Voltage loss

Discussion in 'Electrical Forum discussion & Blog' started by Wilson01, Oct 30, 2020.

  1. Wilson01

    Wilson01 Member

    Joined:
    Jul 15, 2018
    Location:
    New York
    I ran a 6/3 copper with ground 150’ from my panel to a 30 amp 120 volt RV plug. The problem I have is in the summer when my house ac is running the voltage in the RV drops to 106-108 volts. I know this is to low run anything in my RV. Question is would it fix my issue if I changed the breaker to a 50 amp and put a 4 circuit panel box where my RV plug is then reduced it down to a 30 amp 120v circuit? Thanks for any help
     
  2. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    Won't help if you don't increase wire size. What you could do is to get a voltage booster (RV "autoformer") to boost the voltage. RV parks often have sagging voltage, so those items are fairly popular.

    Your RV only uses 120 volts. Are you running 240 to the RV area?
     
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  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Joined:
    Sep 2, 2004
    Occupation:
    Retired Systems engineer for defense industry.
    Location:
    New England
    What gauge wire did you run? With no load, the voltage will be fine. As soon as you try to actually use power, the wire becomes like a resistor, and you get a drop across it. The longer the wire, the smaller the gauge (gauge numbers are inverted...what I mean is a smaller diameter wire which would have a higher gauge number), the more resistance it will have. Small gauge wires are only good for low current devices or very short distances.

    Note, a loose or corroded connection can also act like a resistor, and lower the voltage to the end point. It will also heat up.

    A circuit breaker is used (at least in the US) to protect the wiring. So, there's a limit on how big of a breaker you can use as the wire itself must support the maximum current the breaker allows without damage or overheating. FWIW, a hotter wire ends p with more resistance, so that just increases the heat along it (think of it as an electric heating coil or maybe in the extreme, an incandescent lamp filament).
     
  5. WorthFlorida

    WorthFlorida The wife is still training me.

    Joined:
    Oct 28, 2009
    Occupation:
    Retired
    Location:
    Orlando, Florida
    The problem is at the house, not your run to the RV receptacle. It's low because it is leaving low when the AC is on. I have a list of questions to try to get a picture of what you have. You may ask the power company to check your drop wire that all connections are good. With the AC on and you get a voltage drop say from 120 to 110, they may say that it is within tolerance. Power companies will always respond to check there side of the meter. It has happened with an overhead drop wire that one of the connectors has corroded causing a bad connection, thus you'll get a low voltage condition with a load. I'm assuming that the panel is at your house.
    1. The 6/3, is it two hots, a neutral and a ground? Or one hot, a neutral and a ground? 6/3 means four wires total, 6/2 means three wires total.
    2. Is it one cable or three separate wires in conduit?
    3. What size at the panel is the main breaker? 100 amp or 150 amp?
    4. What is the age of the drop wire from the power company?
    5. What is the voltage at the panel and at the RV connector without the AC running?
    6. Have you tried it with a electric dryer running and the AC is off.
    7. How old is the AC and it's size? Old units take a lot more power.
    8. Anything running at the RV when you check the voltage?
    9. When the AC first turns on, do any lights dim inside your home? (incandescent filament bulbs)

    To use this calculator [http://wiresizecalculator.net/calculators/voltagedrop.htm] enter the expected maximum current that you will draw. It should not be 30 amps. Maximum continuous load should not be more than 24 amps. If you are leaving the panel at 120 volts, at 24 amps, it should be around 116 volts. If you leave the panel at 110 volts with a 5 amp draw it would be less than a volt drop. With no load at the RV, the voltage will the same at both ends. Voltmeters take nearly no power. The RV may recommend a 30 amp breaker to prevent false tripping when AC motors are turned on. On start up is when they take large slugs of current that could trip say a 15 amp breaker.

    Question is would it fix my issue if I changed the breaker to a 50 amp and put a 4 circuit panel box where my RV plug is then reduced it down to a 30 amp 120v circuit? Increasing the size of the breaker will not change anything. The breaker protects the wiring, not the RV. Doesn't most RV's have there own breakers of fuses? I really do not know. A lower voltage at the RV will affect AC motors. If there are any DC motors then the RV is using a converter and low voltage input should not affect it. Reach4 does have a good suggestion.

    http://wiresizecalculator.net/calculators/voltagedrop.htm
     
  6. Wilson01

    Wilson01 Member

    Joined:
    Jul 15, 2018
    Location:
    New York
    Right now I have 30 amp 120volts run out to the pedestal. I’m only using 3 of the 4 wires. The wire I actually ran is well pump wire that was given to me so all 4 wires are 6 gauge copper. I had thought in the future to running 240v to my shed with a small panel box.
     
  7. Wilson01

    Wilson01 Member

    Joined:
    Jul 15, 2018
    Location:
    New York
    I had National Grid at my house this summer and they checked the voltage at my meter pan. The house was built in 2004 so the wires aren’t that old. I have a 200 amp service. When Nation Grid checked the voltage with no load it was 120/120/240. With a load and air conditioners on it was 116/118/235 and no lights flicker when turning the ac on. The ac unit is probably 8-9 years old and 15,000 btu. As far as the wire it’s well pump wire that was given to me. It’s 4 wire submersible and all wires are 6 gauge copper. Right now I’m only using 3 wires for 120 volt off a 30 amp Single breaker.
    With hardly anything running in the house(ac off) I have 117 volts in the camper. When I turn the ac on in the house it drops to 111-112. But if I turn the ac on in my camper it drops to 106-108 volts. The RV does have an inverter and has a small breaker box with a 30 amp main. Thanks for any help
     
  8. JerryR

    JerryR Active Member

    Joined:
    Jul 27, 2011
    Location:
    Florida
    Having a 4 volt drop (120 vs 116) on one leg at the at the meter on a 200 amp service with a 15k btu a/c on is not normal. That points to an issue with the power feed to the house. My remote vacation cabin has a 200 amp service. When my 3-1/2 ton 42k btu air conditioner runs and my 24 amp 240v electric vehicle car charger is charging I barely get a 1-volt drop. Call your power company back, run the house AC and your RV ac and have them measure the service feeder voltage drop.

    I have several of these digital plug in voltage monitoring devices at my home and also in my RV. Here are before and after readings I just took with the vacation cabin 3-1/2 ton ac running and my electric car charger working.

    [​IMG]

    [​IMG]



    As Worth stated, changing the breaker at the house to 50a and putting a sub panel out by the RV will not change your voltage drop issue. Personally I would do that anyway just so you have a disconnect right by the RV 30a outlet and you can add additional devices if needed.

    I also suspect your RV “inverter” is actually a converter. Inverter takes your 12 volts DC and provides 120 VAC so you can run 120vac appliances, TV, etc off your battery when boondocking. A converter takes 120 VAC and provides 12 v dc to keep the RV battery charged and provide 12 v dc to the RV dc devices like your 12 v dc LED lights, slide motors, exhaust fans etc.
     
  9. Wilson01

    Wilson01 Member

    Joined:
    Jul 15, 2018
    Location:
    New York
    At this point I’ll have to wait till spring/summer to have the power company come back. My camper and ac units have been put away for the winter. Thanks for the help
     
    Last edited by a moderator: Nov 14, 2020
  10. fitter30

    fitter30 Well-Known Member

    Joined:
    Feb 2, 2020
    Occupation:
    Retired service tech
    Location:
    Peace valley missouri
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