Whole home surge protection recommendations

[Jamison_IO]

I installed the Eaton one (ultra). Took me about 10 minutes.  Now to see if it helps with those damn fire alarms being when it storms!

[westom]

13 hours ago, Jamison_IO said:

I installed the Eaton one (ultra). Took me about 10 minutes.  Now to see if it helps with those damn fire alarms being when it storms!

Just to be clear.  No protector does protection. That Eaton is useful when it connects low impedance (ie less than 10 feet) to the same earth ground that also connects to the telephone 'whole house' protector, TV cable hardwire, and any other incoming wire.

Kudos for installing a product from a responsible company.  But protection is only defined by earth ground.  How to make that protection better?  Upgrade (if necessary) that earth ground and its connection.

Also inspect your 'primary' protection layer.  That also defined by an earth ground that is too often compromised.

 

 

Edited September 24, 2019 by westom

[westom]

15 hours ago, apostolakisl said:

Oh, lets see.  I suppose you could look at the original post you so authoritatively quoted me on where I respond to another use saying that "I have 3 of those" referring to the model he lists. 

So the protector you are discussing has four connections.  Because in a sub-panel, the neutral and earth ground are separate.  For this protector to be effective, it must make a low impedance connection to what harmlessly absorbs hundreds of thousands of joules.  That is always what effective protectors do.   So what part has you confused?  It does effective protection when that sub-panel makes a low impedance connection to earth ground electrode.  Does it?

[westom]

13 hours ago, larryllix said:

Some day there will be no copper conductors, other than electrical, between buildings. Fibre and RF  forever.

Some day all AC electricity will be delivered by fiber?  And Tesla generators will provide electrical power as RF energy.  Or maybe lamps and vacuum cleaners will be powered by nuclear batteries as predicted in the 1950s.

 

 

[lilyoyo1]

3 hours ago, westom said:

Some day all AC electricity will be delivered by fiber?  And Tesla generators will provide electrical power as RF energy.  Or maybe lamps and vacuum cleaners will be powered by nuclear batteries as predicted in the 1950s.

 

 

Can you just go away!!!??? You keep repeating the same thing over and over. The op had already gotten his answer, decided his path, purchased and installed the device. He's happy and can now move forward. Go troll somewhere else. 

[westom]

On 9/24/2019 at 12:42 PM, lilyoyo1 said:

Can you just go away!!!??? You keep repeating the same thing over and over. 

Reality is repeated when one keeps posting misinformation.   Zero electrical knowledge is repeatedly identified.  As demonstrated by no professional citations, no numbers, barely any electrical concepts, and only subjective statements mostly based in hearsay and justified by insults.  You do not even know what impedance is.  Somehow millimeter gaps in isolation transformers will block what three miles of sky cannot.  You did not even know that TV cable and telephone have and are required to install best protection.  Your misinformation is disingenuous.  Please stop deceiving others with repeated fallacious insults.

Eaton (like all protectors) is effective only if it makes a low impedance (ie less than 10 foot) connection to earth ground.  True today as it was over 100 years ago.   If attention does not focus on earth ground, then an Eaton will do nothing for fire alarms.  Those facts are relevant.  Discourteous slander and subjective misinformation are not.  You do not even know why plug-in protectors can even make surge damage easier if a 'whole house' solution is missing.

If you don't like it, then stop reading it and stop posting.  Or simply answer the relevant question. Where do hundreds of thousands of joules harmlessly dissipate?  Please do it, for once, without any more personal cheapshots. Please go away if you have nothing useful to contribute.

Essential to make that Eaton effective is its earth ground - the 'secondary' protection layer.  And inspection of the other ('primary') protection layer.

 

Edited September 26, 2019 by westom

[lilyoyo1]

50 minutes ago, westom said:

Reality is repeated when one keeps posting misinformation.   Zero electrical knowledge is repeatedly identified.  As demonstrated by no professional citations, no numbers, barely any electrical concepts, and only subjective statements mostly based in hearsay and justified by insults.  You do not even know what impedance is.  Somehow millimeter gaps in isolation transformers will block what three miles of sky cannot.  You did not even know that TV cable and telephone have and are required to install best protection.  Your misinformation is disingenuous.  Please stop deceiving others with repeated fallacious insults.

