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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?
Wow, this discussion is getting a bit heated isnt it?
well my tenpernorth.
our traditional diversity for a "cooker" has prettymuch stood the test of time.
sensible use of the standard clac is allowed providing that we consider if there are any underlying reasons not to use it.
i have, over time, considered a few where oven and hob are on different circuits but together present no more diversified load than a full blown traditional cooker.if someone wants to put those two units on ond ciruit i would not usuallyhave a problem with that unless cir umstances dictate otherwise.
however this combinstion we are discussing is different, two possibly unrelated activities.that is the problem.
the OP suggests that their particular usage pattern would not present a problem and that could be correct in intention and indeed in pratice.
however, the stiuation does leave to open to abuse, either by the OP or others.
I have no problem with a sensible change over/power sharing arrangement that prevents both appliances running at the same time if separate circuits would be too inconvenient to install for some reason. Not the most elegant of circuits but hey ho doable.
what i do feel uncomfortable about is a circuit that invites overloads big or small.
yes we do allow overloads up to 13% as normal and a circuit must not trip. Cable calcs etc give us that headroom.
at 45% overload a circuit must trip , altjough it could take hours to trip.
a masive overload would (should) trip quite quickly.
i would not like to run a circuit that encourages a breaker to run on its curve for any meaningfull duration.
i feel that this circuit encourages the possibility of such overloads even rarely and is best avoided.
so my vote is either two circuits or a switchover such as a shower priority type set up.
by the same token i would not like a ring (or radial) with a 16A mcb in circuit running an oven in most instances, again separate circuits or a low wattage plug in typd if you must.
Wow, this discussion is getting a bit heated isnt it?
well my tenpernorth.
our traditional diversity for a "cooker" has prettymuch stood the test of time.
sensible use of the standard clac is allowed providing that we consider if there are any underlying reasons not to use it.
i have, over time, considered a few where oven and hob are on different circuits but together present no more diversified load than a full blown traditional cooker.if someone wants to put those two units on ond ciruit i would not usuallyhave a problem with that unless cir umstances dictate otherwise.
however this combinstion we are discussing is different, two possibly unrelated activities.that is the problem.
the OP suggests that their particular usage pattern would not present a problem and that could be correct in intention and indeed in pratice.
however, the stiuation does leave to open to abuse, either by the OP or others.
I have no problem with a sensible change over/power sharing arrangement that prevents both appliances running at the same time if separate circuits would be too inconvenient to install for some reason. Not the most elegant of circuits but hey ho doable.
what i do feel uncomfortable about is a circuit that invites overloads big or small.
yes we do allow overloads up to 13% as normal and a circuit must not trip. Cable calcs etc give us that headroom.
at 45% overload a circuit must trip , altjough it could take hours to trip.
a masive overload would (should) trip quite quickly.
i would not like to run a circuit that encourages a breaker to run on its curve for any meaningfull duration.
i feel that this circuit encourages the possibility of such overloads even rarely and is best avoided.
so my vote is either two circuits or a switchover such as a shower priority type set up.
by the same token i would not like a ring (or radial) with a 16A mcb in circuit running an oven in most instances, again separate circuits or a low wattage plug in typd if you must.
