Dis board in shed.

[Guest22]

Im going to install a small dis board in my shed, with a 25 RCBO 100ma feeding it from the main board, (2.5 T&E, then onto 2.5 3c SWA) the plan is to have on the board in the shed to have a 25A 30ma Main switch and 1x16A MCB, 2x1A MCB, 1x1A DP MCB, 1x2A MCB, this equating to 21A in total which i work the design current to be about 18.5A, On these circuits will be:
16A Radial, a few single metal clads for a laptop/PC that sort of stuff.
24V PSU, for a PLC
24V PSU, for control circuits
110V Tx for control circuits
2ft fluorescent
Other stuff I`ve forgotten, basically this all a bit of practice and a little project for myself. If any one can spot some regs ive over seen maybe, around the supply side of things.
I understand someone will say "Silly boy, slap a 32A breaker in with a 6mm armoured in" but i dont see the need really? apart from increasing the cost un-necessarily.
Questions and CONSTRUCTIVE criticism are welcome

Thank you
Ethan

 

[Richard Burns]

Somewhat unconventional on the MCB side but so long as your loads are comparable OK, do you need that close a protection, could use a smaller board if not?
A 100mA RCBO (can you get these?) and 30mA main switch will not have discrimination, would be easier to just have a main switch in the shed or an MCB in the main board (if the T&E does not need 30mA protection).
I assume you have calculated volt drop and considered your earthing arrangements already.

 

[Guest22]

Somewhat unconventional on the MCB side but so long as your loads are comparable OK, do you need that close a protection, could use a smaller board if not?
A 100mA RCBO (can you get these?) and 30mA main switch will not have discrimination, would be easier to just have a main switch in the shed or an MCB in the main board (if the T&E does not need 30mA protection).
I assume you have calculated volt drop and considered your earthing arrangements already.

Yes I have indeed, importing the earth. Sorry my bad, double pole RCD. I think I might be able to get away without RCD protection for the T&E, so just RCD protection on the board in the shed. Yes unconventional MCBs but I have a spare board to use and I thought why not be nice to isolate separate circuits easily. Volt drop of 9.77V. So I hope this covers most things.

 

[Deleted member 26818]

Maximum VD for lighting is 6.9V.

 

[MarkieSparkie]

Why not ditch the T&E and take the SWA direct from board to board. Feed SWA from an MCB in the main board. Check your design voltage drops are within the regulation limits, if not up-rate the SWA if necessary.

 

[Guitarist]

Do you think that 2.5mm T&E is suitable for use with a 25A RCBO, considering any derating factors?
Also, have you calculated whether the cpc in the T&E is suitable protection for your new dis board?
As spinlondon said, max vd for your lighting is 6.9v. Will you achieve this?

Finally, are you part P registered? This is notifiable!

 

[Guest22]

Do you think that 2.5mm T&E is suitable for use with a 25A RCBO, considering any derating factors?
Also, have you calculated whether the cpc in the T&E is suitable protection for your new dis board?
As spinlondon said, max vd for your lighting is 6.9v. Will you achieve this?

Finally, are you part P registered? This is notifiable!

1) Of course I know this is notifiable, who do you take me for? "Don`t answer that " Im going to have it overseen, etc then signed off. Or how ever the friend I know will do it. Also, still learning what would the allowable VD be for a supply like this, as its power really, but is then supplying lighting? Would use the lowest of the 2 being 3% for lighting?

Why not ditch the T&E and take the SWA direct from board to board. Feed SWA from an MCB in the main board. Check your design voltage drops are within the regulation limits, if not up-rate the SWA if necessary.

2) I may do this problem would be terminating it into the Main DB, Either that or maybe conduit in singles? Would that be a better idea?

Maximum VD for lighting is 6.9V.

See 1)


Thank you for you replies

 

[Toby Kuhnert]

Or if you needed the T+E to be RCD protected (9 times out of 10 you would-I don't know many people who run T+E through earthed steel conduit in domestic properties!! ), you could install a 30mA RCBO at the main DB then put in a DP isolator in the DB in the shed... This would provide the sufficient RCD protection right the way through the distribution circuits and all final circuits in the shed. Also having the circuit on an RCBO would stop any earth faults that could occur on the distribution circuit tripping the other RCDs in the property. (assuming you have a newer consumer unit).

Hope this helps