How to avoid damage to your RV electrical system and components.
By Mark Quasius, F333630
May 2024
Technology marches on even in the world of recreational vehicles. Full-featured motorized and towable RVs have become increasingly sophisticated over the years. Large-screen entertainment systems with surround sound, Bluetooth, Wi-Fi capability, and satellite or streaming connections are becoming the norm. Big residential refrigerators and multiple air conditioners are commonly incorporated. The evolution of digital technology has brought us multiplex wiring systems that communicate with and control a large array of components.
One thing these amenities have in common is the need for electricity to operate, but not just any electricity will do. They all require a steady supply of clean electricity with voltage, frequency, and true sine waves that conform to standards. If you throw in a few power supply anomalies, the lifespan of some of these components may shorten quickly.
A campground pedestal with 50-, 30-, and 20-amp circuits.
While the electrical systems in recreational vehicles have become more sophisticated, the same cannot always be said for campground power sources. As campgrounds have evolved, many have added new RV sites and upgraded from 30-amp to 50-amp power pedestals. However, the infrastructure to support the additional requirements hasn’t always kept up with demand, and maintenance is sometimes an issue. I can’t count the number of times I’ve been to a campground where the circuit breaker on the pedestal kept tripping prematurely.
Breakers have a limit in terms of the number of times they can be switched on and off; eventually, they weaken and may trip prematurely. Loose connections at the terminal lugs inside the pedestal can cause more issues, resulting in low voltage, open neutral, hot legs, etc.
Every RV owner should have some sort of power protection device to prevent damage. “Surge protector” is a commonly used term to describe these power protection devices, although they generally guard against much more than power surges. Let’s first define these damaging elements.
SURGES AND SPIKES
Surges and spikes both refer to excessively high voltage, also called transient voltage, that occurs in a power line. Voltage is to electricity as water pressure is to your fresh-water system. Your RV is designed to use a standard 120-volt electrical system. Higher voltage (pressure) can damage your electrical system, just as higher water pressure can burst water lines or hoses. Think of a filament in a light bulb that pops when too much voltage is received. Apply that to tech devices, and it becomes more expensive than simply replacing a light bulb. A surge is transient voltage that lasts for three nanoseconds or more. In the case of a spike, the increased voltage lasts only one or two nanoseconds.
Metal oxide varistors, or MOVs, shunt surges and spikes to ground to protect your RV’s electrical system.
This is where surge protectors come in. A metal oxide varistor, commonly known as an MOV, will act as a shunt to divert electricity to ground whenever the incoming voltage is excessive. An MOV looks like a small disc and consists of metal oxide sandwiched between two semiconductor layers. Each layer has a wire lead, with one wire connected to the incoming power and the other connected to ground. The MOV acts as a variable resistor. When the incoming voltage is within specifications, the MOV has a high resistance, and the incoming power passes it by withoutaffecting the MOV. However, when the voltage exceeds the maximum tolerance level of the MOV, it will go to low resistance, and the current will flow through the MOV to ground, dampening the surge or spike and protecting your RV from a damaging increase in voltage. Think of it as a safety valve on an air compressor that bleeds off excessive air pressure.
Surges and spikes are rated in joules. One joule is the amount of energy that is released in one second when a current of one ampere passes through a resistance of one ohm. In other words, the bigger the surge, the higher the number of joules. So, be sure to search for a surge protector with the highest possible rating in joules. The higher the rating, the better the level of protection. If a surge is significant enough in intensity or duration, it may exceed the capacity of your surge protector. In that case, the MOVs will destroy themselves while attempting to save the electrical system. These self-sacrificing MOVs will then need to be replaced to restore surge protection. Some units may need to be returned to the factory for repair while others are capable of being serviced in the field with a simple plug-in circuit board swap.
OPEN NEUTRALS
A 15-amp, 20-amp, or 30-amp pedestal has three conductors — a hot, a neutral, and a ground. If the neutral conductor has a break someplace, you will have an open circuit, and you won’t have any power to the RV. A 50-amp receptacle has four conductors — two hots (commonly known as L1 and L2), one neutral, and one ground. Alternating current follows the path of least resistance.
