EICR - please advise

[Risteard]

As I said, it's just a matter of personal opinion.

I would personally only ever use 20A radials to supply rooms/areas where I believed that 'large loads' were fairly unlikely. A circuit with multiple double sockets which can theoretically only support about 1.5 'fully-loaded' 13A outlets just feels a bit 'tight' to me.

Kind Regards, John

All I can say is that the facts don't support that concern. The average load in a domestic dwelling is very low, and typically peak loads aren't that great either. Just look at what DNOs & DSOs allow for each dwelling without incident.

 

[jg321]

Indeed. I'm fairly certain that in my house at least, and probably most modern households, with the exception of the kitchen, I could plug in every device I could find, and the total would be not much more than 10A. A big chunk of that would be the vacuum cleaner and iron. OK maybe 11A if I include those!

 

[securespark]

I have only ever found one true ring final on a device <30/32A.
An upstairs ring final on a 20A 3036.

All the others were broken rings put onto smaller breakers.

 

[jg321]

I have only ever found one true ring final on a device <30/32A.
An upstairs ring final on a 20A 3036.

All the others were broken rings put onto smaller breakers.

As it happens, my upstairs socket is actually an intact ring, and on a 20A breaker. I do intend on removing the return leg at some point, to avoid any confusion for future people.

 

[JohnW2]

All I can say is that the facts don't support that concern.

As I said, my only real concern is about a situation in which an MCB might fairly often, and even if only briefly, carry currents in excess of its In. Particularly given that one can't really test them, who knows what effect that might have on their functionality (or lifespan). I'm sure the manufacturers would advise against such situations.

The average load in a domestic dwelling is very low, and typically peak loads aren't that great either. Just look at what DNOs & DSOs allow for each dwelling without incident.

Yes, 'diversity' is all very well, but (as you mention) one has to consider peak situations as well as averages.

Over the past year, my average consumption has been a bit under 24 kWh per day, an average of 1 kW, or about 4A (my supply voltage is usually 245V+). If that were all I looked at, one could argue that I could protect my entire installation with, say, a 6A OPD. However, most days the peak load (during night, with immersion heaters, tumble dryers/WMs/DWs) usually approaches 9-10kW (i.e. 36A - 40A), albeit usually for only brief periods - which I don't think would impress a 6A (or even 20A) OPD for very long

Kind Regards, John

 

[securespark]

I very much doubt that they are 15A MCBs!

Jeez. I wouldn't have suggested it if they did not exist!
http://srselectrical.co.uk/image/cache/data/SRS Electrical/DSC00262-500x500.jpg
http://srselectrical.co.uk/image/cache/data/SRS 2014 /MK LN5915 Front-500x500.jpg

 

[jg321]

As I said, my only real concern is about a situation in which an MCB might fairly often, and even if only briefly, carry currents in excess of its In. Particularly given that one can't really test them, who knows what effect that might have on their functionality (or lifespan). I'm sure the manufacturers would advise against such situations.

Agreed John. As you say, individual views may differ, but for me, this is why I wouldn't want a 20A radial in a kitchen. Something tells me it'll probably be OK, but given that WM, toaster, microwave and kettle may all be on at the same time, even if [just drawing significant current] for just a short period, still makes me a little uncomfortable - therefore I prefer a 32A ring, if, as in my case, the return leg is about 5m of 2.5mm (therefore easy to add), or, if from scratch, probably a 4mm 32A radial.

 

[JohnW2]

Indeed. I'm fairly certain that in my house at least, and probably most modern households, with the exception of the kitchen, I could plug in every device I could find, and the total would be not much more than 10A. A big chunk of that would be the vacuum cleaner and iron. OK maybe 11A if I include those!

It obviously 'depends'.

My house is undoubtedly atypical. It's very large, and a lot of it is usually only minimally heated (LPG is very expensive!), so there are umpteen fan heaters scattered all over the house. Most of them very rarely get used, but, particularly in cold weather, it's far from impossible that a few might occasionally get switched on simultaneously.

Kind Regards, John

 

[jg321]

umpteen fan heaters scattered all over the house.

For the record - in this situation, I would share your "uncomfortable" position regarding 20A radials.

 

[securespark]

As it happens, my upstairs socket is actually an intact ring, and on a 20A breaker. I do intend on removing the return leg at some point, to avoid any confusion for future people.

There seemed to be a period in the 80's when ring finals upstairs were put on 20A devices.

 

[JohnW2]

Jeez. I wouldn't have suggested it if they did not exist!

As I said to EFLI, I hadn't thought about Type 1/2/3/4 ones. However, as I asked him, were they still being installed during rewires in the 80s? I've personally never seen or handled one.

Kind Regards, John

 

[jg321]

There seemed to be a period in the 80's when ring finals upstairs were put on 20A devices.

That's interesting - I wonder why. I'd be lying if I said I wasn't "slightly involved" in mine being on a 20A radial (i.e. it's a much more recent development than the 80s!).

 

[ericmark]

It does seem likely ISO should be 15A and I have in the past talked about the idea of a 15A double pole MCB feeding a ring final. It removes to chance that one leg could be over loaded, and still gives you all of the advantages of a ring final.

However as soon as one leaves the normal method, same splitting house side to side rather than up/down, you also need carefully mark everything or mistakes can be made.

But does not matter how unusual it complies so should not be listed as a fault. And this is the whole point, it seems likely many of the points listed do comply. And where they don't the work required to make it comply is low.

 

[JohnW2]

... I have in the past talked about the idea of a 15A double pole MCB feeding a ring final. It removes to chance that one leg could be over loaded, and still gives you all of the advantages of a ring final.

I presume you are talking about using the two poles for the two (L) ends of the ring - is that correct? If so, then, yes, it would obviously prevent any chance of either leg being overloaded, but at the price of substantially restricting what loads could be supplied, particularly when (as is often the case) the cable of both legs could carry 27A without being 'overloaded'.

Kind Regards, John

 

[securespark]

I've personally never seen or handled one.

Yes! I started working on electrics in 1983 and there were many around.