The 2kW item on its own circuit rule?

[HappyHippyDad]

The customer wants a 2kW heat lamp installed outside.

The existing garage consumer unit is 2 way with no spare ways (16A sockets, 6A lights). I was under the impression that anything 2kW and over needs to be on it's own circuit. However, looking at Fig 15A (iii) in Appendix 15 it states 'exceeding 2kW', in addition this is under the heading for a ring rather than a radial.

The existing 2 way garage CU has a 16A radial, would the 9A heat lamp be suitable for this? The radial feeds 4 sockets in the garage, none of these are in constant use. The chap uses it as a workshop, when he is using it it may well trip if the heat lamp is on, due to overload.

My thoughts are... best practise would still be to fit a new garage consumer unit as it would be poor design utilising the existing CU. However, it doesn't seem to be breaking the regulations, meaning perhaps I have the choice of offering both options to the customer, giving him the facts, and letting him make the choice?

Edit.. It may actually be 2.02kW as it will have a 5w LED light with it! So perhaps it is over 2kW, not on a ring though.

 

[telectrix]

can't seea problem with it on the existing 16A radial, esp.if the sockets are lightlyloaded.could even change the MCB to 20A as long as the cable/s are ref.method D (27A for 2.5mm).

 

[mattg4321]

It’s not a hard and fast rule or regulation, more a guideline.

We don’t worry about people plugging in 3kw heaters or kettles to a ring final.

That said during a rewire/refit/new installation it should be followed.

 

[HappyHippyDad]

can't seea problem with it on the existing 16A radial, esp.if the sockets are lightlyloaded.could even change the MCB to 20A as long as the cable/s are ref.method D (27A for 2.5mm).

I could change the MCB, but it's a C16 at present. Needs to be a C for inrush current on a lift he has to raise the cars he is working on. Plus.. there is a 50m run from this CU down to another little shed feeding one socket and a light (6mm SWA). I'm guessing the Zs is going to be close already and raising the MCB to 20A may mean it doesn't meet Zs figures.

But... a B20 may be ok for inrush current AND better for Zs max compared to a C16!

 

[HappyHippyDad]

It’s not a hard and fast rule or regulation, more a guideline.

We don’t worry about people plugging in 3kw heaters or kettles to a ring final.

That said during a rewire/refit/new installation it should be followed.

That's interesting. I was about to reply and say... well it's a regulation so it needs to be followed. I then looked more closely and in brackets after the words APPENDIX 15 it has (informative).

Does this imply it is not a regulation?

Edit.. Just found this Appendices explained – Electacourse - https://electacourse.com/courses/18th-edition-course/lessons/part-8-appendices-3/topic/appendices-explained/

 

[mattg4321]

Without checking it’s not a regulation as far as I can remember.

 

[Doomed]

That's interesting. I was about to reply and say... well it's a regulation so it needs to be followed. I then looked more closely and in brackets after the words APPENDIX 15 it has (informative).

Does this imply it is not a regulation?

Edit.. Just found this Appendices explained – Electacourse - https://electacourse.com/courses/18th-edition-course/lessons/part-8-appendices-3/topic/appendices-explained/

Interesting link that:​

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[Pretty Mouth]

There's no regulation, or even guidance that I'm aware of, requiring loads > 2kW to have their own circuit.

The sentence in App 15 is often quoted out of context, and is imperfectly worded anyway. It advises not installing cooking appliances >2kW on ring finals, along with other measures, in order to avoid overloading one leg of the ring.

No such advise for radials, it'll be fine on it

 

[pc1966]

It advises not installing cooking appliances >2kW on ring finals, along with other measures, in order to avoid overloading one leg of the ring.

This!

Really it comes back to the assumption in the RFC cable rating that loads are not heavily concentrated in one place making the two "legs" of the ring strongly imbalanced as then the 2*20A-ish 2.5mm on 32A protection is not doing its job well.

Looking at the original request, I would have no issue with a 2kW heater lamp off the RFC so long as it is not coming off at the same place as other heavy loads. Sure it is not ideal from a division of fault protection point of view, but if it is the only reasonably option and there is a DP FCU to isolate any outdoor faults then it is not going to end the world.

I hope...