surge protector - how many joules of protection does yours have?

[Turbonium]

In regards to any surge protectors used with your PC and peripherals (modems, etc.), what is the minimum joule rating you use?

I know it's probably not the only factor in choosing a surge protector, but I'm just curious...

EDIT: What is it with me and typos in polls? Sigh...

 

[Ketchup]

Here is the one I bought last fall, 3996 joules. I had my last one for over 10 years, and apparently that was too long. Lost a printer and modem connected to it in a lightning storm last year.

http://www.newegg.com/Product/Produc...1&ParentOnly=1

 

[Turbonium]

Would you say 1050 joules is too little, then? I found one with really good build quality, meant for contractors, but that's as far as the surge protection goes, unfortunately.

I have one connected to my stereo rated at around 1500 joules, and another to my modem and router at only 500 joules. Currently, my netbook is plugged right into the wall (it's double insulated, but still).

Inadequate? :|

 

[corkyg]

I don't use a surge protector - I use a UPS.

 

[westom]

Would you say 1050 joules is too little, then? I found one with really good build quality, meant for contractors, but that's as far as the surge protection goes, unfortunately.

Typically destructive surges are hundreds of thousands of joules. So what do those protectors do? Protect from a tiny surge that is typically made irrelevant by protection already inside appliances.

Those protectors also need protection. Provided by something completely different that is, unfortunately, also called a surge protector.

Effective protectors are rated by a surge current. One minimally sized 'whole house' protector (to even protect those power strips) is 50,000 amps. These come from companies known for better quality. (What a protector looks like on the outside says nothing about protection.) General Electric, ABB, Siemens, Ditek, Intermatic, Square D, Leviton, etc all provide these superior products. A Cutler-Hammer solution sold in Lowes and Home Depot for less than $50.

A protector adjacent to the appliance can only stop or absorb a surge. How does it stop what three miles of sky did not? Worry about a typically destructive surge. Surges too tiny to even harm dimmer switches and bathroom GFCIs are what those adjacent protectors are designed to protect from. Your concern is the truly destructive surge that occurs maybe once every seven years. A superior 'whole house' protector is part of a solution that also protects from those other tiny and lesser threats.

View protector numbers for a UPS. Even tinier. Near zero. UPS claims surge protection - only from near zero surges.

And finally, a protector is only a connecting device to what actually does protection. Protectors are simple science. Art is what absorbs hundreds of thousands of joules. Earth ground. Most of your attention should focus on what is most important in any protection system - earth ground.

 

[Mark R]

Meaningful surge protectors aren't rated in Joules.

They are rated in clamping current (amps) and the maximum allowable clamping time (microseconds).

A basic level protector will have a clamp current of 50 kA for 20 microseconds. This type of surge protector is typically either a MOV (for protecting high voltage lines such as power; or a gas discharge tube for protecting non-powered lines such as phone).

A top level protector capable of diverting a direct lighting strike will have a clamp current of 100 kA for 350 microseconds. Typically, these are electronically pre-triggered spark gaps.

 

[Turbonium]

Meaningful surge protectors aren't rated in Joules.

They are rated in clamping current (amps) and the maximum allowable clamping time (microseconds).

A basic level protector will have a clamp current of 50 kA for 20 microseconds. This type of surge protector is typically either a MOV (for protecting high voltage lines such as power; or a gas discharge tube for protecting non-powered lines such as phone).

A top level protector capable of diverting a direct lighting strike will have a clamp current of 100 kA for 350 microseconds. Typically, these are electronically pre-triggered spark gaps.

I assumed this to be the case, but I don't see consumer-level surge protectors advertising their reaction time (they only advertise it as a "less than 1 nanosecond" value at best, which is very general and, in my opinion at least, not specific enough - give me picoseconds kthnx). Also: is a clamp voltage of 330V decent? My research shows that consumer-level stuff doesn't get much better than that.

Also: not sure how to compare amps (i.e. kA as you stated), which I assume is current, with voltage which is the potential difference or whatnot (for purposes of clamp current/voltage). It's been a while since I took basic physics...

Basically it comes down to this, for all intents and purposes: where can I find quality surge protectors (generally speaking - I don't need specifics)? Everything I've seen so far just rates itself in joules, which is not even half the story as this thread indicates. I literally want something with super fast clamping time at 330V or equivalent, that isn't over $100.

