Understanding Surge High and low voltage

With all due respect to everyone in this thread, using the term "surge" (true surge, surge guard, etc.) so loosely is what generates confusion and the OP's question in the first place.

MEXICOWANDERER did a great job of breaking things down for someone who has a basic understanding of electricity. Unfortunately, for a novice, it's very overwhelming.

Many times when the Progessive Industries EMS (Electrical Management System) is discussed, more times than not, it's referred to as a surge protector. Sure, surge protection is part of the protection provided by the PI EMS, but it's far from all it does.

IMO, most electrically challenged folks would read this thread and buy a "simple" RV surge protector (usually $75-$100) and incorrectly believe they are "completely" protected.

Just something to think about . . . my two cents . . .

The highest risk of all to an RVer is to plug in a 4 prong male 50 amp into a live pedestal. The dual 50 amp breaker should always be OFF when making or breaking camp. It is also good practice when making or breaking a 30 amp plug as well but not quite as critical.

Gjac

As you can see everyone has a suggestion / opinion on the subject

I assume your rig is a 30amp single phase 120Vac wired machine. If a 50amp rig there are other considerations. One of the highest consideration being an open neutral connection which can cause havoc supplying 240Vac to devices that desire only 120 Vac.

To try and directly answer your question as to what is at risk and assuming it's a 30amp rig along with your dry camping off grid 95% of the time.

You have very little to worry about

Yes devices such as TV's, Microwave ovens, etc. have always on power which typically is a simple internal 5Vdc or 12Vdc power supply. If worried about them simply unplug them. Yes your 120Vac to 12Vdc converter will be always on as well - it's got protection built in and is typically very simple to repair if it goes bad.

I assume you have an on board genset - Do you worry about it producing a surge?

We use hookups 85% and boondock 15%....odds are not in our favor so we have surge protection with HI/LO voltage trips....plus full time monitoring.


Boondock without hookups 98% of time........hookups 2% of time
Odds are in your favor that nothing will happen when hooked up to shore power.

Electrical spikes lasting thousandths of a second beat-up transistors and integrated circuits depending on how many thousands or millions a component manages to see before failing, and how high of voltage the spike achieves.

Constant "high voltage" can do everything from simply shorten the life of an appliance to outright fry it.

"Surge Protector" is a buzz word. From batteries to transistors, the industry treats unseen, unsmelled, electricity fraudulently or stupidly, take your choice.

A SPIKE PROTECTOR is supposed to be one of those power strips. A good power strip costs thirty to fifty dollars. A cheap power strip works about as well as putting a set of Volkswagen shock absorbers on a class A motorhome.

A VOLTAGE CORRECTOR is supposed to do as advertised. Take high or low voltage and correct it. Voltage correction has ABSOLUTELY NOTHING to do with protection from voltage spikes.

Most voltage correction devices are based on a type of transformer called an autotransformer. An autotransformer DOES NOT PROTECT against voltage spikes.

A COMBINATION spike protector and voltage correction device is what you need to offer BASIC protection for RV electrical.

An energy management system works like a bank, when funds (correct voltage) are not available it bounces the "check" with the power company and the lights go off.

Despite the hoodoo voodoo I see just about everywhere in reference to RV systems, the best way to protect electricals from SHORE POWER PROBLEMS happens to be the most expensive way hence almost impossible to find.

A ferro-resonant line transformer adjusts bad voltage from around 70 to 145 to 120 volts. No "Autoformer" has nearly as wide a range of operation. With precise voltage output regulation. Not even in the same league.

An ISOLATION TRANSFORMER will kill ALL electrical spikes (transients) like nothing else ever made.

Sadly, the Chinese haven't figured out the need or sales potential for a reasonably priced combination unit.

Hope this helps. Twelve cents worth of MOV's (metal oxide varistors) in a seven dollar power strip are nearly worthless. Use the seven dollars more intelligently and go have a cold beer.

Yes some things are on even though they are off such as the microwave clock.
The resistance heater in your fridge will be fairly tolerant of moderate high voltage and unharmed by low voltage.
Converter is always on and some are more tolerant than others.

One of the simple $10 plug-in volt meters should be sufficient for your camping style.

If your A/C is turned off then it is protected against LOW voltage. High voltage it is most likely safe from less it is high enough (not likely).

The 10 dollar device you mention is a spike suppressor, all surge protectors contain them so do many other devices, A SPIKE is a very short duration voltage spike (Can't really call it a surge since it only lasts, usually, 1/120 second or less).

IT is of no use at all in a brownout (low voltage) or true Surge (Sustained high voltage) situtation,, Been hit with one of the latter and those 10 dollar firecrackers sounded like July 4th.

Now, the real danger is this: In the summer if you are using your A/C and you have say 110 volts line with poor wires underground in the park the A/C kicks in and the voltage may drop to 100 or less. This means that the compressor does one of two things, it either takes a long time starting, thus overheating the motor and doing damage, or it stalls (Same effect). Over time this damage builds up and you need to replace teh A/C, about 1,000 bucks.

The RV type Surge guards, the good ones with digital displays, will cut you off, wait 2 minutes and try again.. Thus protecting the compressor against this type of damage.

Next is a true SURGE... This can happen in a park if several A/C's cut out at the same time or if a big ticket electricty user on the same high tension branch shuts off his main power sucker. The voltage now goes not to 120 but perhaps as high as 150 or more and remains there for several cycles.. (A Surge) this can blow electronics, TV, Microwave, Sat Receiver, Converter, and such. OR.. More likely... You plug into a 30 amp outlet THINKING it's for an RV only to find it's a 240 volt hole in the wall... The Surge guard says "Hey Stupid, 240 volts is not good" and blocks power from blowing all your expensive stuff.

Thus paying for itself several times over.

Like I use to say back in the motorcycle days. A $10 helmet is fine if you have a $10 head.
I have the Progressive hard wired EMS. I can easily remove and reinstall into any future RV's I own. I am covered for life.
I may drive thousands of miles and never be involved in a crash but I wear my seat belt every time I am in a vehicle just in case.

When referencing "surge" in typical RV use, there is actually the under/over voltage situations, a deviance in the supply that exceeds recommended range of 5% above/below (114v-126v) and an instantaneous over voltage spike introduced by lightning or other induction much above the 120v standard.

Most appliances will survive a small bit beyond the 5% deviation (maybe 108v-130V) for short durations. Most appliances and circuit boards will not withstand a voltage spike with high voltage surge like lightning.

Your $10 surge strip may protect from the high voltage spike, once. They do nothing to remedy low or high voltage deviations, the most common situation in RV parks.

You probably won't need an electrical management system device for 99% of the time. But that 1% can mean a lost circuit board or appliance. If the appliance is not being used, the under/over voltage situation won't effect it. The surge spike, though, can ruin anything that is in contact with the spiked circuit. Televisions seem to be especially prone to this. I use a better surge strip for my entertainment devices. In fact, if powered by the inverter, I use two of them.