I am not an Expert the following is the result of a basic knowledge of electricity and extensive research, specific to this issue. I welcome constructive review and suggestions there is a lot of complex considerations and I have tried to balance brevity with concise and accurate descriptions.
When using electricity provide through a commercial power grid (i.e. plug into an existing supply, or shore power) There are several electrical supply events that can cause damage to your equipment, harm or even kill you. All commercial power grids supply AC (Alternating Current) power, there are 4 primary attributes of AC supply, changes in any of those attributes can cause issues. Further reading
There are two significant divisions in (the US) RV/Camper Surge/EMS protection market.
Amperage: 30 Amp VS 50 Amp. The more electrical draw the more amperage is required to run it. Supply and demand should be balanced. In the United States three options are commonly provided, each uses a different style plug. A supply point may offer only one, any combination of two, or all three.
- 15 - 20 Amp (normal household plug, small 3 prong, 120V = 2,400 Watts)
- 30 Amp (large three prong, 120V = 3,600 Watts)
- 50 Amp (large 4 prong, 240V, split-phase = 12,000 Watts)
- It is important that your protective device has the same amperage rating as your campers expect draw. A 30 Amp circuit provides a single 120V supply, while a 50 Amp Circuit provides two 120V supply, giving the RV 240 Volts.
- Adapters are available, i.e. with the correct adapter a 30 amp power cord can be used on a 20 Amp or 50 Amp supply. Using an adapter can cause part or all of the protection to be ineffective, this varies by surge/EMS/product.
In the above pedestal image we can see three separate outlets. From left to right they are 50 amp, 30 amp, and 20 amp. Each receptacle has its own dedicated breaker sized for that particular outlet. This gives the RVer the choice off choosing whichever outlet they need to best match their RV's electrical service. Source, image and quote
Single VS Multiple: Some surge/EMS/products needs to be replaced. after protecting from a single event, others will reset and can protect from multiple events. Single use devices have a lower initial cost.
I was unable to locate a single comprehensive list of potential risks. The points below are harvested from lists of protections provided by different manufactures. I only found 3 manufactures, I think my search tools are limiting results to the United States.
Amperage: In this context it might be thought of as "Ampacity" how much electrify is being used, and will it damage the supply lines?
Ampacity is defined as the maximum amount of electric current a conductor or device can carry before sustaining immediate or progressive deterioration. Also described as current rating or current-carrying capacity, ampacity is the RMS electric current which a device or conductor can continuously carry while remaining within its temperature rating. Source
- Risk: This is mostly a concern where usage is more than the supply will tolerate. As an example if the supply pedestal is wired to deliver 30 Amps and you use an adapter to plug your 50 Amp RV into a 30 Amp pedestal, then turn on all the lights, TV, and AC units, you will probably draw more then 30 Amps and optimally the circuit breaker in the pedestal will break the connection, power to your RV will stop and you will need to turn something off before resetting the breaker. If the breaker didn't interrupt the flow, electrical lines could melt causing a fire and loss of electrical supply lines.
- Protection: I did not find any RV protection surge/EMS/products addressing this issue. Your Camper/RV's own circuit breakers should protect from internal issues, while supply issues are only a concern for surge protection events which all surge/EMS/products do address.
Surge Protection Protect from voltage spikes. There are at least half a dozen different components used in devices, often in combination. most offer little or no protection for longer durations of high voltage, protecting only from quick short spikes
- Risk: Primary lighting strikes or other weather related events. Electrical devices can fail, personal injury mostly related to fire secondary to device failure.
- Protection: All surge/EMS/products offered Surge protection, the following specifications are important when considering a surge protector.
Reverse Polarity: The hot and neutral wiring is reversed, this is the result of a physical connection being incorrectly hooked up. The reversal can occur anywhere in the supply line after the transformer.
- Risk: Physical electrical shock can occur to people, I don't find any mention of risk to equipment. A real time change would require a physical change up the supply line, like the repair of issues elsewhere in the campground.
- Protection: Some surge/EMS/products indicate the fault, others will indicate and shut down power until corrected.
High/Low Voltage: Appliances like Air Conditioning use a specific amount of watts, if the voltage changes, the watts stay the same but the amperage through wire changes.
The most frequent condition is low voltage at the campground pedestal. You may arrive at your campsite early and check your pedestal voltage with a voltmeter and find it within tolerance. However, once other campers arrive and start to fire up their air conditioners the voltage is likely to drop. Source
High/Low Frequency: Hertz (Hz) is the the rate at which AC (alternating) power cycles. It is determined by the speed (RPM) of the motor generating the electricity at the power station.
