Low Outlet Voltage

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  #1  
Old 06-21-04, 11:31 AM
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Low Outlet Voltage

Hey all,

Newbie to this board & have the following problem...

I have an outlet I've been using constantly for the last 2 months for my 24/7 wireless modem power. Then all of a sudden, I lost my wireless connection - no power at the radio box. I unplugged the adapter (not a 3 prong, but it is a polarized plug) & plugged in a regular lamp & still nothing. I used my digital meter & it says it's only getting 20.4 volts. All breakers are on and NOT tripped. House is old - no GFCI outlets.

Possibly loose wire in a junction box somewhere?

Suggestions?

Thanks,
Dale
 
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  #2  
Old 06-21-04, 11:36 AM
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The reading you got with the digital voltmeter is meaningless and misleading. Ignore it.

You likely either have a weak connection that has finally opened up, or you have a tripped GFCI (perhaps one that you don't even know about yet), or the breaker is really tripped but doesn't look like it.

First, determine the extent of the outage. Figure out everything that is without power. Is it more than just this one outlet?

Next, go turn off and back on every 15-amp and 20-amp breaker in your box.

If you have a ground somewhere (even a water pipe), you can use your voltmeter to measure each of the two slits in your receptacle to ground. If you can do that, post back the results.
 
  #3  
Old 06-23-04, 06:12 AM
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Ok, I went up in the attic & found the junction box the outlet is fed from.

The outlet was one of 4 that was tapped off the line from the breaker box.

I untaped the 2 connections & checked the voltage with my dvm on the group of my twisted wires. It said 20.5 volts, then I tried a different spot on a different area of the same connection & it said 122.3v.

The outlet is working fine now.

What is the cause of the voltage diff on the same connection? Is it a fire hazard? Is there a proper way to connect 4 lines in a junction box?

Thanks,
Dale
 
  #4  
Old 06-23-04, 06:30 AM
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On a digital voltmeter in residential wiring, all voltage readings other than 0, 120, and 240 (plus or minus 5%) should be treated as if they are zero. So your 20.5 volt reading is really zero.

I hope those "taped" connections also had wire nuts on them. All connections should be made with wire nuts that are on tightly. Pull hard on each individual wire to make sure it is securely held by the wire nut.
 
  #5  
Old 06-23-04, 02:20 PM
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Nope, those taped connections don't have wire nuts on them.

I guess I have to put them on???

Can the wire (looks like copper) become tarnished / corroded & have a bad connection? Is that what is giving me the wandering voltage if I touch the same connection with the meter in a different spot?

Dale
 
  #6  
Old 06-23-04, 02:30 PM
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Taped connections are next to worthless. Until you get wire nuts on all those connections, it's not worth investigating any other problems. Read a book on home wiring so that you're sure you know how to properly apply wire nuts.
 
  #7  
Old 06-23-04, 06:33 PM
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I've had several old houses where the wiring was very pimative. Outlets, light sockets and anything else would show weird voltages; 86, 67... In one, the wiring in the attic was two bare copper wires running about a foot apart. Each tap for an outlet or fixture was just another bare copper wire wrapped around the trunk line. I guess corrosion on the wires caused resistance and dropped the voltage. Several connections had gotten extremely hot and caused fires that had extinguished themselves. All this wiring was in an attic that was sealed closed by a re-model to add indoor plumbing. It looked as though nobody had been in the attic since the 1930's.

There is no easy fix. I totally rewired everything to modern code.
 
  #8  
Old 06-24-04, 07:23 AM
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Some old wiring connections were soldered. If a wire is added to this connection, then a wirenut is needed. Just soldered connections, I am not sure, but would just tape be sufficient?
 
  #9  
Old 06-24-04, 04:49 PM
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Electrical tape does nothing to improve an electrical connection. It can insulate bare wires, and you can use it to help keep a wire nut from working loose, but it does not help the connection carry electricty any better.

A good electrical connection requires a good gas tight connection between the two conductors... meaning that they are in such intimate contact that gas (oxygen) cannot get between the two parts to cause corrosion. Corrosion (when the wire is no longer shiney and new) acts as an insulator or resistor.

A good wire nut has a metal spring insert that actually cuts into the wires as you tigten it. The spring also opens up as you tighten it so it keeps strong pressure on the wires to insure good contact. When new, the wires simply touching in the wire nut conduct a lot of electricity, but after many years corrosion/oxidation/tarnish forms on the wires and acts as an insulator/resistor. Then most of the elecrical current is carried by those nice tight interfaces between the wire and the spring insert of the wire nut.

A properly soldered connection is also good. Generally when soldering you work with nice shiney, clean wires and fill the space between them with solder (lead/tin or silver). The solder does not let air (oxygen) get between any of the metal surfaces and muck up the electrical connection.
 
  #10  
Old 06-24-04, 06:07 PM
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Just FYI, soldered connections without wire nuts are no longer allowed by the electrical code.
 
  #11  
Old 06-25-04, 01:55 AM
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Originally Posted by Pilot Dane
I've had several old houses where the wiring was very pimative. Outlets, light sockets and anything else would show weird voltages; 86, 67... In one, the wiring in the attic was two bare copper wires running about a foot apart. Each tap for an outlet or fixture was just another bare copper wire wrapped around the trunk line. I guess corrosion on the wires caused resistance and dropped the voltage. Several connections had gotten extremely hot and caused fires that had extinguished themselves. All this wiring was in an attic that was sealed closed by a re-model to add indoor plumbing. It looked as though nobody had been in the attic since the 1930's.

There is no easy fix. I totally rewired everything to modern code.
The odd low voltages (those other than 0, 120, 240) are probably Phantom Voltages, and are the results of capacitance and the use of the DMM. I think
 
  #12  
Old 06-25-04, 05:17 PM
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Please explain how capacitance on a hot circuit creates an odd voltage??? Would you see the same result with an analog (needle) type volt meter? Now you've got my curiosity.
 
  #13  
Old 06-25-04, 06:09 PM
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Read about phantom voltage here.
 
  #14  
Old 06-25-04, 06:24 PM
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Great! Now I need to go back and re-wire the house with shielded wire and make sure none of the wires run parallel.

Thanks for the link.
 
  #15  
Old 06-25-04, 06:48 PM
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Heh, only if you need megohm loads to function correctly. The thing that makes it a 'phantom' voltage is simply that there is very little current behind the voltage. The voltage may be high (50 or 80V) if _very_ little current is being drawn (say the input impedance of a digital volt meter), but as soon as a fraction of a mA is permitted to flow, the voltage 'vanishes'. You could imagine it as a power supply with _extremely_ high internal resistance; try to draw any current, and the internal resistance eats up all of the voltage.

The only time phantom voltage is a problem in home wiring is that it confuses digital volt meters. You solve this problem by buying a 'wiggy' type meter.

-Jon
 
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