Do I need an electrical surge protection device (SPD) in my RV? I get this question all the time. I tend to err on the safe side of electrical questions in RVs, so my first reaction is, yes, you always need some surge protection. Then the next question is, which one is the best? This article will give you the knowledge to compare and decide which surge protector is best for you.
What is a surge protector?
You might hear a surge protector called many things. Besides surge protectors, they are frequently called spike suppressors, surge suppressors, surge protection devices (SPD), or transient voltage surge suppressors (TVSS). All are designed to protect electrical equipment from voltage spikes in alternating current (AC) circuits. A voltage spike is a transient electrical event usually lasting a few microseconds and frequently exceeding 1,000 volts.
When people think about surge protection, they often think of lightning, a serious concern for electrical appliances. For example, lightning hitting a power line may produce a voltage spike over 100,000 volts and 20,000 amps at the location where the lightning strikes the line. However, as your distance from the strike increases, the voltage decreases. But, even a strike miles away on a power line can create a surge inside the RV.
Assumptions about lightning
The common assumptions about lightning come from ANSI/IEEE C62.41 and UL 1449 (3rd Edition) standards. They say minimum lightning-based power line surges inside a building are typically 10,000 amperes (10 kA). This is based on 20 kA striking a power line and the imparted current traveling equally in both directions, with ten kA traveling into the building or home (RV). You might assume I am good to go if I have a surge protection device on my RV (or home) rated at 10,000 amps.
The graph above shows the huge voltage spike associated with a lightning strike on a 110AC line. The voltage in its characteristic sign wave pattern is 60 hertz. Then, there is a large 10,000-volt spike, and then it goes back to normal. This huge spike is what damages electrical equipment of all types!
Close lightning strikes are often catastrophic, and no surge consumer-level protective device can protect you from them. But even much smaller voltage spikes can damage electrical equipment. The most common source of smaller electrical surges comes from other electrical devices in your RV. Something as simple as your air conditioning or microwave turning on and off can create a spike of several hundred volts that you must suppress. So, surge protective devices have some set amount of voltage that can pass through before stopping the surge.
How a Surge Protection Device Works
When the voltage rises above an acceptable level, the surge protector absorbs the excess voltage to prevent it from causing harm down the line. Specifically, internal components called metal oxide varistors (MOVs) absorb the extra voltage and divert it safely to the ground. The surge protector stops the surge from reaching downstream electrical equipment. Every time a MOV absorbs a surge, its internal structure changes, and its ability to absorb surges is reduced slightly. Over time and after stopping many surges, they age and must be replaced or fail, leaving you without protection.
After many spikes, the threshold voltage can be reduced enough to be near the line voltage, i.e., 110 vac or 220 vac. The MOV will partially conduct, heat up, and eventually fail, sometimes in a dramatic meltdown or fire. Most modern surge protectors have circuit breakers and temperature fuses to prevent grave consequences. Most also have an LED light to indicate if the MOVs are still functioning, and it is something you should be watching for when selecting a surge suppressor.
Surge Protection Device Clamping voltage
Also known as the let-through voltage, it specifies what spike in voltage will cause the surge protection device to work. Typically, the surge protector starts working at a voltage around 3 to 4 times the voltage you’re operating at (e.g., 110v AC) and, through some method, diverts the excess voltage to the ground. SPDs are rated according to how much energy they can absorb in joules before failing. The joule rating value is most important when comparing surge protection devices. The next is maximum surge current. We’ll start by looking at what a joule is.
What Are Joules and Maximum Surge Current?
A joule is a measure of the energy released over some period. For example, an average lightning strike releases about one billion joules of power over a fraction of a second.
A surge protector’s joule rating indicates how much energy it can absorb before failure. The higher the number of joules, the larger the surge protection provided. Key to determining the amount of protection needed include the type and value of the equipment to be protected.
The maximum surge current is self-explanatory. It is the maximum amount of current that the surge protection device can suppress before catastrophically failing and allowing excess current through the system. Again, more is better when it comes to surge protection devices. So, how do you select a surge protector?