Ohm’s law is E=IR, which is defined as voltage equals current times resistance. In a nutshell, if you double your resistance, you can double your voltage and keep the same current flow (amperage). You can have a 5-amp load on the L1 phase and another 5-amp load on the L2 phase, and the current will flow between L1 and L2 without any current flow on the neutral wire. But if you have 30 amps on one hot pole of a 50-amp supply and 20 amps on the other pole, the two phases will not be in balance; the excess (10 amps) will flow down the neutral conductor. If the neutral conductor fails, you will have an open neutral. This will cause 240 volts to pass between the two hot phases, because the resistance in each phase is not equal. Those 240 volts will destroy any electrical component in their path. Skipping all this math, the important thing to remember is that an open neutral can be disastrous to your electrical system, because of the presence of 240 volts on 120-volt electrical components.
HIGH AND LOW PEDESTAL VOLTAGE
Another problem occurs when a campground power pedestal supplies continually high voltage that exceeds the maximum allowed. This can be caused by a utility transformer set too high to provide for long runs to a campground that has power pedestals spread over a large area and an inadequately designed electrical grid. This scenario isn’t as common as low voltage, but it does exist.
As noted, you are more likely to encounter low voltage at the pedestal. Countless campgrounds have added sites over the years or upgraded from 30-amp to 50-amp pedestals. But a campground’s electrical grid may not have been designed for an increased load. Once guests roll in during the middle of the afternoon on a hot summer day and start switching on their air conditioners, the pedestal voltage drops as the demand for more power increases throughout the park.
Electrical components are rated in wattage, which is a true measurement of power. Wattage equals voltage multiplied by amperage. Current is measured in amps. Each conductor is rated for a maximum amperage, and excess amperage causes heat to build up due to the resistance in the circuit, which is why circuits utilize fuses or circuit breakers for over-current protection. Wattage is always constant, so when the voltage drops, amperage increases.
For example, if a 120-volt air conditioner is designed to pull 20 amps as a starting surge, it will pull 24 amps if the voltage drops to 100 volts. The excessive amperage caused by low voltage will increase heat in the wires and eventually damage your compressor motor or capacitors. Other electrical components can be damaged in the same manner.
CHOOSING A PROTECTION DEVICE
As noted earlier, the term “surge protector” tends to be used generically and may not properly describe what the device does. A surge protector guards against surges and spikes, but many units do more than that. Because you are more apt to have issues caused by low voltage than by a surge, it’s important to check the specifications as to what types and levels of protection each device offers.
Not all surge protectors perform to the same level. If you want a unit that will adequately protect your RV from surges and spikes, look for one rated at 3,000 joules or better. Devices that meet or exceed that level of protection are available from various manufacturers, among them Hughes Autoformers, Progressive Industries, and Southwire (Surge Guard). Some units are portable, while others are made to be hardwired into your RV. A portable unit generally will hang on the power pedestal and can be moved from one RV to another. However, portable units are exposed to the weather and potential theft. Hardwired units are mounted inside the RV and thus protected from the elements and theft. They do require installation, although that’s normally just a matter of splicing into the incoming shore power cord inside the RV.
Many units have a remote display that can be mounted inside the RV. The unit may display voltage, amperage, and any error messages that occur. The remote display generally communicates to the surge protector by way of a four-conductor phone cable or via Bluetooth; the latter would be required for a portable unit.
Remember: You don’t want a surge protector that just handles surges, because you also need to monitor voltage levels. Standard tolerances on 120-volt appliances and components are plus or minus 10 percent, which gives you a safe operating range of between 108 and 132 volts. RV surge protectors that have voltage-monitoring capabilities typically lower the minimum voltage by a few volts to allow for temporary voltage dips when heavy loads are applied to a 50-amp power source. So, it’s not uncommon to see units with low-voltage cutout values down to 102 volts. If the voltage exceeds the maximum or drops below the minimum, the device will disconnect voltage from the RV to prevent damage.
