32amp supply OK vs 16?

[Robotstar5]

Thanks for that it sort of validates my suggestion above- aka I could create this same scenario but hard wired into my garage. 32amp breaker and 6mm supply from main garage to back garage. Where that cable comes in at ceiling level fit a small dual MCB wall breaker. And 16 + 32amp cables / supplies off that.

Best of both worlds(?)

View attachment 381966

If you use the unit you've shown the house RCD may still trip under fault conditions due to both RCD's rated at 30mA (discrimination)

 

[Turbo]

And regarding RCD's, not a good idea to have more than 1 30ma rcd in the same circuit. If there's a fault in the workshop it could knock out any RCD, including the house!
It can be done by taking the feed from the main fusebox before the house rcd, wire it through a 100ma rcd, then down the 6mm cable to your garage consumer unit then through a 30ma rcd.

 

[dobbslc]

If you use the unit you've shown the house RCD may still trip under fault conditions due to both RCD's rated at 30mA (discrimination)

Yes not enough discrimination! I can hear the snowflakes coming already

 

[Robotstar5]

And regarding RCD's, not a good idea to have more than 1 30ma rcd in the same circuit. If there's a fault in the workshop it could knock out any RCD, including the house!
It can be done by taking the feed from the main fusebox before the house rcd, wire it through a 100ma rcd, then down the 6mm cable to your garage consumer unit then through a 30ma rcd.

I took the easier route of installing a high integrity CU in the house (it was due to be changed anyway) and fed my workshop from a non-RCD protected MCB, then SWA to an RCD protected CU in the workshop

 

[JOEPRO]

I took the easier route of installing a high integrity CU in the house (it was due to be changed anyway) and fed my workshop from a non-RCD protected MCB, then SWA to an RCD protected CU in the workshop

View attachment 381984

View attachment 381985

My house has 2no consumer units. Inside they are both split half and half. So I can use a non RCD protected outlet from the main Garage AOK. Just MCB there then into am RCD protected board does that sound OK to all?

I regret creating 2x threads now - but ill post the diagram now in the socket location thread! Thanks for all the help I am taking it on board! (Pun intented)

 

[Turbo]

I took the easier route of installing a high integrity CU in the house (it was due to be changed anyway) and fed my workshop from a non-RCD protected MCB, then SWA to an RCD protected CU in the workshop

View attachment 381984

View attachment 381985

Adding a 100ma rcd will give the building protection from fire if it gets damaged.

 

[JOEPRO]

This Is the main house board. I will take this new back garage supply from the right consumer as it has less on it.

There is half non RCD and half RCD protected so from above posts sounds like best go from non rcd side here then put an RCD and 16 / 32 MCBs within the new back garage consumer?

 

[Chippie]

That's a thing often misunderstood, you size the cable according to the max current draw & length of cable then select the correct fuse rating to protect the cable!

I thought that cable sizing was based on volt drop at max current/length of run? BS7671 tables?

 

[Turbo]

I thought that cable sizing was based on volt drop at max current/length of run? BS7671 tables?

That's what I said, just in a different way!

 

[Dave-sparks]

I thought that cable sizing was based on volt drop at max current/length of run? BS7671 tables?

Cable size is based primarily on current carrying capacity.

Cable sizing is a process which takes into account many factors.
Generally you start with applying rating factors to the nominal current of the circuit to select a cable size for its current carrying capacity. Then you you calculate the volt drop to confirm whether that cable complies from the point of view and increase the cable size as required.
After this you calculate the predicted earth fault loop impedance and adjust as necessary.

 

[Pete.]

I sized my cable by finding a 30m roll of used armour on site and ran it up the garden

 

[Bornfree]

I sized my cable by finding a 30m roll of used armour on site and ran it up the garden

That's the way most of us do it. That 120mm takes some bending though.

 

[Robotstar5]

That's the way most of us do it. That 120mm takes some bending though.

But at least it's self-supporting across the 10 metre gap between the house and the workshop

 

[brightspark]

I sized my cable by finding a 30m roll of used armour on site and ran it up the garden

my garage is fed using 35mm swa scored a 25 meter length free so that was the governing factor

 

[dobbslc]

I sized my cable by finding a 30m roll of used armour on site and ran it up the garden

Did the tower crane suddenly stop working?

 

[JOEPRO]

I asked Stahlwerk about the plasma and they came back with the attached. (Maybe this is a result of different countries but the slow blow fuse thing is not really possible here. I presume an RCD / MCD offers better protection anyway?)

 

[brightspark]

it uses a c type breaker . not called a slow blow it takes a higher inrush current before it trips

 

[JOEPRO]

I have put alot of thought into this and my planned uses. It think more than one 32 amp socket in my garage is a total waste. Spatially there is also so much stuff in my garage already, shelves etc that I don't have a spot for a second big socket on the wall!

I will only be using the welder / plasma once or twice a year for a few days at a time. Therefore I can easily work with a suitable trailing cable from one switched 32Amp outlet near the roller door. (So I can also use the heavy consuming tools outside with the lead)

If I ever do need to use a 16 amp product I can use the adopter lead with 16amp trip inbuilt. But I don't see me having additional equipment until my garage extension is done which is a full rewire anyway.

 

[Pete.]

my garage is fed using 35mm swa scored a 25 meter length free so that was the governing factor

Got me wondering now what size my cable actually is. All I know is that it's SWA and about 15.5mm diameter across the black outer sheath.

 

[Dave-sparks]

Got me wondering now what size my cable actually is. All I know is that it's SWA and about 15.5mm diameter across the black outer sheath.

It can vary between manufacturers but the nearest to that on the data sheets I have to hand is 4mm 3 core at 15.3mm overall diameter.