Eaton (like all protectors) is effective only if it makes a low impedance (ie less than 10 foot) connection to earth ground.  True today as it was over 100 years ago.   If attention does not focus on earth ground, then an Eaton will do nothing for fire alarms.  Those facts are relevant.  Discourteous slander and subjective misinformation are not.  You do not even know why plug-in protectors can even make surge damage easier if a 'whole house' solution is missing.

If you don't like it, then stop reading it and stop posting.  Or simply answer the relevant question. Where do hundreds of thousands of joules harmlessly dissipate?  Please do it, for once, without any more personal cheapshots. Please go away if you have nothing useful to contribute.

Essential to make that Eaton effective is its earth ground - the 'secondary' protection layer.  And inspection of the other ('primary') protection layer.

 

Stop repeating your copy and paste posts and go away. Así said before, the op had made his voice so everything you are saying is irrelevant. 

[MWareman]

Impedance is not defined (solely) by distance as a certain poster implies - nor has it been stated what impedance is acceptable for a correct ground able to withstand lightning level surges.

 

A 22 gauge wire at 10’ will not do what’s being claimed - but a much large gauge will work fine out to much more than 10’. The idea of anything within 10’ is OK is a false (maybe not entirely false - but certainly misleading) statement.

 

For protecting against surges - you also have to consider induced surges in wires running parallel to the path to earth. That’s not mentioned either.

 

FUD is also being added. OP asked about surge protectors. Not direct-strike lightning protection. Completely different risks. The latter is much harder (and much more expensive) to protect against. Buying insurance is likely a cheaper option for the average homeowner. For a TV Station, phone company etc - protecting against the direct strike is paramount.

 

Personally, I’ll do my own extensive research and not waste cycles on unsolicited partial information such as posted here...

[westom]

On 9/27/2019 at 5:48 PM, MWareman said:

Impedance is not defined (solely) by distance as a certain poster implies - nor has it been stated what impedance is acceptable for a correct ground able to withstand lightning level surges.

Protection from surges is protection from the many sources including linemen errors, tree rodents, stray cars, utility switching, and wind.  Lightning is simply the typical example that must not cause damage ... if using effective protection.  Effective means connected harmlessly to earth by an earth ground wire that all structures are required to have.  And that wire must be low impedance.  Meaning that wire may need to be upgraded to exceed what the National Electrical Code (NEC) requires.

Nobody said anything about 22 AWG.  AC wires (the most common source of surges) is not that tiny.  22 AWG is completely irrelevant to this entire discussion.  It is not even permitted according to the NEC.

Surge protectors are for transients that are potentially destructive.  That means lightning.  Protectors that avert lightning damage mean spending about $1 per protected appliance.  Not $25 or $100 that advertising and subjective statements promote.  Those tiny joule and expensive plug-in boxes also need lightning protection.  Using the less expensive solution provided by other companies so well known for their integrity.

Impedance is defined by many factors. Reading with greater care would have discovered examples.  Less than 10 feet. No sharp bends. Hardwire not inside metallic conduit.  No splices.  Please read before criticizing.  Every foot shorter decreases impedance; increases protection.

Some facilities that want best protection have no hardwire connection to earth ground.  A connection is made directly to the earthing electrodes - a zero foot connection to make impedance even lower.

The OP asked about surge protection.  Effective protectors come with numbers that define protection from direct lighting strikes.  No expensive plug-in protector does.  IEEE defines properly earthed 'whole house' protection as doing 99.5% to 99.9% of the protection.  Plug-in protectors should not be used if that 'whole house' solution does not exist.  Since this can happens to protectors that do not claim to protect from lightning or the other similar and destructive surges:    

 

Induced surges? Lightning struck only 30 feet from a long wire antenna.  Antennas are designed to maximize the effect of E-M fields.  So the antenna lead saw thousands of volts  Then an NE2 neon glow lamp was connected to that antenna lead.  A resulting less than 1 milliamp current caused thousands of volts to drop to maybe 60.  One is expected to learn numbers associated with induce surges rather than repeat popular and inaccurate fears.  Induced surges are made irrelevant by protection already required to be in every appliance.

In another example, a direct lightning strike hit a building's lightning rod.  So maybe 20,00 amps were flowing to earth.  Just four feet away from that lightning rod's hardwire to earth was an IBM PC.  It did not even blink.  No other office equipment suffered any interruption.  That would be a maximum induced surge.  E-M fields are only destructive when one makes assumptions without first doing research.

