Why you need an intelligent surge protector


I’ve written a number of articles here about surge protectors and the difference between intelligent and basic models. The overview is that basic surge protectors usually cost less than $100 and offer protection from nearby lightning strikes and voltage spikes on the incoming power line. However, they can’t protect your RV from an over-voltage condition that occurs if you happen to connect your 30-amp shore power plug into a pedestal outlet that’s miswired with 240 volts instead of 120 volts, as is clearly labeled on the front of the outlet. When that happens it can destroy much of your RV’s expensive electrical system in seconds.

On the other hand, an “intelligent” surge protector from Progressive Industries or Surge Guard will indeed disconnect your RV from an over-voltage pedestal before damage occurs. But brains don’t come cheap, with the price of a 30-amp intelligent surge protector costing around $300, and a 50-amp version costing as much as $500. So is that much of an investment really worth it? Does this kind of miswiring condition happen routinely or just once in a blue moon?

With that question in mind I ran a survey last week in my RV Electricity Newsletter asking how many of you had encountered a 30-amp/120-volt pedestal outlet miswired with 240 volts. Both editor Chuck Woodbury and I were astounded to discover that 10% of you had indeed found one in the wild. See the survey below, which is still active and will accept your vote.

What does this all mean? Well, I would have guessed maybe 1% of our readers would have encountered a miswired 30-amp pedestal, but it appears to be pretty common. And you know from reading my articles about voltage that many of the electrical systems in your RV will be destroyed in seconds from this kind of abuse.

So what can you do to protect your investment? Well, I know you don’t like to spend money, but in this case I think it’s the wisest thing you can do. Here are two examples of 30-amp intelligent surge protectors on Amazon that I’ve personally tested, and either should do a great job of protecting your RV from static over-voltage conditions as well as any voltage spikes. Progressive / Surge Guard  and here’s the latest Surge Guard model which isn’t available on Amazon just yet.

Who’s to blame for this miswiring epidemic? Well, I don’t think it’s any single party. Certainly the NEMA TT-30 outlet form factor has to take some of the blame since it so closely resembles an old 30-amp/240-volt dryer outlet. (Click the picture on the right for a full-size image.) And the electricians or technicians who install them incorrectly should take some of the blame since the outlets are marked quite plainly for 125 volts. But in the final analysis, you the RV owner must take at least some responsibility for making sure whatever you plug into is within electrical specs. Until there’s some nationwide test-and-tag program for all campground and home pedestals with a bonded/insurance rider that will pay for any RV damage from over-voltage, it’s still up to you to be the final authority on verifying voltage before plugging in. 

So until you get your own smart surge protector, it’s good to brush up on testing your pedestal with a digital meter before plugging in. I’m getting ready to produce a bunch of new Electric Videos on this and other electrical topics in a few weeks, but for now here’s a video on pedestal testing I published a few years ago.

Let’s play safe out there….


Mike Sokol is an electrical and professional sound expert with 40 years in the industry. Visit NoShockZone.org for more electrical safety tips. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.



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B. W. Johnston

Is there some reason why the Progressive Industries EMS-PT30X that you recommended NOT UL certified? I just purchased one and was surprised that it did NOT carry this certification!

Jeff Fuller

Hi Mike, I recently purchased a fifth wheel and also at your advice a 50 amp Progressive EMS for “cheap insurance”. I read Ed Day’s question on 50 amp to 30 amp which prompted me to ask this question. If I have only a 30 amp service available can I use a “dog-bone” adapter (30 to 50) and then connect my 50 amp EMS to check out the pedestal’s electrical status. Will the EMS provide me with the protection I need prior to hook up and while hooked up?

Larry Hearn

Any preference on hardwired surge protector or one use at pedistal ? Getting new 5th wheel & wondering what you would use. Thanks Larry

Larry Hearn

Mike I’v looked But could find answer to this. We’re getting a new 5th wheel 50 amp , my ? Is should I get a hardwired surge protector or one that plugs in at pedistal . What little I know is that your ground wire should be as short as possible. A hardwired unit would be using the whole length of my power cord. I’v read that some use both, that sounds a bit of overkill. What are your thoughts? Thanks Larry

Steve Bennett

Hello Mike!
I just had an unusual, but potentially damaging experience: my 30 amp Cord was knocked partially out of the receptical by a worker. I came back to find my inverter panel reading an Over Voltage and red light, and my RV had switched over to batteries all day, running them down as the refrigerator was set to A/C.
What I found was the Cord was “half” connected, I think the neutral wire was disconnected, and possibly the ground as well.. but the hot leg was still making contact! Fortunately, all the protection devices you have recommended worked, no damage found.. yet!
Thank you so much for your well written articles.. you have saved me from serious damage many times now!


I love my Progressive 30 amp unit. After all the years I have read this Newsletter I would never plug into any campground without using it.
I have encountered at least 3 times where there was a problem and had to move to another site. I bought the unit with all the options and feel so safe with it. I also use a chain and lock on it to the post because I want to keep it.


