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Power Protection Print Email
Keep your motorhome’s electrical system safe from the evils of "dirty" electricity by using one or more power protection or voltage-boosting devices.

By Mark Quasius, F333630
July 2012

The electronics found in today’s motorhomes are much different from those considered to be cutting-edge 20 years ago. Each year it seems new motorhomes include upgraded features that push technology to its limits. The latest trend in new motorhomes is the all-electric coach, which comes without a propane tank. These motorhomes feature electric cooktops, hydronic heating, and large residential refrigerators. Naturally, all of these electrical appliances require ample AC electric. But not just any electric — it must be clean, reliable power. Unfortunately, that type of electric is not always present at campground shore power pedestals.

Your motorhome’s electrical system is susceptible to spikes, surges, lightning strikes, and other anomalies that come through the shore power pedestal. While today’s motorhomes have evolved into sophisticated vehicles, many campground power grids haven’t kept up with the electrical needs. In fact, it’s common to find low voltage at many campgrounds that haven’t had their electrical service updated. Low voltage can cause serious damage to a motorhome’s electrical components, resulting in extensive repair costs. This can be prevented by using a power protection device. In fact, operating your motorhome without adequate power protection is akin to driving without insurance.

Power Protection

Most motorhomes do not come equipped with adequate power protection devices. But the wise owner will consider making this one of the first accessories added.

The term "surge protector" is generically used to describe a device that protects the motorhome’s electrical components. In reality, surge protection is just one area where preventative measures need to be taken. While many devices are marketed as surge protectors, it would be more accurate to describe these units as power protectors. The capabilities of these products will vary, so it’s important to know what type of power protection is included in a device before purchasing it.

We should start by defining what surges and spikes are. Both surges and spikes deal with excessively high voltage. Electrical components are designed to operate at a specific voltage, and when that voltage exceeds the design parameters of the component, damage may result. A good analogy is to compare voltage to water pressure. If you operate your motorhome’s fresh water system at an excessively high water pressure, you risk having the water lines burst. In the same manner, high voltage can cause similar damage to your electrical components. The biggest difference between a surge and a spike is the duration of the elevated voltage. A spike lasts for only one or two nanoseconds, whereas a surge lasts three nanoseconds or longer. In either case, damage can occur, so it’s important to provide adequate surge and spike protection to prevent this from happening.

How A Surge Protector Works

A surge protector prevents these harmful spikes and surges from passing through and damaging your valuable electrical components. This is accomplished by utilizing metal oxide varistors (MOV) inside the device. An MOV acts as a shunt to divert electricity to ground whenever the incoming voltage is excessive. It consists of a piece of metal oxide sandwiched between two semiconductors. One end of the MOV is connected to the hot power supply, while the opposite end is connected to ground. When the voltage is within parameters, the semiconductors have high resistance, and the electric passes by the MOV and into your motorhome. When the voltage is excessive, the semiconductors go to a much lower resistance, sending the incoming power through the metal oxide and to ground. In this way the MOV acts like a safety valve by redirecting the excess energy until it returns to a safe level.

Surges and spikes are rated in joules. A joule is measured as the amount of energy generated when a current of 1 ampere is passed through a resistance of 1 ohm for one second. A large surge will have a corresponding high joule rating. Not all surge protectors are the same, and their ratings can be different, so when searching for a device, try to find one with the highest possible joule rating to provide a better level of protection. It's possible that a surge protector could experience a power spike or surge large enough to exceed its capacity. 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 in order to restore surge protection to your unit.

Voltage Protection

Many power protectors that are marketed as surge protectors also contain some sort of low-voltage and high-voltage protection. This is an important feature, because the majority of RV-related electrical issues stem from low incoming voltage rather than from surges or spikes. Many older campgrounds were designed with a 30-amp electrical system and a small number of campsites. As the campground expanded, more sites were added, but the incoming electrical service wasn’t upgraded. The end result is low voltage, which becomes a major problem on a hot summer weekend when everyone is running their air conditioners. The voltage can drop to unsafe levels across the entire campground power grid.

When the voltage drops, the amperage increases. This creates extra heat, which causes items such as motors and electronic components to fail. Therefore, it’s important to look for a power protection device that includes low-voltage and high-voltage protection as well as surge protection. A good power protector will disable the electric going to the motorhome whenever the incoming voltage falls out of the acceptable operating parameters, typically 106 volts on the low side and 132 volts on the high side.

