Multiple Fixed Equipment off one Spur from Ring Final......

[bmwoner]

Looking at a number of very low current, yet fixed, devices and the current protection for them.

A cooker hood, two electric Velux windows, a boiler circuit and peripheral Nests and a mechanical heat recovery unit all need to have their own fuse, 3amp each.

Can they be run off one spur from a ring final? If they can, I guess that spur in itself needs fusing down to 13amp to protect the cable in the event of overload?

Eg

Connection 1 2.5mm off ring
Connection 2, 2.5mm into FCU from connection 1, at 13amp protecting the cable in the spur thereon from overload
Connection 3, 1.5mm from 2, into first 3amp FCU to appliance X
Connection 4, 1.5mm from 3, into second 3amp FCU, into appliance Y
Etc

 

[EFLImpudence]

Can they be run off one spur from a ring final? If they can, I guess that spur in itself needs fusing down to 13amp to protect the cable in the event of overload?

Yes, they can; you can protect the undersized cable with the 13A fuse in a FCU and then have as many appliances up to the 13A.

 

[JohnW2]

Connection 1 2.5mm off ring
Connection 2, 2.5mm into FCU from connection 1, at 13amp protecting the cable in the spur thereon from overload
Connection 3, 1.5mm from 2, into first 3amp FCU to appliance X
Connection 4, 1.5mm from 3, into second 3amp FCU, into appliance Y
Etc

As has been said, yes you could do that. In fact, given the latest change in regs (lost of distinction between 'lighting' and 'power' circuits) you could theoretically actually use 1.0 mm² cable for everything if you wanted!

However, do each and every one of your loads really need separate 3A fusing?

Kind Regards, John

 

[winston1]

However, do each and every one of your loads really need separate 3A fusing?

I’m sure they don’t. Any fuse is to protect the cable and the loads should be internally protected.
The same items when sold in Europe would be plugged into a 16 amp circuit with no problems.

 

[RandomGrinch]

I’m sure they don’t. Any fuse is to protect the cable and the loads should be internally protected.
The same items when sold in Europe would be plugged into a 16 amp circuit with no problems.

Maybe, but who is to say what cable I am going to connect to the outlet of my FCU?
Not every appliance is prewired.
0.5mm2 flex perhaps?

 

[winston1]

Maybe, but who is to say what cable I am going to connect to the outlet of my FCU?
Not every appliance is prewired.
0.5mm2 perhaps?

YOU decide to use appropriate cable.

 

[RandomGrinch]

YOU decide to use appropriate cable.

Yes, and the appropriate fuse!

 

[winston1]

As I said there items would be on 16 amp circuits in Europe so surely a 13 amp one would do.

 

[JohnW2]

As I said there items would be on 16 amp circuits in Europe so surely a 13 amp one would do.

Is it considered acceptable, in any country, for, say 0.5 mm² flex to be protected only by a 16A OPD?

 

[winston1]

Is it considered acceptable, in any country, for, say 0.5 mm² flex to be protected only by a 16A OPD?

As I said in post 6 use appropriate cable.

 

[SUNRAY]

Is it considered acceptable, in any country, for, say 0.5 mm² flex to be protected only by a 16A OPD?

winston regularly tells us it is.

 

[EFLImpudence]

No he doesn't.

If there were such an item (I doubt it but something supplied with 0.5mm² flex and a plug) then it would be alright to plug it into a 16A circuit as, presumably if necessary, it would have internal fusing.

 

[JohnW2]

As I said in post 6 use appropriate cable.

..and exactly my point, too ...

... when an item is sold for use in the UK, the intention being that it is to be supplied via an FCU or fused plug then (with appropriate recommendations about fuse size) it may well be appropriate for it to be supplied with, say, 0.5 mm² flex.

... however, when it is sold for use in almost any other country, where there are no FCUs or fused plugs, and many/most of the outlets are protected only by a 16A device, then common sense might suggest that a flex appropriate for 16A should be supplied.

..' all that, of course, unless the load is deemed "incapable of resulting in an overload current", in which case (at least ion terms of UK regs) no overload protection at all is required. However, as we know, there are people around capable of arguing that virtually any load may, in very improbable situations, result in an overload current.

 

[winston1]

... when an item is sold for use in the UK, the intention being that it is to be supplied via an FCU or fused plug then (with appropriate recommendations about fuse size) it may well be appropriate for it to be supplied with, say, 0.5 mm² flex.

Hm, intention is one thing, but there is nothing to stop anyone fitting a 15a BS546 plug and plugging it in.

 

[JohnW2]

Hm, intention is one thing, but there is nothing to stop anyone fitting a 15a BS546 plug and plugging it in.

I am talking about things sold in and for the UK market. If it is intended to be used with a plug, it is required to be supplied with an attached BS1363 plug with an appropriate fuse (and instructions not to install a higher-rated fuse). If it is intended to be installed via an FCU, then there will be instructions as to what rating fuse should be used.

There's obviously nothing that a supplier can do, or be expected to do, about someone who replaces the supplied BS1363 plug with something else and/or uses a fuse with a higher rating than that specified.

In a country which does not have BS1362 fuses, in either plugs or FCUs, the supplier presumably has to assume that the cable may well only have 16A OPD protection from the installation, and I therefore would have thought should size the cable appropriately (unless, as I said, they can successfully argue that the cable does not require overload protection).