electrical surge protectors

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banjo5491

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Jan 19, 2010
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Just seen a ad for electrical surge protectors (50 amp and 30 amp) and wondering if they are necessary. If so, can you use a 30 amp with 50 amp service and vice versa.
 
First of all, be aware that there are plain surge protectors and the more sophisticated power line monitors. Despite a lot of talk, surge damage in RVs is relatively rare. Other power line problems are more likely to be damaging. If you are going to buy one at all, I would recommend a combined power line monitor and surge protection device. These check for high & low voltage, reversed polarity, open neutrals and grounds, etc. as well has damping surges. Some surge protectors have warning lights that test these conditions when plugging in, but an active device that continually checks and acts as needed is a better form of protection.

The device you buy should match the power service of your RV, either 30A or 50A.  If 50A, the protection device uses the same adapter that your power cord would if plugging to a 30A outlet.  A 30A device can be plugged to a 50A outlet using 30/50 adapter, but yo are only going to get 30A through it.

Do you need one? Hard to say. Older campgrounds often have poor quality power and newer RVs with lots of electronics can be susceptible. You hear horror stories and the word "surge" is used liberally but often inaccurately. Basically it's insurance - you probably won't need it, but if you do it is a godsend.  Most power problems could be avoided simply  by checking the voltage and polarity to power outlets before plugging in, which most newer surge protectors now do. If yo did that rigorously, you are probaly ok. If, like most, you lack the skill or interest in doing so, A power line monitor and surge device is  a reasonable add-on accessory for peace of mind.

Most newer high end coaches have such systems built right in.
 
Not necessary except in my book and yes you can use a 30 with a 30 amp RV plugged into a 50 receptacle and vice versa.
 
We started out without one, and got one after ac damage that was attributed to "low voltage". Our SurgeGuard monitors low/high voltage (in addition to other faults) and will cut off electrical power if reasonable limits are exceeded. It has tripped several times ... most often for low voltage, and a few times for high voltage (each time I checked the post with a multi-meter to see what the problem was. From my experience over the years, I would not be without one.
 
Well, I agree with most of what Gary said.  I only point I disagree with is that I have found a much more common problem is campgrounds having low voltage.  Even a campground with normally adaquate power reserves can be tested in the right circumstances.  It is also much more likely that your electronics will sustain damage from chronic low voltage.  Several times my Surge Guard has cut power to the MH when voltage has dropped below the preset safe limit.  Usually it has been summer time and the campground had many large rigs all running their air conditioners on high.  I would rather sweat than pay the bill for a fried AC or refer. 

They seem to be a bit pricey at the onset, but only a small fraction of what it can cost you if you are unlucky enough to be in a campground with a weak or old  power system.  I bought a unit that hard wires into the rig.  It is in play anytime that the plug is in the pedestal. 

Sarge
 
banjo5491 said:
Just seen a ad for electrical surge protectors (50 amp and 30 amp) and wondering if they are necessary. If so, can you use a 30 amp with 50 amp service and vice versa.

Most surge protectors are just MOVs with a cord and socket.  MOVs -- metal oxide varistors - have the property of conducting electricity like a dead short above a certain threshold voltage and hardly conducting electricity at all otherwise.  They are rated in the number of Joules of energy they can take before they self-destruct.  Back in the 1960s, before we had MOVs, there were gas-filled tubes, which no one uses anymore, except for special applications.

MOVs are mainly effective at suppressing high-voltage transients caused by lightning strikes, which are damaging to sensitive electronics.  Most higher-buck electronics have MOVs built into them for this reason.  The MOVs themselves are usually just a buck or two, maybe more for a really big one.

With the fancy surge protector boxes people sell, you get a plug, a socket, two MOVs (three for 50A service), and a box to hold the socket and the MOVs.  The MOVs are the cheapest part.  You could, quite literally, built a much better one than any that are for sale, for less than they typically sell for, by using great big giant MOVs.

With great big giant MOVs, the efficacy of your surge protection is going to be limited by the AC properties of your grounding environment.

They don't do much for air conditioners or lighting, because they don't do anything to fix the overvoltage, undervoltage, and dropout conditions that pose problems for these loads.  For that you need one of those voltage regulating autotransformers.

I don't have a surge protector on my TT.  Just saying.

 
Banjo,

Look at it this way.  There's always a first for everything and the very time you don't have one you'll wish you did!  Murphy's Law at work.  It's cheap insurance instead of replacing damaged microwaves, TVs, DVD, washer-dryer, or whatever.