A good power protector also will test the incoming electricity to make sure that the shore power is wired correctly. If a 120-volt-AC outlet is wired for 240 volts, is wired with reverse polarity, or has an open neutral, the power protector should prevent the incoming electric from flowing to the motorhome. Ideally, the power protector also will have some sort of display or, at the very minimum, a series of LEDs that informs the user that the incoming power is incorrectly wired.

Electrical motors in general require three times the current to start them as is needed to run them, and air conditioners, in particular, place a heavy load on a motorhome’s electrical system. Air conditioner compressors can have high head pressures if a restart is attempted before the pressure has had time to bleed off. This creates additional power demand that can trip a circuit breaker. Most modern air conditioner thermostats have a built-in delay that will not allow the compressor to start until a certain time has passed since it was shut down, to allow the head pressure to bleed off to lower the starting amperage. If your air-conditioning system is not equipped with this delay, most surge protectors can be set to add a two-minute delay to restore power after a power supply interruption.

Types Of Power Protectors

Power protection devices can be portable or hardwired into your motorhome. Each style has its pros and cons. The biggest benefit to owning a portable unit is that it requires no installation. You simply connect it to the campground pedestal and plug your motorhome’s power cord into it. It’s also easy to transfer a portable surge protector from one RV to another. The downside is that the surge protector is outside, where it is exposed to the elements and to possible theft. It also requires the owner to hook up the device when arriving at a campsite and to remove it — and remember to take it along — when it’s time to go.

Hardwired units are mounted inside the basement compartment and wired directly into the electrical system between the coach power inlet and the automatic transfer switch, so that the switch is protected from transient voltage. The protector is always connected and no additional steps are required to activate it. You just plug your motorhome’s power cord into the pedestal and it’s automatically put into service. Some units also offer remote monitors that can be mounted inside the motorhome and display information about the incoming voltage and power usage. The downside to a hardwired unit is that when it’s time to transfer it to another motorhome, some electrical work is required to remove it from the old motorhome and install it in the new one. If your motorhome has limited compartment space in the electrical utility bay, your needs might also be best served with a portable unit.

Surge Guard model 34560 50-amp surge protectorAmong the most popular RV surge protectors on the market are those from Technology Research Corporation and Progressive Industries. Each manufacturer provides 30-amp and 50-amp models in hardwired and portable versions.

Technology Research Corporation's Surge Guard 34560 hardwire and 34750 portable units are both 50-amp surge protectors. Model 34560 offers 1,750 joules of surge protection, while the new 34750 portable model provides 3,850 joules of protection. Both also protect against low voltage (less than 102 volts) and high voltage (more than 132 volts) as well as electric from miswired pedestals. LEDs on each unit indicate the status of the incoming power. The 34750 portable also has a built-in LCD display. The Surge Guard 40240 Hardwire Plus is the company’s premier surge protector, with 3,350 joules of protection and a remote LCD display that shows faults and the voltage condition.

The 30-amp Surge Guard offerings include the 34520 hardwire with 1,050 joules of protection and the new 34730 portable with 2,450 joules of protection. Both include the same high-voltage, low-voltage, and reverse polarity protection as the 50-amp models.

Surge Guard also has a pair of 50-amp automatic transfer switch units. Model 41260 provides 2,600 joules of surge protection, while model 40250-RVC provides 3,350 joules of surge protection with communication capabilities on an RVC-compatible device. There is also the 90-amp 41290-RVC automatic transfer switch that has communication capabilities like the 40250-RVC and provides 3,500 joules of surge protection. Be aware that none of these automatic transfer switches offers low-voltage protection.

Progressive Industries offers the EMS-HW50C hardwired 50-amp unit, which is rated at 3,580 joules with an 88,000-amp surge circuit. It includes protection against miswired pedestals plus low-voltage (less than 104 volts) and high-voltage (more than 132 volts) protection. It also monitors AC frequency and will shut down power to the motorhome should it be out of tolerance. A handy remote display panel features an LED monitor that shows voltage and amperage draw on each of the lines as well as the frequency. The less-expensive hardwired EMS-LCHW50 has equal protection but features an LCD display built into the unit itself, which can be a bit harder to read. The portable EMS-PT50C offers identical protection and also utilizes a small LCD display on the unit.