General Electric, ABB, Siemens, Ditek, Intermatic, Square D, Leviton, etc all provide these superior products. A Cutler-Hammer solution sold in Lowes and Home Depot for less than $50.

I take it Belkin is typical consumer-grade garbage then? I hate buying garbage.

Related question: Can you theoretically daisychain a bunch of surge protectors and simply add the total joule rating to figure out how much protection you have, in terms of joules? So say you get a 1,000,000,000 joule lightning strike nearby (for example). Could you daisychain a million 1000 joule surge protectors and, in theory, protect whatever is on the end of all of that? I'm not talking realistically here, just in theory.

 

[Mark R]

Reaction time for pretty much most surge protector elements will be essentially instantaneous - measured in a few hundreds of picoseconds. (There is an exception in electronically triggered spark gaps, where there is a delay while the electronics, usually a MOV and a capacitor/transformer combo, sense the surge and ignite the spark).

Note that although the ceramic in a MOV activates within a few hundred picoseconds, the actual device will take up to 25 ns to activate, because of the inductance of the wires connecting the circuit board to the ceramic. However, this same parasitic inductance in the connecting wires will delay the rise of voltage to sensitive devices, so you don't actually need sub nanosecond response time of the entire device.

Clamp voltage is the maximum voltage that the device will permit to exist at its leads. This needs to be high enough that the device doesn't "leak" energy during normal use (MOVs are highly non-linear, but they do conduct a bit below their nominal voltage). A normal AC supply will have a peak voltage of up to 180 V, so the clamp voltage must be sufficiently far above this so as not to leak. At the same time the voltage needs to be sufficiently low that electronics are not damaged. Most mains grade semiconductors are rated for 400 V, as that is the industry standard, so anything below about 370 V should be adequate. You can go lower than this on a 120 V supply, but with a 240 V supply, you can't really go below about 370 V.

Of course, the device can only clamp the voltage at its leads. During a surge, the high current flow creates intense magnetic fields, and these can store energy and transmit energy, so predicting what the voltage will be at an actual device some distance from the protector is generally not possible (which is why any mains powered electronic device needs to have internal surge protection).

Optimum protection is often done in a tiered form; a large high current protector is connected at the service input. This will divert the biggest surges. A medium sized protector is connected at the panel, and smaller protectors are connected at individual devices/receptacles. In general, the biggest one needs to be most sensitive (i.e. have the lowest clamp voltage) so that it takes the surge in preference to the smaller ones - which just clean up the ringing and effects of the mini-EMP caused by the big surge protector diverting the main surge. In practice, the effects of parasitic inductance/capacitance in wiring are usually sufficient to ensure correct sequenecing of most combinations of protectors without the need for specific attention to clamping voltages.

One of the difficulties with consumer-grade protectors is that they often contain numerous protector elements. E.g. a typical power-strip type one will typically contain 3 elements; one between live and neutral, one between live and ground and one between neutral and ground. If each protector has an rating of 300 Joules, this is commonly marketed as 900 Joules. In practice, in almost all cases, one element will end up taking the overwhelming majority of the surge.

The conversion between the industry standard surge waveforms and dissipated energy is tricky and requires calculating the area under the curves. You can get a rough idea by multiplying clamp voltage, current and about 1/3 the time period. So for a 330 V, 25 kA, 20 us device, this works out at somewhere around 50-100 Joules. But, there's a problem. A device big enough to shunt 25 kA will by virtue of its bulk be able to absorb about 300-500 Joules before being incinerated. This rating refers to the maximum amount of surge energy within a period of time (typically 2-10 ms) where the device is exposed to multiple surges in quick succession. In reality, the biggest surges tend to be single short events in the microsecond range, so the limiting factor is the current handling capacity - going over this current rating will cause instant degradation of the device, even before the energy limit is reached.

Now, you should see why the total surge energy is not a useful rating. Not only is the energy rating not useful for individual protection elements, but in most protector designs, the surge will preferentially affect one element only within the whole device.

-------

In terms of daisy chaining, this is generally not ideal. In some circumstances, it can provide some additional protection, but the protection does not add linearly, and there are other effects, such as ground rise, etc. which can be damaging.

