4mm radials

[JonathanA]

Morning all,

I‘d really appreciate some advice - not a kick in the pants please - from those more knowledgeable than me!

My new kitchen and utility room are each supplied by 4mm T&E radials. Each circuit is protected by a 32A RCBO.

Kitchen

• Single oven rated at 2.5kW connected to single socket at end of radial
• Toaster, kettle, fridge and microwave connected to 3 x double sockets leaving some spare

Utility

• Washing machine connected to single socket
• Vented dryer connected to single socket
• Boiler connected to 3A fused switch
• 2 x double sockets spare

Length of radial in both cases is less than 10m so no worries there.

I was told that a 4mm radial with 32A protection is a ’standard circuit’ but there are issues with the installation that bother me, specifically:

1) The oven is not on a separate circuit so it’s not a ‘standard circuit‘ at least according to the OSG
2) The cabling for the most part is clipped direct but it is boxed in with other loose cables for a run of about 2m.
3) All the cables from the consumer unit descend loosely through a void in an otherwise insulated stud wall before going their separate ways (I suspect my OCD is kicking in with this one)

My worry of course is the possibility of the 4mm cables becoming overloaded at less than 32A.

Please understand that rewiring either of these circuits or installing new ones would involve huge disturbance which I am very keen to avoid.

I would sleep easier if the RCBOs were down rated to 25A but Wylex only make compact types for this rating which wouldn’t match the others in the CU.

I’d really appreciate your advice on this. Best response would be to tell me it’s fine, that I’m overthinking it and should get a life!

Thanks, J

 

[Mike Johnson]

I think the other countries that use BS7671 as a guide to their countries electrical installations are ex or still are British colonies i.e. Gibraltar & Singapore spring to mind.

 

[littlespark]

I'd rather have a open L or N leg on a ring than an open Earth leg on a radial.

I’d rather not have any open legs on either.
That’s where regular testing comes in ?

rule of thumb, 4A per kW... so your 2.5kW oven takes 10A.... kettle? Maybe the same. Fridges, hood extractor etc are very little in comparison.

 

[stevethesparks]

I’d rather not have any open legs on either.
That’s where regular testing comes in ?

Agreed

 

[Mike Johnson]

I’d rather not have any open legs on either.
That’s where regular testing comes in ?

Used to see a lot of those in Amsterdam down by the canal.
And I do think they where subject to regular testing. ?

 

[stevethesparks]

Used to see a lot of those in Amsterdam down by the canal.

Spend a lot of time there?

 

[Mike Johnson]

Sure did, stunning views.

 

[richy3333]

Paignton Pete, to be honest, it may never happen, but if it does it’ll be because I’m the sort of bloke that freak accidents do happen to!

I'd recommend lightening protection and SPD's then ?

 

[timbobelfast]

Morning all,

I‘d really appreciate some advice - not a kick in the pants please - from those more knowledgeable than me!

My new kitchen and utility room are each supplied by 4mm T&E radials. Each circuit is protected by a 32A RCBO.

Kitchen

• Single oven rated at 2.5kW connected to single socket at end of radial
• Toaster, kettle, fridge and microwave connected to 3 x double sockets leaving some spare

Utility

• Washing machine connected to single socket
• Vented dryer connected to single socket
• Boiler connected to 3A fused switch
• 2 x double sockets spare

Length of radial in both cases is less than 10m so no worries there.

I was told that a 4mm radial with 32A protection is a ’standard circuit’ but there are issues with the installation that bother me, specifically:

1) The oven is not on a separate circuit so it’s not a ‘standard circuit‘ at least according to the OSG
2) The cabling for the most part is clipped direct but it is boxed in with other loose cables for a run of about 2m.
3) All the cables from the consumer unit descend loosely through a void in an otherwise insulated stud wall before going their separate ways (I suspect my OCD is kicking in with this one)

My worry of course is the possibility of the 4mm cables becoming overloaded at less than 32A.

Please understand that rewiring either of these circuits or installing new ones would involve huge disturbance which I am very keen to avoid.

I would sleep easier if the RCBOs were down rated to 25A but Wylex only make compact types for this rating which wouldn’t match the others in the CU.

I’d really appreciate your advice on this. Best response would be to tell me it’s fine, that I’m overthinking it and should get a life!

Thanks, J

From the way you have described the installation methods, the only thing I would watch out for is the 'grouping' Cg factor and that the circuits are spaced from each other in that void. Even still there is an element of diversity for the expected loads on these circuits. Personally I believe you are 'over-thinking' this! But without see the installation these are merely assumptions.