Do 16 amp plugs/sockets have fuses?

UKworkshop.co.uk

Help Support UKworkshop.co.uk:

isaac3d

Established Member
Joined
22 Jun 2021
Messages
127
Reaction score
112
Location
UK
My new planner thicknesser is wired to a 13 amp plug on a ring main dedicated for my power tools in my garage. The MCB circuit breaker is rated at 32 amps, the cable is 2.5mm armoured cable, so the system can easily deal with any power that the 2.75 kW motor should pull. 13 amp fuses are able to handle 3 kW. However, when the planner is switched on there is quite a spike of current draw which often blows the 13 amp fuse. Once the motor is running I have never blown a fuse, even under load. I have tried using so-called "slow blow" fuses but they also tend to blow when the motor is switched on.
Now, I could have one of the standard 3 pin wall sockets replaced by a "16 amp" blue socket and use a "16 amp" blue plug. However, as far as I can see, these so called 16 amp blue plugs don't actually have a fuse in them at all. In which case, I'd be relying on the 32 amp MCB, which seems a bit too high.
Does anyone know of a fused 16 amp blue plug?
It's actually a pity that the planner manufacturers didn't include some form of slow start for the motor to avoid this problem entirely.
 

Jake

Established Member
Joined
5 Apr 2004
Messages
5,603
Reaction score
241
Location
London
They are not fused and cannot be used on a ring. They have to be on a radial with an MCB to match (eg 16A socket on a 16A MCB).
 

Sideways

Established Member
Joined
26 Dec 2017
Messages
1,926
Reaction score
716
Location
United Kingdom
Blue (CE / Commando) plugs don't have fuses.
Like continental 16A schuko plugs they rely on the correctly sized (16A or 32A, there are two plug sizes) breaker in the fuse box.
You must not connect a 16A unfused outlet directly to a ring main. It is unsafe and it doesn't comply with the wiring regs.
You would need to install a 16A fused spur to feed the 16A CE outlet.

For info, ring mains are a legacy UK thing for domestic wiring, driven by the post WW2 shortage of copper. They depend on fused plugs.
Broadly, the rest of europe doesn't use ring mains, they have "radial" circuits and unfused plugs.
UK industrial practice is also radial circuits and unfused CE type connectors in yellow (110V), Blue (230V) and Red (3phase 400V).

Induction motors in machines can draw 5 to 8x running current during startup. I would never expect a 2.75kW motor to run on a 13A plug, though yes, under no load, it may draw less than 13A.
1.6kW or thereabouts is the max that will reliably run off a 13A fused plug.
You should have a 16A outlet fitted for your motor and may need a slow blow C type MCB fitted to protect that outlet and the wiring that supplies it.
 

isaac3d

Established Member
Joined
22 Jun 2021
Messages
127
Reaction score
112
Location
UK
Yes the cable to the garage comes directly from the main switch box (fuse box) for the house and has it's own distribution board. The MCB in the house fuse box is rated at 64 amps. From the garage distribution box there is a ring for power sockets on a 32 amp MCB, a spur for lights on a 6 amp MCB and another 16 amp mcb for a spur for lighting and power in an adjacent shed. I may have said the cable size of the power socket ring wrong; the electrician said it was rated for at least 40 amps if I recall. The cable from house to garage is at least 15mm in diameter and the ring and lighting cables are less, about 12mm diameter. Lighting is all LED so takes very little current.
Sideways, what is the difference between a ring main and a radial circuit? Surely they don't have separate spurs for each socket. That would mean endless wires all over the place.
I have 6 double sockets on the main ring in my garage. Not so that they can all be used at once but so that I can use short power cables for each piece of equipment. That has to be safer than a single spur with long extension cords.
If I have a dedicated spur for the planner thicknesser installed, then it would require a long power cable for when I want to move it to a different position (eg when dealing with longer stock). As it is now, I can just unplug it from one socket on the ring and plug it in to another socket in the ring, using a short power cable.
I can understand the need to prevent people from inadvertently drawing too much power from a ring main but surely, that is why we have MCBs.
Is there a possibility for having a spur off of the main power socket ring with it's own 16 amp MCB? If so, what is the difference between that and having a plug with a 16 amp fuse (except that they apparently don't exist anymore. ( I do remember as a young lad seeing 15 and even 16 (I think) amp fuses for normal 3 pin plugs.)
 

flying haggis

Established Member
Joined
7 Mar 2009
Messages
1,571
Reaction score
1,216
Location
norfolk
can you do photos of the garage "fuse box"? if the other shed that is fed from a 16a mcb and doesnt have a huge load on it you might be able to use it to also provide a 16a radial with a blue socket
 

