Fuse for an ex-electric shower cable

Hello again. As you might have guessed from all my posts, there is a lot of questionable electrics in my place that I'm checking over at the moment. another thing I have noticed is that the feed for the (no longer present) electric shower is now used for the top-up (rather than night-time) immersion heater. The cable is obviously easily up to the task. However, there is still a 45A fuse on the fuse board for this. Obviously, this needs to be replaced with a 15A fuse. However, due to the chunky cable (which I might as well keep) I'm thinking it might be better to fit an FCU at the immersion heater switch, in case someone comes along in future and sticks a bigger fuse in on account of the chunky cable (you never know!). Does this sound like a good plan? Or should I just downgrade the fuse at the fuseboard and not worry so much about it?!

P.S. Another thing I have noticed is that two storage heater feeds are connected across a single 30A fuse on the fuse board. Presumably they should have their switches replaced with FCU switches, fused at 15A? One of the cables is only rated at 15A, so I'm uneasy about the 30A fuse. I'm thinking as a temporary measure until I eventually have a new CU put in by a proper spark.

I'd refuse the emmersion at the CU with a 20A and fitted a 20A neon switch at the emmersion end. The neon is to indicate on / off and is necessary if you have kids.

A 13A 230v x 13a or 2990w is JUST under the rating for a 3000w or 3kw element.

As for the storage heaters, if you change the 30A down to 15A it will blow the fuse when both heaters are used.

What cable is rated at 15A the supply cable from the CU ? or the cable between the wall switch and the storage unit ?

I think the immersion heater is rated at 2.7kw. It's on an old style fuse board with fuses you need to re-wire yourself when they go. I suppose my choice (for now) is between 15A or 30A and I think 15A is OK for 2.7kw?

I'll fit a neon switch, even though I don't have kids myself.

RE: the storage heaters, I meant fusing the storage heaters @15A at the switches. Does that sound OK? I would plan to fuse them separately at 15A at the CU once that is replaced in future. a 15A fuse for both at the CU would obviously blow!

15A is plenty for 2.7Kw..

you can't get 15A plug fuses.. it's 13A

and whether you can use a 13A fuse depends on the rating of the storage heaters..

Use a 15amp fuse or B16 breaker for the immersion, for the storage heaters work out the design current from their power rating divided by the line voltage, and fuse accordingly - it may be easier to buy a 2 way consumer unit to feed them, with two appropriately sized breakers, and run it off the existing 30amp fuse, with some 6mm cable.

kai said:

Use a 15amp fuse or B16 breaker for the immersion, for the storage heaters work out the design current from their power rating divided by the line voltage, and fuse accordingly - it may be easier to buy a 2 way consumer unit to feed them, with two appropriately sized breakers, and run it off the existing 30amp fuse, with some 6mm cable.

Click to expand...

Now why didn't I think of that! That's the way I'll go, I think...