Due to the way MOVs work, even "matched" MOVs won't share a surge equally as even slight differences in their threshold voltage will result in large changes in current (sharing ratios of between 10:1 and 100:1 would be expected from "matched" MOVs connected together). Basically, the most sensitive one takes pretty much the whole surge. In practice, inductance/capacitance in the leads of daisy-chained protectors, etc. will improve the degree of matching.

However, daisy chaining protectors brings with it the problem of the surge changing ground voltages along the wires - so that devices plugged into different parts of the chain of protectors will see different ground voltages. If two devices connected to different strips in a daisy-chain are connected together via a signal cable (e.g. a monitor cable), some of the surge current could be forced through the signal connection and actually channel the surge into your equipment, rather than away from it. Ideally, you should have all your equipment plugged into a single surge protector or, in an industrial setting or where there is too much equipment for a single protector, each protector should have its own high quality ground connection which goes directly to a single reference point.

 

[Blain]

I have a surge arrestor and capacitor installed in my breaker box.

After enough spikes, a common "surge suppressor" becomes nothing more than a simple power strip.
What's bad about that, besides no more protection, is that the owners often don't realize the surge protection is gone.

 

[Turbonium]

...

Thanks for this great post. Very informative.

I have a surge arrestor and capacitor installed in my breaker box.

After enough spikes, a common "surge suppressor" becomes nothing more than a simple power strip.
What's bad about that, besides no more protection, is that the owners often don't realize the surge protection is gone.

Isn't that what the "surge" (or equivalent) light is for? I thought it stops being illuminated when it's no longer protected.

Not that I'm counting on it or anything...

 

[westom]

Isn't that what the "surge" (or equivalent) light is for? I thought it stops being illuminated when it's no longer protected.

A light only reports failure due to an undersized protector. A protector should never fail that way. It should only degrade, as Blain noted. Furthermore, a 50,000 amp protector means it shunts many surges to earth without degrading significantly. A sufficiently sized protector should remain functional for decades.

50,000 amps means voltage during a surge is lower. That protector also has a longer life expectancy. And its light should never indicate a failure. Should its light report a failure, a large protector (ie 100,000 amps) is recommended.

Mark R discussed wire impedance that increases with longer MOV wires. Impedance is why a protector must connect to earth as short as possible. Even sharp wire bends, splices, or wire inside metallic conduit compromises protection.

Inspect an earth ground wire (a bare copper wire about 1/4 inch) from your breaker box. Does it go up over the foundation and down to an earth ground rod? Then protection is compromised. Better protection means that ground wire goes through a foundation and down to earth ground. Lower impedance means many feet less wire. Sharp bends over the foundation eliminated. Concepts that demonstrate why a protector is only simple science. Earthing is an art.

Above discusses a 'secondary' protection layer. Also inspect your 'primary' protection layer. A picture demonstrates what defines each layer. And what should be inspected:
http://www.tvtower.com/fpl.html

Protection is always about where hundreds of thousands of joules dissipate. Destructively inside or harmlessly outside. A protector is only a connecting device to that energy sink. Each protection layer is defined by its single point earth ground - the art of surge protection. Light only reports simple science - an undersized protector.

 

[bud--]

Excellent information on surges and surge protection is at:
http://www.lightningsafety.com/nlsi_lhm/IEEE_Guide.pdf
- "How to protect your house and its contents from lightning: IEEE guide for surge protection of equipment connected to AC power and communication circuits" published by the IEEE (the IEEE is a major organization of electrical and electronic engineers).
And also:
http://www.eeel.nist.gov/817/pubs/spd-anthology/files/Surges happen!.pdf
- "NIST recommended practice guide: Surges Happen!: how to protect the appliances in your home" published by the US National Institute of Standards and Technology

The IEEE surge guide is aimed at people with some technical background.

Typically destructive surges are hundreds of thousands of joules. So what do those protectors do? Protect from a tiny surge that is typically made irrelevant by protection already inside appliances.

Nonsense.

Both the IEEE and NIST surge guides say plug-in protectors are effective.

The author of the NIST surge guide investigated how much energy might be absorbed in a MOV in a plug-in protector. Branch circuits were 10m and longer, and the surge on incoming power wires was up to 10,000A . (That is the maximum that has any reasonable probability of occurring, as below.) The maximum energy at the MOV was a surprisingly small 35 joules. In 13 of 15 cases it was 1 joule or less. (There are a couple of reasons why it is so small.)

