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Electric Showers and plumbers

David Stone
I had a phone call from my son yesterday, the shower in his house had broken and not being a plumber/electrician got a couple of quotes. The old one was 6.5 kW with 6mm cable. The plumbers all seemed to think that the cable and MCB should be replaced as the current rating was inadequate for a replacement, the MCB is 40A. I had a quick check what could be fitted as there are many more powerful ones available and this weather the water is not wonderfully warm! I have not really thought about shower cables for a long time as they are almost always in good condition. Table 4D2 6mm clipped direct says 46A, continuous rating. A 10.5kW shower takes 45.65A on 230V so is quite satisfactory on the 6mm cable. In fact, the model I was looking at (Mira fancy thermostatic, expensive) would only take this power at full flow and temperature rise as it has electronic thermostatic proportional control and normal running current would be modulated and somewhat less. I consider this to be perfectly satisfactory, but the plumbers obviously haven't read the regulations. I often find the same with cookers, various sellers suggest 10mm cable, which may well not be the existing size. Should any change be made, and why do would you do this?
  • 0
    A JW video about extreme cable overloading.

    https://www.bing.com/videos/search?q=youtube+over+heated+cable&docid=608019794601117588&mid=CDC0D8932DD1A3ABBED4CDC0D8932DD1A3ABBED4&view=detail&FORM=VIRE


    Z.
  • 0
    I notice on page 6 of the Triton Avena Electric Shower instructions, that it states the Energy Efficiency for the three models (8.5 kW, 9.5 kW & 10.5 kW) as all being 39% Energy Efficient.


    Does that efficiency figure take into account the efficiency of the power station and transmission equipment?  Otherwise 39% seems a little on the low side. ie for the 10.5 kW rating at 240v, just over 4 kW goes into the water and the other 6.4 kW goes where exactly?


    Cheers!
  • 0
    Clearly that is not the VA to heated water  electrical efficiency - that should be fast 99.9 % or some small part is going to melt. Even 100W of your 10kW (1% ) going into warming up the plastic box instead of the water would be pretty impressive..


    I suspect it is the EU water efficienct rating where showers are rated by the no of litres per minute they use during some typical test shower.

    I often think simply saying "XXlitres per minute" would be better. How well it cleans you has more to do with the jet pattern on the shower head.

    Mike.

  • 0
    mapj1:

    I often think simply saying "XXlitres per minute" would be better. How well it cleans you has more to do with the jet pattern on the shower head.


    It's not a car wash!


  • 0
    but wouldn't it be fun if it was.....
  • 0
    Imapj1:

    but wouldn't it be fun if it was.....



    https://www.tlc-direct.co.uk/Products/TTLBD.html


  • 0
    Ah!  So I guess then that Sound Power Level (db) of 15 across the range relates as to how loud you sing in the shower?  There was me thinking it was dB?


    Getting back to Energy Efficiency (%) being 39% of something, The Energy Efficiency Class is A.


    Seems like a dumbed-down exam result....


    Clive

  • 0
    Now that's a product - pity it is discontinued...

    I imagine it is not considered green, but set against laundry and putting bits of towel fluff in the seawater etc it may or may not be that bad.

    Specifications
    Electrical nominal power nominal power

    rating at 240V      9.0kW – (40A MCb rating) 
    rating at 230V   8.3kW – (40A MCb rating)

    Trickle current on OFF mode is 0.04A at 240V     (9.6W) but is not isolated.
    Minimum cross sectional area of supply cable is 6mm².

    Derating factors should always be taken     into consideration when selecting cable size.
  • 0
    The body dryer has a change over switch in it, so it shares the shower circuit and disconnects the shower when it’s running and vice versa.
  • 0
    The first is Andy which is "a floor void is ref method B". I suppose you have looked at number 40, or 47 of the diagrams, but you have not followed the formula provided. a 6mm cable in a ceiling with 8" joists is outside the range, and is clipped to the wood also, in my opinion, is still C.

    I didn't think so. The formula on method 47 seems to say it applies for voids between 1.5x and 50x the cable diameter - so for an 8"/200mm joints the cable would need a diameter of less than 4mm (or more than 133mm) to be outside of that range - which I'm pretty sure 6mm² T&E isn't.


        - Andy.

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