Al80

Mark, thanks for that

The load on in the shed will be no more than 16 amps. The earthing on the house is an earth rod. it would be very very hard to run a new line from the current CU to the shed. To be honest it’s more looking like the welder may not be an option using the current 2.5 wiring going to the shed without running into issues. I could change the MCB to a type C or D but to accommodate for the surge in power but am not in favour. I will have to look further at selectivity between the rcd between the house and the shed

Yep but I could buy a CU online from the UK.

Someone said it would be cheaper to buy a ready made consumer unit. I have found the following which I think will do the job https://www.garo.ie/product-details/main-mcb-type-b-10ka/G13B-7A

As I am not at home I can only guess that the RCD that is on the row where the shed MCB is on is probably 20 A

I was guessing the 2.5 cable may cause me an issue

Old school… doh… ?

The MCB currently feeding the shed is 20A. To allow for downstream discrimination I was sizing the RCB in the shed for 16 A.

Thanks for that. I could buy a 120 amp welder that will work on a 13 amp plug but was worried about it blowing the fuse

My young lad wants to buy an inverter welder. He has found a welder which has a current range of 20A to 140A. The supply required is 16A My shed is currently being fed by a 2.5 SWA cable which runs a number of sockets and a light. The power is from fed the main house from a 20 A MCB. The main reason for installing the CU is the welder as this needs 16A. I was looking at installing the following 1 x 16A double pole 16 amp RCD 1 x 20A MCB - for sockets 1 x 20A MCB - for a welder 1 x 10A MCB - for lights I cannot see myself using more than 16A at one time. Does the above sound ok? I know that there is a risk the welder could pul more than 16A this tripping out the MCB. Thanks.