Hello – I have a tiny little Scotty which needs to plug in to a 30 amp outlet. If I go to a campground that only has 50 amp outlets, will that fry my electrical system? This is probably basic 101 but I am new to rv camping. Only had tents in the past. Thanks for going back to basics.

Dave Kearney

this isn’t a comment it is a question, we bought a Saber 5th wheel with a Hisense fridge in it & it only runs on 120 volts at 1.7amps I would like to know what the start up amps are & if it would be ok to run this on a generator & what size I would need. Also there is an inverter in the trailer & I would like to know approximately how long the fridge would run on a 12 volt deep cell battery. I know there is a lot of variables with the battery but just a guess. I can’t find a web sight for the fridge or I would ask them. any help would appreciated

Ed Day

Question? I have a 50 AMP to 30 AMP short extension cord for times when I pull into a spot with only a 50 AMP receptacle. So far I haven’t run into problems. Does this mean the 50 AMP Receptacle is only 120 Volt or that my extension cord/adapter is only picking up one leg of the 220 Volt 50 AMP receptacle?

F. Gisler

We had an electrical emergency two years ago at an RV park at Diamond Lake in OR (near Crater Lake). We were a group of 5 rigs traveling together. There was an electrical “event” (surge?) at the main power box for our loop of the park. Three of the rigs in our group suffered extensive damage to microwave ovens, A/C units, inverters, compressors, etc. One friends’ RV was completely filled with smoke and ash. The bummer was that it was the first stop of an extended trip and they had to set up repair appointments along the the way to get things fixed.
One of the gals in our group had the presence of mind to go to the office at the RV park and ask for the name of the park’s insurance company and the phone number of the agent. Also, the RV park was very helpful in collecting all the contact information from each of the RV owners who suffered damage. As far as I know, they were all reimbursed for their repair costs after submitting copies of their repair receipts.


My travel trailer has a WFCO 8735 Power Converter. Reading the WFCO specs on the unit, it states “ALL MODELS: Standard Safety Features/Protections: Over Current, Over Temperature, Over Voltage, Reverse Polarity.”
So do I need a separateSurge Protector too?

Bob H

Progressive also offers a lifetime warranty on their EMS products; if there is a product failure (this does not include damage from an electical surge, or from the pedestal) they’ll replace it free of charge. Everyone should have one, it’s easy for me to justify the cost when I added up the $$ it would cost me to replace all of the electrical components in my RV. It would be in the thousands…

Wayne Girard

Hi MIke: This week I had to put the third new surge protector in my 2014 Winnebago. The coach came with a SurgeGuard built in unit. The first one failed 18 months after we picked up the new coach—parked in a 5 star rv resort. We heard a loud bang and electrical smoke filled up the compartment. The second one failed this week by burning up with smoke filling up the coach. Almost caught on fire with wire insulation burnt 6 inches up and the parts inside the SurgeGuard melted. Is this an inherently defective product? Any ideas?

Doug Renken

We are a mobile rv service company. We have come across 30 amp mis-wired outlets twice in the last couple of weeks. With the number of people buying new rigs, they are now getting 30 amp power put in at there house. Here is the problem, most electricians will maybe never or very seldom install a 30 amp box, and when the see it they think no problem it looks like a dryer outlet so they install it the same way. Be sure that the person you hire knows the difference. Also if need be have a RV tech check there work before you plug in.

Ray Houghtaling

Mike, Can an outlet tester with a 30 to 20amp adapter be used to test a 30 amp pedestal outlet.

J hamm

I had my charger inverter damaged by reverse polarity. Then too late I got a progressive device. I think it is important to note that the higher cost devices do more than surge control and they are usually labeled EMS devices. Mine is next to highest level, check 9 codes and covers reverse polarity and under voltage as well as surge or overvoltage along with other things. The undervoltage brown out can damage computers etc. The most expensive EMS actually regulates voltage vs shuts off but I decided did not need that. I paid about 240 on amazon . The other nice feature is a 2min 16 second delay before it transfers power to the rv. This gives it plenty of time to test errors first and you or it can shut off power before any damage.with this device I no longer feel the need to unplug during bad elec. Storms too. So worth it. I encounter reverse polarity a couple times a year.


Hi Mike:

As a rule I usually Plug in my Smart Surge Protector, then power on the pedestal and watch the codes. I have a progressive 50 Amp protector. It runs its cycle and then shows any Error codes that may exist. I usually get E0, meaning the power coming out is correct! I then power down and plug in my power cord and then turn the breakers back on, knowing that the power box is good to go.

I am always concerned at some RV parks where the Power Pedestals are OLD and really Worn looking! Depending on the Campground, I will usually bring to the Parks attention that they should consider replacing some of these boxes with new ones.

John Whitney

Mike, I have a hard wired progressive ind 50 amp smart surge protector. About 10% of the time I plug in, I get a high freq alarm and shutdown. It usually shows 60 hz. Then it resets itself automatically and is fine, just showing the PE7 error. Any thoughts?