Water heater

[davesparks]

Where you see the difference is something like a garage feed (again!) when you might have a planned load of, say, 20A and select a cable to match, then the garage CU has a 20A MCB that provides the overload protection. But the feed for the cable might be a 40A or more fuse that will clear in under 5s on a short but is not offering overload protection for the 20A-rated cable.

This would not comply as the load is not fixed in this case.

A better example would be a feed to a motor starter where the overload protection is incorporated in the starter.

 

[pc1966]

A better example would be a feed to a motor starter where the overload protection is incorporated in the starter.

In an industrial setup that would be the classic example for sure: the feed OCPD is simply for hard faults and there is another system (i.e. the motor starter) that is engineered to have the appropriate time/current characteristics needed to protect the motor against overload in operation.

 

[John-SJW]

For a heater the distinction is probably academic, if you have a load taking X amps then you size your cable for that and fit a MCB at the matching level. So it would be unusual for the OCPD not to also provide overload protection.

I have seen a j box in a 32A ring forming a spur, serving only an a 3kW immersion with only a 20A switch between the immersion heater and j box. Well it had a flash neon light on it to make it look better. No over-current protection whatsoever except the 32A mcb at the main CU. A 3kW immersion's current draw is not constant as it depends on the voltage, which may fluctuate during day for various reason.

 

[davesparks]

Hopefully the mods will find a can of this soon

 

[John-SJW]

Hopefully the mods will find a can of this soon

Someone disagrees with you so they are a troll eh. I noticed you trolled all around my posts - that was not coincidence. When you posted it says, to cut it short, only post relating to the topic, otherwise do not. Take note.

 

[davesparks]

Someone disagrees with you so they are a troll eh. I noticed you trolled all around my posts - that was not coincidence. When you posted it says, to cut it short, only post relating to the topic, otherwise do not. Take note.

Did I say you were a troll? I dont think I did, I just made a comment suggesting that there is a troll on the forum and you made an assumption that I was talking about you.

I haven't 'trolled all around your posts' I have replied to new threads or threads I have previously replied to that I feel I can have some input on.
Please don't flatter yourself that I'm following you around!

Yes I disagree with some things you have said and have tried to explain why or put my pount across along with the logic behind it.