fuses in series

[soulman]

sorry another question! just doing a bit of homework on a sunday.

why would it be wrong to connect a to a 3036 fuse then to a rcd to a mcb then to the load

cheers.

 

[pevvers]

I reckon it would depend on the rating of the fuse and MCB...

 

[flukey]

who says it would be wrong not ideal but not wrong

 

[soulman]

hi i have just read previous post on rcd protection. where on guy was trying to put in a shower, wired directly into 3036 fuse then into a small consumer unit through an rcd into a 40a mcb then to the shower the response was fuses in series is bad practice i couldn't understand why?

as it was 7.5 kw shower the 30a 3036 will support this and so would the 40a mcb so i thought double protection.

cheers

 

[megthemaddog]

when fuse's are used in series the needs to be discrimination between one fuse and the next.

so the fuse closed to the fault blows first leaving the down stream OK.

 

[flukey]

hi i have just read previous post on rcd protection. where on guy was trying to put in a shower, wired directly into 3036 fuse then into a small consumer unit through an rcd into a 40a mcb then to the shower the response was fuses in series is bad practice i couldn't understand why?

as it was 7.5 kw shower the 30a 3036 will support this and so would the 40a mcb so i thought double protection.

cheers

thats the point i was getting at. if there is a rewirable board and customer wants an electric shower the only way to achieve this is to feed an rcd from the existing rewirable.

not ideal but not wrong

 

[bugsy]

All determined by discrimination, which type of mcb are you installing

 

[Had8Lives]

If a Customer wants a shower put in and they have a 3036 Fuse board, you either need to change the board or split the tails. Bearing in mind alot of 3036 boards only have a 60A Main switch, I wouldn't install a 7.5Kw load on one.

 

[AEC]

Perfect answer.