14 y.o. building computer - how to test for current leakage?

[RigidRaider]

My son is assembling a computer from components he bought. He has shown me the main power supply, which is a self-contained enclosed unit, fully insulated, which is mounted in the case, the mains plug comes in through a port in the case and plugs in and there are various outputs sending up to 12v to the various components of the computer. So as far as I can see the 240v part is completely isolated from the case.

I'm pretty confident that there won't be a problem but think it would be prudent to check the whole setup for safety. It is a simple question of putting the multimeter on the case and checking for voltage between the case and earth?

 

[flyingsparks]

I may be wrong but, most computers are class 1 and require an earth connection to the metal chassis. I believe most psu are also class 1 and hence need an earth connection too. Is the psu you have double insulated, with a square inside a square symbol on it?

 

[bernardgreen]

Test for continuity from the case to the earth pin of the 13 amp plug ( fitted with 3 amp fuse ) at the end of the power lead. Should be less than half an ohm.

A voltage measurement may show a few millivolts between case and earth due to impedance of the earth lead at 50 Hz Some PSU's have a filter choke in the earth lead to prevent high frequency noise leaving the PSU on the earth wire.

 

[RigidRaider]

Thanks both. I will check later.

 

[viewer]

After lots of silly negative posts on this forum; I'd just like to say:
Great:::
Good for a 14 year old making his own computer
Good for Dad checking it's safe
Good for sound, clear and helpful replies.

 

[ericmark]

I also had a son who built his own computer and his own power supply for his radio who gained his RAE at the age of 14 years. (Now 30)

I considered the RAE training should have taught him respect for electricity but to be on the safe side I fitted RCD's to all my house electric systems and he did manage to trip them on more than one occasion.

I paid for him to do C&G 2381, 2391, and latter 2382 course and exam which I hope would teach him enough to keep safe. He is now doing a level 5 in electrical and electronics engineering and works as a commercial electrician in a large factory making glass bottles.

So there to me is two things you can do. One ensure RCD protection. It will not protect against all faults but really reduces the risk. And two is train your son in the correct testing procedures.

And give him a pat on the back from all of us and say well done.

(RAE was the exam taken to become a radio amateur but this has now been replaced with a series of tests and stages.)

 

[bernardgreen]

And give him a pat on the back from all of us and say well done.

I agree with that.

 

[ban-all-sheds]

When I saw the title of this topic I thought it was going to be about how to test an old shop or office etc automation system...

 

[Iggifer]

the good thing about building PC's is it's all modular, there's no soldering / crimping connectors onto the PSU, they're all built in so it's all plug and play

I too built my own PC when I was 14 or 15, was a brilliant project and set me in good stead for repairing and maintaining pc's

As long as you buy a decent PSU, there should be no real issues. As has been said, test between the earth of the case and the earth pin of the IEC lead.

I would check the rating of the PSU though, some (many) will need a 5a fuse not a 3a fuse. Any PSU 700w or greater will need a 5a fuse

 

[333rocky333]

When I saw the title of this topic I thought it was going to be about how to test an old shop or office etc automation system...

So did I and was gonna mention about when most computers were checked for the 2000 clock change thing.
We had 15 engineers on standby that night

 

[Lectrician]

The PSU's are self contained, class 1 pieces of equipment.

As said, test for earth continuity from case to plug earth. This unlikely to be an issue (unless you have some dodgy old IEC lead). However, this assumes the socket he plugs into, and your installation as a whole is earthed correctly.

RCD protection is a must really.

I would also point out that it is recommended to keep the IEC lead plugged in (but turned off) when playing around inside a PC - It keeps the chassis earthed, which is meant to help with possibly damaging static.

 

[Astra99]

I keep an IEC lead with the line pin, fuse and connection removed from the plug entirely, specifically to ensure the PC is grounded during maintenance. It's fine until someONE takes it and complains their PC/Printer/whatever (still) does not work!

BTW A pat on the back to the OP's 14 yo son for his initiative!