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 Post subject: Electrical SAFETY Issue? Fractal Design
PostPosted: Mon Dec 03, 2012 6:55 am 
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Just unpacked a new Fractal Design Define Mini and noticed that everything appears to be painted before assembly. Panels, rivets screws, the lot. The result is that none of the panels have electrical continuity to any other. The only bare metal I can find is where the motherboard stand-off holes have been tapped.

My worry is that a PSU fault could leave any of the panels, cards or connectors live without blowing a fuse.

Also, if there is any ground continuity it is through the motherboard mounting holes and the main power connector to the PSU. i.e. the only safety ground is through the motherboard!

Secondary to electrical safety, the electromagnetic compatibility (EMC) looks questionable. With none of the panels properly grounded the case will offer very little attenuation to interference. Pressure fingers are fitted around both side panels but both the fingers and panels are painted so there is no electrical connection. The design also leaves the front of the case completely unshielded.

The packaging caries the CE and Tick marks that should guarantee safety and EMC. Hmm.

My last build was an Antec Solo and every panel is solidly grounded. The PSU mounting holes are masked before painting and are bare metal etc.

Am I being alarmist?

Should I send it back?

I have a number of other niggles with it but my main concerns are electrical safety and EMC.

Anxious to hear you views,
--Dave_G.


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 Post subject: Re: Electrical SAFETY Issue? Fractal Design
PostPosted: Mon Dec 03, 2012 7:49 am 
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Have you tested it somehow? Portable Applicance Testing (PAT) equipment might be out of the question but you could use a multimeter to test resistance between the PSU and panels.

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 Post subject: Re: Electrical SAFETY Issue? Fractal Design
PostPosted: Mon Dec 03, 2012 8:14 am 
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edh wrote:
...you could use a multimeter to test resistance between the PSU and panels.

+1

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 Post subject: Re: Electrical SAFETY Issue? Fractal Design
PostPosted: Mon Dec 03, 2012 8:19 am 
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Yes, analogue multimeter.

One probe in motherboard mounting hole (bare metal) and check continuity to another hole. That's OK, 0.0 Ohms.

Removed paint from inside a PSU mounting hole to bare metal. No continuity.

Tried probing every piece of bare metal I can find - pop rivet cores, card slot screws, USB shields. Nothing. The only panel-to-panel continuity it from bottom to back, and that's one piece with a bend. Not sure I want to plug this in!

Nothing fitted in the case yet - still waiting for other deliveries.

--Dave_G.


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 Post subject: Re: Electrical SAFETY Issue? Fractal Design
PostPosted: Mon Dec 03, 2012 8:28 am 
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Dave_G wrote:
Am I being alarmist?


Yes. Your PSU is painted with insulating color. Your case is painted with insulating color. Where would you expect the current to flow anyway in case of PSU failure ?


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 Post subject: Re: Electrical SAFETY Issue? Fractal Design
PostPosted: Mon Dec 03, 2012 8:40 am 
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Interesting question, i have the same case, and never considered the paint not being conductive.

I have (had) a problem with white stripes apearing on any monitor i connect, it is kinda inpredictable when they start and stop apearing. i conected the problem with the lack of ground in the wall socket as in a socket with ground the problem never apears. so i conected my case to a radiator and the problem is mostly over but sometimes still pops up. that it still pops up from time to time might be due to the lack of conductivity in my case. but this is just speculation ofcourse


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 Post subject: Re: Electrical SAFETY Issue? Fractal Design
PostPosted: Mon Dec 03, 2012 8:48 am 
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Things can and do go wrong. The point of chassis grounding is to make sure the fuse blows before anyone has the chance to kill themself. That requires every external conducting panel and connector to be grounded.

Then there is the less frequent issue of an external live conductor contacting the case. Without grounding, the case is live and the fuse will only blow after you "notice".

The PSU (Seasonic G360) has the mounting holes tapped out after painting. The supplied screws are bright plated and have serrations under the head designed to cut through any paint on the chassis. Seasonic know they need to do this.

