# Can someone explain how surge protector extension lead works?

Found 4th Apr 2017
Hi All

Quick question regarding surge protector extension leads. Im looking at one on amazon and it states "maximum load 13A". Which sounds fine but ive just looked at the plugs that will be plugged in and one alone is rated at 5A (xbox one plug). My other plugs include a samsung phone charger, sky box, etc. Surely these plugs combined is over 13A?

Or am i missing something?

Many thanks
They will be. And if you ever have a fire safety visit they'll tell you not to put any more than a combined 13 in... but people do. And it's a fire risk
It protects against high voltage.

Sometimes electricity generators produce to much voltage. They have a margin of error so voltage in your house will be standard 230-250 volts.

It protects you when they make a mistake.

Nowt to do with amps.
angiexlester

They will be. And if you ever have a fire safety visit they'll tell you … They will be. And if you ever have a fire safety visit they'll tell you not to put any more than a combined 13 in... but people do. And it's a fire risk

So how are you supposed to have multiple things plugged in? Should I buy two seperate surge protectors?
YouDontWantToKnow

It protects against high voltage. Nowt to do with amps.

But why does it state maximum 13 amps on the protector?
angiexlester

They will be. And if you ever have a fire safety visit they'll tell you … They will be. And if you ever have a fire safety visit they'll tell you not to put any more than a combined 13 in... but people do. And it's a fire risk

This is where a bit of physics comes on. Don't go by the size of fuse in the plug but by the power (watts or w) on the device itself.

The supply into your house is 230V.
Current (A) = power (W) / voltage (V)

Xbox is somewhere around 600W.
600/230 = 2.61A

45/230 = 0.2A or 200mA

Phone chargers are negligible, about 0.01A (assuming it's a 2A charger(2A at 5V = 0.01A at 230V))

Total combined current for the 3 devices above is 2.82A. Well below the rated 13A.
BeerDrinker

This is where a bit of physics comes on. Don't go by the size of fuse in … This is where a bit of physics comes on. Don't go by the size of fuse in the plug but by the power (watts or w) on the device itself.The supply into your house is 230V.Current (A) = power (W) / voltage (V)Xbox is somewhere around 600W.600/230 = 2.61AYour sky box will consume about 40-45 watts.45/230 = 0.2A or 200mAPhone chargers are negligible, about 0.01A (assuming it's a 2A charger(2A at 5V = 0.01A at 230V))Total combined current for the 3 devices above is 2.82A. Well below the rated 13A.

Thanks, but im still confused. Why do the plugs say on them 5A or 3A?

I just checked my plugs now and they are as follows:

TV - 5A
Xbox - 5A
Sky - 3A

That is already 13A, and I have another item plugged in? Is this not how the plugs work?

Thanks
bbfb123

But why does it state maximum 13 amps on the protector?

It means dont overload in amps

13 amps should easily power a tv, sky box, laptop, dvd player, router and sound bar etc.

You need to watch it when you add or use things that generate heat like a hair dryer, tumble drier, oven or electric heater, kettles . etc etc which are high amp appliances.

But surge protection covers you from increased voltage supplied by the electricity generator NOT for you overloading the extension by plugging in more than 13amps of appliances.
bbfb123

Thanks, but im still confused. Why do the plugs say on them 5A or 3A?I … Thanks, but im still confused. Why do the plugs say on them 5A or 3A?I just checked my plugs now and they are as follows:TV - 5AXbox - 5ASky - 3AThat is already 13A, and I have another item plugged in? Is this not how the plugs work?Thanks

Different sized fuses contain big margins of error. Say something has a 3amp fuse its probably only using 1.5 amps same with a 5 amp fuse maybe using 2.5amp.

