9.5 kw shower on 6mm ?

[PC Electrics]

Well spotted! I hadn't realised my quick calc was inaccurate. Should have been obvious though.


And as a double check that your calc is correct, I just got out my Triton catalogue and your answer agrees with their power equivalency table on the back page.

Thanks.

 

[Moses]

U R Welcome mate.

 

[i=p/u]

just protect the cable by the book

 

[PC Electrics]

Just realised what I did wrong! It's the current that changes with the ratio of the voltages, not the power:


(39.6 x 230) / 240 = 37.9

Doh!

 

[i=p/u]

but power is current

 

[Philpot]

Looks good to me Moses, I've had no end of trouble in the past trying to explain exactly your conclusion. Not wishing to make things any more complicated that it needs to be but I have been finding very high supply voltages lately. I'm retired now but do small repair jobs for a charity and had to get Scottish Power in to reset to supply voltage. I found it was 251/2volts during the day and after they monitored it it was found to be 253/4 overnight. I recently checked my own house supply and found that it is up to 250/1. Do other people find this?? It makes any calculations extremely difficult. It does seem like an easy way of selling more KWh.
The increase in consumption is not linear but it is quite close to it in a domestic installation.
Philpot

 

[Guitarist]

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

 

[Guitarist]

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.

You sure that your pipe is not considered "conduit". I always bring my oval conduit above the insulation but it is still "in conduit".
If someone can provide me with the area of air space around it that makes a cable "clipped direct" I would appreciate it.

 

[Geoffsd]

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

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.

 

[Guest55]

Agree with Geoff , using baseline of 230v gives you worst case senario for current calcs.

 

[Guitarist]

Agree with Geoff , using baseline of 230v gives you worst case senario for current calcs.

Totally agree.

 

[Top Cat]

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

 

[GLENNSPARK]

only customer got no shower

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......

 

[mickys86]

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

Officer dibble will be after ya!!!

 

[sedgy34]

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......

Errr have I said something!!!
all I was saying last week is I recommend 10mm on a 40a so no iinconvenience occurs to the user

 

[RISElectrical]

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..

No such thing as border line in the regs. If it complies then its safe to do so. On a large job if you over specced everything that was borderline you would end up maybe 30% more than a comparison quote, both complying with regulations.

 

[Moses]

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.

 

[Engineer54]

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.

I doubt that very much, considering a typical shower will be only 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!!

 

[GLENNSPARK]

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!!

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...

 

[GLENNSPARK]

thing is...everyones talking about the MCB tripping.....the only way to eliminate this possibility is to upgrade the cable...and the MCB as appropriate...but i remember a thread in here about this subject a while ago....one of our regular posters said he`d clamped his shower at full pelt (9.5KW)....the result....about 35A....yet again we have manufacturers going over the top with the demand of their appliances.....same with cookers n all...