That said, I agree that many campgrounds have low voltage, especially if they're old and on a full weekend with everyone using their appliances to fix dinner, wash and dry clothes, and all the other things we do that use up a lot of those electrons.  So yes, protect those expensive appliances that surges or drops can damage.

ArdraF
 
Jammer said:
Most surge protectors are just MOVs with a cord and socket.  MOVs -- metal oxide varistors - have the property of conducting electricity like a dead short above a certain threshold voltage and hardly conducting electricity at all otherwise.  They are rated in the number of Joules of energy they can take before they self-destruct.  Back in the 1960s, before we had MOVs, there were gas-filled tubes, which no one uses anymore, except for special applications.

MOVs are mainly effective at suppressing high-voltage transients caused by lightning strikes, which are damaging to sensitive electronics.  Most higher-buck electronics have MOVs built into them for this reason.  The MOVs themselves are usually just a buck or two, maybe more for a really big one.

With the fancy surge protector boxes people sell, you get a plug, a socket, two MOVs (three for 50A service), and a box to hold the socket and the MOVs.  The MOVs are the cheapest part.  You could, quite literally, built a much better one than any that are for sale, for less than they typically sell for, by using great big giant MOVs.

With great big giant MOVs, the efficacy of your surge protection is going to be limited by the AC properties of your grounding environment.

They don't do much for air conditioners or lighting, because they don't do anything to fix the overvoltage, undervoltage, and dropout conditions that pose problems for these loads.  For that you need one of those voltage regulating autotransformers.

I don't have a surge protector on my TT.  Just saying.

I disagree with one part of that statement.  My surge supressor will disconnect me from the pedestal power when the voltage gets too low, and not reconnect until it senses a propper voltage.  In really killer heat I will usually start the generator and let my transfer switch take over. 
 
I would like to thank everyone for the information. It's greatly appreciated                     
 
I disagree with one part of that statement.  My surge supressor willdisconnect me from the pedestal power when the voltage gets too low...

That function is one of the major ones what distinguishes a power line monitor from a simple surge protector.  Low voltage detection and lockout is probably  a much more valuable function than just surge protection alone.
 
When we were in Mx last fall, the line voltage was usually about 132VAC.  Sometimes it would get up to 134VAC.  When the A/C was on it would drop to 128VAC.  Two questions.  One, how high is too high?  Two, which of these voltage control boxes would limit the high voltage and the low voltage and what are the ranges?  I walked around the RV park and I found one RV that was using a line conditioner that would "compensate" for low voltage but did nothing about high voltage.  Everyone else, as best I could tell either by looking or asking, did not pay any attention to the voltage. 

I don't  think we damaged anything... all of the appliances still seem to work ok but I did fret about it.

Thanks, G.
 
SargeW said:
I disagree with one part of that statement.  My surge supressor will disconnect me from the pedestal power when the voltage gets too low, and not reconnect until it senses a propper voltage.  In really killer heat I will usually start the generator and let my transfer switch take over.

That is the difference between a "Surge Protector" which is really a spike supressor, (A true surge and it sounds like the 4th of july with those MOV's blowing up like firecrackers.. Trust me on that, Been there when it happened)

And a Power Line Monitor, which by the way can protect you from a surge, as well as a spike.  Not by supressing the surge (Which lasts longer than a spike) but by disconnecting same as it does with low voltage.

Or a Power Line Guardian (An even better name since "Monitor" implies a gauge, not a protection device)
 
taoshum said:
When we were in Mx last fall, the line voltage was usually about 132VAC.  Sometimes it would get up to 134VAC.  When the A/C was on it would drop to 128VAC.  Two questions.  One, how high is too high?  Two, which of these voltage control boxes would limit the high voltage and the low voltage and what are the ranges?  I walked around the RV park and I found one RV that was using a line conditioner that would "compensate" for low voltage but did nothing about high voltage.  Everyone else, as best I could tell either by looking or asking, did not pay any attention to the voltage. 

I don't  think we damaged anything... all of the appliances still seem to work ok but I did fret about it.

Thanks, G.

The first thing to consider is that many of the voltage meters out there aren't very accurate.  I have a Camco plug-in voltage meter -- with the yellow plastic housing and the meter with the green and red zones.  I plugged it in and it reads about 8 volts higher than my digital test meter which while not of unimpeachable calibration ought to be within a volt or two.