First indication that claims exist without first doing research?  No numbers.

Numbers expose denials as unsubstantiated urban myths.  Not justified by any research.

 

[larryllix]

Forrest Gump comes to mind.

Edited September 29, 2019 by larryllix
typo

[MWareman]

35 minutes ago, larryllix said:

Forest Gump comes to mind.

LOL. 

I had a whole response typed out - reread it - and then decided to delete it. Sometimes, some things are best left unsaid.  

[Jamison_IO]

On 9/27/2019 at 4:48 PM, MWareman said:

Personally, I’ll do my own extensive research and not waste cycles on unsolicited partial information such as posted here...

This was my intention!

 

FYI- the power went out last night. Don’t know why, it went out, but not false smoke alarms! 
 

haha

[westom]

8 hours ago, MWareman said:

 Sometimes, some things are best left unsaid.  

It is taught in elementary school science.  Moldy bread creates maggots. Therefore observation alone proves that moldy bread breeds life.

Something was harmed by lightning.  But no direct lightning strike was observed.  So observation proves that induces surges did that damage.  Both are examples of junk science; conclusions only invented by observation.  

The idea that something is damaged by induced surges means classic junk science reasoning is at play.  Basic science concepts (ie a hypothesis combined with experimental evidence) are essential to have an honest conclusion. Then induced surge myths are not posted (believed).

 Adding facts and perspective (numbers) means junk science (ie induced surges) is an urban myths. Numbers (ie using E-M Field equations) and experimental evidence both expose that myth.  Better is to remain unsaid if one does not even understand the significance of impedance (ie less than 10 feet).  And that AC electricity is not provided by 22 AWG wires.

Professionals discuss what does effective protection.  A low impedance connection to single point earth ground:   www.reddit.com/r/crtgaming/comments/7e0zmv/besides_a_surge_protector_how_else_do_you_protect/dq8qkdf/

BTW, all that is only a 'secondary' protection layer.  Nobody is asking to learn about the 'primary' protection layer.  Many want to argue rather than learn.

[MWareman]

 

Quote

BTW, all that is only a 'secondary' protection layer.  Nobody is asking to learn about the 'primary' protection layer.  Many want to argue rather than learn.

And I feel that this is the issue here. You have sent this thread well away from what the OP asked about. Keeping threads on-topic is what will help OPs learn. Trying to 'bludgeon' others to learn beyond what they are asking about by taking a thread on a tangent is not the best way to approach this.

If you feel you have something to share about primary lightning protection (and it's clear you do - though I wouldn't rely on links to posts Reddit that you authored yourself)  - may I suggest you start your own thread about it. I'm sure there is a lot we can agree on with regards to primary lightning protection. This is a subject of value to this community - it deserves it's own thread.  

[westom]

22 hours ago, MWareman said:

You have sent this thread well away from what the OP asked about. Keeping threads on-topic is what will help OPs learn. Trying to 'bludgeon' others to learn beyond what they are asking about by taking a thread on a tangent is not the best way to approach this.

You can argue only to argue.  Or admit that is exactly what the OP asked.  He posted:

Quote

I think it’s a result of stray voltage during the storms and I’m hoping the surge protector will be able to help that. 

So what type of surge protectors do you have in your homes?

That is the topic. Protection from storms.  Recommendations that will help or that are exposed as only making things worse.  And how a best solution can fail if not properly installed (ie impedance).  What have you posted?  Denials.  And not one honest fact. This thread ended until you posted fables and technical lies that contradict over 100 years of well proven science.  Somehow that is relevant to what the OP asked?

You even deny what virtually every professional organization says.  I did not write that stuff.  Professionals do.  Denied so as to not apologize for posting misinformation.  For some unknown reason, you believe that AC electric wires are 22 AWG.  And did not even know why profit center protectors create fires.

Quote

So what type of surge protectors do you have in your homes?

 Please limit your answers to what the OP asked; without including your feelings.  Somehow a ground wire is 5 times thinner than what the NEC requires?  Even the classic lie about induces surges (that is off topic) was posted.

This discussion ended had you not posted misinformation.  Induces surges being a classic example of off topic as well a mythical fabrication.  You do not even apologized for that 22 AWG mistake - only argue - and have yet to answer what the OP asked:

Quote

I think it’s a result of stray voltage during the storms and I’m hoping the surge protector will be able to help that.

