Surge protector, roll your own

Been snooping around and notice that the cheap (office depot and etc) plastic strip (5 recep) surge protectors have only one MOV but the more expensive ones have one MOV at each receptacle. Looks to me as if you could use metal recep boxes that would hold two or three receps and place a MOV across each recep, put a metal cover on it and a short 3 wire 12 gauge cord and have a much better surge protector to protect sensitive equipment for not much more than the computer/office stores want for the plastic cased ones. I have found MOV's rated at 150 volts and 80 Joules at this web site for $3.81 each, www.electronicplus.com/content/ProductPage.asp?maincat=TR&subcat=TS1
Any Thoughts?? RM ~
PS, Think I would put a 15 amp push button circuit breaker on the box
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There have been some seriously heated discussions about surge protectors. Personally, I feel they are a small part in overall electronics protection, and aren't much good at much more than providing a bunch of convenient outlets. Good grounding is an absolute must, with a direct circuit to the breaker box if possible.
As for the circuit breaker, that will do a fine job in protecting the wires, but it adds no protection to anything else hooked up to it. Better protection would be provided by a fuse, fast or slow blow depending on your equipment. It's more of a hassle, but it'll be a lot faster than a circuit breaker.
Pagan
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Pagan wrote:

Fuses are circuit breakers are the same type of device for generally the same purpose. They protect wiring. For protection of equipment and people you use a different type of device. Thus the CB is of no use.
As for making your own surge protector, go for it. But I hope you know all the ins and outs and don't put yourself or your family or your equipment at undue risk.
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Respectfully,


CL Gilbert
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Your correct. However 80 joules is not a lot of power. My surge strips are rated for 300. My whole house protector in the panel is rated for 1500 with a let through of 300. So far the combination has worked to keep everything safe.
You might want to read this page
http://www.jascoproducts.com/cgi-local/SoftCart.exe/online-store/scstore/go/cea_surge_results.html?E+scstore
If your serious about surges then read some of the information by Mike Holt.
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SQLit wrote:

http://www.jascoproducts.com/cgi-local/SoftCart.exe/online-store/scstore/go/cea_surge_results.html?E+scstore
Joule is not a measurement of power it is unit of energy. Let me put it this way, if you get a direct hit nothing uch will work. Telling from real world experience. And real protector for whole house costs a lot. And surge current is much faster than breaker or fuse. Tony
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Joules are a measure of energy. But that is all irrelevant to MOVs. For MOVs, joules defines life expectancy. More specifically, how fast the MOV will degrade. The manufacturer defines MOV failure mode: degradation - not vaporization. Joules is the parameter that defines that life expectancy.
Tony Hwang wrote:

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w_tom wrote:

For the record, Power is energy over an amount of time. Its measured in Watts which is the same as one Joule per second.
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CL Gilbert
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Rob Mills wrote:

What's wrong with pulling the wall receptacle and placing a MOV across the hot/ground terminals? Gets rid of the ugly box, protects anything plugged into it plus down-stream receptacles. Of course you'd have to remember where it was in case it ever shorted.
Bob S.
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I guess in theory it should work but after seeing one office depot strip surge protector burn a spot in my carpet I don't think I would want one inside my wall. My whole idea was to more or less build a better mouse trap for the money. One that was huskier and retained the heat better than the plastic cased ones sold at office and computer supply stores. I also needed more receps than a single wall recep as I have a several (none that draw a lot of power) sensitive radios, two computers and a printer. RM~
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You are assuming the MOV is the protection. How? What will that MOV do? Absorb the surge? Block it? Since that MOV is so far from earth ground, AND because it is so close to transistors, then it provides the same ineffective protection provided by power strips.
Furthermore, if those $0.10 parts were so effective, then they are already inside the appliance. Anything that is effective on an appliance power cord is already inside the electronics.
How do effectively protected sites do it? Let's take a telephone Central Office computer - connected to overhead wires everywhere in town. They put the connector directly on earth ground AND up to 50 meters distant from the computer.
No earth ground means no effective protection. Those MOVs inside a plug-in box or inside the wall receptacle are not effective.
Don't get mesmerized thinking the MOVs are protection. Protection can be installed with a copper wire or it can be installed with an MOV. The MOV only acts like a wire during a limited time - during the transient. But if wire or MOV does not make that 'less than 10 foot' connection to earth, then no effective protection. Protection is the earth ground. MOVs is only to connect a surge to earth ground. No earth ground? Then no effective protection no matter how many joules are installed.
Rob Mills wrote:

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It might help if you had some clue as to how an MOV works. And they DO work.
rusty redcloud
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Rather than insult, why not demonstrate how MOVs work? If having problems doing something constructive, start with some facts from MOV manufacture datasheets quoted in this 11 July post: http://tinyurl.com/dtn5m
MOVs work; which is not to stop, block or absorb surges. That is why plug-in protectors do nothing effective AND why appliances don't install MOVs where they cannot be effective - on the power cord.
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While I agree that surge protectors are not very effective, its mostly because they are poor quality devices. You can find a good quality surge protector. You need to know what size surge you intend to protect. A device can call itself surge protector if its only protecting a surge the size of say, the vacuum cleaner motor. Or even less.
w_tom wrote:

What do you mean here? They use 2 ground lines? There must be a + and -. One can not be grounded. Please explain what 'connector' is?

The MOV just needs as good or better path to ground than the device it is protecting. The distance is irrelevant.
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CL Gilbert
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Learn by building a protector. Notice what the competition is doing. First, parts cost on the order of $0.10. So how many joules did they install? Why so little cost of parts and yet so such a high price for the protector? Second, minimally sized 'whole house' protectors cost under $50 for over 1000 joules. You may save money by purchasing a 'whole house' protector only to remove its MOVs.
Consider safety - UL1449 2nd edition. One trick is to put inductors in series with the MOVs. Therefore pulse rise time is not as sharp; MOV less likely to vaporize; more likely to pass the UL1449 test. (Others assume that the inductor provides additional electronics protection.) Build it. Its a great way to learn how protection works. You will not save money. You will learn.
The 15 amp circuit breaker is required for human safety when a single plug connects to multiple outlets. If a power strip (with or without protectors) does not have that 15 amp breaker, then the strip should be disposed as a human safety threat.
Rob Mills wrote:

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w_tom wrote:

circuit breakers/fuses protect wiring (and by doing so protect from 'thermal incident' so I'm not disagreeing with you) GFCI protect humans Surge protectors/noise surpressors/filters/etc. protect devices
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CL Gilbert
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One of those transistorized device that requires protection is the GFCI. What protects a GFCI? Just another reason for a 'whole house' protector.
"CL (dnoyeB) Gilbert" wrote:

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