Power lead fuse keeps blowing

[RayD]

Hi my PC is over 5 years old now and it's suddenly started shutting down on it's own and blowing the fuse in the power lead after it's been on for a few hours.
I've checked the temperatures in mt BIOS and they are all fine. My fans are working fine and the PC is always kept clean and dust free.
Is a replacement power lead likely to solve it or does it sound like a more sinister problem?

 

[SpyderTracks]

Hi my PC is over 5 years old now and it's suddenly started shutting down on it's own and blowing the fuse in the power lead after it's been on for a few hours.
I've checked the temperatures in mt BIOS and they are all fine. My fans are working fine and the PC is always kept clean and dust free.
Is a replacement power lead likely to solve it or does it sound like a more sinister problem?

Is this a PCS machine? If so can you post your full specs?

 

[ubuysa]

What's the rating of the fuse that's blowing? Please don't tell me it's 13Amps...

 

[RayD]

Yes i bought it here in March 2015 and yes it's a 13Amp fuse.

 

[ubuysa]

If it's blowing a 13Amp fuse you should stop using it!!

It's worth trying a different kettle lead but if that doesn't help contact PCS. My guess would be it's the PSU, and if that's the case it may well be a serious fire risk.

The 13Amp fuse is an absolute last line of defence and it's never normal to blow one of those....

Later edit: What size of PSU do you have? I have heard of PSUs over 1000W drawing sufficient startup current to trip breakers, but that's not something which would have just started after 5 years......

 

[RayD]

450w.
Have ordered a replacement PSU today so i hope that fixes the problem.

 

[ubuysa]

450w.
Have ordered a replacement PSU today so i hope that fixes the problem.

That would be my first move too. Fingers crossed.

 

[RayD]

Haven't had any issues since changing the PSU.
Many thanks for the help.

 

[Scott]

What brand of PSU was it? If it was a Corsair I would contact them. They genuinely stand behind their products and I think they would be very interested in what has caused this issue with your PSU as it's clearly a fire risk.

Not to say that you would get a freebie or anything but they may well offer you a discount or a voucher or something for your trouble.

 

[shagly]

What's the rating of the fuse that's blowing? Please don't tell me it's 13Amps...

I finally got around to installing my "Pride and joy" in it's permanent home and part of the process included changing the power ("kettle") lead as the one I'd included in my PCS order wouldn't reach. The other 2 I had (supplied with my 2 previous Dells) had 5 AMP fuses but the new one had a 13! The paperwork for my PSU (Corsair RMx850) lists an "AC power cord" so I don't know if the one I paid extra for is that one or a stock PCS one. Either way, it's something to watch out for and I'm betting there are lots of PCS customers out there (and in here) that are using a cable fitted with a 13 AMP fuse.

 

[SpyderTracks]

I finally got around to installing my "Pride and joy" in it's permanent home and part of the process included changing the power ("kettle") lead as the one I'd included in my PCS order wouldn't reach. The other 2 I had (supplied with my 2 previous Dells) had 5 AMP fuses but the new one had a 13! The paperwork for my PSU (Corsair RMx850) lists an "AC power cord" so I don't know if the one I paid extra for is that one or a stock PCS one. Either way, it's something to watch out for and I'm betting there are lots of PCS customers out there (and in here) that are using a cable fitted with a 13 AMP fuse.

It should be a 13amp fuse as standard on any kettle lead plug.

the dells were either non standard PSU’s which is very usual for a micro PC or low power builds.

You should NOT use a 5amp on your current build.

 

[ubuysa]

The 13A fuse in the plug is NOT there to protect the equipment the lead is powering, it's there as a last ditch protection against fire. If that 13A fuse ever blows then there is a very serious problem with the equipment which should be investigated properly before replacing that fuse.

 

[Scott]

As above, 13A is rated for approx 3250W. If your system is drawing that, even at boot up, there is something seriously wrong.

You can get away with putting a lesser fuse in the plug but as suggested, it's there to stop the cable going on fire. Kettle leads/plugs are rated very highly for power and are normally standardised..... hence the 13A in a generic cable.

5A should be more than enough for most PCs if you wanted to reduce that margin.

 

[ubuysa]

Are the PSUs not fused in some way? They certainly used to be....

 

[Scott]

Are the PSUs not fused in some way? They certainly used to be....

Yes, I believe they use self correcting thermally activated fuses, similar to hair dryers.

There will likely be other safeguards in there too though. I'm yet to blow a PSU

 

[shagly]

Even back in my C & G days I found the information confusing and contradictory.

"The fuse in a plug is a safety device designed to protect the lead rather than the appliance."

But then the water gets muddied by adding in reference to appliances...

"It is a deliberate weak link in a circuit which will 'blow' if an electrical appliance or extension
lead draws too much current due to either an overload or a fault.
The blown fuse cuts off the electricity to stop the lead and appliance from overheating and causing a fire."

Then...

"As a rule of thumb, fuses are rated according to the power rating of the appliance.
If you have to replace a fuse, it's essential, having checked and corrected the reason for the fuse blowing,
to replace it only with another of the same rating.
Plugs for appliances rated up to about 700 watts should have a 3-amp fuse.
For example:
Table lamp, standard lamp, television, video, computer, mixer, blender, fridge, freezer, power drill, jig saw, soldering iron.
Plugs for appliances rated between about 700 watts and 3000 watts (the maximum rating of a wall socket) should be fitted with a 13-amp fuse.
For example:
Washing machine, dishwasher, microwave, kettle, toaster, iron.
Manufacturers have now standardised plug fuse ratings to be either 3A or 13A. However, 5 Amp fuses are still used in some older equipment and are available to buy."

Some time ago, I asked the advice of one of the blokes who do our office PAT and he suggested rating the fuse for the appliance, only going up a step if it kept blowing.

"What many people may not realise is that a 13A rated fuse is not designed to actually blow at 13A. In fact a 13A fuse will allow a current of 20A to pass indefinitely without blowing."

We'll leave out the complication of the consumer unit RCD and surge protector...

 

[ubuysa]

Interesting. I grew up in the age of 5A and 13A round pin plugs that were fitted with 5A and 13A fuses . ISTR that when we changed to the square pin plugs they were originally fitted with 3A or 13A fuses and some years later all plugs carried a 13A fuse. AFAIK its always been the case that the fuse in the plug was there in case all other protections failed, in those days every device was separately fused according to its power rating.

 

[Scott]

I can't think of many appliances you are saving with a 13A fuse to be honest. 5A... yes, but not 13A.

The 13A rating, to me, has always been end circuit protection. Be that the appliance internals, plug, the cable or the socket. If you're drawing 4000W for an actual appliance in your house.... you're asking for trouble.

Even thinking about it logically....A broken appliance would allow that sort of draw, a toaster with a short for example, if the ring main was older with an old fusebox & no modern consumer unit it may allow that current flow indefinitely which would lead to MASSIVE heat through the piddly 20A lead = fire. I don't think you would be too concerned about your broken toaster.

In actual fact, I can't think of a single situation where a 13A fuse is protecting a household appliance. Most things that you surged 13A with, or indeed 20A, would probably break while the fuse remained intact.