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Installing electric shower/power shower have got 3 differeing opinions!

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rowwse | 22:09 Mon 28th Sep 2009 | Home & Garden
11 Answers
Hi, thank you for readng in advance.
we're going to be sorting out a new bathroom soon.
We've got ecomony 7 as no gas, and have had 3 different electricians give 3 different views of what can be done. Which one is right/legal with regs etc??
our fuse box is at the bottom of the stairs and we would have to take it up two flights to get to the bathroom. We dont really want unsightly cables running through the house - or maybe with all the regulations we need to do this now??

number 1 - electric shower
take the power for the electric shower straight from the main ring.

number 2 - electric shower
putting a new distribution board, To wire a shower circuit complete from the fuse
board up to the top floor and routed around the bedroom / air cupboard

number 3 -
putting a power shower in and running this off the main ring or something to that effect. This one didn't want to do as number 2 and actually said that he was talking him self out of a bigger job, but didn't like the fact that the cabling would have to go up two flights and go round aprox 10 or so corners.

sorry i'm not not too technical on the terms and trying to remember all the jargon which was thrown around.

could we not have simply a transformer to sort out a electric shower running from the spare bedroom socket mains? apologies for my ignorance!

Thanks again for any help!

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A power shower is an electric shower so I'm not clear how how numbers 1 and 3 are any different from one another.
I'm afraid you simply have no choice other than to have a new cable run installed from the existing CU (consumer unit) to the area of the bathroom. Those are the regulations and it is necessary to do this because the current consumed by the power shower...
08:22 Tue 29th Sep 2009
A power shower is an electric shower so I'm not clear how how numbers 1 and 3 are any different from one another.
I'm afraid you simply have no choice other than to have a new cable run installed from the existing CU (consumer unit) to the area of the bathroom. Those are the regulations and it is necessary to do this because the current consumed by the power shower is so great that it must be on its own radial separate circuit. So all 3 electricians are correct in advising you of that.
As to whether you have a new mini CU installed close to the bathroom or run the new feed off the existing CU really depends on whether there is space to put a new circuit breaker (MCB) into the old box. I can't see an advantage of installing a new CU if there is space to expand the old one - it is just going to cost you more to fit a new one.
In all of this, you are going to have to have a new cable run from the existing CU to the new bathroom - as to the best way to route the cable, electricians are well-used to find ways that hide it to best effect.
Sorry, reading it again, number 3 seems to suggest that it be run off the upstairs ring main. You definitely cannot do that - it must be on its own circuit.
i read the info and thought that 1 and 2 wanted to connect to the ring main, which is a definate no.
to answer number 2 we need some info ie what is the age of the existing board and does it contain fuses (re wireable) or MCBs? does it have any spare ways to accomadate the shower supply?
if you have not had a 10 year inspection on your electrical set up or you are close to one then an updated board would combine the two. i followed this route after an extension that included an electric shower.
i have a new CU with excess capacity for the future, the electrics are tested with a certificate from a registered spark. this includes my 10 year inspection so i know the whole installation is safe and i can prove it for the building inspectors and a HIPS report when i sell the house.it cost more but i think its worth it
The Questioner is basically concerned about the ugly cables through the house, T.
These are unavoidable - the business about whether upgrade the existing CU or fit a new one is surely a mere nicety.
Question Author
Buildermate, I rather have cables running round the house (if it's concealed and it's safe to do so) and be safe rather than have a shower fitted and it's going to eletrocute someone! It all seems so complicated and it was eletrician 2 who put it out that we could aviod all the work by putting in a power shower and running it off the spare bedrrom ring.

T, the fuse board would of been fitted when the house was built roughtly about the 70's? and apparently no rcd (?). To my knowledge there has been no eletrical inspection - is this something we should have?

Because there are 3 different advice given to me by people who know better than me I dont know who is right, or if one is just telling me fibs cause it'll cause them more work etc.

electrcian one is discounted as i've read from you both (thanks for the advice!)

electrician number 3 said that by having all the wires going around the corners the wires wouldn't last too long due to the resistance voltage would heat up?, but when asked how long it would go for, he said well how long is a peice of string. is this a lot of bull?? should the wires actually withstand going round corners?

so if number 2 is going to fit new distribution boards, wire up to the second floor etc it would be the best one??
A ring main is a circle of cable that starts at the fuse box (or consumer unit, CU), goes around in turn to each of your 13A sockets and then returns back to the CU. There are often 2 (or more) ring mains in a house - typically one running around the upstairs, and another around the downstairs. Each ring main will be controlled by a fuse (or a breaker if the CU is more modern). A breaker (MCB) is a resettable device instead of a fuse that cuts the current to that circuit under conditions of overload. Modern CUs contain breakers, not fuses, but they perform the same function.
If any of your electricians are suggesting that they wire up the new shower from the existing ring main, they are not worth pursuing. It will overload the ring main and trip the fuse or breaker. But I do not now believe that any of them are suggesting that - it is probably your use of terminology ('ring main') in your original question.
The shower must be wired directly from a CU - with its own breaker.

