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  1. #11
    Join Date
    May 2008
    Location
    Pacific Northwet
    Posts
    1,418

    Default Re: Whole House Surge protector

    Quote Originally Posted by The Semi-Retired Electric View Post
    Good advice Fencepost and would like your opinion:

    I read somewhere that typical housewiring will tend to limit spikes to about 600V due to clearances in devices etc.

    Also, I feel secondary surge strips located around a house will add further protection to not only the appliances plugged into them but the whole house. By their very nature their MOV's are connected L-L, L-N & L-G so wouldn't "more be better"?


    Good Luck from Columbiana, Alabama
    Maurice Turgeon, [URL="http://thesemi-retiredelectrician.com"]
    I wonder if that "600V" figure is based on the fact that the insulation on most household wiring is rated for 600V. It seems a bit fishy; there could be effectively a spark gap between the internal prongs of a receptacle, say, but there are so many variables and variations that there's no way you can count on some 600V rule of thumb.

    I am of the "more is better" opinion, but still the MOVs should be located near the protected device as voltage transients can be very localalized. For example, a laser printer can draw several amps when it is printing. When it stops printing, the current draw suddenly stops, and a surge can happen on that circuit. If your computer is on the same circuit, it can experience a small surge. Having the laser printer and the computer on a surge protector can protect both. (By the way, laser printers should NEVER be connected to a UPS. It will overload the UPS.)

    When you start talking about stuff that happens in radio frequency ranges, weird things happen. For example, if you get some funky, high-voltage standing wave in the wiring and the MOV happens to be at a node and the device is at an antinode, the device blows up and the MOV doesn't know anything happened.
    The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.

  2. #12
    Join Date
    Feb 2010
    Posts
    16

    Default Re: Whole House Surge protector

    Quote Originally Posted by Fencepost View Post
    I wonder if that "600V" figure is based on the fact that the insulation on most household wiring is rated for 600V.
    A 6000 volt surge flowing down one wire would also be 5400 volts on another. (Actually same since the 600 volt isolation becomes near zero once compromised.) Furthermore, surges are current sources. That means voltage increases only if something foolishly tries to stop or absorb a surge.

    Best protection at an appliance is already inside the appliance. Same protection that also makes internally generated surges irrelevant. Or is a surge from the vacuum cleaner daily destroying dimmer switches and digital clocks?

    One 'whole house' protector protects from all types of surges - including any that might be generated by the vacuum. A destructive surge seeks earth ground. Either that current is earthed before entering a building. Or that current goes hunting for earth destructively via appliances. Protection is only and always about where energy dissipates.

    No protector does protection. Not even that 'whole house' protector. Some protection systems have no protector. But every protection system must always have the earth ground.

    Either a protector connects to what does protection (ie a 'whole house' protector). Or that protector does nothing (ie plug-in protector). Protectors too close to appliances and too far from earth ground can even compromise superior protection already inside appliances.

    Protection is about layers. Each layer is only defined by what absorbs hundreds of thousands of joules. Earth ground. A 'whole house' protector (if properly earthed as others have described) is only secondary protection. Also inspect your primary protection layer. A picture of what does primary protection and therefore what to inspect:
    http://www.tvtower.com/fpl.html

    A minimal 'whole house' protector is rated for 50,000 amps. Then a protector remains functional even after direct lightning strikes (typically 20,000 amps).

    Joules is a ballpark number to rate the protector’s life expectancy. Joules do not decrease (degrade) by subtraction. For example, a protector that has higher joules absorbs even less energy during the same surge. Better protectors absorb less energy. Another reason why a minimal ‘whole house’ protector starts at 50,000 amps.

    To promote sales, profit center protectors are grossly undersized. A protector that fails during a surge (does no protection) then gets recommended by the most naive. “My protector sacrificed itself to save my computer.” Nonsense. Superior protection inside the computer saved the computer. A surge too tiny to harm the computer easily destroyed a grossly undersized protector. A properly sized and earthed protector will earth many direct lightning strikes. And remain functional for decades.

    How to make a protector better? Increase the earthing. A protector is only as effective as its earthing. If any wire inside any cable enters the building without first connecting to single point earth ground, then all protection is compromised. The telco 'installed for free' protector also must connect as short as possible (ie 'less than 10 feet') to the same earth ground. Cable TV needs no protector. It must connect to earth via a hardwire.

    Better earthing is not necessarily a water pipe. Better earthing involves making that connection to earth as short as possible. If a 6 AWG wire from the breaker box goes up over the foundation and down to earth, then the 'whole house' protector has been compromised. Too many sharp bends, wire too long, wire not separated from other non-grounding wires, etc. Surge protection means that earthing wire must go through that foundation and down to earthing electrodes. Protection is not defined by the protector. Protection is defined by how a protector is earthed and quality of that earthing.

  3. #13
    Join Date
    Jan 2011
    Location
    Columbiana, Alabama
    Posts
    644

    Default Re: Whole House Surge protector

    Thanks guys. It's obvious you've studied this issue.

    I too believe earthing is very important and the more the merrier. I've tested ground rods and systems to the point where I can almost smell trouble. Sandy soils (Florida) are real bad, especially where lightning is a way of life.

    I don't believe the 600V number was related to the building wire insulation but was just an average spike voltage seen in most homes.

    I started with a plant that rented a voltage event recorder. They hooked it up to their incoming line an the guy who wanted it left. After I was there a few years the foreman asked me what to do with all the rolls of tape the thing was spitting out.

    I didn't even know we had the recorder and the purchasing agent kept paying the monthly rental! After looking at the readings I discovered we were getting 1000V hits every day on our 120V branch circuits! No wonder we kept losing instrumentation and computers!

    We started putting in MOV's etc. and got the spikes under control. Then returned the event recorder. We could have bought it, several times over for what we paid in rental!

    Thanks again.

    Good Luck from Columbiana, Alabama
    Maurice Turgeon, http://thesemi-retiredelectrician.com

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