing certification either way

We don't actually know the condition of the 10mm2 cable, has it been jointed in any way, has it been tested? Thing a bit deeper I would go along with your thoughts RCD at house C/U CBs in workshop, of course we also have to take into account any other services in the workshop that would need any supplementary bonding. Would that be a consideration? what do you think?

 

[adamgaskin]

No we don't, my above answer would be going with the assumption that the cable is unjointed and tests fine still. For me the supplementary bonding depends on what equipment he is planning on using in there and what installation method. If he runs the cables in any conduit/trunking then obviously I would bond that. I would also bond any metallic workbench he may have in there. I'm assuming that all equipment he uses will have it's own earthing connections. (Correct me if I'm wrong, I am still an improver)

 

[westward10]

It sounds as if the cable doesn't require additional rcd protection assuming fault protection is provided without it, joints or no joints. A metallic bench is not likely to require an earth and by supplementary bonding I assume you mean main protective bonding to any services if required.

 

[Martin Turner]

My house CB was changed and inspected Sep 2010 so the original 10mm cable would have been inspected then. There is going to be one join in the 10mm cable to add length to get it into the work shop but the original shower cable going through a shower isolator would have had two joins if you look at it like that.

All the cables in the workshop will be either clipped to roof joists, walls etc and then the drops in plastic conduit.

The bench may be used for TIG welding so I don't know how that would affect it if it was earthed?, I have worked in the rail and marine industry for a while and to be honest I have never seen work benches earthed before unless it's for high charged electrical/ static repairs etc.

We have a couple of sparks at work that may still be registered outside so I could get them to do a test and inspect once it's all done.

Thanks for the advice so far.

 

[Pete999]

It sounds as if the cable doesn't require additional rcd protection assuming fault protection is provided without it, joints or no joints. A metallic bench is not likely to require an earth and by supplementary bonding I assume you mean main protective bonding to any services if required.

No I mean supplementary bonding, if any water, gas, compressed air lines etc I would expect the main protective will already be in place, do well to check though.

 

[Martin Turner]

I can't remember seeing bonding at our stopcock but I know the gas is 10mm.
Only pipework in the workshop will be comp air via a fixed hose reel and that will probably be fed from the compressor in plastic.

 

[Pete999]

I can't remember seeing bonding at our stopcock but I know the gas is 10mm.
Only pipework in the workshop will be comp air via a fixed hose reel and that will probably be fed from the compressor in plastic.

The video will explain how to test to see if the air line requires bonding

 

[adamgaskin]

If the joint will be inside the building somewhere then you shouldn't really have an issue. Maybe I'm talking pish here but I was always taught to bond any large extraneous conductive parts i.e the bench as a bit of belt and braces. For example if the earthing on the welder fails then the next available fault path is through the bench into you. But then that being said if your using plastic conduit then there will be nothing to bond it to other than the welder supply or the next bit of equipment or a daisy chain back to the CU

 

[adamgaskin]

just watched that video, kinda answers my question to be honest cheers.

 

[Pete999]

If the joint will be inside the building somewhere then you shouldn't really have an issue. Maybe I'm talking pish here but I was always taught to bond any large extraneous conductive parts i.e the bench as a bit of belt and braces. For example if the earthing on the welder fails then the next available fault path is through the bench into you. But then that being said if your using plastic conduit then there will be nothing to bond it to other than the welder supply or the next bit of equipment or a daisy chain back to the CU

Have you tested any of the extraneous parts to determine if they rquire bonding?

 

[Martin Turner]

I will check my stop cocks as its on the same side of my house as the CB so I could run in a 10mm earth if required, the work bench will be wood and may have a sheet of metal at one end for welding, the only other fixed metal machines will be a small lathe and mill but they will be earthed through there isolators.

 

[Toneyz]

I don't know how we came onto the subject of running in 10mm earth cables into the workshop. You state that there is no pipework in the workshop the comp.air will probably be plastic and the workbench is wooden it is unlikely that the metal screen will be a extraneous conductive part. Regarding bonding what needs to be checked is the existing services (gas & water) are bonded this you could do visually and check with the electrical contractor who issued the certificate when you had the consumer unit changed this should of been inspected and tested at this time. Also can the existing installation take this additional load. I f the existing cable is all run surface I would move onto non protected side and install a RCD main switch consumer unit in the workshop. Make sure that the cable in the loft is clipped above the insulation so it does not have to be de-rated.

 

[westward10]

Pesky rats.

 

[Toneyz]

Pesky rats.

The OP didn't say he had a rodent problem.

 

[westward10]

The OP didn't say he had a rodent problem.

Avin a jest see the last word of your post

 

[Toneyz]

Avin a jest see the last word of your post

Very good well spotted.

 

[Martin Turner]

I didn't write that clearly in my previous post about the 10mm Earth, I meant to my stop
cock.