The Fractal Design paint looks like powder-coat and is pretty tough. Just noticed that there is a foam PSU gasket too, plus the little rubber bumpers. In all the PSU looks to be well insulated from the case rather than connected to it.

As for EMC, the panels need to be electrically connected and preferably grounded to do anything beneficial.

Still worried,
--Dave_G.


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 Post subject: Re: Electrical SAFETY Issue? Fractal Design
PostPosted: Mon Dec 03, 2012 9:58 am 
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faugusztin wrote:
Where would you expect the current to flow anyway in case of PSU failure ?

To earth would be nice, preferably not through the user. :wink:

mercyfull_fate wrote:
so i conected my case to a radiator

Well not ideal but better than no earth. Plumbing itself should always be earthed but you can never guarantee it's copper all of the way and it is bad practice to use the plumbing AS the earth. Lacking an earth to the PSU would be far more likely to cause problems than lacking an earth to the case. As you also had monitor problems then this suggests there could have been current passing over the video cable at times. So long as each AC input was earthed this shouldn't happen.

I tried taking a multmetre to my SG03 which is anodised and all the major panels came to 0 Ohms back to the PSU with the only exception being the front fan filter. It's clipped onto a plastic fitting and is therefore insulated very well.

I'm not sure of the significance of no earth to the case for electrical safety on it's own. The PSU itself is hi-pot tested in manufacture and is the only part of the system with AC mains current in it. However, if you were to have a power cable damaged and in contact with the case, you would hope that it should be earthed, therefore tripping something before anything worse can happen.

If you were to use a PicoPSU with an external brick, the brick itself might not even have an earthed input and the power connection through to the system would just be 12V and 0V, not neccessarily the same as earth and with a possibly high resistance.

I previously missed a point here: If the case is covered with such thick, non-conducting powder coat, of course it's not going to conduct but therefore it's no safety issue either! How are you going to electrocute yourself on a case covered in thick insulating material? If the panels were bare metal but were insulated from the other panels, THEN you should be concerned.

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 Post subject: Re: Electrical SAFETY Issue? Fractal Design
PostPosted: Mon Dec 03, 2012 10:23 am 
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Thinking about this practically, it would need a few things to go wrong in order for the case to become live and dangerous.

But simply grounding all the metal panels (and the PSU) would make it unconditionally safe.

With only the motherboard mounting plate grounded through the PSU cables there is a real chance of interference and noise. The 0V conductors will be carying large, spiky currents. The discharge path for static from the case would also be via the motherboard. Hmm.

Think I'll start looking for an alternative.

--Dave_G.


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 Post subject: Re: Electrical SAFETY Issue? Fractal Design
PostPosted: Mon Dec 03, 2012 1:24 pm 
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If you like the case, you could always mod it with copper braid straps between panels. Buff the case down to metal with a dremel tool and use some conductive epoxy or solder to attach the braid.

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 Post subject: Re: Electrical SAFETY Issue? Fractal Design
PostPosted: Mon Dec 03, 2012 1:54 pm 
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I think we're getting in to the realms of re-manufacture here. It's a new case and I don't want to have to chip the paint off.

I have not used the case in "anger" yet, but my expectations and confidence in it have collapsed.

The impression I get is that the Fractal Design Define Mini is a good design let down by poor attention to manufacturing detail. I wish them well. I'll also drop them an email summarising my concerns.

I'm going to send it back (thank you Amazon) and look for an alternative. Any suggestions? The Lian Li PC-A04 looks to be a contender. A separate post is probably in order for that.

Thanks to everyone for listening and chipping in...
--Dave_G.

P.S. Keep posting if you have any strange experiences that may be down to earthing/grounding. How common are they?


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 Post subject: Re: Electrical SAFETY Issue? Fractal Design
PostPosted: Mon Dec 03, 2012 4:47 pm 
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Dave_G wrote:
P.S. Keep posting if you have any strange experiences that may be down to earthing/grounding. How common are they?


This is the ~3rd thread in 6 months. The other two were specifically troubleshooting noise/rfi issues with their existing systems. Both had poor/non-existant house grounds/earthing.

