Homemade Surge Protector, interesting

[sandy43]

Hope I can explain this correctly. At a RV park last week I saw a homemade surge protector and ask about it. This was made to accommodate a 50 amp hook-up (it can be done easily for 30a).

It had a 50a male plug on one end and a female plug on the other end. It looked as though he cut the ends off an old 50a rv cord. In the middle was a plastic weather proof junction box. The wires from each end (in the box) was connected to some type of device that held two 30a fuses. I ask, is this safe? He said, if you took apart an expensive store bought surge protector you would find the same type of hook-up or very similar. This guy was a retired electrical contractor (he said) driving a 6 digit motorhome. He trusted this over any others sold in stores.

Has anyone seen something similar to this or heard of anyone doing something like this? From you electrical guru's, what's your opinion?
Thanks

[cabinfever]

I think that would work fine for surge protection. However it does not have the technology to monitor for low voltage, reverse polarity, or no ground. Also with most surge protectors technology when they detect all is well they turn the power back on.

[bobbecky]

Actually, fuses will not stop high voltage, only blow when the current exceeds the rating of the fuse. So, unless the box also contains a surge arrester, or varistor for each power leg, the devise is no more effective than the breakers in the pedestal or the power panel in the RV. The other benefit of the commercial boxes is as said, circuitry that indicates reverse polarity, low or high voltage, etc.

[sandy43]

Well, I certainly don't plan on making one of these. I just thought is was interesting seeing something like this. I'm quiet happy with what I have. The response from you guys tells me this might not be a good idea. Thanks

[Pmedic4]

It is possible to build you own surge protector, but it will be more than fuses. The guy, if he knew what he was doing would have included some 'metal oxide varistor(s)', plus a few capacitors and diodes. In real simple terms, the Varistor is a important item, and performs the critical function. When voltage goes over a varistor's defined limit, it takes the overage and directs to ground. For example, the incoming voltage is normally 115 to 130 volts, and the varistor does nothing. When that voltage exceeds 130 volts, the varistor (generally a bank of multiple varistors is used) conducts that voltage to ground. The other components prevent the current you directed down the ground, from flowing back up through the ground to your RV.

An issue with many surge protectors, is if they protect you against lighting strike, those varistors did their job, and are now probably fried, and no longer functioning. Without knowing what your looking for, you wouldn't know what to check to see if your still protected.

There are some plans to build a Surge protector, but really isn't that expensive to buy one, plus some have warranties to 'protect your belongings - your's won't. If you really worried, you should look at a Power conditioner, not just a Surge protector. It would protect against high voltage surges and low voltage conditions. Also, Surge protectors won't really protect you much from a lightning strike, but really nothing will from a direct strike. Most Surge protectors are good for 500 to 1000 joules; Lightning is usually over a million joules. Working as an electrician, seen examples of lightning which traveled hundreds of feet through buildings, and still fried a motor of a commercial washing machine in a basement of a 4 story building. The aluminum lightning arrestors were melted in to shiny little puddles.