Otherwise your 2.5amp appliance might blow a 3 amp fuse everytime you power it up.
The fuse is for the cable and not the device using it as they have a built in fuse. i.e. a thinner cable will heat up quicker than a fatter cable at high current ratings. A 5amp rated kettle plug cable will come with a 5amp fuse in case you're daft enough to use it in a 13amp kettle.
YouDontWantToKnow

Different sized fuses contain big margins of error. Say something has a … Different sized fuses contain big margins of error. Say something has a 3amp fuse its probably only using 1.5 amps same with a 5 amp fuse maybe using 2.5amp. Otherwise your 2.5amp appliance might blow a 3 amp fuse everytime you power it up.

​this guy gets it.

if the fuse rating was too close to the actual consumption of the appliance, it would blow all the time. so they usually round up to the next sized fuse, be it 3A, 5A or 13A which are the most common 3. so something using 6A would probably have a 13A fuse, doesnt mean it will ever draw 13A unless something catastrophic failure occurred.

​this guy gets it.if the fuse rating was too close to the actual c … ​this guy gets it.if the fuse rating was too close to the actual consumption of the appliance, it would blow all the time. so they usually round up to the next sized fuse, be it 3A, 5A or 13A which are the most common 3. so something using 6A would probably have a 13A fuse, doesnt mean it will ever draw 13A unless something catastrophic failure occurred.

​It's the physical cable rating that is rated for the fuse in the plug. I can plug a 5amp or 13 amp cable into my PC PSU and it doesn't matter. The main fuse is in the PSU, the cable fuse is to blow if the cable short circuits.
kester76

​It's the physical cable rating that is rated for the fuse in the plug. I … ​It's the physical cable rating that is rated for the fuse in the plug. I can plug a 5amp or 13 amp cable into my PC PSU and it doesn't matter. The main fuse is in the PSU, the cable fuse is to blow if the cable short circuits.

The devices are not always internally fused. The fuse is not rated based on the cable, the cable is rated based on the device and the fuse too. The fuse is there for multiple reasons, if the device / cable shorts out then it will blow at the closest point to the wall socket reducing the risk of fire/shock
mds1256

The devices are not always internally fused. The fuse is not rated based … The devices are not always internally fused. The fuse is not rated based on the cable, the cable is rated based on the device and the fuse too. The fuse is there for multiple reasons, if the device / cable shorts out then it will blow at the closest point to the wall socket reducing the risk of fire/shock

​All good/safe devices are internally fused, you get horror stories where there's no thermal fuse in a cheap imported hairdryer etc. All devices will have a fall back where a component blows open. It's extremely bad practice to rely on a fuse in a plug. Just you can't see it doesn't mean it isn't there, most amplifers have a thermal fuse on the main transformer to prevent overheating/fire.
Surge protection is to prevent voltage spikes from high current fast switching devices damaging sensitive electronic by way of a MOV. These tend to degrade over years so need replacing after the surge light goes out.
Wound extension cables should have a thermal cut out to prevent cable overheating is the cable isn't fully unwound.
Anyway

Surge protection is to do with incoming voltage & not to do with any fuses OR the limitations on cable extensions
bbfb123

So how are you supposed to have multiple things plugged in? Should I buy … So how are you supposed to have multiple things plugged in? Should I buy two seperate surge protectors?

No, another socket.

If you need to plug in more than 3kW of devices then you need to use multiple sockets.
Unless one or more of the items is actually designed to produce heat, it's unlikely that you would be anywhere near maximum loading.

The XBOX One may have a 5A fuse, but I'd be amazed if it used anything like the power of a 1kW electric fire bar
Aha, 70-120 watts, so it only needs half an amp.
... That's average, looks like the PSU is something like 200W output

Mains plug fuses are not intended for precise protection, the old standard was 3A, 5A, 10A, 13A - and I think 5A and 10A have been dropped these days, leaving the 3A for lower power items (maximum about 500W allowing some surge leeway) and 13A for anything heavier.
5A is (or was) good for medium power stuff, or things that may nuisance blow a 3A due to surge current, while the 10A was a pretty pointless distinction

Edited by: "matth9999" 6th Apr 2017