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Two high-power appliances on a single 40A RCD
Former Community Member
I have an electric shower installed on a 40A RCD, in a room adjacent to my kitchen. The shower is only used in an emergency - i.e. when our gas boiler is unable to provide hot water to our main bathroom. I would like to take a spur from this 40A connection to use for a new double oven, which is rated at 32A. Can anyone advise on a safe and legal way to do this, ensuring that only one of the two appliances can be connected at any one time?
That Ib is potentially larger than In is not in itself a problem but perhaps slightly unusual. In this case I suspect that it is entirely satisfactory for the reasons in the OP. The regulations are all limitations to what you can do. This circuit is exactly the same as any other final circuit, it is subject to protection against overload for long periods. There is no regulation simply because it is not prohibited. Surely you have been taught that at some point. Perhaps this is the reason why electrical designers and installation assessors need to be somewhat skilled?
The OP specifically said
Can anyone advise on a safe and legal way to do this, ensuring that only one of the two appliances can be connected at any one time?
Having Ib>In is not proper design. It seems the OP suspects this. David, you are making a lot of assumptions about this existing circuit . Giving advice that it is perfectly okay to increase Ib of an existing circuit is dancing on the cutting edge of worst practice. As I have stated in the past, the regs requirements have a bit of headroom built in for a reason. This over-engineering allows some margin for error for the the whole life service of the circuit. This is not a temporary arrangement that can take a bit of abuse for a few weeks, then on to the next venue. This is in someones home or business.
That Ib is potentially larger than In is not in itself a problem but perhaps slightly unusual. In this case I suspect that it is entirely satisfactory for the reasons in the OP. The regulations are all limitations to what you can do. This circuit is exactly the same as any other final circuit, it is subject to protection against overload for long periods. There is no regulation simply because it is not prohibited. Surely you have been taught that at some point. Perhaps this is the reason why electrical designers and installation assessors need to be somewhat skilled?
The OP specifically said
Can anyone advise on a safe and legal way to do this, ensuring that only one of the two appliances can be connected at any one time?
Having Ib>In is not proper design. It seems the OP suspects this. David, you are making a lot of assumptions about this existing circuit . Giving advice that it is perfectly okay to increase Ib of an existing circuit is dancing on the cutting edge of worst practice. As I have stated in the past, the regs requirements have a bit of headroom built in for a reason. This over-engineering allows some margin for error for the the whole life service of the circuit. This is not a temporary arrangement that can take a bit of abuse for a few weeks, then on to the next venue. This is in someones home or business.
