16amp circuit

[Jacob]

I've got one machine which needs 16 amps. Has a bit of extra fuse wire in the plug to make it up - it's only the start current.
If I do a proper job with blue sockets do I need an extra RCD or switch outside the main fusebox, as well as the female socket?

 

[Sideways]

The easiest way is a 16A breaker in the consumer unit and the proper grade of cable (for me 2.5mm2 "singles" in a plastic or metal conduit, but 2.5mm t&e should also be safe unless it is installed in a way that stops it dissipating the heat due to it's own resistance).

The best outlet is a blue CE 16A switched socket. Get one online or ebay for max £30. Gewiss, Lewden Palazzoli, many other brands. These combine a switch and outlet. They stop you turning the socket on without a plug and lock the plug in when you turn on. Why ? CE sockets have big holes for the pins and no shutters. And if you pull a plug and socket apart under 16A it may spark a little. It's just a bit of extra safety and you probably want a switch there anyway so an all in one saves faff and the total cost maybe cheaper than a socket and red yellow rotary isolator switch.

Lastly, if short of slots you could have multiple outlets on a single 16A breaker as long as you don't draw more than 16A at once. So 1 breaker in the consumer unit could feed sockets for a saw and a PT as long as you're not in the habit of running both at once.

If you have no spare ways in the CU. You could at a pinch run an existing 30A ring through a tiny DIN rail box containing a single 16A mcb or rcb. That would let you take off a spur, properly fused at 16A, to feed the blue CE switched socket.

For £100 ish you will find switched ce sockets with a 16A breaker built in. Those could be wired straight into a ring main I guess. Not a conventional approach but it's properly fused so it should be safe.

And. You are right that all this needs to be protected with a 30mA rcd but if you have a split load consumer unit with all the breakers fed through two big rcds, there's no need for another rcd specifically for this circuit.

HTH

 

[Ollie78]

I don`t have wall switches on my 16 amp blue sockets but they are on individual type C mcb`s in the main consumer unit.

Ollie

 

[mikej460]

My tablesaw draws 16A on startup. It came 2nd hand with a 13A plug but tripped the ring every time I started it. I wired it to a dedicated 20A MCB and wired it to a 16A blue plug and socket from Screwfix. Here are the products they sell 16 Amp 3 Pin Flange Socket Blue - Search Results | Screwfix.com

No problems since..

 

[Sideways]

My tablesaw draws 16A on startup. It came 2nd hand with a 13A plug but tripped the ring every time I started it. I wired it to a dedicated 20A MCB and wired it to a 16A blue plug and socket from Screwfix. Here are the products they sell 16 Amp 3 Pin Flange Socket Blue - Search Results | Screwfix.com

No problems since..

Why did you wire a 16A socket to a 20A mcb ?
I assume (since I don't have the datasheet for yours) that the 16A socket isn't rated for 20A so you have created a long duration overheat hazard.
It would take a particular set of circumstances to manifest any real risk but it is (likely) wrong and compliance with the wiring regs isn't optional.

 

[mikej460]

Why did you wire a 16A socket to a 20A mcb ?
I assume (since I don't have the datasheet for yours) that the 16A socket isn't rated for 20A so you have created a long duration overheat hazard.
It would take a particular set of circumstances to manifest any real risk but it is (likely) wrong and compliance with the wiring regs isn't optional.

Yes you are right and I was talking b**lox. It is a 16A MCB, I did fit a 20A for a short time as it was all I had to test the saw.

 

[ajs]

You don't need a switch but for a cost of perhaps a fiver I wouldn't see any reason not to have one. Yes, it will need to be RCD protected.

But these questions are technically moot. You can't put a 16A socket on a ring, it needs its own radial circuit, at least if you intend to follow the regs. That makes it notifiable work which means in practice getting a sparky in for.

 

[Spectric]

And. You are right that all this needs to be protected with a 30mA rcd but if you have a split load consumer unit with all the breakers fed through two big rcds, there's no need for another rcd specifically for this circuit.

Ideally you want this on it's own residual current device, if you have a modern board then no problems because you should have all RCBO's otherwise ideally you want it on it's own so that you dont lose your fridge, freezer or heating. Have seen many cases of houses freezing whilst owners away for a while because something has taken out an RCD like an outside PIR light or a chest freezer in a damp garage and now no boiler.

but 2.5mm t&e should also be safe

To be sure do the relevant calcs because a 2.5mm T&E only has a 1.5mm cpc and it all depends on several factors that influence total circuit loop impedance.

 

[Sideways]

I don`t have wall switches on my 16 amp blue sockets but they are on individual type C mcb`s in the main consumer unit.

