Wall Power Issue: 2-Prong or 3-Prong w/25FT Ext Cord (Connected to PSU then PC)?

[Sylar Powers]

My first post ever on Anandtech! Long time lurker, as Anandtech is a fantastic site. I will be posting around here for advice on building the ultimate PC, in another thread. But for now I need to solve my wall power question:

The old house in Philadelphia USA that I am staying at has two wall power options for me. The entire house has 2-prong sockets, but there are a few perhaps newer 3-prong sockets 25 feet away from my computer. This served as a computer room to the previous owner, but I am a 25FT away from there, and moving the my PC system is not an option.

Now if I run a 25FT extension cord, I can reach a newer 3-prong socket. However, that is a 25FT extension cord run, plugged into a external battery style UPS, which will then have my entire high end PC system + stereo connected too.

Or if that is too long for comfort, I can plug into one of the original 2-prong sockets one foot away, but I would have to use an adaptor, and who knows how good the grounding is there, if there is any at all. There is no guarantee that the 3-prong one is done right, but it at least has 3-prongs.

So which way should I plug in my PC?

I am inclined to do the 25FT run to the newer 3-prong socket. Anybody have thoughts, please share, as I could use the advice. Thanks in advance.

 

[jonnyGURU]

Assuming that the third prong is actually grounded, I'd rather have the 25' extension cord than do without Earth ground.

 

[HOOfan 1]

You can get a fairly thick guaged extension cord.

 

[Billb2]

In my experience, the wiring in older homes is flakey, at best. I wouldn't trust that a three pronged outlet in an older house is really grounded. I'd have a look and see. If there's only two wires coming into the box (usually blact + white), than there's no ground circut (green) available there. Sometines the 3 prong ground is just hooked to the electrical box the outlet is mounted in. If that's the case, a 2 prong to 3 prong adapter on the closest outlet would be just as effective.

 

[robertk2012]

Jonny,

Can you go into a little detail as to why a good ground is needed and the problems that could come from not having a good ground?

 

[jonnyGURU]

So you've never been barefoot and touched a non-grounded chassis and gotten zapped?

There used to be an arcade in Denver that didn't ground any of their machines. Every time you put a quarter in the coin slot, you'd get zapped... HARD! We'd make it a "challenge" to get the quarter in the slot as quickly and cleanly as possible as not to get zapped. Sort of like playing Operation.

But seriously, a grounded chassis eliminates electrostatic discharge and minimize RF and EMI... and reduces the "tingle".

 

[robertk2012]

Makes sense. Can it cause any problems with the PC?

 

[jonnyGURU]

SURE!

The RF, EMI and the static can ALL cause problems with the day to day operation of the PC.

 

[robertk2012]

I feel like im on one of those infomercials on tv. Now we just need jonny to offer us a 3 for 1 deal that will solve all of our problems.

 

[Billb2]

Originally posted by: jonnyGURU
So you've never been barefoot and touched a non-grounded chassis and gotten zapped?

I think you're confusing him. He'll think you talking about static electricity, not a hot ground.

My best hot ground story:
I'm in my workshop, stocking feet, I have this little desktop high intensity light. When I pick it up I get "the tingle". So I assume the 12v side is shorted to the base. On a whim, I reach up and touch the base to the overhead ductwork ...BLAMMO! Burned a 1/2" hole!!!!

 

[robertk2012]

No he wasnt confusing me.

So what is the best way to advoid a hot ground when you have two prong outlets outlets or 3 prong without a true ground?

 

[Sylar Powers]

Won't a Battery PSU protect me from some of these power issues even if it's not grounded?

 

[Sylar Powers]

Peeked inside the outlet. It was dark, but I was able to see a few things.

There is a main fat wire coming into the socket housing. The protective layers of this are uncosmetically frayed away, and wires are coming out. Two are attached to the socket which are tan in color. Also coming from the main wall wire is a copper looking bare wire that just wraps around a screw in the back of the socket housing. there is a black wire that is just cut going nowhere, not sure where if it is coming from the wall wire or the socket itself.