Terence was asking you whether your existing CU had been upgraded from fuses to breakers. Breakers are safer because they cut the power quicker in the event of overload (excess current being drawn through the system that might overload a cable and cause a fire). If your CU has never been upgraded since the 1970s, it is worth considering now whilst you have an electrician in. This is because the alternative is to fit a new style CU up near the shower room, with its own modern breaker in it. If you are going to have to do this anyway, you might just as well modify the existing CU now to contain breakers.
None of this changes the fact that a new cable of a large size (10 mm square cross-sectional area of the copper wire inside the cable) has to be run between the existing CU and the new bathroom area and hence up 2 flights of stairs. It needs to be a large size because the required current for a power/electric shower is so great and the distance is long. The elect
Part 2 - the dim AB system no longer tells you that you have exceeded 2000 words - it just cuts you off! Read on -

None of this changes the fact that a new cable of a large size (10 mm square cross-sectional area of the copper wire inside the cable) has to be run between the existing CU and the new bathroom area and hence up 2 flights of stairs. It needs to be a large size because the required current for a power/electric shower is so great and the distance is long. The electrician who told you that he cannot get tight 90 degree bends on this cable is correct - and attempting to bend it sharply stretches the cable inside on the bend and makes it thinner at that point. This increases the resistance of the cable and may lead to it heating up a bit. In extreme cases it may overheat and cause a fire. I suggest you ask your chosen electrician to show you how tight he can get the bends, and hence what sort of covering he proposes to put over the cable.
None of this has anything to do with the potential (or not) for electric shock - I am talking here only about getting the basic supply into the shower-area. Because water and electricity do not mix well, it is recommended (but not a Regs requirement) that an RCD be fitted in the CU. An RCD is not the same as a breaker. It senses the current and detects if a leakage to earth occurs. A leakage to earth MAY lead under certain circumstances to a human receiving an electric shock if he was touching the leaking part(s). The RCD cuts the current before serious dmange could occur to a human and cannot be reset until the source of the leak is eliminated. I believe (and Terence please correct if wrong) that an RCD is still not an obligatory Regs requirement. Please correct if wrong. It is nevertheless a very good idea to fit - probably adds about £50 to the overall cost of the job.
I hope that gives you a fuller picture of what your job entails and some of your options.
A power shower is totally different from an electric shower. An electric shower has an element of 8.5, 9.5 0r 10.5 Kw. it heats the water as it is being used. The supply wire must be 10mm cable and the fuse or m.c.b.in the consumer unit must be 45amp. The cable can be run down the cavity of the house to make the shortest and neatest route. (Drop a wieghted string down between the house inner and outer walls and collect at the bottom). A power shower uses your existing hot water and cold water which MUST be tank fed not mains and pumps it out at a higher pressure. as a power shower has no heating element only a pump, it can run safely and happily of a ring mains. As long as you have a good supply of water in your tank. About 200 litres as a minimum.
Technically you are right, Musicman, but if you read the post you will see that all three options use electricity to heat the water. Therefore I took the view that it only confused matters more to do as you have done and get into the niceties of how power showers generally work. I was assuming, perhaps wrongly, that the question author was using the term to mean the same thing.
Now you have opened Pandora's Box, it has to be explained that a 'power shower' when you don't have gas would have to work off the immersion heater - using the hot-water tank to pre-heat the shower water - using electricity anyway. And since you can't connect an immersion heater in the tank off a ring main (which is what Option 3 mentions), and neither do you need a massive new cable running to the new bathroom to feed just the pump, I don't think that's what the question author means.
im confused now and i have a small idea of what to do, so i will have a think about it.
but a couple of points,
i would not have cables in trunking in my home, i would chase out and plaster over
while i agree with the point about a new CCU being a bit over the top i have found out that if you dont maintain and upgrade things, then you seem to stand still.
also i beleive that a bathroom is a special location and electrical items like a shower must be RCD protected, in order to ensure the fastest cut off times in the event of a fault occuring
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