I would expect that anywhere in 110-125 volts would be fine for any well-designed appliance.  Beyond that, it depends.

Some computers and electronics have switching power supplies that will run just fine on any voltage between 90 and 260.  The higher the voltage, the less current they draw.  Often, if these have a voltage switch for 120 and 240, it doesn't do anything but change the fuse size.

Then again, some cheap electronics have poorly regulated power supplies and might be destroyed by overvoltage.

I suspect that most of the modern converters based on switching designs are also relatively unaffected by overvoltage.  Older converters, based on linear designs, will run hotter on higher voltages.

Heating appliances, like toasters, coffee pots, space heaters, hair dryers -- will produce 21% more heat with a 10% increase in voltage.  That's enough that they may overheat.

Induction motors, like those found in A/C units, will draw somewhat less current at a higher voltage but will still run slightly hotter and be more prone to overheating.  Induction motors are most efficient (and run coolest) at their design voltage and run hotter on either higher or lower voltage.

Regarding your second question, in general, the autotransformer-based buck/boost voltage regulators, sold by Autoformer and their competition, can compensate for overvoltage the same way they compensate for undervoltage but in reverse. 
 
John From Detroit said:
A true surge and it sounds like the 4th of july with those MOV's blowing up like firecrackers.. Trust me on that, Been there when it happened

They're typically spec'd at 200 volts, so it takes 144 volts RMS to trip them.  If the voltage is that high, the MOVs aren't the only thing that will blow up.

The power company guys dropped a 68,000 volt line across the 13,600 volt output of a substation near us a couple of years ago, that serves (among 200 other households) a house we rent out to some tenants.  The tenants called us up in quite a state of panic because the whole place smelled like smoke and a bunch of the circuit breakers tripped.  I went over and poked around, and called up the power company.  The conversation went kinda like, "we didn't do it, nobody saw us do it, you can't prove anything, and it will never happen again."  Right.  I think we ended up replacing some light bulbs and everything else was OK.
 
After reading all of these posts, I am wondering, should our worries be primarily under or over voltage , in the normal hookup while camping?
I don't know what to ask for or where to obtain whatever devices are most needed for electrical hook up for a motorhome.
 
I believe that the most common problem would be an under voltage problem, however under or over can occur.  The other issue that a good surge supressor will protect you from is a miswired pedestal.  For instance when I plug into a post, I do not get immidiate power to the rig.  There are two lights that light right away, and one that blinks.  There is also a fourth that indicates a miswire situation.  By not connecting right away it gives me the chance to inspect for a miswire and disconnect if necessary. 

I bought mine from Camping World, but I am sure that they are available at many RV supply stores, both retail and on line. I am not as tech savvy as some of our posters, so I needed to buy one that was ready to go out of the box as opposed to building one.  Either way you go, I would highly recommend one for your peace of mind, and it could save you in the long run. 
 
Well, again, I don't use this stuff, I just plug in.  I do have a voltmeter and will check the voltage with it if I'm suspcious.  If it's bad enough, I can move to another spot, or another campground, or shut off the A/C and live with it, or unplug, or whatever.

In the U.S., overvoltage is rare, and undervoltage is something you might run into on hot, busy days in campgrounds that were wired to older standards or where corners were cut.

 
One, how high is too high?  Two, which of these voltage control boxes would limit the high voltage and the low voltage and what are the ranges?
My digital line meter will alarm at 102v on the low side and 135v on the high side.  My TRC SurgeGuard manual says if power goes below 102v or above 132v for more than 8 seconds, it will cut incoming power. Most of the time, the SurgeGuard will cut power before the line meter gets a chance to alarm.  As I recall, the general rule is 10% over or under ... I presume 120v is the "norm".

We have found low voltage to be more common than high, but have experienced high more often than I would have expected. On several occasions we have had very high on one leg of the 50a outlet with very low on the other -- sign of a loose common somewhere on that circuit. In those cases, all I knew was that the SurgeGuard disconnected power until I checked the shore power outlet with a multi-meter. My digital line meter inside the coach is reading power from only one of the two 50a legs ... I can move it to an outlet on the other leg if I wish. The trick is to know they are on different legs (the only reason I know some in my coach is when we dealt with the aftermath of a lightning strike that melted one leg of our power cord in two!!).
 
I have a Progressive 30A Electrical Management System (EMS) and I paid about $270 for it. I installed it before going on my very first camping trip. I have never needed it and hopefully I never will, but if I ever do... it will be there to protect my camper. 
 

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