whole house surge protectors

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I bet they are just being conservative, but the ratings are not any better. One thing I see on mine, the trip voltage is lower than others.
When I moved in, power company said if I wanted to keep the installed meter suppressor, I would have to pay so much per month. Question is, did they remove it. Knowing the old owners of the house, I can't believe they would pay for something like that.
Greg
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On 10/5/2012 2:42 PM, snipped-for-privacy@optonline.net wrote:

I am speaking as a novice with these minor experiences. My neighbor is an elderly widow that has to rely on others.
We did have a big surge hit the house where high tension wire was shorted to house wires. It knocked out all my surge protectors and a microwave oven that was on a protector that had previously failed. Cost me about $90 for new protectors as once light is out, they are gone. Don't know about whole house protector reset or replacement in an incident like this.
My brother had lightening hit his driveway light pole. Killed everything in the house. Don't think anything would have protected him.
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On 10/6/2012 6:35 AM, Frank wrote:

The protection in almost all surge protectors are MOVs. They can conduct thousands of amps for the maybe 100 microseconds of a lighting created surge.
They will be rapidly burned out by the much longer overvoltage of a crossed power wire (which is not a "surge"). Neither service panel or plug-in protectors will give reliable protection. UPSs might disconnect and some plug-in protectors disconnect on overvoltage.
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On 10/5/2012 12:42 PM, snipped-for-privacy@optonline.net wrote:

Nice description - I agree with all of it. I would only add what is implied - for a plug-in protector connect all interconnected equipment to the same protector and all external wires (power, phone, cable, ...) go through the protector.

And more good information. Many of the major electrical manufacturers make service panel protectors. I would buy only a major name brand.
------------------------- Excellent information on surges and surge protection is at: http://www.lightningsafety.com/nlsi_lhm/IEEE_Guide.pdf
The recommended surge current rating for residential is 20,000 - 70,000A per service wire. For high lightning areas the recommendation is 40,000 - 120,000A.
An investigation of the possible surge on a residential service used a 100,000A strike to the near utility pole with typical urban overhead distribution. Only 5% of lightning strikes are stronger, and the strike is about as close as possible, so this is essentially a worst case. The surge current was 10,000A per service wire. Higher protector ratings are not for a single event, but give a long life.
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*The surge suppressor will blow up when it is not properly grounded. It is designed to absorb the surge and then dissipate it to ground. With no ground it just overloads, but still provides some surge protection though it is only once. Proper surge protection begins with good grounding.
Siemens has a comprehensive online training manual that explains the process in simple terms and also shows their products. Here's an excerpt: "The clamping voltage rating of an MOV is greater than the normal supply voltage. Therefore, when a surge occurs and the clamping voltage rating of the MOV is exceeded, the MOV switches from a high resistance path to a low resistance path and excess energy passes through the MOV to ground, bypassing the connected load".
You can read the whole instructional manual here: http://www.mrelectrician.tv/surgeprotectionbasics.html
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Just a clarification. The surge protector doesn't absorb the surge, it just shunts it to ground, assuming it has a ground. You have that process described below.
With no

With no ground at all, it would seem all it could do would be to clamp the various conductors so that the voltage on any of them relative to the other would be 600V or so.
Proper surge protection begins with good grounding.

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Just a clarification. The surge protector doesn't absorb the surge, it just shunts it to ground, assuming it has a ground. You have that process described below.
*Thanks for the clarification Trader4. You are correct about the shunting.
With no

With no ground at all, it would seem all it could do would be to clamp the various conductors so that the voltage on any of them relative to the other would be 600V or so.
*I'm not sure about that. All I know is that the ones that blow up are usually the ones with no ground.
Proper surge protection begins with good grounding.

