5) Reasons

Most RV Campsite Electrical problems can be summed up with the two phrases “Voltage Drop” and “Inadequate Wire Size”

Voltage drop describes how the supplied energy of a voltage source is reduced as electric current moves through the passive elements (elements that do not supply voltage) of an electrical circuit. Voltage drops across internal resistances of the source, across conductors, across contacts, and across connectors are undesired; supplied energy is lost (dissipated). For example, an electric space heater may have a resistance of ten ohms, and the wires which supply it may have a resistance of 0.2 ohms, about 2% of the total circuit resistance. This means that approximately 2% of the supplied voltage is lost in the wire itself. Excessive voltage drop may result in unsatisfactory operation of, and damage to, electrical and electronic equipment. http://en.wikipedia.org/wiki/Voltage_drop

WIRE Size: A common mistake made by Campgrounds is to use the smallest size cable rated for the circuit breaker in use,  regardless of the length. For a 30A Circuit Breaker #10 wire is indicated. However it is NOT suitable for runs beyond 104 Ft. For sites beyond this distance, larger cable is indicated.

  1. Campgrounds typically advertise 20A, 30A and 50A circuits, but due to the structure of the distribution system, cannot always provide this amount of power to the site, especially to systems that were put into place over 30 year ago.

  2. A few years back we were put on a meter. Prior to this we were not allowed to use A/C Units. This grid is now severely overloaded as more and more A/C units come on line during the hot weather.

  3. Even today some park owners still use #10 wire regardless of the distance. I hope this document provides some insight into what is actually happening out there in the campground. I don’t expect any dramatic changes as the expense of bringing everything up to code would be astronomically expensive. However I would hope that new circuits would take some of this data into account.

  4. The following table shows voltage fluctuations measured on 4 July 2014 (Friday) starting at noon, when the park was lightly inhabited. During the rest of the day campers were coming in for the weekend, and loading down the grid. The lowest voltage reading was at 17:50(5:50pm) dinner time. Ambient temperature was on the cool side around 25°C

    Time

    Voltage

    11:53

    127.8

    15:20

    123.9

    15:45

    120.3

    17:50

    107.8

    18:45

    121.6

    19:50

    119.8

  5. The Rules per The Canadian Electrical Code(Very Similar to the American NEC). Both the American National Electrical Code and the Canadian Electrical Code specify a maximum feeder voltage drop of 3% and a branch circuit voltage drop of 3 % with a combined voltage drop of 5%.

  6. A circuit with a 30A circuit breaker should supply 80% of the circuit breaker rating (24A) to the site appliances with only a 5% voltage drop (6V).
    ie: A 120V, 30A circuit should provide 114V at 24A to the site appliances.

  7. A circuit with a 50A circuit breaker should supply 80% of the circuit breaker rating (40A) to the site appliances with only a 5% voltage drop (6V).
    ie: A 120V 50A circuit should provide 114V at 40A to the site Appliances.

  8. Specifying cable length and size for an underground circuit is an Engineering Design Function and requires a Professional Engineer or Certified Engineering Technologist. I suspect that this little requirement regularly gets ignored and the local electrician just goes about doing what has always done. See Attachment 13 on Professional Engineering.

  9. Most loads can be classified as either Resistive or Inductive.

  10. Resistive loads like light bulbs, heaters, coffee makers, toasters etc. are not generally damaged by low voltage. Resistive loads tend to draw less current(Amps) as the voltage goes down. Ohms Law applies to Resistive circuits (V=IR, or I = V/R)  V=Volts, I=Amps, R=Resistance.

  11. Inductive loads like AC Motors (Refrigerators, A/C Units, and device with a transformer) can be damaged when the voltage drops below 106V and tend to draw more current(Amps) as the voltage goes down. The formula applicable with Inductive Loads is P=IV or I=P/V or P=IZ, P=E²Z Where Z is the impedance of the load.  (I=Amps, P=Power(watts), Z = Impedance(Ohms), E=Volts)

  12. This report deals mainly with Voltage Drop in long runs of power cable. If the wire size is too small, the voltage drop becomes excessive and damage to equipment could result. It has been my personal experience in Industrial Plants, that local electricians have no concept of voltage drop. It appears that the many campground electricians fall into the same category.

  13. This issue of low voltage and voltage drop seems to be a common occurrence in campgrounds across the Province. See Attachment 10.

  14. The Acceptable voltage range according to Hydro One is as Follows (See Attachment 7)

    1. Normal Limits 110 to 125

    2. Exceptional Limits 106 to 110 & 125 to 127
  15. #10 wire seems to be a common wire used to feed sites in my Park. The remainder of this report deals with the theoretical and observed effects for a circuit that has a 30A Circuit Breaker, and ~400ft of #10 Wire
  16. #10 is good for 40A, according to the CEC Table D3 on Attachment 6.
  17. However Table D3 also indicates that it is only good for 40A to 3.9M at 1% VD

  18. and 3.9*3=11.7M (38Ft) at 3%VD.

  19. It works for 24A to 6.2M at 1% VD and 6.2M*3=18.6M(61Ft) at 3%.

  20. I suspect that this 400ft run is an exception rather than a common occurrence, so here are the parameters for some other lengths for a 30A 120v circuit of #10 (CEC Table D3)
    1. Distance

    Amps
    (5%)
    #10

    Amps
    (10%)
    #10

    Amps
    (5%)
    #8

    Amps(
    10%)
    #8

    Amps
    (5%)
    #6

    Amps
    (10%)
    #6

    Amps (5%)
    #4

    Amps (10%) #4

    1. 100Ft

    25A

    ##

    ##

    ##

    ##

    ##

    ##

    ##

    1. 200200Ft

    12.5A

    25A

    19.23A

    38.46

    ##

    ##

    ##

    ##

    1. 300Ft

    8.33A

    16.67A

    12.82A

    25.64A

    20.41A

    40.81

    32.25

    ##

    1. 400Ft

    6.25A

    12.5A

    9.61A

    19.23A

    15.30

    30.61A

    24.19

    ##

    Amps available at several cable selections, ### indicates that the cable can handle more current than the circuit breaker.

  21. I suspect that this 400ft run is an exception rather than a common occurrence, so here are the parameters for some other lengths for a 30A 120v circuit of #10 (CEC Table D3)

A) 100 Ft = 30.4 M , 30.4/3 = 10.1, Use 9.6 on Table =16A, Calculator = 15A

B) 200 Ft = 60.96M, 60.96/3 = 20.3, Use 19.4 on Table = 8A, Calculator =7.5A

C) 300 Ft = 91.44M, 91.44/3 = 30.5, Use 31 on Table = 5A, Calculator = 5A

Voltage Drop from the software calculator for these lengths for 24A is as follows

A) 5.76VD, 4.8% OK

B) 9.6VD, 9.6% Should Use #6

C) 17.3VD, 14.4% Should Use #4

—–   —–   —–   —–   —–

Note: In all my years in factory electrical work, I have never seen an electrical inspector test for voltage drop.


Most RV Campsite Electrical problems can be summed up with the phrase  “Inadequate Wire Size causing too much Voltage Drop”

 

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