Shower cable breaker question

[youngsparky]

Hi all,
My girlfriends mum shower has gone faulty she is planning on a new one. Done some investigating and it's a 9.8 kw on a 6mm on a 32a breaker. Why hasn't the fuse bin blowing?
I havent done any cable calcs as of yet.
Any ideas just curious?
Cheers

 

[youngsparky]

It works out as about 42 amps

 

[High Tower]

Mcb's have a fusing ration of between 1.2 and 1.6, so dependant on its type, age etc etc it could take anything between 38.4 and 51 amps to trip it, the shower will pull around 40-42 amps depending on the supply voltage and VD, cable calcs wont really tell you a lot as apart from VD, there is nothing in there that will affect the current drawn, cable calcs are all about the current carrying capacity of the cable.

however, the cable is undersized for the size of the shower so its probably a good job its only a 32a breaker

 

[IQ Electrical]

Hi all,
My girlfriends mum shower has gone faulty she is planning on a new one. Done some investigating and it's a 9.8 kw on a 6mm on a 32a breaker. Why hasn't the fuse bin blowing?
I havent done any cable calcs as of yet.
Any ideas just curious?
Cheers

It's a short duration overload, my daughter could make it trip with a long duration overload!

 

[Benny_Boy]

I'm wondering whether or not it's on a mains water feed or a header tank. I've seen plenty of old showers burnt out due to inadequate water pressure after they've been fitted by a less than concientious plumber (or spark!). New showers will normally not attempt to heat the water if there is insufficient pressure, so if you fit a new one and it won't get warm you may have the culprit.
Just a thought.

 

[youngsparky]

Cheers guy good bit of advice to keep with me

 

[pushrod]

.

however, the cable is undersized for the size of the shower so its probably a good job its only a 32a breaker

Possibly not - clipped direct it can be up to 47A. As IQ said it is probs fine for showers of 15min duration but the mcb could trip if the whole family want a go one after the other

 

[High Tower]

Possibly not - clipped direct it can be up to 47A. As IQ said it is probs fine for showers of 15min duration but the mcb could trip if the whole family want a go one after the other

Very true!!

However when was the last time we seen a shower cable clipped direct,with no de-ration factors applied. The normally always run through Walls, voids and insulation at some point.

 

[pushrod]

Run in masonry still counts as clipped direct. I came across the very same thing some time ago and thought 'hold on this can't be right' but when i sat down with the brb it turned out ok and the shower had been working ok for years. I could have put it on a bigger mcb but thought why fix it if it ain't broke lol

 

[High Tower]

Run in masonry still counts as clipped direct. I came across the very same thing some time ago and thought 'hold on this can't be right' but when i sat down with the brb it turned out ok and the shower had been working ok for years. I could have put it on a bigger mcb but thought why fix it if it ain't broke lol

Yea I know that chased is the same method, I'm just always wary of 10kw showers on 6mm2 as a shower cable almost always runs into insulation etc etc

The op is by his name still learning hence I made the comment of the mcb holding because of it's fusing factor and was saying it was probably a good job that it was on a 32a as if it was a 40a then the cable would possibly be working at the top of it's tolerances

Having said that the diy'ers in the slums round here install 10kw showers on cooker flex so it's all good

 

[telectrix]

before condemning the 6mm. i would 1. ensure it wasn't buried in insulation. 2 clamp meter the cuurent drawn. bet it will be under 40A, nearer 35A.

 

[Francozola]

I agree with telectrix also to get it at it's max 10kw it would be peel your skin off the water would be to hot to stand under

 

[High Tower]

I had thought that as it was for the mother in law then a upgrade would be in order

 

[telectrix]

for the mother- in-law , a good earth to the shower basin is essential.

 

[High Tower]

Ha ha ha