Computer Earth Leakage

[disinfo]

Afternoon All,

Got a small shock from a computer at work today, I was leaning over a PC to plug my usb drive in and my arm touched between two cases, obviously this sparked further interest

Putting my multimeter between the two PC cases revealed 120V, after reading about computer earth leakage recently I decided to pull all of the desking apart to see what was going on, I was quite disturbed by what I found.

The desk is a row of ten pc's inside the cable management at the back I found a four way adapter plugged into a floor box, into the 4 way was another four way, and another, and another

At the other end of the desk, where I received my shock was another floor box with a single four way plugged in.

The floor boxes seem absolutely ancient and on inspection I found that the CPC on the chained set of four ways wasnt making contact because of debris in the socket outlet of the box.

I am now considering myself very lucky that only one PC in the entire row was switched on.

I am a technician, not an electrician. I have informed the schools health and safety officer of the problems and they have asked me to write a report.

What recommendations would you put in the report other than get a trained spark in asap?

I have mentioned the fact that the floor boxes should be replaced and the new ones should have dual earth terminal connections.

I have also reccomended that multi way adapters should not be used and proper sockets provided wherever possible.

I will add that a PIR was carried out by the council last year as well as pat testing.

 

[oharaf]

Hmm, not untypical in schools I am afraid!!

They love multi-way adaptors and the wear and tear in these hell holes is amazing.

Before I quit teaching, I taught in a school under going a PFI build.

Temporary accomodation had been put in. In my room there was a 3 phase dis. board, easily accessable, there was no lock and the clasps closing the door were completely buggered.

When I opened the door I noticed 5 completely empty ways with no blanks and a simple stupid curious finger could easily have reached in and touched the busbar.

Reported this to Ass. Head in charge of build (it had already been inspec. tested and signed over) he didn't appear to bothered.

After the 3rd day the lovely wall mounted heaters began coming off the walls and suprise suprise MCB's were tripping every where.

Again I reported ALL the problems to the same person, he sent the caretaker down to NAIL the heaters back up!!!

Feck it I thought, went up to the Ass. Head told him what the problems were, told him the possible and very serious consequences of what could happen if they were not attend to properly.

Then told him that unless they were fixed by a qualified sparky by the next day I would not teach in the room and I would reccomend to colleagues not to teach in their rooms and would also put a note in every students planner informing their parents of the situation.

(Having been an Ass. Head I knew how to rattle cages)

If said he would 'see what he could do'

At the end of the day he appeared and said to me ' Your training to be an electrician can you fix the problems'

I said ' Yes I can, it will be after 7 O'Clock, it will be £80 per hour plus parts, fuel etc, and there will be no certificate as I was not yet part P'

He went several beautiful shades of pink, purple and then white.

So I followed it up with, it can't be tonight as I am watching the rugby.

Reminded him he had until tomorrow to sort it or I would refuse to teach in the room.

Next morning all fixed!!!

Pull out the H&S card!!!!!!!!!!

Oh and they had put the small computer network sockets in using T&E 1.5mm, discovered when a child thought it would be great fun to rip the trunking from the wall!!!!


And we think our kids are safe when at school

 

[pompeygit]

definitely a case for high integrity earthing. Each pc as a norm can leak 3mA to earth so with 10 computers on the same circuit a 30mA RCD would nuisance trip . A break in the cpc(earth cable) can have catastrophic consequences.
Choices: Get another PIR done to evaluate if this circuit is suitable for IT equipment. If it is a radial without high integrity earthing get it upgraded including the accessories(sockets). If it is a ring upgrade the accessories and have them connect the cpc's at the dist board in a manner to allow for high integrity earthing. Maybe a 100mA RCD will provide some protection as well. Does seem strange that that a PI Report has not highlighted the need for special earthing requirements when you have so many PC's on 1 circuit. I see nothing wrong with each PC coming connecting a 4way adaptor lead to an outlet socket, provided the circuit cable is man enough for the overall load. Sparkies that do a lot of office work should contribute to this interesting thread because it is not an area I work in.....just wanted to get the ball rolloing

 

[pompeygit]

This is a health and safety issue, and that shock should be reported in your accident book so that there is an indelible record. Quite honestly the room should be closed down as it is unsafe. I wonder if this installation complies with the Regs (having just read Section 607 of the 16th Edition ) I know that this is bit of an advert by MK but it shows how dangerous things can get and it is an interesting read http://www.mkelectric.co.uk/case/cases.asp?caseid=1006

You may want to quote the following Regs in your report
607-02-04 especially item(ii). and 607-03-01 especially items (i) and (ii)

 

[disinfo]

Well, I really hope I've made the right call here because 3 rooms have been shut down as a result of this.

The council sparks will be here first thing tomorrow to take a look.

 

[holmslaw]

..

 

[disinfo]

Thanks guys for your input.

Worst case scenario for me now is the the council sparky comes in and dismisses me as a jobsworth or similar and denies that fact that ten computers connected together would have a potential dangerous leakage current.

Having a wonder around the room I have also found,

No covers on any of the 3 dist boards, the breakers are all accessible and the staff use them to switch pc's off every night

One dist board only has one screw and the cover is hanging off

Several cracked socket faces

Most of the floor boxes have masses of debris inside them things like staples, paperclips, chewing gum paper etc

I asked the cleaner where she plugged in her (class 1) hoover, tested the socket to find again that the plug was not making a good connection to earth.

I cant help feeling like i've pi$s3d loads of my colleagues off at work now, but at least my conscience will be clear

 

[disinfo]

This is a health and safety issue, and that shock should be reported in your accident book so that there is an indelible record. Quite honestly the room should be closed down as it is unsafe. I wonder if this installation complies with the Regs (having just read Section 607 of the 16th Edition ) I know that this is bit of an advert by MK but it shows how dangerous things can get and it is an interesting read http://www.mkelectric.co.uk/case/cases.asp?caseid=1006

You may want to quote the following Regs in your report
607-02-04 especially item(ii). and 607-03-01 especially items (i) and (ii)

Cheers for the link by the way, its in a language my superiors might understand

 

[Spark123]

I said ' Yes I can, it will be after 7 O'Clock, it will be £80 per hour plus parts, fuel etc, and there will be no certificate as I was not yet part P'

Part P doesn't apply to schools, unless they share a common supply with a domestic dwelling of course.
EAWR, HASWA etc do apply though. A cert is normally issued to show the work is being carried out to BS7671.

 

[disinfo]

Well the guy from the council came in, scratched his head a lot, rang his gaffer a few times and left.

He did tell me however that he agreed with my assessment and the power should stay off until further notice.

apparently some men in suits will be coming to visit, i'm just hoping not WHITE suits.

 

[disinfo]

Well, just to finish this thread off...


The head spark from the council came in today, he told me that the installation is totally unsafe and should be rewired with high integrity earth as soon as possible.

They will also be splitting the rings so that no more than 8 PC's are connected at a time.

They will also be changing the dis boards and installing RCD protection.

I'm pleased, its a weight of my mind and has been the rocket up the a rse that certain staff here needed.

The rewire starts on Monday

Result.


Matt

 

[holmslaw]

..

 

[pompeygit]

Well done Matt a great result