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

 

[buzzlightyear]

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.

why would you want to down grade to 25 amp has a 32 on 4mm is good ,and what sort of cu in now.

 

[pc1966]

Neither circuit is going to be at the full 32A unless you plug in some heaters to the spare sockets as well, and even then the proportion of time spend at full load is going to be short (e.g. 5 mins to boil a kettle of water, etc).

So while part of the run may be a little less than 32A rated, I doubt it is going to see that current at all, let along for long enough periods to cause damage. Usually it is poor connections that cause serious overheating!

The main limitation is you don't have much margin for anything larger in the way of oven/cooker, so anything fancy would probably need a new circuit put in for such a change. But for what you have, it seems fine.

 

[westward10]

Whether the circuit may or not achieve 32A in normal use not forgetting this cannot be predicted with socket outlets, if the installation method does not permit a 32A protective device then they should not be used.

 

[Mike Johnson]

To paraphrase your question "your overthinking it and should get a life!" ? the only foreseeable problem could be in the future as pc1966 mentioned if you change your cooker or hob, especially if the hob is an induction type that can't be run off a 13amp plug, these have limitations on how many zones can be on at the same time.

 

[loz2754]

Method 103, in insulation in a stud wall-
4mm² 17.5 amps.

 

[westward10]

To paraphrase your question "your overthinking it and should get a life!" ? the only foreseeable problem could be in the future as pc1966 mentioned if you change your cooker or hob, especially if the hob is an induction type that can't be run off a 13amp plug, these have limitations on how many zones can be on at the same time.

That is not the only foreseeable problem you have socket outlets with an unpredictable loading.

 

[Mike Johnson]

Perhaps my post should have said "one of the foreseeable problems" rather than "the only foreseeable problem"

 

[telectrix]

think P said cables in stud were loose.i.e. insulation moved away from cables.

 

[telectrix]

it'll never even get warm. unless a certain weed is being grown .