16amp Question?

[PeteG]

I have a 40 amp fuse in my workshop, If I buy a 16amp rated machine is it just a case of buying one of these?

http://www.toolstation.com/shop/Electri ... 430/p47166

 

[Deejay]

Afternoon Pete

Short answer is no. If the machine has a 16 Amp. supply it will overload, and most likely blow, the biggest fuse you can put into the three pin plug. If it would run on a thirteen amp domestic plug, the manufacturer would have fitted one.

Get one of these

http://www.toolstation.com/shop/Electri ... 430/p20698

fitted , fed from a type C breaker. (They are less likely to trip when you get a surge of current when you switch the machine on).

Talk to a qualified spark, who can certify the installation.

Cheers

Dave

 

[tomf]

Yes and no.
The proper answer is no, as that plug have probably got a 13amp fuse in it and although your ring main is rated at 32 amps (if it is a ring and not radial and uses 2.4mm cable) each actual socket is rated at 13amps for safety.
You can either brake into a socket to take a spur or run another cable from your consumer unit and stick a 16amp socket on this.

In reality a 16amp machine will most likely not draw 16 amps, start up current may be high but running wont be, what is the rating on the machine?

 

[NickWelford]

I have run machines rated at 16 amp (which is generally just the start up demand) on a 32amp circuit with a standard 13 amp fused plug. Worked for me.

 

[deema]

Fuses are designed to protect the cable and electrical delivery system and not the machine or the user. The fuse is there to stop too much current being drawn which will cause a cable that is too thin to heat up and possible catch fire. Current is best thought of as the amount of water flowing in a stream, voltage is the speed at which it flows. The cable is the banks of the stream, too much water, it overflows.

Power or heat as it becomes, is calculated by current * current * resistance of the wire. So, the lower the resistance of the wire the better. For each thickness of wire, there will be stated maximum current carrying capacity.

When a motor starts up, the arrangement inside the motor results in close to a short circuit. Once the motor starts moving this short circuit no longer exists. When switching on a motor you have what's called the surge current, this is the peak current that is ever drawn by the motor and normally only last a second or two as the motor gets going. A normally household fuse is a 'B' class, which means that if it sees a high current it reacts to stop the supply quickly. The surge current will be much higher than any fuse you would ever put into the circuit. So, to get around the surge current you need to use a fuse that reacts to a big current at a slower rate. This is a C class circuit breaker. If you connect a 16A or a 32A circuit breaker to a machine, that are ba rated it is likely that they will trip when you switch the machine on. You may also get away with it. This is a safe situation. No problem. However, if they trip you need to use a ca class rated fuse.

Never, and I mean never use a device, wire, plug, socket rated at a lower current than the circuit breaker or fuse that is protecting the circuit. Ie. It's safe to use a 32A plug and socket on a 16A breaker but not a 13 A plug.

The main reason for this is that in a fault, the short circuit will potentially cause the under rated item to over heat and catch fire. When using a saw for instance, most of us have at some point stalled the motor on a small circular saw. You have created a short circuit and a big current is rushing down the wire as a consequence. The last time I did it, the motor of the machine I was using caught fire! Exciting! I always have a fire extinguisher close to hand luckily.

 

[OLD]

What no one has mentioned is the 16a plug and socket does not have a fuse, unlike 13a plugs so it needs to be wired directly to a 16a circuit breaker class c fitted to a distribution unit .That in your case can supply up to 40a, so this is a stand alone supply to a 16a socket that will only trip out if 16a is exceeded.

 

[angelboy]

I have a 16amp Jet Conctractors saw with a large yellow 16amp plug which then plugs into a 110v transformer with a standard plug then I plug it into my domestic circuit - works for me.....

 

[Eric The Viking]

I have a 16amp Jet Conctractors saw with a large yellow 16amp plug which then plugs into a 110v transformer with a standard plug then I plug it into my domestic circuit - works for me.....

16A at 110V equates to 7.3A at 240V.

That's one of the reasons why 110V tool power cable is usually heavier than the cable on 240V equivalent tools - it has to be.

. . .

To come back to the original question: those adapters are cheap. It probably does no harm to get one and try it. In the old days fuses were worked around by putting various bits of metal in place instead, but that's a BAD idea in this case, as the only protection would then be the 30A fuse in the ring main.

Incidentally, the purpose of a fuse in either the ring or the plug top is only to stop the cable catching fire in the event of a fault. It does not make the user any safer (except that they don't die in a fire).

The right answer, really, is a properly fused or breaker-equipped 16A circuit with an RCD also fitted.

You can make it work with an adaptor, but not safely.

 

[Newbie_Neil]

The right answer, really, is a properly fused or breaker-equipped 16A circuit with an RCD also fitted. You can make it work with an adaptor, but not safely.