Reverse polarity, miswired pedestals, and open neutrals are real dangers as well. The surge protection device you choose should be capable of disrupting power to the RV should any of these conditions exist. Some sort of notification is also necessary, so you know why the power has been shut off. This can be as simple as a few illuminated LEDs on the device itself, or it can be a digital display, either on the surge protector, mounted inside the RV, or on a smartphone via a Bluetooth app.
VOLTAGE BOOSTERS
(image 1) Hughes Autoformers RV220-50-SP voltage booster
A good surge protector will stop the incoming power if the voltage drops below set parameters. That will protect your RV from damage, but it also leaves you without power. You may be able to run the generator, but that consumes fuel, makes noise, and might not be allowed in certain RV parks. Another option is a voltage booster, such as the 30-amp and 50-amp models available from Hughes Autoformers. The Autoformer monitors incoming voltage. If the voltage is 115 volts or higher, it passes through with a 2 percent boost. If the voltage drops to 113 volts or lower, the Autoformer will boost the voltage by 10 percent. This can allow you to operate with pedestal voltages as low as 95 volts by boosting it to 104 volts or better, depending on the incoming voltage.
If the voltage drops below 95 volts, the Autoformer won’t be able to boost the voltage to an acceptable level, but these conditions are rare. Most voltage drops are marginal, and the Autoformer just might make the difference between having power or not having power to your RV.
While the Autoformer does have surge protection, it does not guard against excessively high or extremely low voltages, so it should be used in conjunction with an auto-shutoff surge protector. In that case, the Autoformer should be used in line ahead of the surge protector; otherwise, the surge protector will cut off the incoming voltage and prevent the Autoformer from boosting voltage. In other words, the Autoformer should be connected to the pedestal, with the surge protector next in line and then the RV.
AUTOMATIC TRANSFER SWITCHES
(image 7) Southwire Surge Guard model 40350-RVC 50-amp automatic transfer switch
Southwire sells a line of surge protectors as well as automatic transfer switches. Some of the transfer switches, such as the 50-amp model 41260, offer some surge protection but no low or high voltage protection. This model is included as original equipment in a number of RVs, so if that’s true of your RV, be sure to purchase a good surge protector that also provides low and high voltage safeguards. The Surge Guard model 40350-RVC is a better choice, because it offers enhanced surge protection and upgraded, heavy-duty, shock-mounted 65-amp-rated contactors, as well as open neutral and low and high voltage protection. It also has RVC network compatibility, so you may find it as original equipment on the latest high-end RVs with multiplex wiring systems that feature a touch-screen display showing incoming power levels. It is also available with a remote monitor panel for non-multiplexed systems that displays information such as voltage, amperage draw on each line, and any status messages.
Transfer switches such as the 40350-RVC also offer the benefit of protecting the power not only from shore power but also from the generator, although generator power issues are extremely rare. If being installed in an existing RV, the new device will replace the present transfer switch, so you won’t have to find additional room to mount the new one, nor will you have to cut into the shore power cord. If your RV has a 40350-RVC transfer switch, you won’t need any additional protection, although you may still choose to carry a Hughes Autoformer for times when voltage needs a bit of a boost. An upgraded 40450-RVC transfer switch features automatic switching from generator power when shore power returns after an outage.
Power outages, low-voltage brownouts, and surges are a fact of life in the RV world, and with increasing demand for power, it’s not likely to get better anytime soon. It’s really not a matter of “if” but “when” you’re going to need protection for your RV’s valuable electrical system components. Having a quality surge protector that can handle these situations is cheap insurance and a good investment.
PRODUCTS
The following are some examples of popular devices available for purchase.
Hughes Autoformers
(888) 540-1504 | hughesautoformers.com
While not a complete power protection system, the Autoformer boosts incoming voltage; the device supplies the RV with power rather than just shutting down power to the vehicle and can be used in conjunction with a surge protector to provide full coverage. The company also offers the Power Watchdog line of surge protectors.
(image 2) Hughes Autoformers Power Watchdog PWD50-EPO surge protector
The RV220-50-SP (image 1) features 4,800 joules of surge protection in addition to the 10 percent automatic voltage boost should the incoming voltage drop below 113 volts. An array of LED lights provides park power diagnostics. The Autoformer can be mounted inside a vehicle with an optional connection kit. A 30-amp model is also available.