 

Edited September 30, 2019 by westom

[larryllix]

You're on the chopping block. Just keep it up.

[lilyoyo1]

44 minutes ago, westom said:

You can argue only to argue.  Or admit that is exactly what the OP asked.  He posted:

That is the topic. Protection from storms.  Recommendations that will help or that are exposed as only making things worse.  And how a best solution can fail if not properly installed (ie impedance).  What have you posted?  Denials.  And not one honest fact. This thread ended until you posted fables and technical lies that contradict over 100 years of well proven science.  Somehow that is relevant to what the OP asked?

You even deny what virtually every professional organization says.  I did not write that stuff.  Professionals do.  Denied so as to not apologize for posting misinformation.  For some unknown reason, you believe that AC electric wires are 22 AWG.  And did not even know why profit center protectors create fires.

 Please limit your answers to what the OP asked; without including your feelings.  Somehow a ground wire is 5 times thinner than what the NEC requires?  Even the classic lie about induces surges (that is off topic) was posted.

This discussion ended had you not posted misinformation.  Induces surges being a classic example of off topic as well a mythical fabrication.  You do not even apologized for that 22 AWG mistake - only argue - and have yet to answer what the OP asked:

 

The OP says he THINKS which means he assumes. He could be wrong. It could be from devices within the home as we as other stuff. At the end of the day he bought a 100 dollar item which can help his home but doesn't hurt. It would cost more than the 90 bucks the Eaton costs just to get an electrician to take a look at his grounding which may or may not be an issue. 

[Jamison_IO]

1 hour ago, lilyoyo1 said:

The OP says he THINKS which means he assumes. He could be wrong. It could be from devices within the home as we as other stuff. At the end of the day he bought a 100 dollar item which can help his home but doesn't hurt. It would cost more than the 90 bucks the Eaton costs just to get an electrician to take a look at his grounding which may or may not be an issue. 

I could definitely be wrong.  <-- see how easy that is guys??

 

 

[apostolakisl]

First off, I say, when all else fails, read the directions.  So, I followed them as per my earlier posting.  My house is 12 years old and was wired by qualified electricians, so I will take the leap of faith that it will work as spec'd.

Second, there is no way in the world that 12g wire and a 20amp breaker (which is what the instructions call for on the surge protector I installed) are going to shunt thousands of amps anywhere.  Those items would simply explode in a cloud of vaporized copper and plastic.

My take, electric destruction occurs because of current, after all, electricity is current, otherwise it is just electrons.  Electrons move in the presence of potential differences between point a and point b when a conductor sits between.  Voltage is all about your reference point.  Perhaps at its most fundamental level, voltage could be measured relative to having equal number of protons and electrons, but who can measure that?  And that serves no point anyway, since we are looking to define electricity and electricity is all about the potential difference and its affect on current.  Anyway, make point a and point b equal, there will be no flow, there will be no harm.  My suspicion, is that protection is achieved by allowing neutrals and grounds to rise in potential to meet the rise in potential on the line.  All 3 could rise to a million volts and you wouldn't even know it provided the rise on all 3 happened in unison and then dropped off  in unison.  So in short, I believe this is about charging everything equally, to prevent current, not re-directing current.  

Looking at it a different way.  The wire that is theoretically bringing in the surge is very fat, 2-0 I think on my sub-panels.  That wire can handle vastly more amps as compared to the 12g wire that the surge protector uses.  So the surge suppressor can not possibly protecting by outflowing the amps that might come in my service wire.  Tell me how it could be otherwise?

[MWareman]

4 hours ago, westom said:

 For some unknown reason, you believe that AC electric wires are 22 AWG.  And did not even know why profit center protectors create fires.

Just more FUD and non-truth. This was NOT stated at all. Please cease from making such statement without any basis in truth. to remind you what I actually posted:

On 9/27/2019 at 4:48 PM, MWareman said:

A 22 gauge wire at 10’ will not do what’s being claimed - but a much large gauge will work fine out to much more than 10’. The idea of anything within 10’ is OK is a false (maybe not entirely false - but certainly misleading) statement.

