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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?
One person having a shower whilst the oven is in use could end with catastrophic damage to the electrical installation and house.
It is just not worth taking the risk.
Andy Betteridge
Again for clarification: if the proposed solution is for a switch which prevents both appliances being connected to the same circuit simultaneously, doesn't this complete;y remove the risk?
433.1 Co-ordination between conductor and overload protective device
Every circuit shall be designed so that a small overload of long duration is unlikely to occur.
I replaced a fused switch with a 30-amp cartridge fuse in it after the whole thing blew off the wall, the customers teenage daughter was spending around twenty five minutes in a shower with a 8.5 kW electric shower, her dad kept packs of fuses ready to replace the fuses as they blew, then one day he went into the garage and there was just a big soot mark on the wall where the fused switch used to be.
Interesting debate! To further clarify, in case of any doubt, the circuit in question has no sockets. It is a hard-wired connection which was installed specifically for the electric shower, 10 years ago. The proposed solution would add a 2nd hard-wired connection, for the oven (with a switch to ensure that only one can use the circuit at any one time).
..something to ensure that they cannot be used simultaneously is fine.
To David, the reg number is a few pages back.
This is an existing circuit. A shower circuit. Not relevant how often it is used. I It was designed " as is". So Ib has been decided before any inkling of adding to it. Your motor example is a different application and environment.
To add another load increases Ib by dint.
It does,however raise another issues of the bar for safe for continued service as opposed to compliance with BS 7671.
You could, for example, install to your own judgement, ignore BS7671 and bang test it. It works (up to a point). It could then be subjected to trial by EICR code , have a load of C3's and be found "satisfactory"......essentially avoiding BS7671.
Do you think that is a good thing? Your margin for error is gone or reduced. How does this not adversely affect the process as being fit for purpose? It is worth repeating; this is someone's house.
perspicacious: None of you have yet found a regulation number which is in opposition to my suggestion. BOD is being BAD because he doesn't have one either.
Crikey, that was a very quick swerve there, to quick to even use indicators when being presumptive...............