Plug-in protectors with much higher ratings (like 1050J) are readily available. High ratings mean long life. A plug-in protector, wired correctly (see below), is very likely to protect from a very near very strong lightning strike.

Those protectors also need protection. Provided by something completely different that is, unfortunately, also called a surge protector.

More nonsense.

Effective protectors are rated by a surge current.

Surge current is equivalent to energy (joule) ratings.

In the US there is not a standard (UL) method for specifying the joule rating. As a result some manufacturers use deceptive ratings, which puts honest manufacturers at a disadvantage. Some manufacturers no longer supply joule ratings. (This is discussed in the IEEE surge guide.)

One minimally sized 'whole house' protector (to even protect those power strips) is 50,000 amps.

The author of the NIST surge guide also looked at the surge current that could come in on residential power wires. The maximum with any reasonable probability of occurring was 10,000A per wire. That is based on a 100,000A lighting strike to a utility pole adjacent to the house in typical urban overhead distribution.

Recommended ratings for service panel protectors are in the IEEE surge guide on page 18. Ratings far higher than 10,000A per wire mean the protector will have a long life.

These come from companies known for better quality. (What a protector looks like on the outside says nothing about protection.) General Electric, ABB, Siemens, Ditek, Intermatic, Square D, Leviton, etc all provide these superior products. A Cutler-Hammer solution sold in Lowes and Home Depot for less than $50.

Provide a link to a Lowes or Home Depot protector for less than $50 that has westom's minimum rating of 50,00 amps.

All these '="quality" manufacturers except SquareD make plug-in protectors and say they are effective. (Westom says plug-in protectors do not work.)

SquareD says for their "best" service panel protector "electronic equipment may need additional protection by installing plug-in [protectors] at the point of use."

Belkin and some others make good plug-in protectors.

A protector adjacent to the appliance can only stop or absorb a surge. How does it stop what three miles of sky did not?

It doesn't. Neither service panel or plug-in protectors work by "stopping" or "absorbing".

As explained in the IEEE surge guide (starting page 30) plug-in protectors work primarily by limiting the voltage from each wire to the ground at the protector. This has been explained many times for westom, but it does not fit his simple beliefs about protection and is ignored.

If using a plug-in protector all interconnected equipment needs to be connected to the same protector. All external connections, like coax also MUST go through the protector.

A superior 'whole house' protector is part of a solution that also protects from those other tiny and lesser threats.

Service panel protectors are a real good idea.
But from the NIST guide:
"Q - Will a surge protector installed at the service entrance be sufficient for the whole house?
A - There are two answers to than question: Yes for one-link appliances [electronic equipment], No for two-link appliances [equipment connected to power AND phone or cable or....]. Since most homes today have some kind of two-link appliances, the prudent answer to the question would be NO - but that does not mean that a surge protector installed at the service entrance is useless."

Service panel protectors are very likely to protect anything connected only to power wires from a very near very strong lightning strike. They may or may not protect equipment connected to both power and phone/cable/other wiring. The NIST surge guide suggests most equipment damage is from high voltage between power and signal wires. An example is in the IEEE surge guide starting page 30.

View protector numbers for a UPS. Even tinier. Near zero. UPS claims surge protection - only from near zero surges.

The type of UPS that is commonly used has no inherent surge protection. The same protection that is used in plug-in protectors is added to UPSs. High ratings are more readily available on plug-in protectors.

And finally, a protector is only a connecting device to what actually does protection. Protectors are simple science. Art is what absorbs hundreds of thousands of joules. Earth ground. Most of your attention should focus on what is most important in any protection system - earth ground.

The author of the NIST surge guide has written "the impedance of the grounding system to `true earth' is far less important than the integrity of the bonding of the various parts of the grounding system."

Worry about the length of the ground wire from cable and phone entry protectors to the common connection point on the power earthing system. An example of a entry protector ground wire that is too long is in the IEEE surge guide starting page 30.

If a strong surge is earthed, the potential of the building "ground" will rise thousands of volts above 'absolute' earth potential. Much of the protection is that all wiring rises together.