[c-nsp] Multiple power supply failures. Advise needed

[Justin Shore]

Unless you scrapped the paint off of every joint between the chassis 
through the mounting brackets to the rack then you aren't guaranteed a 
good connection.  That's why most telco screw kits come with the star 
washer to help scrap the paint of the rack and why most telco equipment 
frames and mounting kits are a non-painted alloy.  Data equipment isn't 
generally made to the same standards.  So for example if you rack up a 
3750 you're using non-painted mounting brackets on a painted 2-post. 
The chassis is also painted so you most likely aren't making a 
connection between the chassis and the bracket and thus not the 2-post.

The ground in the power plane should never be connected within the 
chassis to the chassis itself.  The power plane should never share 
anything common with the chassis.  The chassis should always be grounded 
separately.  Now beyond the panel at the site ground they'll likely meet 
up again but within the powered equipment they should never touch.  Ie, 
the ground conductor in the L5-20R that your colo provider dropped in 
your cage should not internally connect to the chassis of the device. 
The electronics within the device should be insulated from the chassis 
and the chassis should have an external ground connection that you 
connect either to the frame or to a ground bar on the frame.  Depending 
on the equipment (thinking telco for a minute) the equipment is 
sometimes insulated from the frame and connects to a ground bar that is 
also insulated from the frame as well.  There are a lot of telco 
standards out there that are meant for specific applications.  Bottom 
line, always ground the chassis with the supplied hardware either to a 
grounded frame or to a ground bar within the frame that goes back to a 
site ground bar.  Not all manufacturers adhere to those standards though...

Justin


Michael Ulitskiy wrote:
> Sure, but what the proper grounding is? Does it mean that I have to run a 
> dedicated grounding wire to every piece of equipment?
> The racks are properly grounded (according to provider) and every server is screwed to them. 
> The power is provided via NEMA L5-20P twisted lock connecter with proper grounding 
> (according to provider). There I currently have tripp lites followed by managed APC PDUs.
> All equipment is plugged in into APC grounded outlet. Does it not qualify for "proper grounding"?
> 
> I also personally went there with a voltmeter and check for voltage between metal parts 
> per Seth Mattinen suggestion and I found 0 voltage. This may sound silly, but I'm taking any chances.
> What else I can do?