Older installation: RCD protecting oven circuit

vsn

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Hi all,

I have a 90s-built house where pretty much only the sockets are RCD-protected.

I would like to move over the oven to the RCD-protected side.
Just move the MCB from the red side to the green, and feed it from the RCD.


This is a modern Neff oven so I guess the risk of unwanted trips is low.

I have two questions:
  1. Is there a disadvantage that I haven't thought of?
  2. Would this fall foul of any regulations?
I am a DIYer but competent enough.
 
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well I wouldn't bother. Likely to cause more problems, than you would fix.

However if you did, you need to move the oven neutral/ black wire in the CU, to the other block, otherwise the RCD would trip as soon as the oven was switched on
 
1. Probably not.
2. No.

What advantage do you think there will be by having the oven on an RCD?
 
1. Probably not.
2. No.

What advantage do you think there will be by having the oven on an RCD?
From 2018 Australian regulations require that newly installed ovens (and other hard wired devices) be fed via RCDs/RCBO.
RCDs/RCBOs have been required on new/rewired lighting circuits for about ten years.

(Queensland requires that "protection" be brought up to "current standards" within three months of a house being sold.)
 
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1. Probably not.
2. No.

What advantage do you think there will be by having the oven on an RCD?

Well I'm used to European installations where everything is fed via RCD.
The RCD is even placed before the main switch.
It'll help me sleep better.

AndyPRK, good point about moving the neutral of the circuit also.
What problems am I likely to cause (apart from possible unwanted trips) ?
 
Well I'm used to European installations where everything is fed via RCD.
That's not the case.

The RCD is even placed before the main switch.
That is probably because the earthing was inadequate to operate the fuse/MCB and not the personal protection RCDs you have in your present consumer unit.

It'll help me sleep better.
Perhaps you should not have been sleeping so well in Europe.
 
First of all, I would check that that MCB in question actually does supply the oven.

You don't give details of the oven, but if it is a single oven they quite often come with 1.5mm flex fitted with a 13A plug. As this cable is not suitable for direct connection to a 32A MCB, the ovens are often plugged into an existing nearby socket which in your case will be RCD protected. Other times the cooker circuit will be connected to a socket or FCU to incorporate a 13A fuse, in which case it won't be RCD protected.
 
It also says hob

It's both. A double oven (well, one and a half really) and the hob, which used to be ceramic.
So you can see the necessity for 32A.

The hob has since been replaced with a gas hob.

Assuming it's the correct MCB (which I will check), why shouldn't I protect the circuit
via the RCD? The trend is towards RCD everywhere anyway. In Europe, even light circuits
have earth connections and are RCD-protected.
 
Assuming it's the correct MCB (which I will check), why shouldn't I protect the circuit via the RCD?
You can - but ultimately if you want to improve the installation you need a new consumer unit to replace that 25+ year old obsolete one.
Moving a single circuit to the RCD side will achieve very little, and of the circuits which would benefit most from the RCD, an oven and hob is at the bottom of the list.

In Europe, even light circuits have earth connections and are RCD-protected.
UK lighting circuits have required earth connections for over 50 years.
Most circuits in domestic properties have required RCDs for at least a decade.
 
Assuming it's the correct MCB (which I will check), why shouldn't I protect the circuit
via the RCD?
Today found the RCD had tripped and the freezer had stopped working. This is the problem as you add more and more to a single RCD, with RCBO then if one trips it only takes out that circuit, but with just two for whole house, the chance of them tripping is greater than when you have 14.

Every installation shall be divided into circuits, as necessary, to reduce the possibility of unwanted tripping of RCDs due to excessive protective conductor currents produced by equipment in normal operation. Only way to reduce unwanted tripping of RCDs is to have each circuit on its own RCD.

In spite of loosing a freezer full of food in old house, still fitted RCBO's in new house, but not had a unwanted tripping of a RCBO to date, they have tripped, but there was a good reason for them to trip, the old house tripped one RCD when resetting the other, there were simply too many circuits on the RCD so any spike will cause them to trip.
 
Today found the RCD had tripped and the freezer had stopped working. This is the problem as you add more and more to a single RCD, with RCBO then if one trips it only takes out that circuit, but with just two for whole house, the chance of them tripping is greater than when you have 14.

Understood. Perhaps replacing that MCB with RCBO is the way to go as replacing the whole CU with one of those modern ones with dual RCD might be overkill.
 

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