Circuit cuts out with a load

Discussion in 'General Electronics Chat' started by dmadam, Sep 21, 2016.

  1. dmadam

    Thread Starter New Member

    Sep 21, 2016
    I replaced an old line and the outlet tester reads it OK and the voltage reads good. But as soon as I put a load on it the line goes dead but the breaker does not kick out. It is totally baffling to me. Ideas anyone? Searched for articles here but found nothing like this.
  2. #12


    Nov 30, 2010
    There is a bad connection somewhere. Most famous in wall outlets is the, "stab" connectors. Two tiny pieces of metal make contact at tiny points on the wire. A tiny bit of corrosion will stop significant current from flowing. I have also seen the fins in the breaker box go bad. Pop the breaker out and see if the back plate is good.
    Hypatia's Protege likes this.
  3. be80be

    AAC Fanatic!

    Jul 5, 2008
    Just don't stick your fingers on the back plate. You just don't know how many that want to touch the buss of a breaker box when you show them a brunt back plate.
    It's like they need to feel it Ok right. I've grab a many a hand in 34 years to stop them.
    Sinus23, dmadam and #12 like this.
  4. dmadam

    Thread Starter New Member

    Sep 21, 2016
    Thanks guys for the suggestions. What is confusing me is that it won't even take a light load of a CFL Bulb. I put the line if for a new 110V 20gal hot water heater. As a test I put a plug on the heater wires and plugged it to wall socket and it worked so ruled out a defective heater. Forgot to mention I misspoke when I said breakers. This is an old place with fuses. I used one side of the 220 and used a new feeder 10/2 wire. Tried it also on another fuse and did the same thing. I have installed water heater and stoves before and never saw anything like this.
  5. MrSoftware

    Senior Member

    Oct 29, 2013
    It does sound like a bad connection somewhere. Retrace all your steps. It's possible the point of the bad connection could get hot if a load is attached. Also make sure you didn't grab a pair of 110v lines from the same phase, instead of a 110v line and a neutral. Test both of your wires relative ground. One should show 110v and the other should show 0v relative ground.
  6. AnalogKid

    AAC Fanatic!

    Aug 1, 2013
    Here are some round numbers to simulate what you are seeing. If your load is 1 ohm (120 W light bulb in the US) and your meter input impedance is 10 megohm (typical for a DVM), and you have a bad wiring connection that should be less than 0.1 ohm but actually is 10 K, then that resistance is the series leg of a 2-resistor voltage divider. The meter's input impedance is the shunt leg. With a 10 K series and 10 M shunt, the meter will read 99.9% of the source voltage. But when the load is connected, it is a 10 K series and 0.1 ohm shunt, so the load sees 0.001% of the source voltage.