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Old 7th March 2010, 11:00 PM   #1
royd55 is offline royd55  United States
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Default household sockets

I am sure that everyone on this list knows more about electronics than i do. That said, i wanted to mention something i had to deal with concerning electrical sockets used for powering my SSE.

As you well know electrical grounding on a tube amp is ultra critical for safety and operation. I took the cover off the ac socket that i selected for my SSE and checked all wiring. Sure enough even though the socket was a 3 wire socket there was no ground!! I ran a ground wire back to the system ground (not fun). I also checked the hot and neutral to see if they were correct with the plug polarization. This one was correct.

Older homes can have all sorts of weird wiring problems. It is very easy for an electrician to cheat on an older house rewire. There is no guarantee that a ground wire on a socket is really grounded. This is not the first time i have found problems in my house.

Roy
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Old 7th March 2010, 11:25 PM   #2
msb64 is offline msb64  Canada
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It is fairly common to find homes that were built before the 60s with recepticles that are not grounded. Many people will upgrade the recepticles, but usually don't bother to run a proper ground. All ground runs should terminate at the ground lugs in your main panel. Be extremely careful if you decide to do this yourself.

You can buy a little plug in device at most hardware stores, that you can check all your plugs with, for proper grounds as well as correct polarity.
Every home owner should have one of these in their toolbox.
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Old 7th March 2010, 11:26 PM   #3
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If anyone is curious about the polarity (neutral vs. hot) and grounding of their household outlets, visit the local hardware store and buy a polarity checker. The one I have is made by "Ideal". Cheap and easy to use, it will display a sequence of lights, indicating correct (or not) wiring at the receptacle.

Regards,
"The Cat"

Edit: msb64 just beat my post, but the picture shows the right tool for the job.

Last edited by neonthecat; 7th March 2010 at 11:28 PM.
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Old 7th March 2010, 11:33 PM   #4
rknize is offline rknize  United States
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It really depends on your wiring. For example, if your house is wired with conduit or BX (flexible steel armored cable), the ground path is through the conduit itself. Outlets typically connect the ground lug to the mounting bracket for this purpose. In older homes built before the 70s, you need to make sure that the ground really returns to the main electrical breaker. One of those testers can check this.

Romex (plastic sheath) has a separate ground that needs to be attached to the box or to the ground lug on the outlet for this purpose.
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Old 7th March 2010, 11:41 PM   #5
msb64 is offline msb64  Canada
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In Manitoba, the BX or conduit ground is not sufficient for ground protection.
The code requires that a dedicated ground wire be used, and it has been this way for many years. I imagine many locations have the same safety requirement.
With BX, there is also an internal ground wire, and with conduit you need to run a green covered ground wire (X-link) as well as hot and neutral conductors.
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Old 7th March 2010, 11:47 PM   #6
rknize is offline rknize  United States
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Yes, those are the modern standards here too. BX only has a thin, aluminum strip. Not really a wire per se. Anyway, the point was that his outlets do have a ground despite lacking a wire for it. My house was built is 1947 but the outlet boxes all have decent grounding.
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Old 8th March 2010, 01:46 AM   #7
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My house, built in 1978 used the conduit itself for the ground. The ground and the neutral are connected together in the breaker panel. The conduit connections do corrode over time, and this practice is no longer common.

There is another major issue that I have not seen discussed here. The shared neutral. It was common in the 1970's to run ONE neutral wire for several circuits running on each phase. The theory is that the neutral current will always be lower than the current through the loads on each phase. For example if the total load on one phase is 10 amps, and the load on the other phase is 5 amps, only 5 amps flows through the neutral. This works fine, until the neutral goes open. Then the phase with the smallest load will see more than 120 volts. The neutral wiring is daisy chained through each wall outlet.

Combine that with the (still common) electrical outlets that you simply strip the wire and stick it into a hole in the back of the outlet. The spring steel contacts will loose tension over time, and ZAP! One outlet fried after 10 years, but it might have been a bit overloaded with Christmas lights. It was the hot wire that fried, so only the outlet was damaged.

The second incident came when Sherri plugged in the vacuum cleaner (serious start up current) and stepped on the switch. She said that lights flashed, the clock radio in another room caught fire and the offending outlet started smoking. It also casued the MOV's in two surge supressor strips to blow up (saving the TV). One looks like it was near flames before the breaker popped.

That incident resulted in the replacement of every wall outlet in the entire house.
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Old 8th March 2010, 02:07 AM   #8
rknize is offline rknize  United States
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I never use those spring clip holes. Take a broken one apart once and see how they work...scary. I can't believe they still make those.
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Old 8th March 2010, 02:08 AM   #9
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Yee-haww! My house was built in the early part of the 20th century, and has a bastard chimera mix of romex and ancient post-and-tube wiring. I plant to strip it out and rewire it a circuit at a time, if for no other reason than to know absolutely where things are going (and adding grounded receptacles, of course). Ancient electricians had a habit of just tapping into existing wiring, with the result being a maddening crazy-quilt. Fortunately, I have a full basement, so rewiring need not be all that harrowing an experience.
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Old 8th March 2010, 02:36 AM   #10
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I have seen some rather scary stuff, so comparitively this place isn't too bad.

Sherri's mothers house, built in 1921 sounds like yours. The original wiring is still live, and most of the cloth insulation is intact. The sacry stuff is all of the "additions" made by previous and the current owner. The electric meter spins with all of the fuses removed from the box! After I cut the wires to the detached garage the phone started working and things in the basement don't shock you any more.
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