J
John-SJW
How do you guys get over taking an appliance which is 16A off a 32A ring?
thx
thx
You just wouldn't to it and give the 16A item it's own dedicated circuit.
I wouldn't, I would install the item on it's own dedicated circuit
J
John-SJW
If easy to to do, but in some cases not so. The ring can take a 16A draw off it as from a spur using a MF junction box, and 2.5mm cable, is fine. These commercial plugs can do it, but boy are they clunky. But the ring would have to be dropped to a 20A mcb.
Also using a Wylex 104 switch fuse which will take a 16A cartridge off the 32A ring and the above commercial socket and plug off the 104 switch.
Also splitting the ring into two 16A radials - if it can be done of course.
How have others got around it? Must be a number of ways. Many Continental appliances state 16A.
A spur using MF JBs may sound OK but remember an FCU will have a 13Amp fuse in it,
Last edited:
J
John-SJW
Was think of the Wylex switched fuse with 16A fuse in it off the ring, then the commercial 16A socket.
Basically we don’t “get around it” as you so charmingly put it. Anyone worth their salt will comply with BS7671. It is not allowed for the reasons above.
The ethos of a ring final is for distributed loads with a maximum of 13A on any point. See Appendix 15 for clarification.
Many continental appliances indeed state 16A. Jonny foreigner doesn’t indulge in ring finals and the standard circuit is a 16A radial. Which is what you need to install!
J
John-SJW
I have actually seen this done. It may be against 'regs' but electrically sound and safe. Only the one 16A appliance could use the socket outlet because of the commercial plug & socket.
Just wondering how people got around it without running a new radial back to the CU.
As I mentioned splitting the ring into two radials is an option. But this raises another flag. A 16A radial may have a number of 13A sockets in series on it. Either the 16A appliance can be hard wired into the radial, with cable outlet, or fit the commercial plug/socket.
Last edited by a moderator:
Suggest you ask on another forum. The Screwfix one maybe has the sort of getting around the regs ‘advice’ that you are looking for.
So if I read that right - and paraphrase:
I know/agree it is wrong, and could result in prosecution against a professional electrician if they do it.
So please could people confirm if they have done it?
What next: times, places, details - please also provide details of your defence lawyer?
J
John-SJW
All say a 16A appliance cannot be taken off a 32A ring because the regs say so, even though it can be done quite safely - and I have seen this done. Fine, I go with that, as we are all best going one way
I pointed out splitting the ring into two 16A radials, bringing up the point that a radial created out of the split may have 13A sockets on it, but a 16A commercial socket/plug can be fitted for a 16A appliance - unlike the Continent we do not have 16A sockets/plugs. I see no one took this one up.
I pointed out splitting the ring into two 16A radials, bringing up the point that a radial created out of the split may have 13A sockets on it, but a 16A commercial socket/plug can be fitted for a 16A appliance - unlike the Continent we do not have 16A sockets/plugs. I see no one took this one up.
Last edited by a moderator:
It would not be a good idea in my opinion.
The whole idea of a circuit feeding several sockets should be able to provide for the expected loads placed on it.
So a 16A appliance on a 20A circuit would lead to a circuit breaker tripping every time more than 4A was spread across the 13A sockets.
I suggest you do some diversity calculations and see if it is acceptable.
The whole idea of a circuit feeding several sockets should be able to provide for the expected loads placed on it.
So a 16A appliance on a 20A circuit would lead to a circuit breaker tripping every time more than 4A was spread across the 13A sockets.
I suggest you do some diversity calculations and see if it is acceptable.
Mainly because it's clearly described in the regulations
A ring, and multi-radials are designed around the use of bs1363 fittings, they each are protected by a fuse up to 13A - or have one in the appropriate plug.
Industrial 16A and so on type fittings do not have any guarantee of a fuse protecting the cables, flexes, or end appliance.
Therefore they need to realistically be on single dedicated radials, generally you use these where greater than 13A is required and therefore you are unlikely to be able to apply diversity sufficient to manage multiple 16A outlets.
I do suggest that you familiarise yourself with the regulations rather than just decide what should be ok even if its not allowed by them.
Last edited by a moderator:
Mate... it’s the regs. It might be electrically sound, but if it’s not and you end up in court what are you going to say... ‘Erm yes you honour, it’s against the regs but I did consult aload of random people on a forum till someone said it’s alright so I did it’
Dartlec
Arms
Figure 15A clearly recommends against connecting something like an Oven >2kW from a rfc, but it doesn't seem to entirely prohibit it, if diversity calcs suggest the load current is unlikely to exceed for 'long periods' (whatever those are) the current-carrying capacity of the cable.
With a new install it's clearly sensible to install a radial circuit to any fixed appliance with significant load.