In North America all electrical power is 60Hz while in Europe and most of the rest of the world electrical power runs at 50 Hz. Hz is basically a counter of how many electrical pulses or waves occur in one second. Source
A 50 Hz motor operating on 60 Hz will attempt to rotate at a 20% increase in speed. The load will become 1.23 (1.2 x 1.2 x 1.2) or 1.73 times greater (173%) than on the original frequency. Source
- Risk: The risk of damage to electrical devices varies greatly; it can range from poor performance, to no impact, to increased risk of total failure and burnout. The only cause of change I could find was the speed of generator/alternator rotation at the supply point. Personal injury potential would be secondary to fire from electrical failure.
- Protection: Some surge/EMS/products do not monitor frequency, others will monitor and shut down supply.
Time delay reset: When a surge/EMS/product stops the flow of power between the pedestal and the camper/RV, and the supply power issue is immediately corrected the surge/EMS/product may delay providing power to the camper/RV for some period of time.
- Risk: Rapid on and off supply can be hard on some devices, devices like Air Conditioners are particularly impacted and need up to 2 minutes off before being powered back on.
- Protection: Delay times vary by surge/EMS/product, some have adjustable delay times.
Accidental 240V: Much like Reverse polarity, accidental 240V comes from mis-connecting two wires someplace in the electrical supply.
If you put a voltmeter across lines L1 and L2 you'll see 240 volts. But if you test L1 to N or L2 to N you'll see 120 volts. Source, image and quote
- Risk: The risks are the same as any increase in voltage (device failure, fire, etc) but most surge only protection to does not occur until 300V.
- Protection: Some surge/EMS/products don't monitor, some monitor and display, some monitor and shut down supply.
Ground, Neutral, Home & RV
Overview Open Ground and Open Neutral are are one of the most difficult areas to understand and describe. Firstly; Homes and Camper/Rvs are wired differently and subject to different codes. Secondly; there are a bunch of variables. Thirdly; issues can be transient (come and go). Fourthly; I am not an expert, this is a summery of some of what I have learned in my research.
In many references that are not RV specific Neutral and Ground are used interchangeably as synonyms. In an RV this is not the case, the two are very distinct connections with different risks.
Both conditions can be due to a broken/disconnected wire, a loose connection or they may develop sporadically from any number of causes.
all RV electrical systems are wired with their Ground and Neutral buses floated (un-bonded from each other). There’s lots of good reasons for this, most specifically that it’s an NEC and RVIA code requiment that the safety ground wire never carries any load current, and there can be only one Ground-To-Neutral bonding point in any distributed electrical system in the USA. Now, when you’re plugging your RV into power from a building (your garage outlet) or campground (pedestal outlet), your RV has its Ground and Neutral buses “bonded” (connected) together externally as part of the service panel’s earthed safety ground system. Again, lots of reasons for this, but the fact is you can only have a single G-N bonding point according to the National Electrical Code and RVIA building codes. Source
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If the Star Point of Unbalanced Load is not joined to the Star Point of its Power Source (Distribution Transformer or Generator) then Phase voltage do not remain same across each phase but its vary according to the Unbalanced of the load.
As the Potential of such an isolated Star Point or Neutral Point is always changing and not fixed so it’s called Floating Neutral. Source
Selected References:
Open Neutral: The Neutral wire is the path for electricity that is doing work, to complete it's circuit. Normally an open or floating neutral results in no electrical flow. BUT Depending on the electrical supply in your campground, it can also cause fluctuations in voltage between 1 and 240 volts.
- Risk: No power, high or low voltage, devices not working, devices working on incorrect voltage leading to device failure. Personal risk is related to fire secondary to device failure.
- Protection: Some surge/EMS/products don't monitor, some monitor and display, some monitor and shut down supply.
Open Ground: This is the path for potential electrical energy that is not doing work. Your home is grounded by a grounding rod and metal pluming. Your RV is insulated (not grounded) by the rubber tires, plastic leveling blocks, plastic garden hose water supply. Metal landing leg and/or jacks touching the ground DO NOT provide a reliable ground path.
- Risk: An Open or Floating Ground, means the third wire (ground) is not connected, this is your fail safe. Your RV may develop "Hot Skin" and you may feel a slight tingle when touching the side of the RV. The difference between tingle and death are very close.
If you do feel a tingle it means there's at least 30 volts AC on the chassis and body of the vehicle. And as little as 30 or 40 AC volts through your heart can cause it to go into fibrillation. Source
- Protection: Some surge/EMS/products don't monitor, some monitor and display, some monitor and shut down supply.
