RVelectricity – Do I need a surge protector on an inverter generator?

9

By Mike Sokol

Dear Readers,
I’ve written a number of times about the reasons for using an advanced (Total Electrical Protection or EMS) surge protector on your RV, even when you’re plugged into your generator. And I’ve noted that I’ve seen cheap clone generators fail and go over-voltage, but I had never seen a Honda inverter generator fail and put out too much voltage – UNTIL NOW.

Yep, just last week a reader sent me an email about his new Honda EU3000i inverter generator that went over-voltage (up to 195 volts instead of 120 volts) and damaged several of his cabin appliances. He normally used this generator to power his RV, but then it did double duty to power the appliances in his little cabin in the woods. Read on for details and what you can do about it.

Dear Mike,
A month ago I somehow broke my Honda EU3000is inverter generator. I was getting 195 volts coming out of it until I put a load on one of the outlets and then it stabilized down to 125. My Honda dealer has been looking at it for weeks and they can’t figure our why it output 195 volts – which they confirmed when testing in their shop. I didn’t use a bonding plug at the time, but I don’t see how that could affect it one way or another.

I use this generator on my RV, but also connect it to my cabin in the woods when I visit. The cabin has a small circuit breaker panel just like in a house, and there’s a generator inlet and separate generator circuit breaker that was wired by the cabin’s previous owner’s electrician. So now, since we blew a microwave and a water pump and some lights, I wanted to put an EMS RV surge protector on the 30-amp cord going to the cabin from the generator.
I use the 30-amp twist-lock dogbone adapter on the generator that goes to the cabin power panel and energizes it. But after reading more of your articles I’ve realized the power panel in my cabin is supposed to be neutral ground bonded, so I shouldn’t need a bonding plug with the generator when it’s plugged into the cabin’s electrical panel.
So will I be able to use my new Portable EMS/Surge Protector when the generator is plugged into the cabin? How about when the generator is powering my RV: Should I use a bonding plug and use my new EMS surge protector? And what about when my RV is plugged into my house power? Does it make sense to use an EMS surge protector when my RV is plugged into the outlet on the side of my house? How does this all work? —Jeff T.
Dear Jeff,

Wow, some great questions, and this is the first time I’ve heard of a Honda inverter generator failing this way. So I’m going to cover your problem at length because a lot of my readers are keeping their RV connected to house power in their backyards, and many more are boondocking with an inverter generator of some sort.

Everyone, please read on as this is important to the electrical health of your RV. I’ll also make a video about this next week and publish it in my monthly RVelectricity newsletter (coming on December 6).

Just the facts, please…

Okay, let’s review these three basic power scenarios and show how to make them work. And yes, I recommend that you use an advanced (Total Electrical Protection or EMS) surge protector in all cases.

1. Inverter generator feeding my RV

In this case, your aforementioned twist-lock to TT-30 dogbone adapter will let you connect your inverter generator to your new EMS Surge Protector, which can then connect to your RV’s shore power cord. However, because the inverter generator has a floating (unbonded) neutral, you’ll need to add a Neutral/Ground bonding plug on the spare 20-amp outlet of the generator. That will provide the proper voltages on the ground and neutral so your advanced surge protector won’t think you have an open ground and shut down. Southwire sells a G/N bonding plug HERE.

2. Inverter generator feeding my cabin

In this case you can still use your twist-lock to TT-30 dogbone adapter, plug it into your advanced (EMS) surge protector, then plug your cordset into your cabin’s electrical service panel. That panel should already have its neutral and ground bonded together, and you’ve confirmed it already has a ground rod connected to the ground bus in the panel.

However, you will still need for a G/N bonding plug plugged into your generator for this type of connection with a surge protector since the G/N bond in your service panel won’t been seen by the ground testing circuit inside of your advance sure protector. But without an advanced surge protector you don’t need a generator G/N bonding plug. Take a look at this diagram which shows how your cabin’s service panel should be wired with a green bonding screw in the neutral bus bar.

3. RV plugged into my house outlet

In this case, because your house service panel should already be Neutral/Ground bonded with a grounding rod, you can plug your RV into a standard 20-amp or 30-amp outlet without any kind of G/N bonding plug. Just be aware that if you plug into a GFCI-protected outlet in your home, you could have random trips from additive leakage in your RV appliances. But that’s another story….

Am I paranoid enough?

You may think I’m paranoid, but I think that every RV should use an advanced (Total Electrical Protection or EMS) surge protector at all times, even when you’re connected to your house power. That’s because power company electricity ain’t always perfect and can do damage to your RV’s electrical system, even if it’s been wired properly by an electrician. Plus, nobody can plan for when lightning might hit in your area (unless you’re Marty McFly in “Back to the Future”). And a lightning strike in the area can cause a voltage spike that’s easily thousands of volts.

Read below for two real-life failures I personally witnessed and figured out before the power company did. (Hah!)

A tale of two failures….

Take a look at my diagram which shows how an open neutral in a 120/240-volt split-phase service will allow the incoming 240 volts to divide unevenly.

Just last year my dad’s rental house developed an open neutral on the power line coming in from the transformer on the pole. So the split-phase 120/240-volt feeder coming into the house from the pole no longer divided into 120/120 volts evenly. I measured around 160 volts on the one hot leg, while the other hot leg dipped down to 80 volts.