The company’s Power Watchdog series of high-end surge protectors includes the PWD50-EPO (image 2) 50-amp model. It offers 6,100 joules of surge protection plus full protection against open neutral, reverse polarity, and high or low voltage. The Power Watchdog is available in either portable or hardwired models, and in 30-amp and 50-amp versions. All models feature wireless Bluetooth communications with a free smartphone or tablet app to view the power status at any time in the immediate vicinity of your RV.
(image 3) Progressive Industries EMS-HW50C hardwired 50-amp electrical management system
Progressive Industries
(800) 307-6702 | progressiveindustries.net
Progressive Industries provides surge protectors described as electrical management systems for 30-amp and 50-amp power supplies in both hardwired and portable models. The EMS series offers a full load of features. Some models are equipped with embedded displays, while others have remote display capabilities. These EMS systems have a limited lifetime warranty and can be repaired in the field rather than needing to be sent back to the factory.
(image 4) Progressive Industries EMS-PT50X portable 50-amp electrical management system
The EMS-HW50C (image 3) is a hardwired 50-amp electrical management system that offers 3,580 joules of surge protection at 88,000 amps, low (104 volts) and high (132 volts) voltage protection, as well as open neutral, open ground, reverse polarity, miswired pedestal protection, and frequency protection. A bright LED display is included as standard equipment and will scroll through the various voltage, amperage, and frequency readings, as well as status or error codes. This display can be mounted near the device or in a remote location inside the RV. The unit is field serviceable in the event of a major surge and comes with a limited lifetime warranty. A 30-amp model EMS-HW30C is also available.
The EMS-PT50X (image 4) is a portable 50-amp electrical management system that offers 3,580 joules of surge protection at 88,000 amps, low (104 volts) and high (132 volts) voltage protection, as well as open neutral, open ground, reverse polarity, miswired pedestal protection, and frequency protection in a Lexan housing. A bright-green LED display in the face of the unit scrolls through the various voltage, amperage, and frequency readings, as well as status or error codes. A 30-amp EMS-PT30X model is also available.
(image 5) Southwire Surge Guard model 35550 50-amp hardwired surge protector
Southwire
(800) 444-1700 | southwire.com/recreational-power
Southwire’s Surge Guard brand offers surge protectors for 30-amp and 50-amp power supplies in both hardwired and portable models, as well as a line of automatic transfer switches.
The model 35550 (image 5) is a 50-amp hardwired unit that provides 3,850 joules of surge protection, low (102 volts) and high (132 volts) voltage protection, as well as open neutral, reverse polarity, and miswired pedestal protection. The unit mounts in the basement, but an optional remote LCD monitor is available to display voltage, amperage, and any status or error messages. The model 35530 is similar, except it is designed for 30-amp power supplies and provides 2,450 joules of surge protection.
(image 6) Southwire Surge Guard model 34951 50-amp portable surge protector with Bluetooth
The model 34950 is a 50-amp portable unit that provides 4,200 joules of surge protection, low (102 volts) and high (132 volts) voltage protection, as well as open neutral, open ground, reverse polarity, and miswired pedestal protection. This device plugs into the pedestal and accepts your RV’s power cord. LED lights and an LCD display indicate voltage, amperage, and status or error messages. The 34950 also will shut off power if the plug or receptacle overheats. A 30-amp version, model 34930, is also available and provides 2,450 joules of surge protection. The 34951 (50-amp — image 6) and 34931 (30-amp) models also use Bluetooth to connect to the Surge Guard app and the optional 40301 wireless display.
The model 40350-RVC (image 7) is a 50-amp automatic transfer switch offering 3,350 joules of surge suppression, low (102 volts) and high (132 volts) voltage protection, as well as open neutral, open ground, reverse polarity, miswired pedestal protection, and high or low frequency. It uses upgraded 65-amp shock-mounted contactors and is equipped with LED status lights. An optional monitor displays voltage, amperage, and power system status messages. The model 40450-RVC is similar, except it features shore power sensing that transfers automatically to generator power when energized. Once the generator shuts down, shore power activates after a three-second delay.