DBT85

Established Member
Joined
19 Dec 2015
Messages
1,820
Reaction score
634
Location
Pershore, Worcester
Yes the cable to the garage comes directly from the main switch box (fuse box) for the house and has it's own distribution board. The MCB in the house fuse box is rated at 64 amps. From the garage distribution box there is a ring for power sockets on a 32 amp MCB, a spur for lights on a 6 amp MCB and another 16 amp mcb for a spur for lighting and power in an adjacent shed. I may have said the cable size of the power socket ring wrong; the electrician said it was rated for at least 40 amps if I recall. The cable from house to garage is at least 15mm in diameter and the ring and lighting cables are less, about 12mm diameter. Lighting is all LED so takes very little current.
Sideways, what is the difference between a ring main and a radial circuit? Surely they don't have separate spurs for each socket. That would mean endless wires all over the place.
I have 6 double sockets on the main ring in my garage. Not so that they can all be used at once but so that I can use short power cables for each piece of equipment. That has to be safer than a single spur with long extension cords.
If I have a dedicated spur for the planner thicknesser installed, then it would require a long power cable for when I want to move it to a different position (eg when dealing with longer stock). As it is now, I can just unplug it from one socket on the ring and plug it in to another socket in the ring, using a short power cable.
I can understand the need to prevent people from inadvertently drawing too much power from a ring main but surely, that is why we have MCBs.
Is there a possibility for having a spur off of the main power socket ring with it's own 16 amp MCB? If so, what is the difference between that and having a plug with a 16 amp fuse (except that they apparently don't exist anymore. ( I do remember as a young lad seeing 15 and even 16 (I think) amp fuses for normal 3 pin plugs.)
A ring is a loop from a through b to c and back to a. A radial is simply a line from a to b to c, typically with fatter cable. It means when a socket dies it can easily be traced backwards on the line. On a ring you can have one half of it die and not know until you try to run multiple things down a single side of the ring and things get upset.

If it keeps tripping 13a plugs then just pay an electrician a small amount and he'll put a 16a socket in wherever you like. If the length of cable is an issue then get a 16a extension for when you need it.
 
Last edited:

porker

Established Member
Joined
15 Oct 2009
Messages
783
Reaction score
118
Location
Butlers Cross, Buckinghamshire
A ring is a loop from a through b to c and back to b and back to a.

The two ends of the ring end up back at the consumer unit in the same MCB after looping through all the sockets
 

Sideways

Established Member
Joined
26 Dec 2017
Messages
1,926
Reaction score
716
Location
United Kingdom
A UK domestic ring is wired in 2.5mm twin and earth. This is rated for 20 odd amps (how you install the wires makes a difference but just call it 20A). The ring is fused fused at 30 or 32 amps. Normally this would be a non no as the wiring must be rated to carry more current than the breaker. You want the breaker to trip before the wires in the wall get too hot.
Because the ring is wired the way it is, two lengths of cable are are always sharing the current to any socket in parallel and all is well.
If you break the ring, the wire is undersize for the total load that can be plugged into multiple sockets. You could end up pulling 32 amps down one cable rated for only 20 odd. Under this load it would get hot to the point of damaging the insulation.
If you deliberately break a ring in the middle and feed each end from a separate 20 or 16 amp MCB, you have the same type of "radial" circuit the continentals use. These can have multiple sockets connected, but are fused at the 16A maximum rating of one single socket. You can draw 16A total, from one or between several sockets.

Lastly. Yes, you can T off a spur from any point of a ring main to just one single or double socket.
The T is frequently taken out the back of an existing socket on the ring. It can also be taken from the MCB where the two ends of the ring connect in the consumer unit. It must be wired in 2.5 twin and earth (or bigger). If you wired in a spur and connected a 16A CE socket with an integral 16A mcb (they are available, a little expensive but tidy) that would be safe and good.
You cannot have more than one socket on a spur because this limits the amount of current that can be drawn through the single (not doubled) wire that makes the spur and which is rated at 20A.
Note that all UK double sockets are rated at 20 A total, not actually 2x 13A even though you could plug that load into them.
 

MarkAW

Established Member
Joined
21 Aug 2020
Messages
105
Reaction score
68
Location
Worcestershire
Though isn't ring main safer, because if you have a break In earth wire, you have earth coming from the other side still
 

isaac3d

Established Member
Joined
22 Jun 2021
Messages
127
Reaction score
112
Location
UK
Hi Sideways, you obviously have a lot of knowledge in this area. Indeed a 16A CE socket with an integral 16A mcb would be a simple solution. However, a quick search on the internet only produces CE sockets with RCD protection, which seems to be something different, not to mention the fact that they are indeed very expensive (around 300 pounds from what I've seen). A 16 amp mcb costs under a fiver and a wall mounted CE blue socket can be had for under 30 pounds, so surely combining both in to one unit shouldn't cost hundreds of pounds.
 