Progressive Industries EMS-HW50C 50-amp surge protectorProgressive also has a trio of 30-amp models (EMS-HW30C hardwire with remote display; EMS-LCHW30 hardwire; and EMS-PT30C portable) that include the same features as the 50-amp models but with 1,790 joules protection and a 44,000-amp surge circuit.

One other benefit of the Progressive surge protectors is that they all display an error message if the MOVs are destroyed after absorbing a large surge. Many units on the market won’t indicate that the MOVs have blown and will continue to pass current without offering any surge protection. All Progressive devices can be serviced in the field, so any blown MOVs or components can be replaced without having to return the unit to the factory for service, and they come with a lifetime warranty.

Boosting Power

Utilizing a power protection device will safeguard your motorhome from transient voltage, but it does this by shutting down shore power to the coach. The shutdown may be a short interruption that could leave you without air-conditioning for a brief period. Your refrigerator will hold its cool for a while, and your coach battery bank will supply 12-volt-DC power to run the lights, furnace, and water pump for quite a while.

If the pedestal voltage continues to be low for a long period of time, you have a few options. If you don’t want to wait it out, you can run your auxiliary generator to provide power to operate 120-volt-AC electrical accessories. If running your generator is not an option, most surge protectors do offer a bypass mode that will allow you to supply power to the RV during low-voltage conditions, although this practice is generally not recommended. Be aware that you should do this only when power is absolutely needed. In such a situation, switching off your air conditioner(s) and entertainment system is advised. Use this mode only to power the most basic and critical electrical appliances.

Hughes Autoformer RV220-50 voltage boosterAnother option is to use a voltage booster. A voltage booster, such as the popular Hughes Autoformer or the Surge Guard Voltage Regulator, will boost the incoming voltage by 10 percent if the voltage is below a preset level. If the voltage drop is extreme, a voltage booster won’t help. But most low-voltage situations aren’t that extreme, so a voltage booster generally can be used to compensate for the low voltage and raise it to a level that is safe for your motorhome. If you rely heavily on your AC power and encounter frequent low-voltage situations, you might want to consider adding a voltage booster to your motorhome.

These devices are normally sold as portable units, but optional hardwire kits are available that make it possible for you to install them in your coach. The kits consist of a socket and cord that attaches to your RV’s electrical system, so that the booster can be removed or inserted as needed. These units are basically stepping transformers with voltage-sensing circuitry that determines when a boost is required. A booster may or may not include surge protection, so an additional power protection device also may be needed. In every situation, the voltage booster should be placed ahead of the power protection device.

The Hughes Autoformer was introduced in 1995 as the first RV power booster, and the company still holds the patent on RV power boosters. The original voltage booster has been replaced by a pair of offerings. The RV220-50 is a 12,000-watt, 50-amp unit, while the RV2130 is a 3,600-watt, 30-amp unit. Each device automatically provides a 10 percent boost when needed (between 95 volts and 115 volts). Both units provide spike and surge protection and are portable. The boosters should be plugged into the pedestal prior to any surge or power protection devices. Hardwire kits are available that make it possible for the Autoformer to be installed in a storage compartment. The plug and socket make it easy to unplug the Autoformer and bypass power when removing it from your electrical system. The heat produced by these units is minimal, so locating them in a small compartment is not an issue. A company spokesperson said that Hughes soon will introduce a new product that will incorporate high-voltage spike protection, over and under voltage protection, and abnormal condition protection, along with its boosting ability.

Surge Guard 10175 voltage regulatorSurge Guard recently entered the market with its model 10175 50-amp and 10176 30-amp voltage regulators. These units also offer automatic 10 percent voltage boost and an optional mounting bracket that makes it possible to install them on the wall of a basement electrical utility bay. Note that these regulators do not offer surge protection, so you will need a good power protection device to adequately protect your coach’s electrical system.

Regardless of which device or devices are selected, every motorhome owner should consider some sort of power protection. Considering the value of the electrical components in your motorhome and the potential for expensive damage from electrical anomalies, RVing without one is a gamble that just isn’t worth the risk when you consider the affordability of these devices.

Further Info

Hughes Autoformer
(888) 540-1504

Progressive Industries
(919) 462-8280

Technology Research Corporation
(800) 780-4324


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