Ollie

An MCB in the consumer unit does qualify as a functional switch for turning the circuit on and off.
If it's in a garage thats fine.
If it's a 100yd walk down a commercial workshop every time you want to use the switch to isolate while you change a sawblade, that's dangerous. You'll be tempted not to bother, and you can't see each other when someone else switches it back on while you have the guards off.

 

[Spectric]

It is a 16A MCB, I did fit a 20A for a short time as it was all I had to test the saw.

The protective device is only there to protect the cable and the fixed installation not the load plugged into the socket.

 

[Spectric]

An MCB in the consumer unit does qualify as a functional switch for turning the circuit on and off.

Slight correction, an MCB should not be used as a switch but can be used as a means of isolation if either properly locked off or under line of sight of a person working on said circuit, personally I always lock off. The reverse is also true, a switch should not be relied upon as a means of isolaton, the contact separation is closer than in a true isolator.

 

[Sideways]

Slight correction, an MCB should not be used as a switch but can be used as a means of isolation if either properly locked off or under line of sight of a person working on said circuit, personally I always lock off. The reverse is also true, a switch should not be relied upon as a means of isolaton, the contact separation is closer than in a true isolator.

I can't remember the table number, and they could have changed it in the blue book, but I think you'll find that an MCB does count as a functional switch under the regs.
I remember this as I doubted it myself
Is it ideal ? Nope !

I agree about isolation. An operator doesn't want to be faffing about with lockout kit every time they want to change a blade, so far better to have the correct type of isolator close by where they can see it and anyone tempted to reset the switch can see them at the machine.

 

[Ollie78]

An MCB in the consumer unit does qualify as a functional switch for turning the circuit on and off.
If it's in a garage thats fine.
If it's a 100yd walk down a commercial workshop every time you want to use the switch to isolate while you change a sawblade, that's dangerous. You'll be tempted not to bother, and you can't see each other when someone else switches it back on while you have the guards off.

This is true, I normally just unplug it if I need to, I work alone mostly.
My planer runs off one ( this has an isolator on the machine ) and the spindle or edge sander off the other one. It was installed by a sparky when he did my 3 phase saw, that does have a great big isolator on the wall with an awesomly positive clicky handle.
Thinking about it I could/should change the sockets for switched ones.

Ollie

 

[Sideways]

Unplugging is a perfectly good way to isolate in your situation.
https://www.gewiss.com/ww/en/produc...cked-socket-outlets-iec-309-standards/GW66004Something like this is my suggestion if you are ever getting an extra socket fitted.

 

[Gandalfs Staff]

Ideally you want this on it's own residual current device, if you have a modern board then no problems because you should have all RCBO's otherwise ideally you want it on it's own so that you dont lose your fridge, freezer or heating. Have seen many cases of houses freezing whilst owners away for a while because something has taken out an RCD like an outside PIR light or a chest freezer in a damp garage and now no boiler.


To be sure do the relevant calcs because a 2.5mm T&E only has a 1.5mm cpc and it all depends on several factors that influence total circuit loop impedance.

Sorry to jump in on someone elses thread but given I am about to have two 16A sockets installed in my garage - this thread was of interest.

You mentioned 2.5mm T&E - these are the items the electrician has recommended to me ....

The blurb on the suppliers website says this about the cable ;

• A 3 core mains cable with special core insulation / sheath which allows the cable to remain flexible at temperatures as low as -20°C. Ideal for use with tools or equipment used outdoors or in a cold environment.
• Current Rating: 16 Amps

It is however only 1.5mm and you said it needs to be 2.5mm? Has my electrician made a mistake?

Thanks

 

[Sideways]

Artic flex is what it says. Flexible cable. You wouldn't normally use it to install fixed wiring.
And even for the flexible lead between the wall and the machine, a heavy rubber flex (H07RNF) is much more durable and easy to buy by the metre (off the roll at most branches of CEF).
We've all seen photos of round flex run along walls with hammer in cable clips. That's not a professional job. It's amateur work.

If you are having a new install, it seems silly not to put in a 16A switched interlocked socket.

The parts list doesn't fill me with confidence in your electrician. It's just what he can get over the counter from Screwfix or toolstation.

How much current a cable can carry depends on how it is used. It gets warm when you run current through it because all wire has some resistance and acts as a very mild heating element. This heat has to be conducted away or the temp goes up and eventually the insulation softens.

