Mira shower help/ ratings please

[Simon_]

I have upgraded an old wylex CCU to modern and removed the separate Isolator box with a 40a rccb that was connected to a Henley block and then powering the shower from the CCU. The cable is 6mm and it's a Mira sport but fairly old. There was no shower switch so it was permanently on all the time and some of the cable was run on the outer wall of the house and back in the brick. Length from CCU to shower is approx 10-15m and obviously now a switch will be put in just before the bathroom. Was the Mira sport a specific kw to that model? It says on some sites that it's 10.8 kw in which case it will need a 10 mm cable and 45a mcb as it has a 240v sticker on the inside. I.R. Test on the old cable came back fine.

 

[malcolmsanford]

Was fitting a new switch and checking over the Shower circuit part of the CU change?

If it wasn't I would be clamp testing the shower to get a "working" reading and depending on what you get would be my next step. If it is running on max over that 40amp protection device rating, then I would be advising the client that I'm switching the circuit off as it contravenes reg 433.1.1 and note it on your EIC under existing installation and you have isolated the circuit.

 

[Simon_]

Yeah fitting the new switch and cable will be part of the cu change. The installation has not been re-energised yet since being installed.

 

[malcolmsanford]

Well then you now have the responsibility of the circuit.

You can not energise the circuit if the appliance is pulling more than the load ie 40amp protection device pulling 42 amps as in reg 512.1.2 the equipment must be suitable for it's design current, so a 42amp appliance is not suitable for a 40 amp protection device.

As I suggested I would clamp the unit of maximum power and see what you get. If it is below the 40amp then yes energise the circuit, but make a note on your EIC about existing installation, if it is above 40 amps then you really have no choice but to isolate the circuit and advise your client what to do

1 upgrade the circuit
2 fit a smaller shower.

 

[MarkieSparkie]

As you have found there are 6 models in the range, the Mira Sport 7.5, 9.0 and 9.8Kw, plus the Mira Sportmax 10.8Kw, plus the Mira Sport Thermostatic 9.0 and 9.8Kw. As you have an older model it's likely to be one of the basic Mira Sport models, most likely a 7.5 or 9.0Kw model.
If you remove the shower unit front cover you will find the units rating label, remember when calculating the nominal current demand that elements are rated at 240V (NOT 230V) so that should be the divisor in your calculation.

 

[DazBav]

I quite sure the Mira Sport is 9kw. What type is it as there are 2 or 3 variations? The newer has the control knobs one above the other and the older type side by side.

 

[DazBav]

As per MarkieSparkie says there is no chance you have the 10.8kw as this is a new model.

 

[Simon_]

I think an upgraded circuit would be best. I've just found the factory sticker on the shower and it's definately a 10.8k. The cu is crabtree but they don't make a 45 amp mcb, think I'll have to use a 50a mcb with the 10mm.