I have a mira 9.5kw shower fitted.......had problems with it and as I had no confidence in the plumber and leccy that fitted it(had many problems with them) I rang mira and they sent an engineer out to it.....appeared that it had not been fitted to the wall correctly and the guy said that the cable supplying the shower was only 6mm and not enough for a 9.5kw shower(before I bought the shower I asked the leccy what size shower I could go upto) the engineer also said the fuse for the shower should be 47amp. The shower keeps tripping....can I just get an 8.5kw shower and fit that instead? Your help would be much appreciated!
shower
- Thread starter karlywarly1969
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Generally, 6mm cable is good for max 40amps, but it depends on the routing of the cable as to the maximum current that it can handle.
If the cable is 6mm then it will need a 40amp MCB
So you'll probably be OK with an 8.5KW shower
I'm assuming there's an RCD fitted to protect you when you are in the shower?
If the cable is 6mm then it will need a 40amp MCB
So you'll probably be OK with an 8.5KW shower
I'm assuming there's an RCD fitted to protect you when you are in the shower?
I think you may have misunderstood or the engineer really does not know what he is talking about.
6mm² cable has a maximum Current Carrying Capacity of 47A.
9.5kW @240V is 39.6A.
So assuming the cable runs through NO thermal insulation or conduit then all is satisfactory with a 40A fuse or MCB.
What rating of fuse/mcb is there at the moment?
6mm² cable has a maximum Current Carrying Capacity of 47A.
9.5kW @240V is 39.6A.
So assuming the cable runs through NO thermal insulation or conduit then all is satisfactory with a 40A fuse or MCB.
What rating of fuse/mcb is there at the moment?
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There's no way to keep the 9.5kw in then and put bigger fuse? Dunno what an RCD is....thats why I got a plumber and leccy in. Think the fuse at the moment is 30amp and trips most times the shower is used.
"In some cases 6mm² cable will be adequate for a shower rated up to 8kW. For showers above 8kW it may be necessary to install 10mm² cable. "
Seems reasonable - what do you think is a wind up?
A wind up????? Thought it would be cheaper to just replace the shower with a 8.5kw rather than rip all tiles out and fit 10 mm cable....just need to know if I can keep the 9.5kw if I change the fuse as it keeps tripping nearly every time we shower.......pain in the arse when your the only one in the house and cant shout down for someone to flick the fuse.
The wiring was al;ready in as I had an over bath shower before.
If you have a 30A fuse then it will trip - doing its job.
You need to replace it with a 40A then all will be well.
That is if the cable runs through NO thermal insulation or conduit.
You need to replace it with a 40A then all will be well.
That is if the cable runs through NO thermal insulation or conduit.
So I can keep the 8.5 and just put a 40amp fuse in and it will be fine....no tripping?
You mean 9.5.
Yes, but you must make sure the cable does not run through any thermal insulation nor conduit.
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6 mm cable does not have a rating. A type of 6 mm cable fitted is certain way does so 6 mm means very little. Somewhere between 23.5 and 58 amp is not really helpful.
As to 8.5kW = 37A
9.5kW = 41A
Well that is a little more helpful. If you look at the curves for a B32 MCB it's more then the 10,000 seconds shown on the tables. So you should be able to use a B32 MCB if your shower time is under 2.5 hours.
In real terms not quite so cut and dried as using a MCB over it's rating will cause the MCB to over heat and degrade and as time goes on it will trip more and more. Often there should be spacers between MCB's for cooling which are often not fitted.
So hard to say your electrician was wrong or that the guy from mira is wrong it is their opinion.
Likely reducing to 8.5kW and renewing the MCB will give years of trouble free use. Also just renewing the MCB would likely work for quite a time.
Up rating the MCB is hard. How it is run and what cable has been used will dictate if it can be uprated. Thermoplastic and thermosetting look very similar. Clearly not a DIY job. I would tell the electrician what the mira man said and see what he says.
I have also trained as Electrical Engineer and as an Electrician and the training for my degree did not help at all in selecting the right cables or MCB sizes. So the Electrician could well be right and the Engineer wrong. Why anyone would send out an Engineer to that type of job I don't know.
As to 8.5kW = 37A
9.5kW = 41A
Well that is a little more helpful. If you look at the curves for a B32 MCB it's more then the 10,000 seconds shown on the tables. So you should be able to use a B32 MCB if your shower time is under 2.5 hours.
In real terms not quite so cut and dried as using a MCB over it's rating will cause the MCB to over heat and degrade and as time goes on it will trip more and more. Often there should be spacers between MCB's for cooling which are often not fitted.
So hard to say your electrician was wrong or that the guy from mira is wrong it is their opinion.
Likely reducing to 8.5kW and renewing the MCB will give years of trouble free use. Also just renewing the MCB would likely work for quite a time.
Up rating the MCB is hard. How it is run and what cable has been used will dictate if it can be uprated. Thermoplastic and thermosetting look very similar. Clearly not a DIY job. I would tell the electrician what the mira man said and see what he says.
I have also trained as Electrical Engineer and as an Electrician and the training for my degree did not help at all in selecting the right cables or MCB sizes. So the Electrician could well be right and the Engineer wrong. Why anyone would send out an Engineer to that type of job I don't know.
35A & 40A - the headline ratings for showers are always at 240V.
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