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 Post subject: Re: Electrical SAFETY Issue? Fractal Design
PostPosted: Mon Dec 03, 2012 6:28 pm 
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No one's said this explicitly yet, so I will: poorly grounded cases are not just a safety issue. One of the primary purposes of a computer case is to act as a Faraday cage, and if it isn't grounded, it's effectiveness at shielding against EMI/RFI drops dramatically. That means buckets of electronic noise leaking out into the surroundings, creating hum/hiss on your audio cables and causing the display interference problems others have mentioned.

And even if your display is fine and your audio hiss-free, some of that EMI/RFI will end up on your power lines, which are like giant noise antennae, broadcasting it everywhere. In most of the places I've lived, I could tell if my neighbors were using a dimmer switch by listening to my sound system without a power conditioner. It makes me grateful that none of them were tech enthusiasts. I shudder to think what a computer in a crap enclosure would sound like.

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 Post subject: Re: Electrical SAFETY Issue? Fractal Design
PostPosted: Mon Dec 03, 2012 9:42 pm 
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It's come up on other threads.

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 Post subject: Re: Electrical SAFETY Issue? Fractal Design
PostPosted: Tue Dec 04, 2012 1:29 am 
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Irrelevant wrote:
No one's said this explicitly yet, so I will: poorly grounded cases are not just a safety issue. One of the primary purposes of a computer case is to act as a Faraday cage, and if it isn't grounded, it's effectiveness at shielding against EMI/RFI drops dramatically. That means buckets of electronic noise leaking out into the surroundings, creating hum/hiss on your audio cables and causing the display interference problems others have mentioned.


I'd be more worried about EM interference going the other way. My concern is because most heatsinks are only connected to earth via the chip that they're cooling. Hence any big interference can go right through a CPU and crash it, I have demonstrated this before with placing a mobile phone right beside the CPU cooler of a laptop: it crashes every time. Earthing down the heatsinks would be a better solution for this than earthing the case.

In over 5 years of troubleshooting ECG signal quality (this is far more important that audio quality as someones life may be at stake) I can say that of all of the electrical equipment I have had problems with causing intereference, a computer itself has never been one of them. Recklessly earthing everything down can have a bad impact itself by creating earth loops, hence leave this kind of thing to the manufacturer and their design decisions. I have had many issues with power conditioner equipment itself causing noise and this is serious medical grade units, not overpriced audiophile tat.

Irrelevant wrote:
And even if your display is fine and your audio hiss-free, some of that EMI/RFI will end up on your power lines, which are like giant noise antennae, broadcasting it everywhere. In most of the places I've lived, I could tell if my neighbors were using a dimmer switch by listening to my sound system without a power conditioner.


Something is wrong in that case. You shouldn't have noise being injected back into the mains by dimmer switches, even though dimmer switches are bad. Did these buildings have aluminium wiring? How was the cabling installed? If you have twisted cabling (like twisted pair in CAT5) then RFI should be cancelled out and any parts of the cable that are exposed should be in metal pattress boxes, junction boxes, consumer units or similar. There should be no opportunity for it to act like an aerial to that great an extent. You definitely shouldn't have to have a power conditioner anyway.

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 Post subject: Re: Electrical SAFETY Issue? Fractal Design
PostPosted: Wed Dec 05, 2012 12:04 am 
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edh wrote:
Irrelevant wrote:
In most of the places I've lived, I could tell if my neighbors were using a dimmer switch by listening to my sound system without a power conditioner.
Something is wrong in that case. You shouldn't have noise being injected back into the mains by dimmer switches ...
Absolutely true. A properly wired residence should be largely immune to that kind of thing. The problem is, properly wired residences are rarer than diamonds (or at least they are here in the US). Assuming the electricians did what they were supposed to is like parking your car with the door unlocked and the key in the ignition and assuming no one will steal it.

Similarly, you can't trust manufacturers to properly ground their products, particularly since there's no such thing as "proper grounding". There's a reason why audio engineers love ground-lift switches.

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