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

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)
    

    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
    100Ft	25A	##	##	##	##	##	##	##
    200200Ft	12.5A	25A	19.23A	38.46	##	##	##	##
    300Ft	8.33A	16.67A	12.82A	25.64A	20.41A	40.81	32.25	##
    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

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

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

 

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