Sideways

Established Member
Joined
26 Dec 2017
Messages
1,926
Reaction score
716
Location
United Kingdom
Especially these days now that we have RCD's to help protect against shocks even if the earth is broken (an RCD compares current in the live and neutral and trips if they aren't the same - ie current must be going somewhere it shouldn't) one of the harder problems to catch is the "small overload of long duration".
Fuses especially and breakers too take a long time to trip (hours) with small overloads. This gives time for wires in walls to heat up and pose a fire risk. Because of this, design of an electrical installation must include oversizing electrical cables to be safe with continual overloads of just under 50% (MCB circuits) or a little over 70% (fuses) to give the hours needed for the fuse to blow or breaker to trip.
The hazards here are plug in electrical heaters and the like which draw a lot of current for a long time. In a (smaller commercial) workshop, possibly also a big dust extractor which could be left on much of a day.
Ring mains are vulnerable here, because a break in the ring can go undetected long term and because the resulting wires are already undersize, they have no margin to tolerate long duration overloads which an RCD doesn't help with.
 

Sideways

Established Member
Joined
26 Dec 2017
Messages
1,926
Reaction score
716
Location
United Kingdom
Hi Sideways, you obviously have a lot of knowledge in this area. Indeed a 16A CE socket with an integral 16A mcb would be a simple solution. However, a quick search on the internet only produces CE sockets with RCD protection, which seems to be something different, not to mention the fact that they are indeed very expensive (around 300 pounds from what I've seen). A 16 amp mcb costs under a fiver and a wall mounted CE blue socket can be had for under 30 pounds, so surely combining both in to one unit shouldn't cost hundreds of pounds.
Well spotted :)
Now you know what you are looking for, you can see that a 16A MCB can be fitted in a one or two slot plastic box (like a garage consumer unit but much simpler (and only £10 to £20)) with a couple of inches of round plastic conduit down to a switched CE socket.
Don't use the very cheapest surface mount sockets. Pay £30 and get a gewiss, lewden or some other brand of switched 16A socket. These lock the plug in place while the power is turned on.
Two reasons. 1. It stops the plug being pulled out by accident. 2. It stops the plug being pushed into a live socket and a machine possibly being started up when it wasn't intended and may not be safe.

You're on the right track now.
 

Sideways

Established Member
Joined
26 Dec 2017
Messages
1,926
Reaction score
716
Location
United Kingdom
20211029_123840.jpg
 

isaac3d

Established Member
Joined
22 Jun 2021
Messages
127
Reaction score
112
Location
UK
Those are the beasties.
Ah, I see you are using fuse wire. I didn't realise that was still in use.
 

Spectric

Established Member
Joined
19 Feb 2015
Messages
3,918
Reaction score
2,070
Location
North Cumbria
A radial circuit with a 32 amp protective device is run in 4mm Csa cable and a radial with a 20 amp protective device is run in 2.5mm Csa cable.

But that 2.5mm Csa armoured that supplies your workshop is on the light side, it is what they run to a garage when they just want a light and a double socket to be able to say there is power in the garage. In a workshop synario you want a larger supply cable to a dizy board in the garage that then provides local protective devices for the circuits in that building. This requires some design to ensure the instalation is safe, complies with the regs and correct means of earthing used which depends on the type of supply to the house from the dno.
 

isaac3d

Established Member
Joined
22 Jun 2021
Messages
127
Reaction score
112
Location
UK
I'm not sure what a "dizy board" is but the electrician installed a distribution board (...er is that what you mean by a dizy board?) in the garage from which the ring and two radial lines originate. As mentioned, the lights radial is protected by a 6 amp mcb, the shed radial has a 16 amp mcb and the power sockets ring has a 32 amp mcb. If I remember, I'll take a photo of the set up tomorrow.
 

MikeJhn

Grunkel
Joined
2 Sep 2014
Messages
4,524
Reaction score
374
Location
Kent
If you deliberately break a ring in the middle and feed each end from a separate 20 or 16 amp MCB, you have the same type of "radial" circuit the continentals use. These can have multiple sockets connected, but are fused at the 16A maximum rating of one single socket. You can draw 16A total, from one or between several sockets.
Continental (France) radial sockets are restricted to 12 on 2.5 and 8 on 1.5, but all conductors have to be the same c/c so no T&E, but there are rules on dedicated circuits for certain white goods that have to be separately wired, only nine MCB's to any one RCB, so most continental distribution boards are much bigger than we are used to seeing and all MCB's are dual pole.

DSC00487.jpeg
 

Spectric

Established Member
Joined
19 Feb 2015
Messages
3,918
Reaction score
2,070
Location
North Cumbria
Does anyone know of a fused 16 amp blue plug?
They do not make fused 16 amp plugs in blue, red or yellow because they are just a means of connection that relies on an upstream protective device.

but all conductors have to be the same c/c so no T&E
That is why T&E is only used in domestic installations in the Uk, the smaller CSA protective conductor used in T&E is often to small for long runs and gives higher circuit impedance, so in more industrial enviroments I always run singles in conduit and trunking. In the Uk we still use a PME supply to domestic properties where the Neutral is also the means of earthing, so at the point of supply the properties Earth is taken from the neutral. Having two pole protective devices would only add cost and no added benefit to the domestic user.
 
Top