Measuring 116Vac but no power??

Reply

  #1  
Old 09-19-04, 01:23 PM
DamianG
Visiting Guest
Posts: n/a
Measuring 116Vac but no power??

Hi all,

I lost power in two adjacent bedroom outlets. These two rooms are on
the same 20amp breaker.

I checked all the connections on all the bad outlet in both rooms, and they
are making physical/electrical contact to the proper screw terminals on the outlets.

The odd thing is on all the bad outlets, I measure with a voltmeter
116Vac but they won't even power-up a nightlight.

The rest of the outlets (good ones) are measuring 124Vac.
I replaced the circuit breaker to make sure that wasn't the problem.
(thought it might be a high impedance problem)

I measure at the breaker box after the breaker feeding the suspect circuits and it measures 124Vac the same as the good outlets.

I was doing this troubleshooting at my sister house.... One thing I failed to
do is mapout every circuit on this breaker.

Apparently after speaking with brother-in-law there are other circuits in
another room that are on this breaker also.

But how is it possible to have 116Vac but not have power to drive a
nightlight?

thanks
Damian.
 
Sponsored Links
  #2  
Old 09-19-04, 02:33 PM
Andrew's Avatar
Member
Join Date: Apr 2003
Location: USA
Posts: 930
Sounds to me like an open neutral somewhere. Get one of those testers that has three lights, and plugs in. That will tell you for sure.
 
  #3  
Old 09-19-04, 03:30 PM
Member
Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
It sounds like you are using a digital voltmeter for your testing. This is useless for an AC circuit if this type. You need to use an analog meter for accurate results.

Use an analog meter, or use a simple two wiore tester or a plug in type tester and repeat your test. I am also betting on an open neutral.
 
  #4  
Old 09-19-04, 04:26 PM
Member
Join Date: Sep 2000
Location: United States
Posts: 18,497
Most people would be better off spending $2 for a neon circuit tester than spending $15 to $20 for a digital multimeter. As Andrew suggested, you will also want to spend $8 on an outlet tester. Put your multimeter away.
 
  #5  
Old 09-19-04, 05:17 PM
Member
Join Date: Sep 2002
Location: welland ontario
Posts: 5,599
Problem could be in a good working outlet, light fixture or switch on the same circuit.
 
  #6  
Old 09-21-04, 08:38 AM
DamianG
Visiting Guest
Posts: n/a
Originally Posted by John Nelson
Most people would be better off spending $2 for a neon circuit tester than spending $15 to $20 for a digital multimeter. As Andrew suggested, you will also want to spend $8 on an outlet tester. Put your multimeter away.

I will go out and buy an outlet tester. But from a technical point of view, I
don't understand why a multimeter will not work; and I still don't get how I am measuring 116Vac with an open circuit... if that is what the problem most of you are suggesting it might be.

I have a degree in Electronics Engineering... but I am not familiar with Basic
home wiring.. and its codes. But I'm sure I can get up to speed on this really fast. There is a lot of good info on this site!

What does an outlet tester tell you that a multimeter can't????


thanks for the help..
I'm sure I'll have this licked in a few days....I will repost
 
  #7  
Old 09-21-04, 08:49 AM
Member
Join Date: Sep 2000
Location: United States
Posts: 18,497
Read this. Voltage is cheap. You may have seen Van de Graaff generators that generate 100,000 volts, but wouldn't hurt a fly. Voltage means nothing without current.

An outlet tester or a neon circuit tester puts a load on the circuit. A multimeter does not. The lights on the outlet or circuit tester demonstrate that there is some current behind that voltage.
 
  #8  
Old 09-21-04, 08:55 AM
Member
Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
A digital multimeter gets confused by the circuit. It works great if all the wires are properly connected, but if a wire is not connected them the results are meaningless.

The outlet tester will require enough current through the circuit that the open neutral (if that is what you have) will show as an open circuit. A digital multimeter does not require significant current to determine the voltage, so it can register the voltage without needing a complete hardwired circuit, but does so inaccurately, hence the low voltage reading.

With your outlet tester you want to determine if you have voltage between the hot and neutral, the hot and ground, and as a final test the neutral and ground. If your receptacles have no ground slot then use a decent ground instead. By decent ground, I suggest the ground slot on a properly wired and working receptacle or a nearby vold water copper pipe.
 
  #9  
Old 09-21-04, 01:57 PM
DamianG
Visiting Guest
Posts: n/a
I got it...

Your right voltmeters have a high impedance and don't place a
load on the circuit. I'll go out and purchase a cheap outlet tester..

thanks
 
  #10  
Old 09-22-04, 09:16 PM
jughead's Avatar
Member
Join Date: Oct 2003
Location: Davenport, Iowa
Posts: 597
Come on guys.....You can use a digital multimeter in this application just fine. If you want to put a small load on the line just plug in a lamp with a small bulb in it and then measure the voltage. If there is a large drop when the lamp is turned on you obviously have a large resistance (loose connection) in the line. You are correct, most digital multimeters are very high impedance devices, but it doesn't take much (simple light bulb) to alter that reality. Some old electricians use Wiggies to prove the source will supply a small load and that's useful, and handy, to know, but when you don't have that kind of equipment in your hand, use what you have to gather the information you need to solve the problem. I've been using digital multimeters for a long time, and yes it was hard to get away from the old analog instrument, but I'll never go back, there is no need to.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes
'