That high voltage blew out his home’s furnace controller twice, and took out a bunch of light bulbs. Cost was over $1,000 for the furnace controllers with installation, and Dad DOES NOT like to spend money. However, he didn’t tell me about it until the second furnace controller fried. He didn’t think I knew anything about furnace controllers…. Yikes!

And last year I had one of the 120-volt legs coming into my own house from the power company develop an intermittent connection that caused half of my house power to drop out when the wind blew and some tree branches were hitting the power wire coming from the street. There was a less-than-perfect splice by the power company which caused the intermittent connection. But if that would have been on the neutral, then I could have had the same problems my dad encountered. Once I sorted it out, the power company put in new compression splices and trimmed the tree branches back from their power lines. So no cost to me, but it could have been worse.

What have we learned?

Over-voltage failures can happen anywhere, anytime, no matter what you’re plugged into. So an advanced surge protector (called EMS or Total Electrical Protection) is your best friend since it will shut down the over-voltage before it can ever reach your RV’s electrical system.

Please note that the basic (inexpensive ones like the one shown here) surge protectors will do nothing to stop that 160 or 200 volts coming into your 120-volt shore power line. You’ll have to spend around $300 for an advanced surge protector from Surge Guard, Progressive Industries, or Hughes.

My personal pick is one of the Surge Guard Total Electrical Protection units, since I’ve tested all brands on my bench and personally feel that the Surge Guard engineering is the best of the breed. However, all three major brands will protect your RV from an over-voltage failure, so feel free to buy whichever brand you like, but expect to pay $200 to $400 for one.

If you want a great deal on a Surge Guard model, please visit my friends at TechnoRV and tell them Mike Sokol sent you. These guys are great with product support and do a lot of their own training videos. Find the right surge protector for your RV by clicking HERE and look for the Surge Guard category.

Okay everyone. Electricity is a powerful friend, unless you don’t respect it. Let’s play safe out there….

Mike Sokol is an electrical and professional sound expert with 50+ years in the industry. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.

For information on how to support RVelectricity and No~Shock~Zone articles, seminars and videos, please click the I Like Mike Campaign.

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Bill Morgan
1 month ago

Mike, a number of years ago the lights and air conditioning in my house went off. I checked breakers and everything seemed normal so I figured some sort of power outage. Then to my consternation I discovered that the refrigerator was still running and the Television would come on. After some head scratching and checking voltages I discovered that one leg of power coming into the house was dead. And my neighbors were experiencing the same thing. It turned out a transformer had failed and was only sending one leg to the neighborhood. It was a couple of days before SCE managed to replace the transformer. In the meanwhile my neighbor had no power to her refrigerator so we ran an extension cord from a hot outlet in another room to keep her food safe.

Brad Kowerchuk
1 month ago

I have a Champion 3400w portable inverter generator and a wired in EMS. The Champion will not charge with the EMS turned on, and on the Champion support site, they indicate that this is normal and that EMS needs to be disconnected or turned off. I do so, and it works. I do not know if that is normal for Honda inverters but it is for Champion models and I think I recall reading on forums that this is common for other brands. Thoughts?

Mike Sokol
1 month ago
Reply to  Brad Kowerchuk

I’m pretty sure that the Champion inverter generators are wired with a floating neutral just like the Honda generators. I did have a contact at Champion a year ago, but I’m not sure if they’re still available for a call. I’ll try to make contact with him and have them try my G/N bonding plug.

Arnold
1 month ago

I had a open neutral in a 50 amp extension cord that I used for my welder and travel trailer. It was a 2 piece riveted together in the female connector. The rivet was loose. Had used it on the welder and it worked ok as it did not use the neutral.
Went camping and 50 amp post was too far away and had to use extension cord.
It took out the converter, TV and Tv converter power supply, microwave, ref heating element and fuse. Total cost just over $1000 dollars. That was with me doing all of the repairs myself. This was just after the TV conversion to digital.

Mike Sokol
1 month ago
Reply to  Arnold

Open neutrals can be very expensive.

Larry
1 month ago

How many hits can your surge protector take and how do you know when you need to replace it?

Really
1 month ago
Reply to  Larry

What do you mean by HITS? Surges from poorly wired commercial connections, RV parks, etc. or from Lightning Strikes or other electrical surges.

Case in point: my Progressive EMS took a lightning strike and the Entire EMS burned up! Fortunately, it did it’s job and no harm came to my RV!

Progressive Replaced the EMS Free of Charge!

chris
1 month ago
Reply to  Larry

Mine takes one.

Mike Sokol
1 month ago
Reply to  Larry

It depends on the number of Joules the MOV devices are rated. Note that 1 Joule = 1 watt-second of energy. So a 2,400 Joule surge protector can absorb 2,400 voltage spikes (hits) of 1 joule each. Or 240 spikes of 10 joules each. Or 24 spikes of 100 joules each. Or one really big 2,400 joule hit that destroys the unit, but stops the energy from getting into your RV. All of the quality surge protectors have an LED that remains ON if you still have Joules left in the MOVs. So when that light is out, it’s time to replace your surge protector, or the MOV devices. As far as I know there’s no way to know how many Joules are left in your MOVs. But I’ll let you all know if I think of something clever.