We just moved our home office to a different room with two-prong outlets. One outlet was on the fritz, so it got my attention enough to realize the lack of a ground connection was probably not a good thing. I wanted to understand it better, so I consulted the good ol' Electrical Wiring FAQ (written back in the days when FAQs weren't written by marketing people).
The FAQ first explains that without a ground, your surge suppressor is working at a disadvantage:
And then it goes on to give three more good reasons to have a real ground installed on the outlets where your computer lives:A word about grounding: most suppressors and EFI filters
require real grounds. Any that don't are next to useless.
For example, most surge suppressors use MOVs (metal oxide
varistors) to "clamp" overvoltages. Yes, you can have a
suppressor that only has a MOV between neutral and hot to
combat differential-mode voltage excursions, but that isn't
enough. You need common-mode protection too. Good suppressors
should have 3 MOVs, one between each pair of wires. Which
means you should have a good solid ground. Eg: a solidly
connected 14ga wire back to the panel. Not rusty BX armour or
galvanized pipe with condensation turning the copper connection
If you ever open up the case and have the habit of discharging static electricity on the metal frame, it's not going to do any good if the case isn't actually connected to ground.Without a ground, a surge or spike is free to "lift" your
entire electronics system well away from ground. Which is
ideal for blowing out interface electronics for printer ports
Secondly, static electricity is one of the major enemies of
electronics. Having good frame grounds is one way of
protecting against static zaps.
If you're in the situation of wanting to install computer
equipment on two wire groundless circuits take note:
Adding a GFCI outlet to the circuit makes the circuit safe for
you. But it doesn't make it safe for your equipment - you need
a ground to make surge suppressors or line filters effective.
This has been a public service announcement about the importance of upgrading your hardware infrastructure.