Taking a more edge case, where a cheap oven with moulded plug is run from a socket on a small kitchen rfc, would that be considered as non-compliant or case dependent? I've seen that on a few 'kitchen fitter' specials on more recent properties where they haven't run a large cooker or hob feed.
Plenty of the higher quality Ovens I've seen that are made for European markets come with a requirement to fit to a 15A feed, so then trying to replace a plug mounted one in that scenario immediately causes an issue. I always install a 16 or 20A radial when I've been involved in the design, so have not run into the problem yet.
Wonder if it might become more of an issue after the B word though, since suppliers may be less interested in providing ovens with BS1363 plugs?
With a new install it's clearly sensible to install a radial circuit to any fixed appliance with significant load.
Taking a more edge case, where a cheap oven with moulded plug is run from a socket on a small kitchen rfc, would that be considered as non-compliant or case dependent? I've seen that on a few 'kitchen fitter' specials on more recent properties where they haven't run a large cooker or hob feed.
Plenty of the higher quality Ovens I've seen that are made for European markets come with a requirement to fit to a 15A feed, so then trying to replace a plug mounted one in that scenario immediately causes an issue. I always install a 16 or 20A radial when I've been involved in the design, so have not run into the problem yet.
Wonder if it might become more of an issue after the B word though, since suppliers may be less interested in providing ovens with BS1363 plugs?
There is nothing to stop you splitting the ring, turning it into two separate 16A (or 20, if you like) radials and connecting your 16A appliance to this radial.
You do, of course, have to take note of the existing loads on the circuit. This is contained right at the very start of BS7671 under the jazzy title "Fundamental Principles".
Well, welcome to the real World of electricianing. Its not always easy. sure there might be a more simple and cheaper way, but you forgot to put an important adjective in your sentence: WRONG
Last edited by a moderator:
J
John-SJW
Some sense at last.
Also, this inserting a 16A mcb in a circuit creating radial, would apply to changing the 32A ring to a 16A ring and inserting the 16A appliance in the 16A ring - as I suggested for a solution, to ripping apart a house unnecessarily.
One thing I do know is that many conflate recommendations (you do not have to) to actual laws (you have to do).
[automerge]1600189676[/automerge]
I have seen people put in a dedicated radial for a '16A' appliance, even though it draws less than 13A, because the expensive Continental appliance instructions says must be protected by a 16A mcb or fuse. They insisted on a dedicated 16A supply in case the guarantee is invalidated.
Last edited by a moderator:
Here is something that may be of interest to this thread. It's from the OSG, App. H2 -
Final circuits using socket-outlets complying with BS 1363-2 and fused connection units complying with BS 1363-4.
Unless I've missed something, it appears to apply to ring finals. With this in mind, what do other forum members feel about a 16A socket on a ring final, locally protected by a 16A breaker?
Final circuits using socket-outlets complying with BS 1363-2 and fused connection units complying with BS 1363-4.
Unless I've missed something, it appears to apply to ring finals. With this in mind, what do other forum members feel about a 16A socket on a ring final, locally protected by a 16A breaker?
J
John-SJW
[automerge]1600191878[/automerge]
It looks like the rule of thumb that not higher that 13A off a ring is not true.
That is what I asked and other way to around a problem.
Interesting. So the installation I saw with a Wylex switch on the ring with a 16A fuse to a commercial socket outlet appears to fall in line with the regs, at least in part. Although, would a 16A commercial socket/plug comply or would it have to be permanently connected.
It looks like the rule of thumb that not higher that 13A off a ring is not true.
Last edited by a moderator:
J
John-SJW
[automerge]1600193245[/automerge]
Does that mean the rating of the switching contacts?
"A circuit breaker not exceeding 16A."
Does that mean the rating of the switching contacts?
Last edited by a moderator:
Thread tidied up now keep it civil and move on.
What's the point of having a RFC on a16 Amp OCPD? just to accommodate a 16 Amp socket simpler to run the socket from a dedicated 16Amp circuit
Hi Pete. The 16A breaker would be local protection rather than whole circuit protection. It would protect only the 16A socket, and the ring would be protected by the usual 32A breaker
.
I must admit I thought he (the OP) was on about splitting the radial and putting it on 2 x 16A breakers?
I must admit I thought he (the OP) was on about splitting the radial and putting it on 2 x 16A breakers?
Dartlec
Arms
Seems like there might be a market for some sort of premade unit that would comply with that to allow the 15A oven example to be connected (where diversity and other loading conditions allow). Doubt it would be pretty enough to be on show though....
There are small, cheap units available that would take MCBs such as this one from wylex:
Wylex NH ESE2 IP40 2-Module Unpopulated DIN Enclosure - Screwfix
Order online at Screwfix.com. Insulated enclosure for double pole RCDs. FREE next day delivery available, free collection in 1 minute.
