Hi guy
I'm new to the forum and have a simple job that is causing me to scratch my head a bit! (By the way this isn't a post from a DIYer asking you guys to do the job for me, I'm Part P registered to test, certify and notify my work under Part P!)
I have been asked to change a consumer unit from a rewireable Wylex to a 'modern' one by an old aquaintence. I'm due to go there tomorrow to have a look at it but over the phone he has given me the following info. Currently he has a cooker, up ring, down ring, up lights, down lights and garage. The garage part is the bit that's got me struggling. It is fed by a 15A at the mo running a 4 core 2.5mm plastic covered pyro under the floor, then under the drive in plastic conduit for 3m and into the garage, total run around 20m. It currently feeds a 63A 30mA RCD, then a 63A B breaker. This then feeds another old rewireable box with sockets, lights and a couple of radials for some of his juicier tools. What he wants to do is fit a TIG welder in there. He has asked the manufacturer the requirements and they have advised a D32 breaker for the welder due to the start up current. The type of welding he said he will do is not going to be flat out and at maximum juice, but you never know! The supply is TNS and the water and gas are easy access to the fuse box if the bonding needs upgrading.
In the BGB it lists a 2 core 4mm at 40A clipped direct in table 4G1A. Now I'm not used to wiring machines up and their start up characteristics. My thoughts initially were to fit a dual RCD board and have the garage on it's own non RCD protected MCB, with the pyro doubled up to make two 5mm cores, but would the sheath be suitably sized now to serve as the cpc? Ok, so in the garage if I fit a D32 in with the RCD and existing breaker (and perhaps downsize that!), but feed the garage with a B40, I guess the B40 will trip on start up. He's reluctant to up the cable size with SWA as it runs under the tarmac drive. I'm feeling it's a bit too close for comfort at the mo. All of this is relying on the Zs being low enough, which would need to be 0.29 on the D32 welder circuit. Being pyro (and old at that) I would imagine the IR to be getting low too.
So after all that rambling on I'm unsure what breaker to fit at the house end to feed the garage. If needs be he'll have to up the cable and that's final, but what MCB and type would you fit that won't trip before the D32 ?? I'm finding this one a struggle to be honest!
Your advice would be very much welcome!!!
Thanks Stu
I'm new to the forum and have a simple job that is causing me to scratch my head a bit! (By the way this isn't a post from a DIYer asking you guys to do the job for me, I'm Part P registered to test, certify and notify my work under Part P!)
I have been asked to change a consumer unit from a rewireable Wylex to a 'modern' one by an old aquaintence. I'm due to go there tomorrow to have a look at it but over the phone he has given me the following info. Currently he has a cooker, up ring, down ring, up lights, down lights and garage. The garage part is the bit that's got me struggling. It is fed by a 15A at the mo running a 4 core 2.5mm plastic covered pyro under the floor, then under the drive in plastic conduit for 3m and into the garage, total run around 20m. It currently feeds a 63A 30mA RCD, then a 63A B breaker. This then feeds another old rewireable box with sockets, lights and a couple of radials for some of his juicier tools. What he wants to do is fit a TIG welder in there. He has asked the manufacturer the requirements and they have advised a D32 breaker for the welder due to the start up current. The type of welding he said he will do is not going to be flat out and at maximum juice, but you never know! The supply is TNS and the water and gas are easy access to the fuse box if the bonding needs upgrading.
In the BGB it lists a 2 core 4mm at 40A clipped direct in table 4G1A. Now I'm not used to wiring machines up and their start up characteristics. My thoughts initially were to fit a dual RCD board and have the garage on it's own non RCD protected MCB, with the pyro doubled up to make two 5mm cores, but would the sheath be suitably sized now to serve as the cpc? Ok, so in the garage if I fit a D32 in with the RCD and existing breaker (and perhaps downsize that!), but feed the garage with a B40, I guess the B40 will trip on start up. He's reluctant to up the cable size with SWA as it runs under the tarmac drive. I'm feeling it's a bit too close for comfort at the mo. All of this is relying on the Zs being low enough, which would need to be 0.29 on the D32 welder circuit. Being pyro (and old at that) I would imagine the IR to be getting low too.
So after all that rambling on I'm unsure what breaker to fit at the house end to feed the garage. If needs be he'll have to up the cable and that's final, but what MCB and type would you fit that won't trip before the D32 ?? I'm finding this one a struggle to be honest!
Your advice would be very much welcome!!!
Thanks Stu
