Thursday, December 17, 2009

I'm tired... of RV resort excuses for voltage

/rant on

Over half of the RV resorts I frequent have low voltage. I've seen voltages under 100 volts, when powering up the microwave. It's one of the reasons I have the microwave on the inverter side of the 120 volt system. RV techs warn RV'ers that continuous operation of motors under 108 volts will damage and shorten their life expectancy. I recently purchased a Hughes Autoformer to combat the problem. Autoformers boost the voltage by two percent whenever they are plugged in, until the voltage gets to 116 volts, then a boost feature kicks in, boosting the voltage by ten (10) percent. When at 116 the voltage will magically jump to 127 or 128 volts, which everything happily consumes.

We as consumers have been slowly led to believe 110 volts is normal, IT IS NOT.. Check your labels, 120 volts is what everything has been designed for, and the appliances are happy with anything up to 132 volts, 135 volts is when most overvoltage situations kick in. Voltages lower than 120 lead to more heat, and then lead to shorter life of the appliance. It's a conspiracy, shorter life of product means more sales over the consumers life, and it's all about money, folks. /rant off

A friend emailed me a question recently.

"Is the autoformer the voltage regulator/booster device?
Why are you
getting it? I know I have hit a few older parks with shakey power, is that why?
They looked kinda pricey just for the voltage regilator.

Just curious and also where you gonna put it?"

You hit the nail on the head, unfortunately the the majority of the parks I've stayed in have low voltage. I define low voltage as anything under 110 volts. It's one of the things I keep track of.

As you may or may not know, in a travel trailer there are two types of loads, resistive and inductive. That is, heaters/lights/fridge (resistive)(fans-inductive) and air conditioning/ microwave (inductive), the converter (120 to ~12v) is inductive. Getting a little deeper into electric theory, Power is made up of two things, the voltage and the amperage. They have a direct relationship as expressed by the formula (P=EI) (P)ower is expressed in watts, (E)lectro motive force is measured in voltage and I (current) is measured in amperage.

Resistive loads are usually happy with whatever they are fed, if they get low voltage, they may be a little dimmer, but it doesn't hurt the resistive load, the amperage/current is used to heat directly. (an incandescent light bulb heats a wire until it glows and gives out light.)

However, most lights in trailers are 12+- volts, so the actual 120 volts doesn't affect brightness or performance.

Onto inductive loads, anything with a motor or transformer, they are most happy and will last longer with higher voltage and lower current/amperage. The reason is current flowing through a wire heats it to some degree, resistive loads depend on the concept, unfortunately the motor/transformer does not need heat, it literally can destroy the motor (usually by melting the wire covering, be it enamel or vinyl/plastic/rubber and shorting out the device.) Motors and transformers in converters are wire wrapped devices and a short (or open) makes it not want to work, (an open causing the current to stop flowing, and a short causing the current to flow more with the possibility of fire.)

Motors need a certain amount of Power to run, for an easy example, say a motor requires 1200 watts of power, that would be 10 amps at 120 volts. The motor is usually (if 100% duty cycle) designed to handle the amount of heat 10 amps produces. If your voltage drops to 100 volts, the motor now requires 12 amps to run continuously, producing more heat, and over time it will affect the life of the device because it's running hotter than design. However, the air conditioner (13.5k BTU) will pull about 23 amps/120 volts (~2800 watts) to start, then settle down to run at 10 amps. If starting at 100 volts, it will pull at least 28 amps, a great increase in amperage (and heat.) (remember, heat destroys)

By the way, these are real world figures for my trailer,(Nash 22H,) as I had some time and voltage problems on my hands in Rock Springs, Wy. The problems were cured by the power company changing the center tap on the pole transformer (a larger autoformer) and giving the house/shop it's rightful 124 volts.

To sum it up, higher voltages (to about 135v) are better because they produce lower current (heat.) The electric company doesn't care, they get paid for "power" (kilowatts actually). You ever wonder how they get away with using such small lines across the country to deliver it? They use the same theory, very high voltage and small current, (remember, current heats) and then use various transformers/pole transformers to reduce the voltage to something usable by us little guys.

The autoformer/power booster helps the trailer to be more reliable and your appliances to be longer lived. A popular booster increases the voltage by 10% whenever the voltage drops below 116v, ie: 116 + 11.6 volts = 127 volts, if the voltage goes to 110 volts (very common) your voltage would be 121 volts.

