9.5 kw shower on 6mm ?

[jonthesparks]

just been to a job , saw that the shower 9.5 kw is on 6mm t&e the cable goes in the wall and under floor boards ,No insulation, to the board (A cable run of no more than 10 m) . I said downgrade the shower to 8.5 max. Is it really necessary ? never quite sure , its borderline to me .

 

[Guitarist]

lol nope but i did she a shower not sure what the kw rating was ran off a 30 Amp BS3036 fuse in 1.5mm 3 core!!!

At first glance i thought it was 4mm, looked in the loft and it was all melted under the insulation.

Still worked though i found it as i was installing a loft light.

You probably saved them from their house burning down.

 

[Risteard]

Yes , but many CU brands dont have 45A mcbs , next one up is 50 which will need 10mm cable.

The shower doesn't need overload protection but only fault protection.

 

[Guitarist]

Remember, the MCB is there to protect the cable, not the appliance.

 

[Engineer54]

I also doubt that they will be having the shower running at full whack, not unless they have skin like leather.

Honestly don't understand these shower unit being 9.5 TO 10.5KW, The shower unit that i currently have in China is 4.2 or 4.6KW (do they do this sort of rating size in the UK??) and i can't have the thermostat turned up more than half way.

So what's the story with these Mega Watt shower units that seem to abound in the UK?? ...lol!!!

 

[Guitarist]

The shower is either "on" or "off", and therefore always at full wack electrically. The temperature is adjusted by varying the flow. Granted, most showers have an "economy" setting which is normally half-power, but I don't know anyone who uses this unless it is a very hot summer day.
7.5 kw is the smallest UK size (formerly 7.2 kw) and on a normal British day it delivers something between a trickle and a sprinkle

 

[Engineer54]

Never having had or wanted an electric shower in the UK, i can't say how they operate. What i can say is that the unit i have, has a thermostat controlled element. It doesn't however have an economy setting. The water flow is either on or off, it's not exactly (or anywhere near a power shower levels) powerful, but more than adequate for a decent shower.... lol!!!

Would anyone in the UK use an electric shower, if and when they have gas/oil central heating systems or is it just those without a gas supply etc???

 

[Guitarist]

I have an oil-fired combi-boiler and it supplies all our hot water, including to a very nice mains thermostatically controlled shower. However, as we have had a few problems with our very old boiler over the last few years I decided to fit an electric shower as a backup in the kids' bathroom. It is only 7.5 kw, and the flowrate is very poor, but it is adequate. Plus, it saves me money

 

[telectrix]

So what's the story with these Mega Watt shower units that seem to abound in the UK?? ...lol!!!


​just because it's bigger than next door's. same with cookers. next door's just had a 10kW unit, so we must have a 12kW. one.

 

[Engineer54]

So what's the story with these Mega Watt shower units that seem to abound in the UK?? ...lol!!!


​just because it's bigger than next door's. same with cookers. next door's just had a 10kW unit, so we must have a 12kW. one.

Think you have the same basic views as myself, on these silly high KW shower units...lol!!!

 

[1shortcircuit]

In this situation all you can do is present the client with the facts and explain that if a new installation were to be added today then the way it is wired currently would not be acceptable.

This is where a clamp meter is worth it's weight in gold as you can prove to the client what current is being drawn. It doesn't take a mathematician to evaluate the results recorded on the meter.

I personally would sow the seed for installing a new 10mm radial circuit and make the client fully aware that there is the possibility that the shower as it is may become a nuisance if the shower is used for a longer period of time BUT it's THEIR decision.

I live in a property where the shower would trip the MCB which meant having to wipe bubbles from my eyes, get out and go down to reset. The problem was though as the MCB had got to a certain temperature it would take about 10 minutes to reset. Once reset there was normally just about enough time to get rinsed off and get out. The worst time was I was sat next to the CU trying to reset because the wife had been washing her hair, trip, trip, trip, trip, trip..... Haven't you done it yet? Trip, trip lol

Eventually I replaced the board and used 60898 mcb's and never had a problem since, everything the same apart from the breaker (Old 30A mcb replaced with to a 32A EN60898 on 6mm cable)

As mentioned though, So long as the MCB is rated lower than the maximum current carrying capacity of the cable (taking into consideration any influences such as insulation) then the only bother is the inconvenience. The protective device is only doing exactly what it is designed to do therefore eliminating any risk to the user - Well, unless they drip water all of the mcb/CU when trying to reset? lol

 

[telectrix]

what's wrong with a watering can on a pivot, pulled with wet string (10mm wet string, of course)

 

[ezzzekiel]

Found plenty of 9kw showers fed with 2.5 and never been a problem

 

[Guitarist]

Found plenty of 9kw showers fed with 2.5 and never been a problem

Don't tell the DIY'ers that....

 

[Mark_Burgess]

just been to a job , saw that the shower 9.5 kw is on 6mm t&e the cable goes in the wall and under floor boards ,No insulation, to the board (A cable run of no more than 10 m) . I said downgrade the shower to 8.5 max. Is it really necessary ? never quite sure , its borderline to me .

I have a feeling you will be told, "well it has worked like this for ages, and we have never had a problem!"

 

[Lester Lecky]

To give yourself piece of mind, just do a full cable calculation and find out what the current carrying capacity of the cable is. In most installations i have found Insulation (Ci) and cable grouping (Cg) at least affect the cable capacity. These figures often make the current carrying capacity requirement much higher than that offered by a 6mm cable.
Depends on how precise you want to be! I have only seen a couple of heat damaged 6mm cables in my time caused by overloading. One was very bad at the consumer unit - a house full of females - shower on A LOT and for long periods.
I always go on the side of caution to cover my ---. So would always point out issue and recommend a downgrade of shower or upgrade of cable! Up to the customer then and you can sleep at night!