The original installation should be ok as the original shower had this 40A supply and the max rated socket in the workshop will now be only 32A, this socket may never get used anyway as my current TIG welder uses a 16A supply but if I ever upgrade the welder I may buy a 32A water cooled TIG next hence the reason I want this socket.

Some of you have said put the 10mm supply cable on the non protected side of my house CB and fit a RCD/MCB CB in my workshop but then the supply cable between both CB's won't be RCD protected?, does it need RCD protecting in my loft?.
I appreciate you won't get any nuisance tripping of the house if it's wired this way as the RCD will be in the workshop.

 

[westward10]

See #13 as rcd protection may not be necessary.

 

[Martin Turner]

This is your post:-

If any part of it is buried in a wall at a depth of less than 50mm and without earthed containment it requires additional rcd protection. If this is not the case and fault protection can be maintained without the use of an rcd then you can omit rcd protection.

Mine is run up the outside wall in plastic conduit and clipped through my loft space so needs RCD protection then ?

 

[Toneyz]

This is your post:-

If any part of it is buried in a wall at a depth of less than 50mm and without earthed containment it requires additional rcd protection. If this is not the case and fault protection can be maintained without the use of an rcd then you can omit rcd protection.

Mine is run up the outside wall in plastic conduit and clipped through my loft space so needs RCD protection then ?

From what you describe no. Where does it go from the loft straight through into this new workshop roof ?.

 

[westward10]

From what you say it doesn't but your earthing system will be a factor and if not TT, which would require an rcd for fault protection then a test is required to ensure an mcb without rcd protection would provide fault protection.

 

[Martin Turner]

I will check my earthing type but I think it's either TNS or TNCS.
Regarding the 10mm cable it runs through my loft space and where it connected to the original shower isolator it will be now going into a junction box and connecting to a black round double insulated 10mm 3 core cable that runs to the workshop.
As my workshop is only 3.4M the black 10mm will be dropped through my soffit and clipped to the house wall for approx 1.5M's before it goes into the workshop.

 

[Pete999]

I will check my earthing type but I think it's either TNS or TNCS.
Regarding the 10mm cable it runs through my loft space and where it connected to the original shower isolator it will be now going into a junction box and connecting to a black round double insulated 10mm 3 core cable that runs to the workshop.
As my workshop is only 3.4M the black 10mm will be dropped through my soffit and clipped to the house wall for approx 1.5M's before it goes into the workshop.

Where will you be putting the JB, Will it be MF, why use 10mm2 flexible cable, never seen double insulated cable, seen cable that is insulated with a PVC outer sheath though.

 

[westward10]

Won't need to be MF in a loft space.

 

[Pete999]

Won't need to be MF in a loft space.

Maybe not, but wouldn't fancy crawling about in all that fiber glass to check a JB with 10mm2 cables better MF imo but as you say not required.

 

[Toneyz]

I will check my earthing type but I think it's either TNS or TNCS.
Regarding the 10mm cable it runs through my loft space and where it connected to the original shower isolator it will be now going into a junction box and connecting to a black round double insulated 10mm 3 core cable that runs to the workshop.
As my workshop is only 3.4M the black 10mm will be dropped through my soffit and clipped to the house wall for approx 1.5M's before it goes into the workshop.

This is not swa cable is it ?.Not sure what you are using as a junction box that would be rated 40A+ or will take 10mm cable outer sheath included.

 

[westward10]

You can get 40A+ Wiska boxes.

 

[Martin Turner]

I have just had a look and we have a PME TNCS system.

The 10mm round cable is just 3 core with a PVC outer so sorry I called it double insulated.
The cranes and straddle carriers I work on usually use this type of cable on motors and heavy draw equipment and PVC singles in trunking for PLC/ control gear etc.

The junction box I was going to use is like this one:-
Click 60A Junction Box 3 Terminal (WA222) - https://www.electrical2go.co.uk/60a-junction-box-3-terminal-i-brown.html?utm_source=google_shopping&gclid=EAIaIQobChMImPSovvzU1QIVbL7tCh0zbwVpEAQYByABEgIrA_D_BwE

 

[Toneyz]

I have just had a look and we have a PME TNCS system.

The 10mm round cable is just 3 core with a PVC outer so sorry I called it double insulated.
The cranes and straddle carriers I work on usually use this type of cable on motors and heavy draw equipment and PVC singles in trunking for PLC/ control gear etc.

The junction box I was going to use is like this one:-
Click 60A Junction Box 3 Terminal (WA222) - https://www.electrical2go.co.uk/60a-junction-box-3-terminal-i-brown.html?utm_source=google_shopping&gclid=EAIaIQobChMImPSovvzU1QIVbL7tCh0zbwVpEAQYByABEgIrA_D_BwE

Can't see anything wrong with that screw it a good foot up on one of the roof trusses so it don't get trodden on & as said try to get cable above roof insulation so not to de-rate.