Not too promising. I think my only option is the 2-prong to 3-prong adapter. Using this, I have no ground, I know. But If I use a battery PSU, which supplies power from the battery itself to my plugged in PC and stereo-wont this protect me somewhat? Also, what are the risks of not having a ground-should I be afraid to use a high end gaming machine?

In the end, it really does not matter though. I can't move out for about a year, and I can't live without the internet. Well maybe I COULD live, but I'm hardly going to test that idea out. But it would be nice to know just how big a risk I am undertaking, and what I can do to minimize that risk.

 

[bruceb]

It would be in your best interests of personal & property safety (fire)
to hire a profession electrician. From what you describe, it sounds
like those wires are from pre 1960 and the home is in desperate
need of electrical upgrades. It will be costly, but you can put a price
on your life.

 

[jonnyGURU]

I'm surprised they changed the outlets but not the wire run. If the panel is grounded then a new wire run would have a ground wire to ground to both the panel and the outlet. If the ground wire isn't grounded, then they just switched out an outlet, probably just so it could accomodate plugs with an earth prong.

 

[Martimus]

Take a look at the fuse box, if there is a ground wire going to that section of fuses, then it is probably grounded. Most likely, that extra prong goes nowhere, and is only there because the socket was recently replaced.

 

[bruceb]

What worries me and why he should have an electrician look things over are here in his response:

There is a main fat wire coming into the socket housing. The protective layers of this are uncosmetically frayed away, and wires are coming out. Two are attached to the socket which are tan in color. Also coming from the main wall wire is a copper looking bare wire that just wraps around a screw in the back of the socket housing. there is a black wire that is just cut going nowhere, not sure where if it is coming from the wall wire or the socket itself.

 

[Modelworks]

Or you can just buy one of the old 3 prong to 2 prong adapters and attach the screw (the part most people skip)
In a modern house the white wire (neutral) is connected to the same bus bar as the houses ground wire.
The separate ground wire was only added so that if there is a short in an appliance the voltage would return through a dedicated wire back to the breaker box instead of using the already loaded neutral.

You can check the grounding on an outlet by setting a meter to AC and measuring between the ground hole and the side of the socket with the longest slot.
There shouldn't be even 1 volt on the reading if the ground is good.
Then measure between the short slot and the ground hole, should read 110~125v.



If you don't want to add a ground wire you can also install a gfci outlet.
Thats really the only thing that is allowed by code.
Taking out a 2 prong outlet and putting a 3 prong in its place is against code.

 

[bruceb]

That is not against the NEC Code, if it is done correctly.
This means, that if the home was wired with Romex
that the bare wire in the Romex connects to the Green
ground screw on the outlet. Hopefully, whoever wired the
home connected the same wire at the breaker panel to ground.
If, on the other hand, the home is older and was wired with BX
or Armored Cable, then the cable's metal sheath provides the
ground and this is usually used with a Metal Box ... So a wire,
Green in color, to the box shell would be fine as well. The main
item you need to watch when swapping from 2 wire to 3 wire
outlets, is to be sure the White Wire goes to Wider Slot on the
outlet. This is by standard, the Silver Colored Terminal Screw.

 

[Billb2]

Originally posted by: Modelworks
If you don't want to add a ground wire you can also install a gfci outlet.
Thats really the only thing that is allowed by code.
Taking out a 2 prong outlet and putting a 3 prong in its place is against code.

Where I live (Chicago subburb) , a GFI is only required if the outlet is 6 feet or less from a water source.

Adding GFI to an old wiring system is usually problematic (false trips). As you note the potential between the ground and the current may be a high as a couple of volts, and a miliamp will trip the GFI.

 

[Modelworks]

code with pics
http://www.codecheck.com/250_50_commentary.html

 

[Modelworks]

Originally posted by: bruceb
That is not against the NEC Code, if it is done correctly.

I meant putting a 3 prong in a box with no ground at all.
Happens alot.

 

[bruceb]

Very true. That is why I explained the correct
steps to be sure it is done properly to the NEC Code.