Discuss 9.5 kw shower on 6mm ? in the UK Electrical Forum area at ElectriciansForums.net
Until he resets the mcb.
strewth.
Agree with richard , showers rarely used longer than 5-10 mins , too short a time for cable to heat up.
Reset the MCB while wet and naked, sounds dangerous and embarrassing !
Some people like to have sex in the shower. Could upset your 5-10minute rule. They would have to get out every 20 mins to turn the mcb back on. Dangerous with wet hands hurrying to get back:rolleyes2:
remember a few years back one of the sheds was doing 10.5kw showers for about £45 well a bloke fitted one on 6mm replacing his old 7.5kw cable ran on outside wall of house and it melted it from one end to the other,guy was well peed off.asked for a price and said the cost of cable alone was more than cost of shower,got quite funny about it so I told him that my shower worked fine so either way it didnt bother me if he had it fixed or not.lol
I was always of the understanding, the higher the kw rating of the shower, doesn't mean it gets hotter, just allows more water to flow at the required temperature.
The lower the power rating the less amount of energy it has to heat the water so it flows slower to maintain the temperature.
9.5KW shower at 240V takes 39.6A
9.5KW shower takes 37.9A at 230V
40A Circuit Breaker will hold indefinitely for a 9.5KW shower.
Will not trip what ever you have to do in the shower.
The debate is that some people believe 6mm cable is adequate for a 40A MCB, not that a 40A MCB is ok for a 9.5 kw shower.
Supply Voltage = 230 Volts
Power factor = 1
Ib - Design current = 41.3 Amps
Protective Device Type = MCB type B (BS EN 60898)
In - Protective Device Rating = 45 Amps
Cable Type : Twin & Earth
Length of run of cable = 10 metres
Installation Method : Single-core or multicore cable direct in masonry having a thermal resistivity
not greater than 2 K.m/W - without added mechanical protection.
(method C)
Ambient temp = 30 °C
Number of circuits including this one = 1
Length of cable in thermal insulation = none
Apply Correction factors:
From TABLE 4C1 : Cg = 1 (Grouping)
From TABLE 4B1 : Ca = 1 (Ambient temp)
From TABLE 52.2 : Ci = 1 (Insulation)
Protective device factor for Buried cables : Cc = 1
Cd = 1
Cs = 1
Protective device factor : Cf = 1
It = tabulated current carrying capacity
It = In / (Cg x Ci x Ca x Cf x Cc x Cs x Cd)
It = 45 / (1 x 1 x 1 x 1 x 1 x 1 x 1 )
It = 45.00 Amps
From TABLE 4D5 Cable selected = 6 mm²
Current capacity of cable selected = 47 Amps
TABLE 4D5 For 6 mm²: mV/A/m = 7.3
mV/A/m corrected for power factor = mV/A/m x Power Factor = 7.3 x 1 = 7.3
Voltdrop = (mV/A/m x Length x Design current) / 1000
Voltdrop = ( 7.3 x 10 x 41.3 ) / 1000
Voltdrop = 3.01 Volts
(Maximum permissible voltdrop (regulatuon - 525) = 11.5 Volts)
Calculated Cable size = 6 mm², Actual Earth conductor size = 2.5 mm²
Maximum Cable Length = 38.1 Metres
Supply Voltage = 230 Volts
Power factor = 1
Ib - Design current = 41.3 Amps
Protective Device Type = MCB type B (BS EN 60898)
In - Protective Device Rating = 45 Amps
Cable Type : Twin & Earth
Length of run of cable = 10 metres
Installation Method : Single-core or multicore cable direct in masonry having a thermal resistivity
not greater than 2 K.m/W - without added mechanical protection.
(method C)
Ambient temp = 30 °C
Number of circuits including this one = 1
Length of cable in thermal insulation = none
Apply Correction factors:
From TABLE 4C1 : Cg = 1 (Grouping)
From TABLE 4B1 : Ca = 1 (Ambient temp)
From TABLE 52.2 : Ci = 1 (Insulation)
Protective device factor for Buried cables : Cc = 1
Cd = 1
Cs = 1
Protective device factor : Cf = 1
It = tabulated current carrying capacity
It = In / (Cg x Ci x Ca x Cf x Cc x Cs x Cd)
It = 45 / (1 x 1 x 1 x 1 x 1 x 1 x 1 )
It = 45.00 Amps
From TABLE 4D5 Cable selected = 6 mm²
Current capacity of cable selected = 47 Amps
TABLE 4D5 For 6 mm²: mV/A/m = 7.3
mV/A/m corrected for power factor = mV/A/m x Power Factor = 7.3 x 1 = 7.3
Voltdrop = (mV/A/m x Length x Design current) / 1000
Voltdrop = ( 7.3 x 10 x 41.3 ) / 1000
Voltdrop = 3.01 Volts
(Maximum permissible voltdrop (regulatuon - 525) = 11.5 Volts)
Calculated Cable size = 6 mm², Actual Earth conductor size = 2.5 mm²
Maximum Cable Length = 38.1 Metres
Ive seen a 9kw shower ran on a 32 amp MCB
^^^ that is truely an excellent effort , doff my cap to Kenny.
