Circuit tripping causing damage to IT equiptment

[JameZZ]

Here's an odd one...

A year or so a room which has its own ring final on a 32A RCBO, tripped out due to a live-earth fault on a damaged extension lead.

After resetting the RCBO the computer in the room would not power on, and the HDMI input on the TV it was plugged into stopped working (TV worked fine apart from that). The PC was replaced and plugged into another HDMI input.

Recently the room had a faulty appliance which again tripped the RCBO (I would guess another live to earth), and after resetting the PC (new but same model as the previous one) would not power on and other HDMI input on the TV will now not work.

The PC has been replaced again, and as there no working HDMI inputs left has been connected to the VGA input.

There must be some underlaying issue here, I really don't know but could the RCBO be tripping out slightly too slowly allowing voltage to travel into the IT equipment through the CPC and cause this (rather specific damage)?

 

[opps]

Does the PC reach POST?

Edit- sorry, just noticed that you said the PC will not power up.

 

[JohnW2]

That is a very strange story, which is very difficult to make much sense of. I've had plenty of PCs which have survived, unscathed, far worse than you seem to be describing.

If it were me, whilst I was 'scratching my head' I might be tempted to consider running the latest replacement PC' via a UPS !

Kind Regards, John

 

[AdrianUK]

By the time the RCD trips ... the current is already flowing so the damage is done. The RCD is to help protect humans & against fire ... not to protect equipment.

I think Id be looking for an open circuit CPC that is allowing a fault current to find a path via the HDMI leads outer screen.

 

[SFK]

JesZZ
The common and unchanged item is the TV.

(The voltage regulators in computers and laptops, both in their 'brick form' and onboard, tend to be very stable and rugged.

I would suggest (guess) that the TV has a short on its PCB that is occasionally putting a higher than tolerated voltage down the HDMI. Taking out the TV HDMI port and taking out the whole PC motherboard.
Sfk

 

[JohnW2]

The common and unchanged item is the TV.

Yes, that occurred to me, although I forgot to mention it.

(The voltage regulators in laptops, both in their 'brick' and onboard, tend to be very stable and rugged).

Indeed - as I said (in relation to OPCs, but also applies to laptops), I have known them to survive quite a lot of 'power-side'insults!

I would suggest (guess) that the TV has a short on its PCB that is occasionally putting a higher than tolerated voltage down the HDMI. Taking out the TV port and taking out the whole PC.

Yes, quite credible. I suppose we should be asking the OP whether the PCs 'failed before or after he connected them to the TV.

 

[plugwash]

I'm going to read between the lines, and assume this is a conference room or similar setup, with the TV used for presentations.

Desktop PCs are nearly always "class 1", with their DC ground tied to mains earth. TVs are usually "class 2" without an earth. So if isolation between input and output of the power supply breaks down* the only way back to earth is via the connected PC.

What strikes me as strange is that it seems this did not happen spontaneously but as the result of other incidents in the room.

One possibility that comes to mind would be a moderate resistance fault from the mains neutral to the DC side in the TVs power supply. Under normal conditions the neutral to earth voltage is low, so little current flows down the signal cable, but in the event of a phase to neutral or phase to earth fault on another appliance there is suddenly a much larger voltage between neutral and earth.

* Which is *supposed* to be extremely unlikely on a class 2 PSU but.................

 

[Jurassicspark]

A failed class Y capacitor (either from secondary side or from L to E) can cause all weird issues.

 

[ericmark]

A RCB/RCBO tripping removes the supply like any other power cut, but be it the DNO supply or unplugging from the wall, or RCD/RCBO it is the same. There may be read/write problems with any power cut, however not used a desk top in years, and laptops have built in batteries so they can't fail with a power cut.

An IT supply is not normally permitted, in the main we have TN or TT supplies, is it really a supply isolated from terrestrial? I have only once worked on an IT supply, with a tunnel boring machine in Hong Kong, it seems very unlikely you have an IT supply.

 

[JohnW2]

A RCB/RCBO tripping removes the supply like any other power cut, but be it the DNO supply or unplugging from the wall, or RCD/RCBO it is the same.

Indeed - but, as has been said, if the end-problem is damage to semiconductor devices, they may well be killed long before the RCD/RCBO 'removes the supply' - just a few microseconds could enough to be 'fatal'.

 

[SUNRAY]

I'm going to read between the lines, and assume this is a conference room or similar setup, with the TV used for presentations.

Ditto...

A first guess of mine is the TV has several devices connected to it and most are likely to be class 1, including the TV network cable, any one of those devices, or even the supply it's on, could be faulty

 

[ericmark]

We are told that surge protection devices (SPD) will reduce the problem of spikes, however it seems impossible to say if they do or not, I have two in this house, and I do not seem to renew as many LED bulbs as my son, but can't prove it is because he has no SPD fitted.

 

[JohnW2]

We are told that surge protection devices (SPD) will reduce the problem of spikes, however it seems impossible to say if they do or not,

Quite so.

Indeed, as I often say, having experienced hardly any 'unexplained' premature failure of electronic devices (of which I've probably had more than 'average') over many decades (with no 'surge protection'), in my case there would have been virtually no scope for SPDs to offer me any 'benefit'.

 

[Murdochcat]

Quite so.

Indeed, as I often say, having experienced hardly any 'unexplained' premature failure of electronic devices (of which I've probably had more than 'average') over many decades (with no 'surge protection'), in my case there would have been virtually no scope for SPDs to offer me any 'benefit'.

The addition of SPDs was driven by the manufacturers and the need of the regs to make changes to justify the next amendment.

Nothing more, nothing less

 

[JohnW2]

The addition of SPDs was driven by the manufacturers and the need of the regs to make changes to justify the next amendment. ... Nothing more, nothing less

Quite possibly true, although I suspect that, as with so many increases in requirements of the regs, it's probably at least as much as case of 'requiring' something simply because it has become technologically possible.

However, it represents a new, and somewhat worrying, conceptually change. Previously, BS7671 (and the Wiring Regs) have almost entirely, directly or indirectly, been about the safety of human beings (and other animals), but SPDs have virtually nothing to do with that.