Fixing up a property, we found one outlet in particular that when the mouse sander or shop vac was plugged into it, they ran really slowly, like almost no juice. So i did what any contractor would do, I removed the outlet and tested it with a voltage meter. Here's what I found: Hot->neutral: ~113V, 59.9 hZ Hot->ground: ~113V, 59.9 hZ Neutral->ground: ~0V

Now, just as I did, any of you reading this are probably saying to yourself that that seems totally normal. 113V at just about 60hZ is what it should be (approximately). But for some dang gone reason, plugging a device into this yields about 10-20% of what the expected speed would be. The only thing I could guess, and I don't have an oscilloscope to confirm, is that maybe the 110V waveform is screwed up somehow? But how and why? This is a single fam home. Someone please shed some light. Thanx

  • Scary. That suggests you aren't getting the amps you need. Yet the breaker isn't blowing. That sounds to me like fire waiting to happen, but I'm not a professional electrician. My immediate reaction is that you want a pro to look at it. – keshlam Mar 9 '16 at 7:08
  • 2
    can you test the voltage again while a lamp (of known wattage) is plugged into it. (using a extension cord with multiple receptacles). – ratchet freak Mar 9 '16 at 8:57
  • 2
    The obvious conclusion is that there's a marginal connection somewhere that, when you draw significant current, is dropping the voltage. The corollary is that, when you draw significant current, that connection is dissipating significant heat. Indeed: sounds like a fire hazard. Be careful! – Daniel Griscom Mar 9 '16 at 10:56

One possibility is that the contacts in the receptacle are corroded or burnt. Or there may be some other fault in the wiring or connections to that receptacle. Perhaps a loose wiring nut or an undersized conductor.

This would create a resistance. When no current is flowing, no voltage is dropped across the resistance - so you measure nearly full voltage. However when a load is connected and a significant current is flowing, a voltage drop will occur across this resistance.

This is of course a fire hazard. The resistive part will heat up considerably.

ratchet-freak's diagnostic suggestion is a good way to verify this - use an extension cable so you can simultaneously plug in a high-wattage lamp (as a test load) and volt meter. See if the voltage dips when you plug the lamp into the extension.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.