B and B+ Type R.C.D.s.

Oven, lights Type AC

Assume nothing - the last oven I fitted came with instructions that any RCDs should be A-types (presumably because of the electronic controls/timers) and these days with most lighting being LED with electronic drivers (sometimes class I) I'm not sure an assumption of AC would be safe there either. I think we're moving to A-types across the board as it were.

   - Andy.

AJJewsbury: 
 

Oven, lights Type AC

Assume nothing - the last oven I fitted came with instructions that any RCDs should be A-types (presumably because of the electronic controls/timers) and these days with most lighting being LED with electronic drivers (sometimes class I) I'm not sure an assumption of AC would be safe there either. I think we're moving to A-types across the board as it were.

   - Andy.

If the oven became live due to a fault, and excepting a TT earthing arrangement, would it really need an R.C.D. at all? The over current protective device would trip off.

Z.

Are these findings in the Valleys where time stands still?

 

Z.

I did go down the Rhonda last week, having done four jobs.

• Down the Rhonda TT upfront 30 mA Type AC RCD, installation just about acceptable, but they did have an electrical fire some time ago, there’s still soot marks on the walls.
• Coventry TNCS no RCD protection, house needs rewiring no earth on lights with metal switches and fittings, also loads of dodgy DIY work such as a ring spur connected with an exposed strip connector supplying the kitchen, utility and a water feature down the garden.
• Stoke on Trent TT upfront 30 mA Type AC RCD, installation just about acceptable, but there had not been an earth rod since it was it was rewired around forty years ago.
• Loughborough TNCS installation generally acceptable, but no RCD protection apart from the shower which has its own consumer unit.
• Then yesterday in Worcester as an installed TT installation with an upfront ELCB, which is actually as good as the day it was installed because it’s never been messed about with.
• None of these installations are suitable for the installation of EV charger points or heat pumps, neither should new appliances such as some washing machines be used. Though in the houses without RCD protection there won’t be tripping issues.
• The general condition of electrical installations in the UK is absolutely disgraceful and they are not fit for purpose anymore, if people want new appliances most of them should be having a considerable amount of work carried out updating or replacing their existing electrical installation, including the installation of the correct RCDs. However it Is not at all unusual to find people have had PV panels installed on the roof and battery storage without the correct RCDs being installed and so on and so forth.

If the oven became live due to a fault, and excepting a TT earthing arrangement, would it really need an R.C.D. at all? The over current protective device would trip off.

Yup 30mA RCD needed (twice) for additional protection - T&E concealed in walls, and supplied via a 13A socket outlet.

  - Andy.

AJJewsbury: 
 

If the oven became live due to a fault, and excepting a TT earthing arrangement, would it really need an R.C.D. at all? The over current protective device would trip off.

Yup 30mA RCD needed (twice) for additional protection - T&E concealed in walls, and supplied via a 13A socket outlet.

  - Andy.

But why does your plug-in oven need additional protection, ain't the earthing good enough?

Z.

But why does your plug-in oven need additional protection, ain't the earthing good enough?

The oven might not, but the socket/circuit does -  BS 7671 demands it, as I'm sure you're aware. Earthing doesn't protect against direct contact (nails into concealed cables) or high Zs (long extension leads fed from the socket).

   - Andy.

AJJewsbury: 
 

But why does your plug-in oven need additional protection, ain't the earthing good enough?

The oven might not, but the socket/circuit does -  BS 7671 demands it, as I'm sure you're aware. Earthing doesn't protect against direct contact (nails into concealed cables) or high Zs (long extension leads fed from the socket).

   - Andy.

I can not for a moment imagine that a careful person like you Andy, would drive a nail into a cable in a wall, or have a long extension lead supplying your oven. Perhaps we are having too much confidence in R.C.D.s these days. 415.1.2. Run cable in good steel conduit and earth everything well. It worked in the past, why not now?

Z.

I can not for a moment imagine that a careful person like you Andy, would drive a nail into a cable in a wall, or have a long extension lead supplying your oven.

As it happens that particular oven wasn't at my house, so no guarantees there (I wouldn't trust me anyway, not after the incident with the loppers and the chainsaw flex). The issue with extension leads is that they could be plugged into the socket instead of the oven (it would actually be the closest socket to the back door, and easily accessible with the cupboard door open, so not entirely implausible). 

Perhaps we are having too much confidence in R.C.D.s these days. 415.1.2. Run cable in good steel conduit and earth everything well. It worked in the past, why not now?

Certainly if it hadn't been supplied by a soft skinned cable plastered into the wall and via a socket, the RCD could have been omitted …. but as the saying goes, we weren't starting from there.

    - Andy.