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That's interesting. I take your word for it. It's just that I'm having a hard time figuring out why that would happen. With a proper ground almost all the surge energy passes directly through the surge protector. Without it, it would seem a lot less energy would pass through it. Maybe Bud or one of the other guys has some thoughts.
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On 10/6/2012 7:00 AM, snipped-for-privacy@optonline.net wrote:

IMHO the service panel protector would not have a problem with grounds that are not as good. Since a lightning surge is a current source, the current through the protectors might be about the same, but not more. (But in about all cases there are multiple paths to earth, which would result in a lower surge current.)
Suppose you threw all your beer bottles in the back yard then built a metal shack on top of the bottles. Power, telephone and cable come in adjacent to each other and are all surge-protected to the metal shack. There is no earth connection. Everything in the shack would be protected. The power surge protector would work fine and would not blow up. (You might not want to be entering the shack when a surge hit.)
I agree with trader.
------------------- Suppose you have a 2,000A surge current to earth and the resistance to earth is a very good 5 ohms. The "ground" at the house rises to 10,000V above 'absolute' earth potential. This happens even with very good earthing.
If the earthing is not as good the building "ground" rises to a higher potential above 'absolute' earth potential.
This can show up at equipment like a pad mounted air conditioning compressor. The compressor can be at about the potential of the earth the pad is sitting on. The power wires can be at about the potential of the building "ground". During the surge they can be thousands of volts different. A service panel protector does not prevent this. And it can happen even with good earthing.
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wrote:

This ground shift is a very real thing. When I was in the computer biz I have seen 35 volts between the ground in 2 buildings that were not really that far apart. In a lightning event this can be a huge number.
In extreme cases we have even run bonding conductors between buildings to protect LANs. These days an optical isolator is a better solution or just WiFi the whole thing.
I have a huge ground plane at my house (ufer, lots of rods and an in ground pool). That may be why I have survived a number of direct lightning hits. It really likes my weather station. I was in the driveway, running to the house and saw one of the hits so there was no doubt what got hit. The only thing I lost was the station hub and the serial port on the PC it was hooked to.
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The devices in the protector do not last once hit. They either reduce capability or completely fail. One shot, blow up. MOV. Surge protectors or anything else, are not designed to deal with a direct lightning strike. The common connection is the same place ground is, unless it goes to a different ground stake or stakes.
Greg
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On 10/6/2012 11:28 AM, gregz wrote:

That is all complete nonsense.

Not obvious what you are saying.
You do not want multiple earthing systems. You create an earthing system, which may have multiple earthing electrodes, and connect it at the service to the power system ground, which is bonded to the service neutral. Entry protectors for phone and cable must connect with short ground wires to a common connection point on the power earthing system. Dish entry protectors also connect there.
Multiple earthing electrodes can be at far different potential during a surge 'event' or a nearby lightning strike. Much of the protection is that during an 'event' the building wiring may rise far above 'absolute' earth potential, but they all rises together.
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bud-- wrote:

Please refrain from confusing people with silliness:
"A varistor remains non-conductive as a shunt-mode device during normal operation when the voltage across it remains well below its "clamping voltage", so varistors are typically used to suppress line voltage surges. However, a varistor may not be able to successfully limit a very large surge from an event such as a lightning strike where the energy involved is many orders of magnitude greater than it can handle.
"Follow-through current as a result of a strike may generate excessive current that completely destroys the varistor. Lesser surges still degrade it, however.
"Degradation is defined by manufacturer's life-expectancy charts that relate current, time and number of transient pulses. The main parameter affecting varistor life expectancy is its energy (Joule) rating. As the energy rating increases, its life expectancy typically increases exponentially, the number of transient pulses that it can accommodate increases and the "clamping voltage" it provides during each transient decreases. The probability of catastrophic failure can be reduced by increasing the rating, either by using a single varistor of higher rating or by connecting more devices in parallel. A varistor is typically deemed to be fully degraded when its "clamping voltage" has changed by 10%. In this condition it is not visibly damaged and it remains functional (no catastrophic failure)."
http://en.wikipedia.org/wiki/Varistor
What's important is that a MOV may be completely degraded without showing outward signs. Of course if the MOV is black and partially melted, you have a clue... but baring that, you just don't know.
And can't really know inasmuch as there's no way to non-destructively test the thing.
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I think the issue here is that your statement that "devices in a protector do not last once hit" is misleading. It depends on what the rating for the protector is versus what it is hit by.
Case A: It's a 20K Amp whole house surge protector and it's hit by a typical surge that might occur from a lightning strike that occurs somewhere down the street. In that case the current/energy is going to probably be two orders of magnitude less than the rating of the protector. In that case, the surge protector survives, is still functional and it's capacity has minimal degradation.
Case B: It's a 20K Aamp protector and it's hit by a very close strike and it sees 50K amps. In that case it could either be blown up or as you say, have significantly reduced capacity.
And the far more common occurence for any protector is that it will likely see a lot more of the Case A type surges, because direct or near direct hits are rare. A direct hit can't even really reach the surge protector. If it hit the service near where it enters the house, typically a lot of the energy is going to go elsewhere, via arcing, leaving only part of the strike for the surge protector to deal with.