You would have to decide if a plastic one was ok, or if a metal one would be more appropriate. But yeah, you'd want it hidden in a cupboard out of view!
[automerge]1600196972[/automerge]
Personally, I think a 16A socket on a ring final, locally protected by a 16A MCB may be safe, and may be compliant.
Here is a comparison of the time/current characteristics for a 13A BS1362 fuse vs. a 16A BS60898 MCB. Appologies for the poor quality of the image, but hopefully you can see that for most of the curve, the 16A breaker opens quicker for the same overcurrent.
Last edited:
"16Amp socket from a rfc protected by a 16 Amp breakerWas what was said Mate
I think we may be at cross purposes Pete? Are you referring to someone else's post?
or try B&Q. just use a choc block and 2 layers of insulating tape.
I would stop short of saying a 16A fuse definitely complied, but I couldn't say that it didn't comply either. The 16A breaker is mentioned in the OSG (in the 17th edition too, so it's not a new thing), being an IET publication we can assume it carries some weight.
The actual regulations concerning ring finals are surprisingly sparse. The design guide in app 15 will ensure compliance, but is not actual regulation, and deviation from it doesn't automatically mean non compliance.
A double socket is designed to run at 20A, so yes, it is expected that a load of greater than 13A will be placed at a point on the ring for at least some of the time.
J
John-SJW
[automerge]1600242694[/automerge]
That may not always be practical - such as ripping a house apart for one cable, or no spare slot in the CU.
Last edited by a moderator:
I can't answer 'how I get around the problem' because I've never encountered it, but it's an interesting theoretical question.
It might be acceptable for a 16A point load to be applied to a 32A RFC, especially if the diversity applicable or the manner of operation of a permanently-installed appliance can be foreseen and factored in. An oven that requires an average of 15A for a few minutes and then drops back to below 13A average, is not much different from one with a smaller element that draws 12A solidly for a longer warm-up time (It is different, though, because the heating in the circuit cables is proportional to I² but the heating in the oven is proportional only to I.)
We must distinguish between three possible kinds of problem arising from a large fixed load on a general-purpose RFC:
1) Risk of overloading cables, since on a 32A RFC conventionally In>Iz. Normally, this does not happen. If it does, it's very minor, which is why houses don't burn down when RFCs get broken near one end.
2) The load accounts for too great a fraction of Ib to allow the circuit to fulfil its role of supplying general purpose socket outlets. This is not specific to RFCs, it is a simple diversity conflict, that would occur equally on a 32A radial S/O circuit. If the circuit is intended to provide a useful amount of power elsewhere, a 32A circuit with a 16A load is probably better than two 20A circuits with a 16A load on one of them. The bigger the circuit, the better diversity works.
3) The accessories are not suitable for a 16A load. This is simply a practical consideration that is easily overcome by careful selection of equipment.
My view is that it is bad practice to burden a general-purpose socket-outlet circuit with large single loads unless their duty-cycle is known to be modest. I think this is actually a more significant consideration than the point loading of an RFC affecting current distribution.
It might be acceptable for a 16A point load to be applied to a 32A RFC, especially if the diversity applicable or the manner of operation of a permanently-installed appliance can be foreseen and factored in. An oven that requires an average of 15A for a few minutes and then drops back to below 13A average, is not much different from one with a smaller element that draws 12A solidly for a longer warm-up time (It is different, though, because the heating in the circuit cables is proportional to I² but the heating in the oven is proportional only to I.)
We must distinguish between three possible kinds of problem arising from a large fixed load on a general-purpose RFC:
1) Risk of overloading cables, since on a 32A RFC conventionally In>Iz. Normally, this does not happen. If it does, it's very minor, which is why houses don't burn down when RFCs get broken near one end.
2) The load accounts for too great a fraction of Ib to allow the circuit to fulfil its role of supplying general purpose socket outlets. This is not specific to RFCs, it is a simple diversity conflict, that would occur equally on a 32A radial S/O circuit. If the circuit is intended to provide a useful amount of power elsewhere, a 32A circuit with a 16A load is probably better than two 20A circuits with a 16A load on one of them. The bigger the circuit, the better diversity works.
3) The accessories are not suitable for a 16A load. This is simply a practical consideration that is easily overcome by careful selection of equipment.
My view is that it is bad practice to burden a general-purpose socket-outlet circuit with large single loads unless their duty-cycle is known to be modest. I think this is actually a more significant consideration than the point loading of an RFC affecting current distribution.
Similar threads
OFFICIAL SPONSORS
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc
Advert
Thread Information
Advert
Thread statistics
Advert
TrueNAS JBOD Storage Server
-
-
Understanding TrueNAS JBOD Servers: A Comprehensive Guide- Started by Dan
- Replies: 8
-