This was a ridiculous small gauge of wire stated as an example of a connection less than the 10' which passed your stated directive (many time) of "less than 10 feet" without providing any guidance yourself on gauges acceptable. Witness:

On 9/24/2019 at 8:13 AM, westom said:

That Eaton is useful when it connects low impedance (ie less than 10 feet) to the same earth ground that also connects to the telephone 'whole house' protector, TV cable hardwire, and any other incoming wire.

Another example where you imply that only length has any implication for impedance. Another lie:

On 9/29/2019 at 7:14 AM, westom said:

Numbers (ie using E-M Field equations) and experimental evidence both expose that myth.  Better is to remain unsaid if one does not even understand the significance of impedance (ie less than 10 feet). 

Yet another - this time a true statement - again omitting the need to ensure wire gauge is large enough:

On 9/28/2019 at 9:27 PM, westom said:

Less than 10 feet. No sharp bends. Hardwire not inside metallic conduit.  No splices.  Please read before criticizing.  Every foot shorter decreases impedance; increases protection.

The first example where you claim that as long as it's less than 10 feet - the connection is fine:

On 9/18/2019 at 8:02 PM, westom said:

Instead, effective when connected low impedance (ie less than 10 feet) to the same item that made Ben Franklin's lightning rods so effective.

You then go on to suggest that gauge of wire has no effect on final impedance by claiming it's irrelevant to the discussion. It is not.  you you rightly state - the NEC has a lot to say about minimum wire gauges for this purpose - yet you have repeatedly only posted the 10' distance figure with zero advise on wire gauge - something that's very dangerous to do to a non-professional electrician who may well just visit the local home depot and buy the cheapest wire found thinking is satisfies the need.

On 9/28/2019 at 9:27 PM, westom said:

22 AWG is completely irrelevant to this entire discussion. 

To assert my point clearly.

Length absolutely affects impedance (shorter wire = lower impedance for a given wire gauge). However - so does wire gauge (smaller AWG number = bigger wire = lower impedance for a given wire length). The two are related. 10' max for this purpose is sound advise for sure. but you need to also specify a minimum gauge as well. 

[MWareman]

1 hour ago, apostolakisl said:

Second, there is no way in the world that 12g wire and a 20amp breaker (which is what the instructions call for on the surge protector I installed) are going to shunt thousands of amps anywhere.  Those items would simply explode in a cloud of vaporized copper and plastic.

Well - physics says that wires will melt when the high current causes the conductor to heat - melting the insulator (possibly causing a short, spark and possible fire) and (ultimately) the conductor itself (causing a break).

This takes time. The material in the wire cannot heat instantly.

Fortunately, surges from most events like lightning are just too darn quick to allow such heating to generally occur. I suspect that the rated wire used in this example can in fact handle this - especially since it's the manufacturer that stated so.

[apostolakisl]

35 minutes ago, MWareman said:

Well - physics says that wires will melt when the high current causes the conductor to heat - melting the insulator (possibly causing a short, spark and possible fire) and (ultimately) the conductor itself (causing a break).

This takes time. The material in the wire cannot heat instantly.

Fortunately, surges from most events like lightning are just too darn quick to allow such heating to generally occur. I suspect that the rated wire used in this example can in fact handle this - especially since it's the manufacturer that stated so.

I won't argue with this.  I guess what it comes down to is the actual current and the actual time.  But, no doubt, you can flash vaporize a metal really stinking fast with enough juice.  Ever hammered a nail through a wire?  The nail vaporizes faster than the circuit breaker can pop.  I once had a failed AC compressor vaporize a 12 gauge wire (3 phase unit).  Though I have no idea how long it took.  Fortunately it didn't set the building on fire because the wire in question was in an outdoor conduit about 20 feet from the unit.  We had a discussion after finding the fried wire as to what the odds were that there would be more damage elsewhere and if we should run an entire new wire from the panel.  In the end, we decided not to run a new wire but rather just the section from the j-box at the building entrance to the unit.  3 years later, all is oK. 

It may also be that voltage spikes aren't accompanied by current capacity.  So once you give a path to ground, the voltage may drop precipitously when there isn't any available current to keep the voltage up.  A static electricity discharge.

[westom]

3 hours ago, apostolakisl said:

I won't argue with this.  I guess what it comes down to is the actual current and the actual time. 

Numbers define all this.  Accurately noted is that the parameter called time must also be included.

