Tricky Double Voltage - Beware!
Beware of double voltage i.e. 220 vac instead of 120vac input ,when connecting separate computer components with USB, Firewire, TV -S connector or sound cables such as a printer, monitor, external hard drive or home theater system. This is especially noteworthy when the remote components are in separate room of the house or across the room and plugged into a separate outlet.
Electrical power is supplied to your house from the utility company with three cables; two power and one common. The power cables are identified as line one and line two. The voltage between line one and common is 120VAC . The same is true for line two at 120VAC. The voltage between line one and line two is 220VAC. The three cables are routed into the circuit breaker box and connected to separate buss bars. The breakers are plugged into the box and make connection to the buss bars for line one and line two. The arraignment of the breakers are alternating between line one and line two.
That is the first breaker is connected to line one, the second is connected to line two the third is connected to line one and so on to the bottom. The same arraignment is on the other row of breakers. If you need 220VAC for an electric dryer, an A/C unit or range, you connect the wires to adjacent breaker, so each breaker is supplying 120VAC and the common goes to the grounding screw on the appliance cabinet.
When connecting wiring for wall plugs, the black wire of the 12-3 romax cable is connected to the breaker, the white wire is connected to the common buss bar and the bare wire is connected to the ground buss bar. Collectively, the power to that wall plug is 120VAC, with a ground. At the wall plug, the black wire in connected to the receptacle opposite side from the (green) grounding screw. The bare wire goes to the green ground screw. The white wire is connected on one of the screws located on the same side as the grounding screw.
This provides 120VAC of the correct polarity to the appliance. The receptacles are keyed to prevent plugging a cord in the wrong way. There are two slots and one hole, the common wire was connected to the wide slot, the power was connected on the narrow side and the ground (bare) wire was connected to the round hole.
Now comes the problem. Some of the wall plugs in the house are on line one while some others are on line two, and each is connected correctly and supplying 120VAC respectively.
If your computer is plugged into a receptacle that is on line one and some interconnected device, such a your home theater system is plugged into a receptacle that is on line two, you could have a real problem.
While each unit is correctly connected to a 120VAC outlet, because of the interconnection wiring, collectively the two units are experiencing 220VAC and the electronics of both devices could be burned out, or happily blow the internal fuse.
A GFCI (ground fault circuit interrupter) receptacle is a good way the protect your electronic equipment, but even with a GFCI in place, when the two units are plugged in to different power lines and the devices are turn on, the GFCI will trip off.
Make sure both receptacles are on the same line.It doesn’t matter which, line one or two, but it must be the same line. If your are electric appliance skilled, you could use a volt meter between the two receptacles and test for a mutual connection. Set the meter on 200 + VAC scale and plug one meter lead into the narrow slot of one receptacle. Get a small wire that is long enough to reach to the other receptacle and plug it into the narrow slot there. When the small wire is connected to the other meter lead, it should regester zero.
If not, you have two options, individaully plug either device into another receptacle and test again. If that fails it is time to call an electrician to come out and move one of the breakers to another place in the breaker box.
My first time to blog at this site.I hope this information is of some use to you.
Best regards. Bob T.
Ed: Great stuff Bob! Thanks for contributing!
Wouldn’t it make sense to use one line for outlets and lights exclusively, and another for large appliance and outside lights, for example? Don’t electricians already do this?
Is there a big surge (ha!) of equipment blowing up because it’s plugged into the wrong socket that I haven’t heard about? Do we really need to worry about this?
Responce to Alex Bertran coments:
No Alex, electricians don’t use line one or line two exclusively for wall receptacles. A single room may have individual wall outlets that are on opposite lines. There is another problem when dealing with electronics, “phase shift”. Even if having interconnected components connected to opposite lines and there is no resulting catastrophic failure of the separate units, there is a problem with the sine wave of each line being out of phase with the other by 90 degrees. While line one is at the upper tangent of the curve, line two is at the lower tangent and this will create a 60 cycle buzz of flicker between the two units. It may not be perceptible with a cursory observation, but it is there nevertheless and will have a adverse consequence of the clarity and fidelity of the receiving components such as a HDTV or high end surround sound system. It would be very perceptible to a discriminating ear for the reproduction music.
