Maximising 10mm SWA to garage CU.

[sparkysy]

No one will sign it off with mixed manufacturers installed in a fuseboard.
Either split the tails into a switch fuse or.
Do as you originally stated, but 10mm swa is only rated at max 60a ref method D so I would say typeC 50a MCB in the house fuseboard and then go all RCBO in the garage fuseboard same as the house, they are not expensive and will stop everything going off if one thing developed a fault.

 

[MattH]

No one will sign it off with mixed manufacturers installed in a fuseboard.
Either split the tails into a switch fuse or.
Do as you originally stated, but 10mm swa is only rated at max 60a ref method D so I would say typeC 50a MCB in the house fuseboard and then go all RCBO in the garage fuseboard same as the house, they are not expensive and will stop everything going off if one thing developed a fault.

Where are you getting 60A?

Every chart I’ve looked at says 71A for 10mm 2 core method D.

 

[sparkysy]

Where are you getting 60A?

Every chart I’ve looked at says 71A for 10mm 2 core method D.

From the book of books 4D4A. are you looking at the table for XPLE cables 4E4A per chance?

 

[MattH]

From the book of books 4D4A. are you looking at the table for XPLE cables 4E4A per chance?

Yes, I’ll need to check the sheath to see which one is installed.

 

[mtt.tr]

What's the earth arrangement?

Confirm disconnection time for distribution circuit this night influence wether it's type b or c or you might need a time delayed rcd, as new I'd expect pme so easily made

Confirm installation method for highest current capacity
Confirm volt drop

 

[dobbslc]

From the book of books 4D4A. are you looking at the table for XPLE cables 4E4A per chance?

Yes worth checking, We use XLPE so has a higher rating.

 

[Robotstar5]

Yes worth checking, We use XLPE so has a higher rating.

Does anyone use PVC these days?

 

[mike os]

Do you actually need the extra capacity?

I can run my compressor and plasma togetheroff a 20a, mig and tig up to 200a has never tripped in 18 years

 

[MattH]

What's the earth arrangement?

Confirm disconnection time for distribution circuit this night influence wether it's type b or c or you might need a time delayed rcd, as new I'd expect pme so easily made

Confirm installation method for highest current capacity
Confirm volt drop

Earth is the armour on the cable.
I’ll need to check the earth arrangement on the supply.
Installation is D and the run is less than 10m so voltage drop even at XLPE current spec of 71A is still within limits.

 

[AVI_8]

Hind sight is great when it comes to things like cable runs isn’t it, I had a similar question here after running a 10mm SWA to my workshop a few years ago, spark told me a 45a RCBO was the highest rating I could get due to the run, so far I’ve not had any issues with that, I can simultaneously start 2 x 3hp compressors at the same time and it doesn’t trip, if it did I was going to put a higher capacity one in its place just to cope with the start up current but so far that’s not been needed.

 

[MattH]

Do you actually need the extra capacity?

I can run my compressor and plasma togetheroff a 20a, mig and tig up to 200a has never tripped in 18 years

It’s a good question.

I will be running my CNC mill, it’s probably pulling 15a continuously whilst running but it has a 7.5KW 220v 1ph - 380v 3ph dual stage vfd, this pulls a lot of start up current.
There will also be a CNC router running with a 2.2kw side channel blower and a 2hp extractor.
Plus various other bits.

Better to have it and not need it than the other way around.

 

[dobbslc]

That lot might by tight on a 30ma RCBO/RCD.

 

[MattH]

That lot might by tight on a 30ma RCBO/RCD.

Yep, lots of vfd’s and servo drivers, industrial stuff can have fairly high leakage.
I personally feel that an MCB in the house and RCBO’s in the garage CU would be better. The Mill and the Router would have their own circuits so would get 30mA each.

 

[dobbslc]

Mmm! Just the plasma and router/blower at over 9kw will draw over 40 amps.
What size is the main cut out fuse?

 

[MattH]

Mmm! Just the plasma and router/blower at over 9kw will draw over 40 amps.
What size is the main cut out fuse?

Probably wouldn’t run the mill and router at the same time because of this.
I’m presuming the incomer is 100A but it might not be.

I’m looking at adding 8kwp of solar plus 10kwh of batteries and an 8kw Sunsynk hybrid inverter, this unit can output the full 8kw from either the PV, or batts, or both combined. It can also load shave so it could assist the grid in supplying all my gear. That’s for another thread lol, and pending G99 approval.

 

[Dave-sparks]

Yes, I’ll need to check the sheath to see which one is installed.

You can only use the current rating for 90 degree operating temperature of the terminals that the cable is to be connected to are rated for a 90 degree operating temperature.
At the moment, with it connected to standard 70 degree terminals, you need to use the 70 degree current ratings.

 

[MetalMonkey]

If you are intending on pulling that much power, I'd think splitting the tails and taking a feed directly to the workshop with local RCD protection would be a better overall solution and will keep the house completely independent.
Otherwise stick to the 50A MCB and RCBO sub board as suggested. Either way, you want the RCD protection in the workshop really.

 

[sparkysy]

As @mtt.tr says check your maximum Zs for the circuit, it may be tight on a 60a!
And as @Dave-sparks says you can only use the 90deg if the equipment is rated for 90deg.

 

[MattH]

Yep, saw the temp rating after digging a little about the terminals last night.

I think the 50a MCB will be fine. Splitting the tails would be the best option but I need to get it up and running ASAP and at the moment it’s got a 45a feed sorted and tested.

 

[dobbslc]

Max Zs for 50 amp MCB's in my 18.2 edition pocket guide is,
B type 0.73 ohms.
C type 0.36 ohms.

63 amp,
B type 0.58 ohms.
C type 0.29 ohms.
See if you can get the test results off the sparks.