1. 2019 ECR Presentation “HOT SKIN”
Presentation by:
Randy T. Agee, D.Ed (RandyA)
EE, Master Electrician, CET

2. Licensed Electricians
Electricity or Power Distribution is a complex subject that cannot be explained or understood in only a few hours.
Licensed Electricians have spent at least two years learning the trade as a journeyman with approximately 400 hours of classroom instruction and successfully passing a comprehensive written knowledge exam.

3. Licensed Electrician
Many unlicensed individuals believe that they can safely wire a RV park power pedestal with minimal training or experience.
Many well intentioned individuals make changes to their personal RV’s electrical system that can result in a potentially dangerous situation.

4. Finding a Qualified Electrician
Unfortunately, even licensed electricians may lack the experience and knowledge needed to safely make changes to the AC wiring inside an RV.
When choosing an electrician to work on your RV always select an experienced individual that understands the complexity of RV wiring and follows all NEC rules.

5. NO, This is Not the “Hot Skin” condition we will exploring.

6. The “Hot Skin” we will explore is a condition where the metal of a RV is electrified through a fault that can result in a severe shock or even death.

7. An individual who is standing on the ground (earth) and at the same time touches any metal on the RV is shocked

8. A “HOT SKIN” can have enough voltage and current to cause death.

9. Quick Review
VOLTAGE – This is the pressure of electrons in a circuit. The higher the voltage the greater the force of the electrons.
AMPERAGE – The number of electrons flowing in a circuit. The higher the amperage the greater the count of electrons.

10. Quick Review
AC – Alternating Current. The direction of electron flow is reversed at a specified interval. US power systems do this 60 times per second, also noted as 60 Hz.
DC – Direct Current. The flow of electrons is always from the negative pole to the positive pole.
RV’s have both AC and DC power systems.

11. Quick Review
120 Volts AC – “Nominal” term. Actual voltage can range between 110 VAC and 125 VAC
240 Volts AC – “Nominal” term. Actual voltage can range between 220 VAC and 250 VAC

12. Quick Review
15, 20 and 30 amp park outlets are all 120 Volts AC at 60 Hz.
A properly wired 50 amp park outlet supplies 240 Volt AC. The 240 VAC is “split” into two 120 VAC circuits with each supplying 50 amps. This results in two 50 amp 120 VAC circuits supplying a total of 100 amps.

13. 240 VAC 50 amp Park Outlet
NEMA 14-50R 50 amp 125/250 Volts

14. RV Power distribution (50-50 amp circuit breaker box)

15. Correct wiring for 50 amp outlet

16. Dual trace sine wave for 50 amp (240 volt) power to park outlet

17. 240 VAC Operation
The voltage from X to Y should be 240 VAC. As X goes positive Y should go negative. This is called the “Phase Differential”. This is important as this differential provides a balanced flow of current (amperage) on the single neutral conductor.

18. 240 Volt AC Operation
If a park 50 amp outlet is wired with “straight” 120 VAC to both X and Y the neutral wire must carry the combined current of X and Y without the benefit of the phase differential. The result will commonly result in burned neutral wiring and plug contacts.

19. Current overload damage to 30 amp RV male end.

20. NEMA Standard 120/240 VAC Wiring Color Codes

21. Residential bonding of neutral and ground is different than RV

22. CORRECT Bonding for a RV
Neutral and ground are NOT bonded in RV

23. SAFE GROUNDS TO PREVENT “HOT SKIN” CONDITION FAULTS
The NEC requires the ground to come from the main Service Entrance Panel (SEP).
Metal landing jacks or stabilizer jacks WILL NOT safely ground your RV.
A metal rod or stake driven in the near-by earth or next to a park outlet WILL NOT safely ground your RV.

24. BOOTLEG GROUND
In United States building wiring installed with separate neutral and protective ground bonding conductors, a bootleg ground (or a false ground) is a connection between the neutral side of a receptacle or light fixture and the ground lug or enclosure of the wiring device. This connects the neutral side of the receptacle to the casing of an appliance or lamp. It can be a hazard because the neutral wire is a current-carrying conductor, which means the casing can become energized. In addition, a fault condition to a bootleg ground will not trip a GFCI breaker or receptacle that is wired from the load side of a GFCI receptacle.

25. The grounding wire is NOT a circuit current carrying conductor

26. Checking Park Outlets
Unfortunately, it is not uncommon to find park outlets that are incorrectly wired, have burnt wires or broken outlets. ALWAYS run a through check on any outlet you anticipate connecting your RV to.

27. Which Parks are Safe?
“Older” parks are the most likely to not have the required ground wire returning from your outlet box to the main service entrance panel (SEP).
“YOU” are not authorized to open a park box to check their wiring. If the power doesn’t check out OK with your testers then leave.
It is not worth the risk to you, your occupants or equipment to stay where a power outlet is “questionable:

28. Typical underground wiring in older parks was with “Tri-Plex”
Typical underground wiring in older parks was with “Tri-Plex”. Current NEC standards call for a 4th grounding wire shown here as a green colored wire.

29. Correctly wired 30 amp park power unit.

30. Bad RV Power Pedestal Wiring #2

31. Bad RV Power Pedestal

32. Typical 50-50 amp RV Service Entrance Panel (SEP)

33. Typical Residential SEP
Note dual alternating bus bars allowing 240 VAC distribution.

35. How Hot Skin Happens Often takes TWO faults at the same time
Reversed neutral and hot at supply
Bonding of neutral and ground in RV
Broken or no ground at supply
Other RV’s on a shared power circuit that have internal faults.
Induction from overhead power lines
Incorrect installation of an inverter or generator
Any situation that connects supply neutral or hot to the metal frame of a RV

36. SO, How to check for and prevent a “HOT SKIN” condition
ALWAYS check your campground outlet with a volt meter, my 50 amp outlet tester, or a commercial EMS BEFORE plugging in your camper.
Change your amp main circuit breaker to a GFCI.
Use a commercial EMS that will shut down power if an external fault creates a dangerous condition.

37. Before you do anything else test your RV for faults NOW by using an Ohm Meter to make sure there is no connection between neutral and ground

38. A small amount of resistance is expected (2-6 Ohms)
A small amount of resistance is expected (2-6 Ohms). A reading showing a solid connection between the two is a serious fault.

39. Incorrectly wired RV

40. Correctly wired RV

41. Replacement 50-50 amp GFCI Main Breaker

42. INVEST IN A QUALITY EMS SYSTEM – AND USE IT!
This unit is from
Progressive
Dynamics

43. This type of unit ONLY protects from power surges – it is NOT an EMS

44. Use a Non-Contact Tester
Non-contact or inductive proximity testers offer the safest and fastest way of checking for a “Hot Skin”. It is not a bad idea to test often as other RV’s near you come into the park.

45. Look closely at this drawing
Look closely at this drawing. What do you think would happen if the neutral and one of the hot wires were reversed?