Completely Ungrounded outlets

[maytagman]

Well here's a dilema for you guys to stew over. I live in military housing (factory built units during the cold war, straaaange wiring conventions), which means I cannot in any way modify the electrical system. Now I have a mixture of both two and three-prong outlets throughout the house, and I simply brushed it off that only certain circuits were updated with an earth line at some point while others (IE switched runs) were left alone. Well, come to find out that the 3-prongs I Have are only connected to the 2-wire run and were installed merely for convenience by previous residents.

So... the question is raised.. just how important is ground to a small HT system (5.1 with a H/K receiver, nothing fancy)? If its quite important, is there a solution to creating a temporary ground line, or some sort of cap that can be wired to ground to readily absorb some discharge and dissipate it? Your advice is much appreciated!

 

[audiofox]

Earth ground is primarily for protection from shorts to the chassis so the user doesn't get electrocuted-most systems do not use earth ground for signal return. The best solution for you is to install GFCI (ground fault circuit interrupter) outlets-they are approved for installation where there is no earth ground wire. That should protect you from any problems that would usually require annearth ground (ie, shorted wire to a metal chassis). Of course, you at least need access to the circuit breaker to shut off the electricity so you can replace the 2/3 prong outlets with GFCIs.

 

[ohio]

Bumping this old thread to see if there is any new knowledge.

I'm moving into a small apartment that has only 2 prong outlets in the living room area. Am I putting myself or my equipment at risk by running it off a power strip-->2-prong adapter--> ungrounded outlet?

It's a relatively low power 5.1 setup that won't be played very loudly. However, I am also running an Epson Powerlite 400 projector...

 

[m_vanmeter]

the term "ungrounded" outlet is a bit of a misnomer. The "neutral" line is connected to ground in the circuit breaker panel box. The third ground on modern three wire systems is a "safety ground" running directly back to the common ground buss in the panel box. So, in a 3 prong outlet you have two paths to the same "ground". In a 2 prong outlet you only have one.

I think, if I remember correctly (and others more knowledgeable please chime in), the safety ground was added because there are cases where the neutral can get crossed and carry live voltage, and it can get reversed in an run of outlets and the "ground" would become hot. That goes back to the days when you could get shocked by the metal case of an applience if the wiring was reversed.

As mentioned in a previous post, adding a ground fault interrupter outlet to a circuit will give you the additional protection of a rapid acting circuit breaker if there is a fault to ground in a two wire system.

The "BEST" thing to do, if possible, is rewire the critical electronics circuit with new 3 conductor romex and home run it all the way to the panel box.

It's also a good idea to get one of those inexpensive "outlet testers" that plugs into an outlet and the lights tell you if the wiring is correct or if the neutral/hot leads are reversed.

 

[dallen341]

x2 on the outlet tester. However, are they not 3-prong to begin with?