Contrary to popular belief and despite what park managers will tell you, an autoformer does NOT steal power, it merely makes what is AVAILABLE more efficient, the autoformer by itself only drops about 1 percent of the load making it 99% efficient.

So while in Palm Desert/Palm Springs, I installed my new (to me) autoformer.

Area formerly under the Jack Knife bed, (now storage area-see blog) where 120/12 volt wiring and panel are. Seems there is some room in betwixt those wires.

A slight modification to the cord box, a little insulation and presto, it fits along all the other wiring.

I converted the 30 amp power cord with appropriate plugs/receptacles so I can use any 30 amp extension. I can also bypass the autoformer if needed.

For a wiring diagram, see my other blog posts on installing the 3000 watt inverter.

I am not affiliated in anyway with Hughes Autoformer, Franks RV power booster, Surge Guard Voltage Regulators or Powermaster Voltage Booster.

By way of CV, I graduated from Denver Institute of Technology with an Electronic Engineering Certificate (AAS) and spent a couple of years working for Texas Instruments (North Building) in Dallas, Tx. A couple of years working on televisions and radios in Rock Springs, Wy. then years of hobby electronics, including hidden cameras, power supply's, building and troubleshooting my own computers, becoming a computer forensics expert, and designing simple circuits for jobs around the house/trailer.

Also see Valiant Sacrifice my hughes autoformer dies


  1. Sounds like you are an expert at electrical and would appreciate your opionion, I have blown several relays in both AC units on my 40 ft fleetwood coach. I have gotten several reaons, one being low power could casue it. It starts with a burning smell coming out of the AC like an electrical fire. Then compressor stops working and only blows hot air. Until recently, I did not realize that 50 amps of service was not enough to run all the equipment in my rig, not very electrical minded, so it could have been my fault for running too many devices including electrical water heater, microwave, etc. I am going to pay closer attention and run water heater on propane and possibley frig as well to keep demand low for power. Do you think a volate regulator and surge protector would be a wise investment at this point? Also, I read where the surge protectors will shut off power completey if deemed necessary but wont that fry the same relay in the AC if the power is shut off abruptly? Thank you for you input.

  2. Lets take each question separate:

    1. I am not an expert, I am a hobbyist and as such have a familiarity with electrical circuits, but do not have any certification with electrical code, and cannot guarantee my musings will fit your particular scenario.

    2. Low voltage can indeed cause parts (more than relays) to fail in the A/C, the A/C should be checked out by a certified RV technician, and faulty parts replaced. Troubleshooting the exact problem is hard over the internet.

    3. 50 amps is actually a misnomer, a RV "50 Amp" plug is actually two 120 volt circuits of 50 amps each,(total 100 amps) many coaches will take advantage of this fact with the inside wiring, using one circuit for heating and A/C and the other circuit for everything else. Unfortunately, your manufacturer has wired the exact same model of coaches differently at times, yours will need to be traced out so you can be sure. Again, I doubt many (if any) RV resorts actually have a full 100 amps available for you to use at the pedestal. unless it's off season, then you might get lucky (if you are close to the main.)

    4. A voltage regulator can certainly help, up to a point, First, get a voltage meter you can watch from inside the coach, there are many models available, some in conjunction with surge protectors. Easy and cheap to start with is this one.

    5. Surge protectors will cut off the electricity, therefore the relay will not fry, most will not turn back on for 2-2.5 minutes giving the A/C compressor a chance to depressurize.

    6. If you are traveling at all and going from park to park, a voltage regulator and surge protector are well worth their weight, if you get portable ones, they can move with you to the next RV also if needed.

  3. It is useful to try everything in practice anyway and I like that here it's always possible to find something new. :)

  4. I am not going to be original this time, so all I am going to say that your blog rocks, sad that I don't have suck a writing skills

  5. good share, great article, very usefull for us...thank you

  6. "power supply's"? Your spelling sucks!

  7. It is pretty ridiculous that some of the campgrounds I am sure all of us have been to do not provide a proper amount of voltage to our RVs. We pay to stay there, we should be able to have enough power to our RVs. I have bought plenty of RV electrical supplies from to help adapt to this. Park power is a great brand for such products.