How low is too low?
What’s the lowest campground voltage that won’t damage your RV appliances?
The heat is on!
Since we’re now heading into summer heat the campgrounds are filling up and more air conditioners are turning on. And that means that the voltage at campgrounds is dropping during the heat of the day.
What can be damaged by low voltage?
Surprisingly most modern devices in your RV will be fine with a wide range of voltages. At 100 volts Microwave ovens cook slower, battery chargers reduce their amperage, and electric water heaters take a lot longer to make hot water.
But computers, cell phone chargers and modern televisions mostly have universal power supplies rated for 90 to 250 volts so they can be plugged into an outlet in any country in the world. So low voltage doesn’t affect them at all.
How low is too low for air conditioners?
In my bench testing, once an air conditioner compressor gets down to 100 volts, the current rises steeply and it starts humming like it’s not happy. I’m convinced that a steady diet of 100 volts for an air conditioner will cause overheating of the compressor and early failure. But keeping it above 105 volts would be better for compressor longevity, and 110 to 115 volts is optimum.
Be aware that if you’re checking voltage at the pedestal there will be at least another 2 volts of drop through your shore power cord and load center. So I would say that 104 volts at the pedestal, which is 102 volts at the air conditioner, is as low as I would ever want to go.
Here’s what NEMA says
The standard for voltage at the main service panel in the USA is 114 to 126 volts. But it’s acceptable for it to go as low as 104.4 volts at the campground pedestal during full load. That feels too low, but it’s what the power company goes by.
What about advanced surge protectors?
Most of them will shut off the incoming power when it gets down to 104 volts for a specified period of time. But remember that your RV shore power cord could create another 2 volts of drop. So 104 volts at the pedestal could mean 102 volts in your RV.
Can a Hughes Autoformer help?
Actually, autotransformers like the Hughes Autoformer can help boost the voltage back to acceptable levels for your air conditioner. And while all autotransformers were listed as a code violation in the last NEC code cycle, they’re now allowed as portable devices for RVs in campgrounds once again.
Stay tuned for my article on Autoformers Part 4 next week!
Let’s play safe out there… Mike
Electric utilities in the U.S. try to maintain voltage levels within +/- 5% of the nominal voltage level however the voltage levels may be at a high of 6% to a low of 13% for a short period, ANSI standard C84. Winter storms causing icing on the lines presents additional issues with the voltage due to the attempt to heat up the lines to melt the ice away, many years ago we would simply drop the voltage at the power plant for short periods of time to heat up the lines, especially the larger 230,000-500,000 volt transmission lines. Nowadays they are using a controlled short circuit for short periods to accomplish this especially on the smaller transmission and distribution lines, all of which causes problems with the line voltage.