Joined: 29 Nov 2006 Posts: 2 Location: Wight, United Kingdom Thanked: 0 times
Posted: Wed Nov 29, 2006 10:32 am Post Subject:
More Showers
I currently have a Gainsborough RE600 shower (rating unknown) and intend replacing it with a Triton 9.5kW shower. The cable is 4mm.
Is this a problem? I think the RE600 is 9.5 but am not sure.
By the way, I'm a clanky type, not a greeny!
Joined: 18 Jan 2006 Posts: 338 Location: Merseyside, United Kingdom Thanked: 0 times
Posted: Wed Nov 29, 2006 12:13 pm Post Subject:
the RE600 is 8.5Kw, so 4mm is okay but you need to upgrade for a 9.5Kw shower. As crafy said, 10mm should be okay - unless you have a long run or the cable is affected by external factors (eg run through insulation)
Joined: 09 Aug 2007 Posts: 1 Location: Surrey, United Kingdom Thanked: 0 times
Posted: Thu Aug 09, 2007 12:38 pm Post Subject:
Voltage Drops
Crafty wrote:
4mm²?????
Do me a favour. Open the shower switch up with the power off, and tell me what you see.
50p says its full of melted plastic and the switch no longer operates. If it isn't you've been very lucky indeed.
Dont use the shower again until you've replaced it with at least 6mm². However, since you're replacing the cable, you might as well go for 10mm².
4mm² will carry 37A IIRC, if run in free space. Your shower is 41 amps (ish)
Hi Guys, I am not an electrician, but doesn't the current draw go up as the voltage goes down? i.e. if the voltage dropped to say 220V(I have seen this many times) the cable will need to carry nearly 39 amps.
So I am assuming that 4mm should not really be used???
Any thoughts????
Joined: 17 Jun 2004 Posts: 4540 Location: United Kingdom Thanked: 10 times
Posted: Thu Aug 09, 2007 12:59 pm Post Subject:
Re: Voltage Drops
WF100 wrote:
Hi Guys, I am not an electrician, but doesn't the current draw go up as the voltage goes down? i.e. if the voltage dropped to say 220V(I have seen this many times) the cable will need to carry nearly 39 amps.
if the voltage goes down, then you need to increase the current *in order to maintain a constant power* (Power = Voltage x current), in a resistive load this doesn't happen, the current actually reduces as well (Current = voltage / Resistance),
9.5kw shower on 240v will take 9500/240 = 39.58A and has a resistance of 240/39.58 = 6.06 ohms
Put the same shower on 230v and the resistance is still 6.06 (its about the only thing thats constant-ish here), which means it'll draw 230/6.06 = 37.95 Amps, which gives it a power of 37.95 x 230 = 8.73kw (the change in power is in proportion the the change in voltage squared - [ P=V²/R])
Regardless of which, neither 4mm² nor WF100 would do! (I wouldn't put it past some though!)
Joined: 29 Jun 2007 Posts: 117 Location: United Kingdom Thanked: 0 times
Posted: Thu Aug 09, 2007 1:05 pm Post Subject:
I remember once being told by a drip that they always use 6mm2 cable on a shower as it is easier to work with
He tried to use it on mine until I said he was putting in 10mm2 and I watched him do it.
Joined: 27 Aug 2003 Posts: 21989 Location: London, United Kingdom Thanked: 78 times
Posted: Wed Jul 29, 2009 12:19 am Post Subject:
Ah - that's a difference between you and I.
I see absolutely no point in mincing around with euphemisms - the meaning is clear and doesn't change, so what's the point in putting lipstick on a pig? Use the L word....
__________________ I mustn't warn people that the "experts" on the plumbing forum can't be trusted to tell the truth.
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Hi Guys, I am not an electrician, but doesn't the current draw go up as the voltage goes down? i.e. if the voltage dropped to say 220V(I have seen this many times) the cable will need to carry nearly 39 amps.
