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Hi All,
I am fault finding some one elses work today.
Had some nusance tripping on a supply to a workshop, and a ring main in the workshop. Everything tests out ok. The only time I could get it to trip was when a welder was plugged in (16A BS4343), and a big isolation transformer was powered up supplying a bench for electronic testing. The isolation transformer is on a ring final. Both circuits are fed using RCBOs with an RCBO upstream. So we have a type b 16a for the ceeform and a type b 32a for the ring.
The supply is fed via a type b RCBO upsream. I need to work out the discrimination here. I think this upstream RCBO should be type s so that the downstream devices trip in a fault not the upstream devices. I am not even sure why there is an RCBO feeding the workshop. The run is in 10mm SWA to 16mm t + e inside with the gland bolted into a metal enclosure, a din rail terminal setup and the t+e entering via a stuffing gland. Nice job all IP66 by the looks of it. With a seperate g/y 10mm fed to this metal enclosure. The enclosure is earthed via the SWA gland and a earth block inside connects the t+e earth, a flying lead to the box, and the 10mm g/y fed to this. The t+e is feed from a crabtree starbreaker 10 way board, a submain from split meter tails. This board has a mix of RCBOs of the correct type and MCBs.
Looking over my results I don't think an RCBO is needed upstream. Just add local protection inside the workshop. Its just going to lead to a discrimination headache.
Why would there be an RCBO on the feed? I cannot think of anything and had a look in the red book to see if I over looked anything today and the OSG.
My plan, replace the type B RCBOs with type C to feed the ring and 16A BS4343. Its a domestic setup and I have never fitted any type c breakers in a domestic install, only industrial where there are loads with large inrush. In on a type c is 5 to 10 and type c is usally used for inductive loads. Where In on a type b is 3 to 5. So ideal for this situation.
Would this be deemed ok?
Next problem the exterior lighting circuit is on a type C 10A RCBO. I have no idea what the spark was thinking. There is a SOX lamp and lots of fluros that's about it. Why is there a type C there? I can understand the thinking of an RCBO.
The installation is really nice but there seems to be allot of RCBOs and no discrimination.
What are you thoughs?
Adam
I am fault finding some one elses work today.
Had some nusance tripping on a supply to a workshop, and a ring main in the workshop. Everything tests out ok. The only time I could get it to trip was when a welder was plugged in (16A BS4343), and a big isolation transformer was powered up supplying a bench for electronic testing. The isolation transformer is on a ring final. Both circuits are fed using RCBOs with an RCBO upstream. So we have a type b 16a for the ceeform and a type b 32a for the ring.
The supply is fed via a type b RCBO upsream. I need to work out the discrimination here. I think this upstream RCBO should be type s so that the downstream devices trip in a fault not the upstream devices. I am not even sure why there is an RCBO feeding the workshop. The run is in 10mm SWA to 16mm t + e inside with the gland bolted into a metal enclosure, a din rail terminal setup and the t+e entering via a stuffing gland. Nice job all IP66 by the looks of it. With a seperate g/y 10mm fed to this metal enclosure. The enclosure is earthed via the SWA gland and a earth block inside connects the t+e earth, a flying lead to the box, and the 10mm g/y fed to this. The t+e is feed from a crabtree starbreaker 10 way board, a submain from split meter tails. This board has a mix of RCBOs of the correct type and MCBs.
Looking over my results I don't think an RCBO is needed upstream. Just add local protection inside the workshop. Its just going to lead to a discrimination headache.
Why would there be an RCBO on the feed? I cannot think of anything and had a look in the red book to see if I over looked anything today and the OSG.
My plan, replace the type B RCBOs with type C to feed the ring and 16A BS4343. Its a domestic setup and I have never fitted any type c breakers in a domestic install, only industrial where there are loads with large inrush. In on a type c is 5 to 10 and type c is usally used for inductive loads. Where In on a type b is 3 to 5. So ideal for this situation.
Would this be deemed ok?
Next problem the exterior lighting circuit is on a type C 10A RCBO. I have no idea what the spark was thinking. There is a SOX lamp and lots of fluros that's about it. Why is there a type C there? I can understand the thinking of an RCBO.
The installation is really nice but there seems to be allot of RCBOs and no discrimination.
What are you thoughs?
Adam