220V Circuit question

Discussion in 'General Electronics Chat' started by vcastagnoli, Sep 18, 2015.

  1. vcastagnoli

    Thread Starter New Member

    Sep 18, 2015
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    My Dryer was working the other day, and then the breaker popped. After resetting the breaker the dryer no longer gets hot, and the 220V electric water heater on the same circuit does not heat. I checked from the neutral to each hot lead and get a 110V reading, but across the two hot leads I don't get a voltage reading (I was expecting 220V). It is acting like the two 120V leads are on the same phase leg. I did not move the breaker, so how would they be in the same phase now? Is the breaker bad? I'd really like to have hot water and a working dryer.

    Please help.

    Thanks,
    Victor
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    You need to start at the breaker, there obviously should be 240v at this point, start from there and work toward the dryer/water htr.
    It sounds unusual to have both on the same breaker, I would expect two separate breakers.
    Max.
     
  3. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    You are using the meter in AC volts mode, correct?

    Did something break and short the live 220 to chassis on either the dryer or water heater?
     
  4. KeepItSimpleStupid

    Well-Known Member

    Mar 4, 2014
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    This is a good question and sometimes mis-understood.

    There are Phantom voltages that can be generated by capacitively coupling of wires. When you try to draw current from these wires, the voltage drops to zero. Some Fluke meters have the ability to set a low Z mode.

    Suppose, that one side of your breaker as faulty. I'm not saying it is. The water heater looks like a low value resistor, so it in esscence will show you that you have 120 V to ground on the bad side as well as the good side, the voltage goes from the good side to your meter to ground. the bad side, goes from the good side through a low value resistor (the dryer), to where you measured. 120 V measured through a <100 ohm resistor with no current flowing will still be 120 V.

    Sometimes voltages across the breaker or across the switch, can tell you things when you know what;'s happening downstream. If the device is on, you expect a very low voltage across the switch/breaker.
     
  5. vcastagnoli

    Thread Starter New Member

    Sep 18, 2015
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    I tested across the plug prongs on the dryer and find no continuity, so I don't think it has a short. The leads to the water heater show about 13 ohms, which is expected for the elements. I'll check the breaker once the sun comes up.
     
  6. KeepItSimpleStupid

    Well-Known Member

    Mar 4, 2014
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    You might want to concentrate on the water heater first with the dryer plug removed. Also check the water heater for shorts to ground. Even though the dryer was working, it COULD be the water heater.

    Just, so you get the idea, a water heater consists of a thermostat (upper and lower elements), so both are a possibility. here's http://waterheatertimer.org/How-to-wire-water-heater-thermostats.html a typical water heater wiring diagram.

    Since you have two things on the same circuit, somewhere the devices have to be paralleled. if your in the US, I don;t think the NEC allows two wires at the breaker. You have to pigtail.

    The breaker can be bad. A "test light" may be a better tool. e.g. pull the dryer plug. and disconnect the water heater. Go to the source. Meaning the breaker.

    When, you don;t have the resistive element paths. i.e. an open circuit as the load, THEN you will see zero volts.

    With loads, you can check the "quality" of connects by doing un-obvios things. Measure ACROSS each pole of the breaker. A difficult measurement, but not impossible. Even connections can be checked when there is a LOAD. A probe on the wire itself and a probe on the lug can show a voltage drop between the wire and the lug.

    Dryers can be wired strangely because of the 3 and 4 prong versions. See: http://electrical.about.com/od/appliances/f/3-Wire-And-4-Wire-Dryer-Receptacles.htm

    If you need a 220/240 volt load you can put two 120 V incandescent light bulbs in series.

    You now, at least see how you can have 220 on both sides of a breaker when say only one side is working when there is a load connected.

    Even if you disconnect the wires at the breaker, you STILL have to be careful. You could still read 120 to ground from both sides. If one path is resistive, then it won't support much current. That's where a "test light" may be more helpful.
     
  7. vcastagnoli

    Thread Starter New Member

    Sep 18, 2015
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    Tracked it down. There is a fuse box with the old 30A cylindrical fuses and one of those had blown, breaker was fine, and all seems to be working again. I've only been in this house a month, so still learning how they did things in 1955.
    Thanks for all the ideas, and things to check.
     
    Sinus23, ErnieM and GopherT like this.
  8. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Thanks for checking in and letting us know the solution.
     
    Sinus23 likes this.
  9. KeepItSimpleStupid

    Well-Known Member

    Mar 4, 2014
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    The dryer piggybacked to the water heater is probably not a good idea. Maybe, one has to turn off the water heater when using the dryer or minimize the chance by not showering or using hot water when doing the laundry? I suspect it will happen again.

    The house I live in was built in the 1960's. I think all of the 2-prong polarized outlets have been replaced. Fortunately, a ground was run to the outlets. The service has not been upgraded to breakers yet and the only GFCI protected locations are outside/porch. Not too long go, I painted a room and replaced all of the outlets with "tamper proof" outlets.. This new standard makes it impossible to stick something in one side oft he outlet. Something that kids might do.
    I'm not worried about the bathroom because only toothbrushes are plugged in and the hair dryer has a built-in GFCI.

    The two to 3 prong outlet upgrade is generally difficult, but can be managed more easily with ideal term-a-nuts and ground clips. The metal outlet boxes do not have the tapped ground hole. Code wise, your not to allow the outlet tab to make the ground contact (there are exceptions), so you have to ground the box and the outlet with a wire. Termanuts are basically a pigtail wirenut with a single wire out the wrong end.

    For the ground, you end up with a termanut attached to the two ground wires (assume daisy chained), a wire to the box via a ground clip and a stranded termanut with an integral fork terminal to the ground screw. Hot and ground can be pigtailed via the termanut rather than the double-poke method.

    Also note, that industrial wiring may put the ground prong in the up position while residential uses down. Up is cafer because it's more difficult for a falling object to contact hot and ground at the same time (Say loose plug) with the ground tap first.

    Thanks for the update.
     
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