6mm shower

[tom1]

I have a couple of Guinee pigs I was kinda hoping I could get them into the pot before the wife noticed they were gone

I've heard they are very tasty Guiness Drink

tell her they are hibinating some place warm

 

[musicspark]

can you recommend spices for cooking?

 

[tom1]

http://www.shelfordfeast.co.uk/guineapig.html

 

[Apache]

Good luck SL, I'm going to bed whilst you quietly marinade in honey and thyme..........

 

[tom1]

Good luck SL, I'm going to bed whilst you quietly marinade in honey and thyme..........

no need to sneak off we are not cooking cow yet

 

[SPECIAL LOCATION]

Hello again Music...

Getting back on track... (I have just replenished my beer glassGuiness Drink.. but don't tell the DONBlushing: O)

Ths problem is the sort of scenario where you have to apply a bit of common sense and judgement based on ..

1/ Your knowledge of the regs

2/ Your knowledge of the installation, circuit arrangements, length, cable sizes, fuse ratings etc..

3/ the age and structure of the property. (e.g. insulation levels, air spaces etc..)

So... just thinkings bits off one at a time..

How long IS th shower circuit?

What proportion of that run is actually buried in insulation?

How many people live in the property and are likely to use that shower?

Have you EVER seen a cable that has melted at a random point somewhere in the middle?

More likely to be around the ends / terminations at, isolator switch or at CU end!

You need to apply this sort of info to the problem...

 

[paul b b]

I have been asked to reconnect a shower which was installed "two or three years ago" The customer is therefore reluctant to believe there can be anything wrong.

The shower is a "Myra Sport" on a 6mm cable It has a nice Merlin Guerin RCD next to the CU but on a 40A breaker. I realise that something has to change but I don't know the rating of this model of shower can anyone help?

Hi music,

myra showers have a sticker on the top nr the 2 screws to take the cover off it will say the modle No. etc and will have some thing like 7.5 or 9.0 next to it.

good luck

 

[PC Electrics]

I think there's some confusion going on about shower ratings. Most quoted shower ratings are at 240 volts. So, an 8.5kW shower is 8.5Kw at 240 volts and its equivalent 230 volt rating is 8.15kW. There's some info about this in the (paper) Triton catalogue - can't find it on their website though.

So for a 40amp breaker the max rating at 230 volt is 9.2kW. This is equivalent to 9.6kW at 240 volts.

So you could happily fit a 9.6kW shower on a 40amp 6mm circuit provided the cable is clipped direct.

Indeed, I did just that a couple of weeks ago (actually it was a 9.8kW Mira Sport, but what's 200 watts between friends). Since I was fitting the circuit I was able to ensure clipped direct by going up and over the rafters rather than along the joists where the cable would have got covered in insulation.Where the cable had to pass through the insulation I used 250mm lengths of 100mm waste pipe to prevent the cable being surrounded by the insulation. The cable is capable to 47 amps continuous rating and the breaker will allow 40.5 amps all day. I also placed the breaker 1 blank space away from the rest in the CU as per manufacturers recommendations for continuous running. Anyways, when was the last time anyone saw a shower being run continuously (ie for more than 1 hour)?

Fair enough, a 10.5kW shower would've needed a 45A (50A) breaker and 10mm. Although I reckon it'd be okay on a 40A/6mm - I've seen plenty of 8.5 & 9kW showers on 32 amp breakers that have never had any problems.

The showers themselves are not designed for continuous running anyway - I'm sure I've seen 20mins ON 20 mins OFF quoted as the duty cycle on some model or other.

When it comes to showers and cookers circuits, some people seem to perceive problems that just don't exist (especially judging by some of the posts on that other forum)

 

[musicspark]

Cheers mate

 

[kme]

Well!!!!

This far through, and nobody else mentions it.

Music: Mira sport can be (generally) up to 10.8KW. Put a meter across it, on ohms range, and *calculate* the load? Have done this many times.

Further thought: the rating plate on those showers is normally attached to the "can"; the small heating unit with 4 spade terminals on top

PC is correct r.e. the 240V/230V variance; but I don`t see the relevance here. We`ve been told that Nominal voltage is now 230V; but National Grid (PLC) haven`t "turned down" the generators, to provide a 10V reduction!!!!! The calcs are on supply voltage - again measurement will provide the answer, if necessary.

NB If cable traverses more than 500mm of rockwool; derating is 50% FYI

HTH

KME

 

[Evans Electric]

what it if turns out to be a 10.6kw shower

There has to be a label in it somewhere, if not power it up and read the current. If its one of the stupid great big 'uns , the MCB will trip.

 

[Evans Electric]

PC makes a good point about MCBs next to each other, as they are thermal they can be warmed up by adjacent breakers and start tripping . Had it on some 3ph lighting this summer, hot day, hot print room , plus heat from adjacent breaker, tripping problem.

Boiler rooms can be a problem for MCBs sometimes.

 

[Tooold]

Just to add, i worked in a mira design engineers house and asked a couple of questions. One of which was cable size etc. If the mira 9.8, 10.8, 7.8 or whatever uses its full capacity for any length of time and I quote "It will probably have blown off the wall". Consequnetly I use 6mm for the mira sport 9.8kw on a 32 amp mcb, I do and try to talk customer into 10mm but doesnt always work. And apparently "if you get 10 years out of the shower your doing well". Of course the 6mm cable has been sized accordingly!!

 

[PC Electrics]

Hhmm, according to the curves on page 249, 41 amps won't trip a 32A mcb even in 10,000 seconds (2hrs 46 mins). So I fail to see what advantage you believe you're getting here. Could you elucidate, please?

Surely in this application BS7671 requires a 40A MCB?

 

[wozz]

how are people getting the cable in to shower? surely its enclosed in trunking or similar and therefore a different reference method required?

 

[musicspark]

I think I'll try to get the cable out of the rockwool