Valuable electronics need higher joule ratings
As a rule of thumb, the higher the value of the equipment you’re trying to protect, the higher the joule rating should be. Think about what equipment you have in your RV. If you have a travel trailer or 5th wheel, you may not have the fancy digital control and display systems in newer Class A and C motorhomes. You can get by with a surge strip in that case.
If you only have a couple of electronic devices, TV, microwave, etc., in your RV, you may get by with simple surge strips that plug into the wall. Make sure you are using surge protection strips, not outlet strips. The two are easily confused. Look for the term surge protection on the packaging before purchasing one.
More joules equal better surge protection
Again, more joules are better. However, premium custom electronic control systems that run everything from holding tank levels to raising and lowering the blinds and turning lights on and off must have a whole RV surge protection device. Do not assume the manufacturer included one.
Those fancy control systems are highly susceptible to power surges. Most have some level of surge protection installed, but adding more is just cheap insurance and will protect you from costly repairs! Plus, installing whole RV surge protection will protect all the electronic equipment in the RV—more on entire RV surge protectors in just a bit.
Is Your Surge Protection Device Still Working?
As I mentioned, every surge the protection device absorbs reduces its lifespan, but most models include an LED that lets you know protection is present. The take-home message is no surge protector lasts forever. If you’ve had a major electrical event, such as lightning, that caused a power failure, or if your units have been in use for a few years, today is a great time to make a small investment in new surge protectors and greater peace of mind.
How to Select a Surge Protection Device
Selecting a surge protection device is straightforward. The first thing is to remember the value of what you are protecting. Since the electronics in RVs are costly to repair or replace, err on the side of too much protection rather than not enough.
For an RV with 30-amp connections, a minimum of 3000 joules and 6500 amps of maximum current is a good compromise. In 50-amp RVs, keep the minimum joule rating above 3500 and 6500 amps of max current. I like the Southwire line of RV surge suppression devices. They are very well made and offer other features we haven’t addressed yet in this article.
Most well-made RV surge suppression devices will have other important features to consider when selecting one for your RV. Over and under voltage is often overlooked. In addition to surges, electronics are sensitive to over and under-voltage conditions.
Over & Under Voltage
A good rule of thumb is 132 volts for the overvoltage and 102 volts for the under-voltage. Technically, most electronics will tolerate 10% fluctuations in voltage. It is not uncommon to experience these, particularly in RV parks. A surge suppression device will disconnect the line voltage and monitor the line until the voltage returns to the acceptable limit and reconnects. Therefore, matching the number of amps to your RV is crucial. A relay turns power on and off; the surge protection device must be rated for current matching your RV connection type (e.g., 20, 30, or 50 amp).
Hard-wired vs. pedestal mount
I prefer hard-wired systems. They may not be as feature-rich, but you don’t have to worry about them getting stolen. I’ve seen all sorts of wacky methods used to secure pedestal-mounted surge protective devices. In my opinion, the tradeoff is worth it unless you want to be able to use it on multiple RVs.
Other nice features
- Open ground
- Open neutral
- Reverse polarity
- Mis-wired pedestal
- High neutral current
All these items are additional safety features that are nice to have. Open wires (e.g., grounds, neutrals) can cause serious safety issues. Remember that current flows from hot to neutral, and the ground is there for safety. However, if neither is connected, the current from both will flow on one wire, creating a fire hazard. Another fire hazard is high neutral current flow, so knowing you have protection there is nice.
Reverse polarity and miswired pedestals are the same thing. They can cause serious safety issues and damage sensitive electrical devices. It’s not live or die with this, as finding an improperly wired pedestal is rare but unheard of!
I mentioned my preference for the Southwire line of surge protection devices because the value received vs. the feature set is above average in my comparisons. They have relatively inexpensive units that offer good protection for all the essential things you need to monitor.
The 30- and 50-amp units are the ones I have used most for the hard-wired units, so I know they work well. The pedestal mounts are feature-rich and compare favorably to competitors’ more expensive units.
I welcome your questions or comments. Thanks!
For more great maintenance ideas, check out these articles on my website:
- New RV Owner Top Tips
- Spring RV startup and maintenance
- Winter Maintenance on your RV
- How to Sanitize an RV Freshwater Tank
- Top 18 Tips To Prepare Your RV For Storage