4mm T&E for ring circuit

[nicks electrix]

Evening Forum

Quick question. New kitchen is being fitted and i have been asked to do the wiring. There are quite a few integrated appliances such as washing machine, dishwasher, microwave and tumble dryer. There are also 6 under wall unit lights and then 6 double socket outlets. I have decided to use 4mm T&E on a new ring circuit. How easy is it to get 2 4mm conductors in a terminal?

Thanks

 

[Zeespark]

Depends on accessory manufacturer bud, the likes of MK isnt a problem.

AndyGuinness

 

[danny7299]

I wouldn't like to make it off in a fused spur but it's fine in a double sockets am I right in thinking your going to have a 4mm ring ? Why ?

 

[a1spark]

AS Above .

Does your method of installation require it...rating factors etc ?

 

[rugbymacc]

what about 2 20amp radials instead.

My Napit assessor said as far as he was concerned it was a better set up

1~)40 amps instead of 32 amps

2~)If theres a fault on the circuit you only lose half of the kitchen. (thus allowing for life to continue till the fault can be sorted)

 

[Stevie h]

Hi, could you not just install a standard 2.5 ring and pull in a separate 1.5 feed in for the lighting? or as suggested, 2 x 20a 2.5mm radials .... 2 x 4mm's in single sockets/ fuse spares can be a bit of a pain to terminate.

Ste

 

[batty]

Not sure why you want to use 4mm on a ring you still will only have 32 amp available. Other options are put two rings in that is what I would do personally. Or put machines on radials and have ring for sockets.

 

[a1spark]

I would only install 2.5 radials in a kitchen if they terminated in fused connection units.supplying fixed loads .If they supply socket outlets then the circuit is likely to be overloaded and some one is likely to extend from them at a later date making matters worse...4mm radials are preferrable.

 

[nicks electrix]

Thanks for the overwhelming response.

The reason why i wanted to use 4mm ring is 2.5 reference method C can only carry 27amps and the loads might not be distributed evenly on the ring.4mm can carry 37 so with it being protected by 32amp breaker i know i am safe.

Thanks

 

[NozSpark]

I would only install 2.5 radials in a kitchen if they terminated in fused connection units.supplying fixed loads .If they supply socket outlets then the circuit is likely to be overloaded and some one is likely to extend from them at a later date making matters worse...4mm radials are preferrable.

TBH I was wondering about 32A 4mm radials.. I have installed them in the past in kitchens and it is ok so long as installation methods are ok and the circuit isn't too long

 

[a1spark]

Thanks for the overwhelming response.The reason why i wanted to use 4mm ring is 2.5 reference method C can only carry 27amps and the loads might not be distributed evenly on the ring.4mm can carry 37 so with it being protected by 32amp breaker i know i am safe.

Thanks

I can see where you are coming from Nicks, each leg of a ring is only permitted to carry 21A continuous , however overloadings for short periods of time are permissable { not 3036s ]. Your the designer of the installation,, you know the loadings on the circuit so yeah go for it if you consider it correct . Bear in mind though the max current capacities of the terminals of the accessories ,if you have not distributed the loads evenly then you may overheat the terminals ...just a thought

 

[Sidewinder]

Ahh, now to stir up debate, how do you define a "leg" of a ring circuit?

What about aplying Kirchoff's law to the circuit and calculating the complete ring circuit design to ensure compliance?

(ALA C&G 2391-02 / 2400)

Paul

 

[Chr!s]

Ahh, now to stir up debate, how do you define a "leg" of a ring circuit?

What about aplying Kirchoff's law to the circuit and calculating the complete ring circuit design to ensure compliance?

(ALA C&G 2391-02 / 2400)

Paul

Paul, to calculate this way we would need to know where all the loads are on the circuit, the problem with rings is we don't know where most of the loads will be.

I don't see a problem with a standard 2.5 ring, providing you pay attention to the loading where possible, You probable know where the dryer etc. will be put.

Although there may be many appliances rarely are they all on together, add to this the fact that many of the appliance only heat for a short period of time, and even the dryer element cycle on and of via a toc. so even if they were on at the same time the likely hood of the loads being all at there peak at the same time are slim indeed.

Lets not forget maximum capability is limited by temp rise caused by the load, this can take up-to an hour, so some short time high current demands may be acceptable.

Regards chris

 

[Lee321]

deffo plumb

sometimes we come across 4mm rings on industrial more often but this is usually a crazy designer trying to justify his job or large lengths so vd is a concern

 

[Sidewinder]

Plumber,

I know the workings and how it is to be done, I was just trying to promote some debate and discussions on the design of ring circuits rather than installing them to the std ccts in the OSG.

Your intermittent scattered loading is diversity is it not.

Lee,

It is not necessarily a crazy designer, it may be a crazy customer or specifier putting on additional constraints over and above those in 7671.

It is acceptable for the customer to raise the bar, as he who pays the piper calls the tune as it were!

 

[Chr!s]

I know the workings and how it is to be done, I was just trying to promote some debate and discussions on the design of ring circuits rather than installing them to the std ccts in the OSG

Well to design a circuit for socket outlets in a domestic situation would be difficult as i explained before, but yes i agree if you understand the design aspect of a ring circuit then you would be able to make a approximation as to whether the ring is acceptable or not.

regards chris

 

[Lee321]

It is not necessarily a crazy designer, it may be a crazy customer or specifier putting on additional constraints over and above those in 7671.

It is acceptable for the customer to raise the bar, as he who pays the piper calls the tune as it were!

yes those ppl too

 

[VoltzElectrical]

DIVERSITY!!!

 

[Megaohm7]

what about 2 20amp radials instead.My Napit assessor said as far as he was concerned it was a better set up

1~)40 amps instead of 32 amps

2~)If theres a fault on the circuit you only lose half of the kitchen. (thus allowing for life to continue till the fault can be sorted)

The NICEIC chappie that I was talking to the other day said that he only does radials these days and gave the same reason .. ..Looks like things going back to the good ol days

 

[batty]

The NICEIC chappie that I was talking to the other day said that he only does radials these days and gave the same reason .. ..Looks like things going back to the good ol days

I am not convinced with using 20 amp radials the way I see it ring mains have been used for the last 50 odd years and I can't remember having problems with one being overloaded but I have had customers say they have had 20amp circuit breakers trip when vacuum cleaners are plugged in not commen I admit but a few times I have been told this. I would imagine its because the starting of the vacuum the 20 amp breaker cannot withstand the motor current start up. I cannot see the advantage of 20 amp radials and will carry on using ring mains unless there is a real convincing argument to say they should not be used.