How much voltage is too high?
Should a new campground pedestal measure 136 and 138 volts?
I just found this post on the Rockwood Mini Lite Group.
We are at a state park. It’s a brand new section they just finished up. We hooked up our 50-amp EMS surge protector and it flashes red and says the voltage is too high with one leg reading 136 volts and the other reading 138 volts. Â
Park maintenance guy came and checked it then said our surge protector must be bad. He also confirmed the pedestal was reading 136 and 138 volts but said it’s no big deal.
We went home and got our 30 amp Surge Protector with says the 30 amp outlet is 135 volts, so we checked with a multi meter inside camper and it measures 135.2 volts. The campground keeps saying people have camped with no problems, so we need to disconnect our surge protector and not worry about it.
When we went back home we plugged our Surge Protector into our garage 50 amp outlet and it works just fine showing voltages in the 120’s. These are Southwire EMS surge protectors that test for high and low voltage. Should we be worried about the campground power being too high?
Something is rotten in the state of Denmark…
Dear Angie,
The park maintenance guy is wrong. That campsite voltage is above the upper limit of when these surge protectors will shut off the power. And for good reason… While many of your smaller electrical appliances such as computers and television sets have universal power supplies that are rated for 100 to 250 volts, your larger appliances such as Air Conditioners, Residential Refrigerators and Microwave Ovens will not be happy with a steady diet of electrical power over 130 volts.
The power company needs to reset the taps on the transformer to get the split-phase service closer to 120/120-volts. I consider any electrical service with a sustained voltage under 105 volts or more than 128 volts to be dangerous to your RV appliances. The power company needs to be contacted and they should send a field engineer out to the site immediately.
Is this really damaging?
While you may not have an immediate RV equipment failure at this campground, the higher voltage will stress many of the motors and high power devices in your RV, causing them to fail. And that’s the expensive stuff. The real bad news is that while your microwave oven or Air Conditioner probably won’t fail immediately while you’re plugged into this campground pedestal, it could happen a few weeks later when you’re plugged into a different campground. The damage caused by moderate over-voltage is cumulative.
Who tests these things?
There is no way this campground passed an electrical inspection, so the local AHJ (Authority Having Jurisdiction / Electrical Inspector) should be notified. But I suspect this campground probably didn’t pull a permit or have the installation inspected. That’s because permit requirements vary state by state, and many campgrounds don’t feel inspections are necessary at all. But I disagree because of campground power situations exactly like you described.
Please Watch This…
Here’s my 9-minute video on how Advanced/ EMS Surge Protectors test for over- and under-voltage conditions. They do a great job of protecting your RV electrical system from dangerous voltage, so believe them when they tell you something is wrong!
Let’s play safe out there… Mike
The Public Service Commission with jurisdiction in the particular areas sets the allowable voltage range. (I worked in the utility industry and at a manufacturer of meters and meter reading systems for electric utilities.)
Excellent article. In my area, St. Louis County. Missouri, the allowable voltage at the electric meter (the entrance for the electrical service) is 120.0 VAC +/- 5%. which equates to 114.0 VAC to 126.0 VAC. I worked in the utility industry. Many years ago, prior to the advent of sophisticated remote monitoring equipment, the manner in which the electric utility would become aware of overly high voltage was complaints from customers that their (incandescent) light bulbs were wearing out too quickly.