So , even by the book , 6mm ok.
When you replace it unnecessarily you will.Recommend upgrading to 10mm for sure, who knows what the cable is running through or under.
No such thing as borderline. It complies or it doesn't.In my opinion, if its borderline then it's wrong. No room for maybe's in this game..
I'm putting a new shower circuit in today. Here's how I ensure method C, by maintaining an air gap around the cable where it passes through the insulation layer.
This isn't finished yet. There's a Crabtree shower pull below that joist and there's another cable to put in yet.
I've left slack in the cable above the isolator just in case the cables should ever need reterminating. To reduce the chances of that happening the ends are treated with cord end ferrules which stop the strands spreading and improve the quality of the connection.
Kenny my friend, you will find that the manufacturer states 9.5KW at 240V and this equates to 8.7KW at 230v.
Therefore the Ib you refer to is 8725/230 = 37.93Amp
Nice fabrication!
Well done!
I'm putting a new shower circuit in today. Here's how I ensure method C, by maintaining an air gap around the cable where it passes through the insulation layer.
This isn't finished yet. There's a Crabtree shower pull below that joist and there's another cable to put in yet.
I've left slack in the cable above the isolator just in case the cables should ever need reterminating. To reduce the chances of that happening the ends are treated with cord end ferrules which stop the strands spreading and improve the quality of the connection.
That doesn't matter.Trouble is, whenever I test the actual voltage at a premises, it is always around 243v. Never come across a 230v supply yet. Now do the calcs
Agree with Geoff , using baseline of 230v gives you worst case senario for current calcs.
so what would be your answer sedg?...sod it lets make sure the MCB dont let go and go for a 50A eh?....look sedgy, a 40A MCB to BSEN60898 aint gonna trip anyway for up to an hour with this load on it.....MCBs are there to PROTECT THE CABLE/INSTALL...so if it does let go its doing its job......only customer got no shower
God, i used to just wire showers. Been in this business for 40 years so i must have killed hundreds and burnt down thousands of properties! Lol
so what would be your answer sedg?...sod it lets make sure the MCB dont let go and go for a 50A eh?....look sedgy, a 40A MCB to BSEN60898 aint gonna trip anyway for up to an hour with this load on it.....MCBs are there to PROTECT THE CABLE/INSTALL...so if it does let go its doing its job......
Recommend upgrading to 10mm for sure, who knows what the cable is running through or under. In my opinion, if its borderline then it's wrong. No room for maybe's in this game..
That doesn't matter.
We have to use 230V for calculations and this will ensure safety - all variations in the voltage must have been considered for the values.
If the manufacturer states 9.5kW @ 240V (39.58A) then you can convert this to 8.7kW @ 230V (37.82A) if you wish but not much point.
On the contrary, there is a very important point to be made here and all electricians must understand that while the nominal volts in UK are 230V, the actual volts are anywhere from 255V to 218V as already mentioned on in this thread.
For a 9500W shower for example, the currents are:
at 218V = 35.96A
at 230V = 37.93A
at 240V = 39.58A
at 252V = 41.56A
If you are consistently getting 252V at a property, and you install a 40A breaker for a 9.5Kw shower, then you will be called back to rectify the tripping shower, although you can try to explain to the customer as much as you like that the BRB states......, the nominal voltage is supposed to be ........ etc etc.
cant see it letting go for the time it takes an avarage person to take a shower....but as you say...depends on what you call `avarage`...lol...I doubt that very much, considering a typical shower will be anything from 10 to 20 minutes!! Maybe, just maybe, if you have a couple of pre-maddona teenage Princesses you could have a point!! lol!!
Reply to 9.5 kw shower on 6mm ? in the UK Electrical Forum area at ElectriciansForums.net
We get it, advertisements are annoying!
Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.