An 18 AWG (lamp cord) wire will conduct a surge current that exceeds 50,000 amps.  That same wire is rated to safely conduct 10 amps constantly.

A 20 amp (12 AWG wire) is sized to conduct 21 100 watt incandescent bulbs simultaneously.  If all bulbs power on at the same time, it must and does conduct 150 amps during a power on period - safely.  Just one of many reasons why 20 amp circuits use wire so thick.

OTA TV antennas must be earthed by a 6 AWG hardwire.  That means it should be able to conduct something around 200,000 amps during a surge.  Obviously it need not since a 100,000 amp surge is quite rare; most surges are only 20,000 amps.

Numbers that another should learn before posting denials, myths, and lies. 

National Electrical Code is only about protecting human life.  It says nothing about protecting appliances.  For example, a ground hardwire from breaker box can go over a foundation and down to an earthing electrode.  That provides human safety as defined by the NEC.  And it compromises protection.  That wire would be too long.  It is probably bundled with other non-grounding wires.  Those sharp bends over the foundation further increase impedance.

To upgrade for appliance protection means a hardwire goes through a foundation and down to electrodes.  Many feet shorter decreases impedance; increases protection.  Eliminating sharp bends decreases impedance.   Electricians are only taught what must connect to what to provide human protection.  Appliance protection means an electrician must also exceed what code requires.  But many electricians are never taught these electrical principles.  Are only taught and required to know what code demands.

Code does not require any protection on AC mains (in the breaker box or meter pan).

Effective protectors are rated at least 50,000 amps.  Since a protector must not fail even after many to direct lightning strikes.  That means a connection to earth ground must be low impedance (ie less than 10 feet, no splices,  not inside metallic conduit,etc - as was repeatedly stated previously).  And, of course, it cannot be 22 AWG.  That protector's wire to conduct 50,000 amps is typically a 12 AWG wire.

Wire gauge is irrelevant to this topic. Because all wires are already thick enough.  As stated so many times previously, impedance is about wire length, sharp bends, and other parameters.  The most critical item that requires a homeowner's attention is a single point earth ground.  Since that (not a protector) and the connection to it defines protection during each surge.

A final point. Voltage is not the relevant parameter.  Surges are a current source.  That means that current will flow no matter what.  Voltage exists when something foolishly tries to 'block' or 'absorb' a surge - such as a plug-in protector. Voltage increases as necessary so that the current will flow.  Or when wire impedance is high due to being too long, sharp bends, splices, etc.

A 'whole house' protector connected less than 10 feet to better earthing electrodes means that current (ie 20,000 amps) creates a tiny voltage.  Sharp bends, a wire too long, etc create increased voltages; decreased protection.  Effective protection is about the current and associated conductor impedance.  Informed consumers worry about that less than 10 foot hardwire connection.  And the quality of earthing electrodes.

As noted previously, if the OP has further problems, then an investigation looks for the human mistake.  That starts here with inspection of earthing electrodes and associated low impedance (ie less than 10 foot) connections.

 

Edited September 30, 2019 by westom

[larryllix]

While your explanations are much better and less "preachy" this time, I have to  agree with most of what you last posted.

However, the Leviton Whole House Surge Protector does not have a discharge circuit to ground as it utilizes the Faraday principle, not involving or requiring any discharge to ground. As @apostolakisl  posted previously, It is the Faraday cage principle that is important for equipment and humans. If ground is included  and connected into the "cage circuit", it can cause the transient damage to be  more or less. In my lightning induction case, grounding  made the damage worse and damaged  my equipment inputs.

https://www.amazon.com/gp/product/B00081K55Q/ref=as_li_tl?ie=UTF8&camp=1789&creative=390957&creativeASIN=B00081K55Q&linkCode=as2&tag=stejenblo-20&linkId=QG5BWIFQ3UOVTTBG

Edited October 1, 2019 by larryllix

[apostolakisl]

Like I said earlier, I have 3 of the leviton branch panel devices.  With this thread, I found myself at leviton's website where they discussed the "best" protection as also including a main panel protector in addition to subpanel units (plus point of use devices).  I think I may go ahead and do that.   It appears I need two of them since my main power feed from the meter splits to two panels, a 150 and a 200 amp.  The main panel leviton model is considerably less expensive than the sub-panel model. I presume this is because it  works by shunting to ground as opposed to whatever more complicated way it deals with surges at the sub-panel.