That does seem to be an inherent problem.
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snipped-for-privacy@optonline.net wrote:

Actually I said: "And, like a fuse, an MOV only works once (or at best a few times)."
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It's more like a fuse that increases in ampacity every time it reaches 25% of its ratings. Perhaps not quite as useless but caution is advised.
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On 10/7/2012 4:44 PM, snipped-for-privacy@optonline.net wrote:

So you use a larger MOV.
I showed why a plug-in protector with high ratings is not likely to fail right after your (HeyBub's) post.
I show how a service panel protector can survive very strong very near lightning strikes in another post and below.

But you don't get 50kA on the power service to your house.
An investigation, which is described somewhere in this thread, used a 100kA strike to a utility pole adjacent to the house. Only 5% of strikes are stronger, and the strike was about as close as you can get. It is the worst case that is likely. The surge current to the house was 10kA per service wire. 10kA per wire is the worst case with any probability of occurring. There is a reference to it in the IEEE surge guide.
Your 20kA protector can protect from 2 100kA strikes to the utility pole adjacent to your house. And that is with the minimum rating that you and the IEEE recommend.

Yes, exactly. There are multiple paths to earth lightning arestors on the distribution wire, and earthing at the transformer and other houses.

Not obvious what this refers to.
You can get follow-on currents in arc-type voltage limiters, where the surge initiates an arc and the normal voltage can continue the arc briefly. MOVs are not arc-type limiters.
Failing MOVs start to conduct at lower voltages and eventually conduct on normal voltage. Then they go into thermal runaway. UL listed protectors have thermal protectors to disconnect these failing MOVs.
<....>

Actually you can test them but it is quite impractical.
When MOVs fail UL requires (since 1998) they be disconnected. Decent protectors will tell you if that happens.
For plug-in protectors the IEEE surge guide explains the protected load can be connected across the MOVs, and be disconnected with them, or can be connected across the incoming wires. If connected across the MOVs the protected load is not exposed if MOVs fail. Connecting this way is one reason some manufacturers can have protected equipment warranties. Starting 2005 UL requires manufacturers notify buyers if disconnecting the MOVs does NOT disconnect the protected equipment.
With high ratings a plug-in protector is not likely to fail anyway (as covered in a post to Bub).
Also use high ratings for service panel protectors.
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On Sun, 7 Oct 2012 15:44:42 -0700 (PDT), " snipped-for-privacy@optonline.net"

What if your electric service is underground? There are still surges induced from lighning hitting trees, right? Etc?
My phone service is on poles until 400 or 500 feet from my house, where it goes underground, but I don't know where the electric does. ,
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wrote:

FPL in conjunction with the University of Central Florida determined a typical lightning strike can penetrate the ground by more than a meter. They have fulgurites (sand turned to glass) that are almost 5 meters long tho.
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In cases where the service runs mostly underground the profile for the possible lightning hits and magnitude would be substantially different I would think. If there is no utility pole and wires running down the street, no overhead service cable to the house, the targets for lightning are greatly reduced. At my house, all that is available is a transformer sitting on the ground that serves a few houses. Lightning could hit that, but it would be less likely than it hitting exposed overhead wires. And if it did, I would bet that a lot less than the 10K that Bud referenced would make it to the house via the service wires.
Lightning can of course hit the house itself. In which case, all bets are off. If it hits say the chimney, it could take various paths and there would seem to be a low probability that the surge protector at the panel would do much good. If the lightning made it's way to AC circuits in the house, the surge protector might help, but if the strike is at one end of the house, gets to circuits there, it's a long ground path back to the surge protector at the panel and hence I would not expect it to do much good.
Even a nearby lightning strike to say a tree could have effects by raising the ground potential near the house, etc. But I think realistically, the most frequent kind of surge is one that winds up coming in on the service conductors. And with underground service, IMO that is probably at least an order of magnitude less likely. At least for big surges, the kind that would make it to the house if the utility wires close to the house were hit. You could still see more modest surges that make it to the house from an exposed utility getting hit blocks away, etc.

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