Surge protection question

[defboater]

Researching surge protection for the fifth wheel 31' Cameo. We are praying to be snowbirds soon. From the bit of time we have had to research CG, we are seeing a lot of 30 amp. We are 50 amp and are wondering about surge protection.

 

So the question is what should we buy? Should we buy a 50 amp surge protector and use an adapter

or go with a 30 amp surge protector and adapt to a 50 amp?

 

Is there some research we should do?

 

Any advice appreciated.

 

 

[Ranger Smith]

You should buy a 50 amp protector and use an adapter at the pedestal.

[Daveh]

What Ranger said. Also see the discussion regarding EMS going on in the techinical section right now as they address this issue.

[Kirk W]

You should buy the one that matches your power cord. Since you have a 50A plug you need a 50A device in order to be able to ever use 50A power. A 30A device and only pass 1 phase of power while the 50A will pass two phases. When you do need to use a 30A pedestal, just use an adapter to the surge protective device as you would if you did not own one.

 

The other thing that I would comment is that you need more than just a simple surge protector if you want real power line protection. Pure surge protectors such as this one, will protect from surges due to lightning or power problems, but they do not protect you from under voltage, voltage sags, or high voltage situations. By far the most common problem for RV owners is a power supply that checks OK with a meter when you arrive but as more RVs come in and hookup the load causes the voltage to sag to dangerous levels that can damage the equipment and electronics in your RV. For good protection you need to get a device like the Surge Guard line monitor or the EMS from Progressive. Both of these products do what they profess to and if it were me, I'd choose based upon which I could get for the better price.

 

If you don't really understand the discussions of the types of devices available and how to select which is best for your RV, let me invite you to read this article on our website that I wrote and which was published in Escapee's Magazine.

[wa_desert_rat]

Yes, it's easy to imagine that an EMS is the same as a "surge protector" but as Kirk pointed out, the EMS is really what you want.

 

WDR

[defboater]

Thank you all for your expertise. There is so much to learn about RVing and this is the place to learn it.

 

How often do you suppose these have saved an RV? Surge Guard line monitor

 

We can't wait to read all the info you provided, Kirk, thank you all, again. When we finally have time to read everything I'm sure DH will have more questions.

 

Love this forum!

[Mastercraft]

^{I put a Progressive Industries HW50C unit on a couple months ago. I installed it a little different than the instructions suggested since I have two shore power inputs, front and rear. These go to the transfer switch as shore and generator. I put the HW50C between the transfer switch and the breaker panel so it covers all power coming into the coach. Well......kind of. It will be fine for voltage, frequency out of the acceptable range and detecting park wiring issues but for surges, I'm not going to kid myself.}

 

^{The surge protection feature is achieved by installing a couple MOVs (Metal Oxide Varistor) on the two hot lines. Other than having a few hundred pf of capacitance, they are out of the picture unless the line sees voltage spike into their operating region.......then they try to clamp the line voltage and eliminate the spike. Good luck on that for a part the size of a nickel. If called upon to protect the line, its kind of like a bee sting......a one time deal and the device is dead unless the surge is sub single digit ms duration.}

 

^{The other thing that bugs me a little is I now have two relay contacts in line on the power. Good thing I will really only ever draw ~20 amps max per line unless both A/Cs are on and the dryer is running, or my batteries are getting pushed hard by the Magnum. Oh - the Progressive unit has a little remote display that scrolls though the two line voltages and currects as well as the line frequency and any "faults" detected. The remote is a bit ugly with an RJ11 connector coming out the side, so it will likley be mounted in the belly storage area}

[Kirk W]

How often do you suppose these have saved an RV? Surge Guard line monitor

As I say in the article linked to, it is impossible to say how often these devices save you from damage, or in most cases, even when it has happened. Both high and low voltage problems are very rarely far enough out of range to cause immediate issues but each time that it happens the effect is to shorten the life of the equipment exposed to it. I spent my 40 year career in this type of service work and experts tell us that these short term exposures to problem voltages are cumulative and so the more that it happens the more you need one. We have known RV folks who seem to have appliances fail in relatively short periods of time over and over, yet never know why. They are nearly always people who have chosen not to use a device like the two listed above. Only rarely does an appliance fail at the time the power problem occurs and even when it does so, unless that problem is constant and not one that comes and goes, the victims never realize that the power supply is what caused the failure.

 

^{Well......kind of. It will be fine for voltage, frequency out of the acceptable range and detecting park wiring issues but for surges, I'm not going to kid myself.}

 

^{The surge protection feature is achieved by installing a couple MOVs (Metal Oxide Varistor) on the two hot lines. Other than having a few hundred pf of capacitance, they are out of the picture unless the line sees voltage spike into their operating region.......then they try to clamp the line voltage and eliminate the spike. Good luck on that for a part the size of a nickel. If called upon to protect the line, its kind of like a bee sting......a one time deal and the device is dead unless the surge is sub single digit ms duration.}

I must disagree with your opinion on this part based not only upon the design perameters of the two devices I mentioned, but also based upon reported experiences of several owners of them who have been subjected to lightning strikes on power lines where they saw no damage to the

RV while those around then experienced catastrophic failures. In both brands of device, the MOV's used are designed to fail in such an event and if the strike is near they usually blow apart in opening the circuit. While a strike in the immediate vicinity of the subjected RV would likely jump that opening, as lightning does for some very large gaps across open circuit breakers and switches in such extreme situations, the majority of such strikes are not that close to the protected RVs and so the device does what it was designed to do and the owners experience no failures. I don't know of anything that will protect your RV or anything else from a surge created by a strike that is on your your side of the power company transformer.

[Dennis M]

Get a Progressive Industries EMS - see Kirk's post for a like - ours has found open grounds and mis-wired pedestals a number of times. As Kirk said you never really know when it has protected from high or low voltage.

 

A small investment to protect your large investment!

[Mastercraft]

The MOVs are rated to absorb a certain number of Joules in a given time frame. Most of the 20mm devices ( as in the Progressive box) are rated for about 200 Joules, single event, for 2ms.....and their trip point is likely in the 180-200Volt zip code with the 120 line going to 170v peak normally. 200 Joules with 200 volts across this device is good to hold back a 500 amp surge with a duration of 2 ms. (I wonder how the 2 oz copper on the circuit board inside the Progressive unit feels about 500 amps? )

 

The condition the Progressive box could be most effective protecting a rig from is a spungy park neutral. Since the RVs don't connect neutral to earth ground in the breaker panel, a highly imbalanced load or wiring issue somewhere else in the park may cause the normal 120/120V condition to shift to 160/80V. The earth ground isn't there to keep things in line like it is on a residential system. I guess we take it on faith that someone has the neutral and earth ground connected somewhere in the park.

 

We may be at greater risk of lightning sneaking in on the cable TV coax.