+ 1

 

[PeteG]

Apologies for the reply gentlemen, been busy the past couple of days, but all the replies are fantastic and really appreciated. I'm totally baffled when it comes to electrics, but Deemas' analogy now makes sense. "Current is best thought of as the amount of water flowing in a stream, voltage is the speed at which it flows. The cable is the banks of the stream, too much water, it overflows."

I've taken a couple of shots of my fuse box. I have six strip lights and eight double wall sockets. Five wired coming from the left and three coming from the right, I think the electrician said they weren't on a "Daisy Chain".
From the images would you say it wouldn't take much to have a 16amp socket installed?

 

[graduate_owner]

Hi,
I'm not a qualified electrician, so this may not be a definitive answer, but I would say you need a separate 16A MCB for the 16A socket you intend to install. Therefore either a separate MCB in it's own enclosure fed from the existing distribution unit (via the RCD trip), or replace the existing consumer unit with one that will take an extra MCB ( a 5 unit enclosure will have room for the RCD which is double the width of an MCB, plus the 3 MCBs you need). You could alternatively get a full size consumer unit which will have 2 RCDs ant about 10 MCBs for about £60 which is really good value (I think Screwfix sell MK ones at this price) and that will give plenty of room for possible future expansion - you probably won't need one that size but smaller ones are not always that much cheaper.

That's my 2p worth anyway. I don't mean to be unkind here but your comments suggest to me that you are not too confident about wiring. If that is the case then bite the bullet and get an electrician to do the work, then you'll know it's done right and you can sleep soundly at night. This forum is totally brilliant for advice, but sometimes advice is not enough to get the job done safely.

K

 

[PeteG]

Appreciated K, and you're right, this would be a job for someone qualified. I really thought it was just a case of buying the adapter as seen as I had a 40 amp fuse!

 

[graduate_owner]

Yes, I see that the adaptor may have looked tempting but the basic problem is the 16A socket is only protected by a 40A fuse (MCB actually). That's why it really needs a separate MCB rated at 16A. As Eric the Viking said, you could try the adapter but the tool would probably not be fitted with a 16A plug if a 13A fuse in the plug would be adequate. Worth a try. And if it does work then you are protected by a 13A fuse.

K

 

[Deejay]

Evening Pete

Graduate owner said

bite the bullet and get an electrician to do the work, then you'll know it's done right and you can sleep soundly at night.

+1

Cheers

Dave

 

[n0legs]

Please follow Deejay's advice, from the photos it appears you may have some issues.

 

[OLD]

Nice tidy installation you have there i would replace the 40a to sockets with a 20a that should be fine for you requirements then fit the 16a wired from the buss bars in a separate box or expand the existing thus maintaining the protection of the rcd.

 

[Jinxy]

I am a qualified spark. Get an electrician to fit you a 16a socket where you need fed off the sockets circuit. It's all surface PVC conduit so I wouldn't expect a charge of more than £90-£100.

My only advice is, not meaning to sound rude. If you are in doubts over electrics just bite the bullet and get someone qualified to do the work for you. You get a minor works certificate at the end to prove it is safe and complies with the BS7671. We all have expensive testing equipment which will ensure the circuit is safe. I've been to hundreds of properties and seen some horrific things where people have just 'had a go'

 

[Eric The Viking]

I am a qualified spark. Get an electrician to fit you a 16a socket where you need fed off the sockets circuit. It's all surface PVC conduit so I wouldn't expect a charge of more than £90-£100.

My only advice is, not meaning to sound rude. If you are in doubts over electrics just bite the bullet and get someone qualified to do the work for you.

You're not being rude at all, you're being very sensible.

While you're about, do the regs presently say anything about workshop lighting being on the same RCD as power?

Whatever one thinks of RCDs on lighting circuits generally, this seems to be a bad idea, as you'd get plunged into darkness just when something 'interesting' happens.

Mine is a variation of those small consumer units, and I've wondered about splitting it - there is room on the rail (just about). Is that allowed?

E.

 

[Jinxy]

The present regs (17th) don't specify need to separate RCD protection but you will probably notice we make provisions for it. If you house has an up to date consumer unit you will notice it is 'split load' with 2 RCDs and circuits distributed to prevent such problems.

The best solution to your problem is what I've got in my shop and what I've fitted to others before. Replace the main RCD with a non RCD model (standard 63a main isolator) then replace each MCB with RCBOs. An RCBO is a circuit breaker and an RCD conbined. So all circuits will still be protected by RCD but if a fault develops only the offending circuit will trip out.

 

[Eric The Viking]

Thanks for that - not sure if I have room for an RCBO in the box, but I certainly have a gash breaker knocking about somewhere.

Regards,

E.