1.5mm arctic flex may be technically rated to carry 16A max as an unrolled flex but just say you plug in a 4kW trotec garage fan heater and run that for an hour, that flex will be pretty warm to the touch. If he uses it for the fixed wiring and you ever retrofit any insulation over the top of the cable, it will overheat, but that's not his problem as he has no responsibility for any changes you make after he's gone.

I'd get someone else frankly. If you go with him, ask to see and take photos of his qualifications (city and guilds exams), his part P scheme membership and his insurance. And of course he's responsible for registering your work with building control so you receive their sign off.


What might be best in class for a DIY workshop ?
Electrical installations have to be designed to suit the environment they are in. In a factory, wiring would be installed in steel conduit to protect against impact damage from heavy materials tools and equipment being moved around. Steel wire armoured cable is extensively used indoors too for the same reason but faster to clip.
In a woodworking shop, we swing planks about and move our machines. We also have to deal with dust.
My personal take on wiring a small workshop is that best practice - a compromise between cost and dealing with the hazards - is to fit 20 or 25mm round plastic conduit on the surface where it's never hidden, easy to access for maintenance or more likely moves and changes, but reasonably robust. Individual live, neutral and earth wires are run inside the conduit. Sparkies call these 'singles'. This is more of a "commercial" grade of work than "industrial". Plastic conduit is pretty cheap but it does take a little time to install.

Conduit like this matches the 20mm or 25mm knockouts you'll find on 16A and 32A switches, isolator switches, consumer units, wiring boxes, metalclad 13A sockets, etc. So everything can be screwed together to keep the dust out.

 

[ajs]

Sorry to jump in on someone elses thread but given I am about to have two 16A sockets installed in my garage - this thread was of interest. ...

It is however only 1.5mm and you said it needs to be 2.5mm? Has my electrician made a mistake?

It'll probably be fine - it depends on the specifics of the installation. Reading between the lines it appears your electrician is installing or replacing a second consumer unit in your garage, makes a lot of sense especially in a detached garage.

It may seem an odd question but how is your garage decorated? If it's bare brick and the cable is simply being clipped to the wall it's fine. The cables need to be heavier gauge in e.g. studded walls or especially if amongst insulation since they can't cool as easily.

 

[Ttrees]

And even for the flexible lead between the wall and the machine, a heavy rubber flex (H07RNF) is much more durable and easy to by by the metre. We've all seen photos of round flex run along walls with hammer in cable clips. That's not a professional job. It's amateur work.

I'd like to get some of that stuff for my machines, cost doesn't seem over the moon,
and it does look rather fetching in a sorta skookum appearance kinda way.

How on earth do you remember "H07RNF"
I presume it all stands for something which makes this easy to remember?

(nothing with google of help)
What is H07 cable?


H07RN-F cable is a heavy-duty rubber flexible cable that is designed for electrical power supply that has a voltage rating of 450/750V. H07RN-F power cables are manufactured with a conductive copper core, ethylene propylene rubber (EPR) insulation and a polychloroprene (PCP) outer sheath.



Sorry for jumping on the bandwagon, no need to answer, as I presume Jacob and Gandalf's staff has more pressing concerns than I do,
AsIcan'NaeFitInDaShedWitAllTheStuff

 

[Spectric]

Artic flex is what it says. Flexible cable. You wouldn't normally use it to install fixed wiring.

I think @Sideways has picked up on an interesting point, this is not used for a fixed installation and it just looks wrong. Why a split way consumer unit with 2 RCD's when really it would be better to just use a board with a single mains switch and RCBO's ! I would not want any cables clipped direct to a wall in a garage / workshop enviroment, better to use trunking and conduit drops to the sockets. I must say on initial thoughts I don't get any confidence from this guy, maybe he is a domestic installer who is treading outside of his depth.

 

[Sideways]

How on earth do you remember "H07RNF"
I presume it all stands for something which makes this easy to remember?

There are two grades of rubber cable that are useful to know about.
H05xxx and H07RNF. You just memorise them.
These are really good quality rubber that will stand up to a lot of use, that tend to lie flat when unrolled, and last for ages.
H07 is the strongest, the RNF letters describe it's resistance to chemicals and so on. I have a garden extension cable made of this stuff that I've used for 30 years. Because of the blend of strenth and flex it's become my favorite for cables from the CE round wall socket to machines. You can get it in single and all sorts of 3 phase configs. Price isn't bad and over the years you'll come to appreciate its quality.
H05 is a little less strong and a little more flexible. You will find an H05 rating on the good rubber power cords fitted to old Bosch and Metabo power tools.
If you buy rubber flex by the reel in b&q (don't it's overpriced) you'll find it's H05 type. Rubber is good in the garden because it's very resistant to UV.