Best regards: Bob T.
Bob, thanks for explaining how I can fix a problem existing in my home. Until your explanation on 120-240 I have been lost. Now I see how to correct the issue and stop burning out a component. Do you have any hints on how to circumvent Thermal Voltage issues found with surge and or sag? It seems my Surge suppresor handles the Surge but those slow build ups and or voltage loss over time sneak through.
Bill, I am not sure I understand your question regarding “thermal voltage” surge.
What components have you been burning out? Regards: Bob T.
Um, this is a lot of Huey….
First off. “Line one” and “line two” as you call them are pulled by the power company through the same coil from a 240 supply line. The third wire you call “common” is the same thing as “ground” that third wire is called common because for AC current to work it must be “grounded” or earthed. yes that third wire actually eventually terminates to a 3 - 4 foot poll that goes directly into the ground. On a receptacle the 1st wire provides between 100 - 120 volts. the second wire supplies ground and the third wire provides ground. the reason for two grounds is simple, a surge suppressor will attempt to push over voltages directly to the third wire so as to not cause a spike within the electrical appliance it is protecting, it also provides a second conduit to “ground” if the first should fail thus protecting a person/device from a horrific shock.
There is no difference that can cause any problem from “1st wire” or “2nd wire” electricity since they both come from the same 240 volt supply line.
In addition only electronic equipment improperly grounded can be effected from a reversed wired outlet. with AC it doesn’t matter which wire is ground or which wire is positive since it only pushes electricity and pulls electricity through one of the two cables. it’s not like DC where that would cause a reverse current and blow something up or make a motor run in reverse.
Now the real reason you can’t wire lights and outlets and such in seemingly organized manor is simply that you want to balance as much of the current in use between the two poles. This is because if you load one pole up to say 90 amps and the other pole is sitting at 0 amps you will be charged by your electric company as if you were using 90 amps on both poles. The meter will read the highest usage between line 1 or line 2 and charge you double for it. So you want to have that usage balanced as much as possible.
It’s one of the many reason to use a 240 volt appliance over a 110 volt appliance, especially AC Units, Electric dryers and the like.
I bet that your common/ground is your problem, there is probably “noise” on the outlets you are using. I work for a copier company as their IT manager and I hear the techs talking about power supplies and main control boards (mother boards) getting blown out all the time because of “noise” on the circuit through a building or room.
Here is how “noise” is caused. a bad ground connection. Plain and simple somewhere in the circuit or at your circuit breaker box and/or meter the ground is corroded, loose or you are using aluminum wires to feed your electricity and have gone over their amp rating.
Also another common problem that causes “noise” is how your outlets are wired. most outlets today have multiple connections for the feed. Lazy electricians will cheap out on their labor and “daisy chain” the outlets, meaning they feed one outlet then connect another outlet to that outlet and so on down the line for the rest of the room and sometimes rooms. While that will work for fine for motors and coffee makers and those type of appliances for electronic equipment it can be catastrophic, when one appliance misbehaves and sends some noise down that third wire instead of it going back to a “common” location and being sent right to “ground” it instead passes in all directions equally through all your outlets being absorbed by anything and everything plugged into them. Also if a large appliance kicks on down the line of outlets in the daisy chain you can experience a “brown out” or a drop in voltage below 90 volts which can also blowout power supplies and the like.
Not one of those things will effect a good power supply in a computer on a good surge suppressor with a built in line conditioner like the APC Pro 7. The built in line conditioner send “noise” right back down that third wire and it never hits your appliance and then it sets off it’s little red light letting you know there is a wiring fault, and it can handle brown outs that happen occasionally like when a refrigerator kicks on by storing some electricity and then releasing it when it drops too low, however if the voltage drops below 80 volts it won’t help and you’ve got a real bad problem with your wiring.
‘Mitch
http://www.tvbydemand.com -Watch TV On-Line FREE
http://www.garageaction.com - blog anything (PG RATED)
P.S. “daisy Chaining” outlets is against building codes in many states and in most states where it is not illegal most of the local municipalities have outlawed it in new construction.
‘Mitch
http://www.tvbydemand.com -Watch TV On-Line FREE
http://www.garageaction.com - blog anything (PG RATED)