# Is your metal chimney grounded ?



## planman (Sep 2, 2013)

Hi all, been wondering if the ground wire attached to the blowers in my Inglenook Zero Clearance Fireplace is enough of a ground. Im in North East PA (poconos) at an elevation of about 1800 ft. Just wondering how many of you installed a separate ground wire from the top of chimney to the house ground wire ?????


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## brenndatomu (Sep 3, 2013)

I asked the same question here last year, I didn't get much of an answer really. Sounds like most people don't worry about it. I don't know if there are building codes on this in some places?


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## planman (Sep 3, 2013)

Thanks, my inglenook ZC fireplace is grounded through the blowers, but since I have an open floor plan and often am standing between the fireplace and the sink I thought may be a good idea to attach an additional grounding wire from the top of the chimney down the outside of my house to the grounding rod. I dont want to be cooking one day and have a lightning bolt come trough the kitchen.


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## jhoff310 (Sep 3, 2013)

this question got the best of my curiosity. I called a contactor friend of mine and my insurance co and asked if a metal chimney needed to be grounded. They both said they have never heard of a building code requiring a ground wire. My insurance co. said if it was installed per the directions there would be no need for it unless the directions called for it. He reminded me "thats why you pay insurance...incase something happens.

With that being said.. I grew up with wood heat. We never had a ground wire on our metal chimney and never had a problem. I cant say if it will do any good or not. I personally think the ground wire on your plug would be sufficient.

Jeff


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## planman (Sep 3, 2013)

Thanks, Jeff. I did my own install. Im an accountant but after getting price quotes from the local "pros" I was looking at 11K to save 3K a year in oil. I decided to read the directions, which were great, but they did not indicate a separate ground was necessary. That being said Lighting hit a tree next to my house recently and it got me thinking now that I have 3ft of SS pipe with a helmut on it up there.


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## brenndatomu (Sep 3, 2013)

I started thinking about this topic after I put my SS liner in. There had been lightning rods on my roof and chimney until I had a new roof put on, they were removed then and not re installed due to being in questionable condition. Later on I put in the chimney liner and it occurred to me that now the tallest part of my house is stainless steel instead of brick and clay, that means I have a 8" lightning conduit strait into my basement! Which by the way, is connected to my metal furnace, which is connected to my metal duct work (which runs all over the house) and my electrical wiring system. Now, the electrical wiring is grounded to a ground rod or two (and the well casing too) so I guess in a round about way, the chimney is grounded. 
I'd say if the chimney ever took a direct lightning hit, it would likely take out plenty of my electrical/mechanical systems no matter if the chimney is _directly_ grounded or not. In the end, the people in the know on these things don't seem to be too concerned, so I guess I decided for as for me and mine, I'm not gonna worry about it either.


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## dwasifar (Sep 3, 2013)

Yes, it's grounded. I caught it smoking.


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## Whitespider (Sep 3, 2013)

Anything metal, that is outside your home, and connected to something inside your home should be _properly_ "grounded", regardless of its height/location... but I don't know of any code forcing you to do so. The only "grounding" codes I'm aware of are those pertaining to the electrical service panel.
But be aware, if “grounding” is done improperly it has the potential to do more damage than no “grounding”. Grounding to conduit, duct work, plumbing and whatnot is not correct, it is not the same as connecting to the service panel ground... it has the potential to create separate ground paths or planes and can be extremely dangerous (more about that in a minute).
And funny thing about lightning and grounding protection… it don’t always follow the “rules”.

For example, once we had lightning strike a metal grain leg on top of a concrete silo at a large farm cooperative. We had four point-to-point data radios/antennas mounted on the outer walls of the concrete head house. When first installed, all four were grounded to the metal electrical conduit (which, in this case is OK because its an outdoor concrete structure and the conduit was outside, putting the radios on the same ground plane as the electrical service ground). At some point one of the radios failed and had been replaced; the guy who did the replacement forgot to hook up the ground (might have been me?). Anyway, of the four, only the non-grounded radio survived… the other three were completely destroyed.

We have radio equipment installed on hundreds of different towers, grain legs, and other structures spread-out over five states… some of them several hundred feet in the air. Most of those structures have never been struck by lightning (at least, not hard enough to damage the equipment)... yet there are a few that get hit once or twice every single year without fail. And I don’t mean just a little hit… they get hit hard enough to totally wipe-out all the radio equipment, take out all the electrical service and even get to any sensitive electronics in surrounding buildings. Heck, one grain leg just thirty miles from here got hit six friggin’ times in just one spring/summer season!!! We built a tower for farm cooperative in Illinois a few years ago, just two years later they had us come take it down… because lightening had struck it eight times in those two years, wiping-out all the office computers every time!!! So much for the old saying, “_Lightening never strikes in the same place twice._”

Living out in the sticks I was forced to use a dial-up internet connection for years and lost three computers in that time from lightening strikes (well, assuming lightening). All three times it came in on the phone line, taking out the computer, phones, and anything else connected to the phone line (like the satellite TV tuner)… once it even blew some of the modular connector boxes clean off the walls!! But I’ve never once had my TV antenna tower get touched… it’s likely the tallest thing for a mile radius at least, the damn phone line is underground!!

OK, the proper way to ground a vertical steel structure, such as a metal chimney entering your home. You need two _[copper_ ground wires, 6 gauge minimum… one should be connected above the roof near the top, the other should be connect inside the home close to the stove. Both wires need to be connected to the electrical service panel earth grounding wire… either inside by the panel, or outside where it enters the earth. This puts everything in the home on the same ground plane… two separate ground planes can actually cause the “zap” to travel all through the house as it heads for the “other” ground, or even go out on one and back in on the other. In the case of a “strike” the top ground wire should route most of the “zap”, the bottom wire routes any left-over or transient charge. But a more common cause of (so called) “lightening strike” damage isn't caused by an actual “strike”, and this is where the two ground wires are most important. During storms the wind and rain cause friction in the air and on the structure causing a static charge build-up… and as well, lightening in the vicinity can add to this “build-up”. At some point this charge can become large enough that it starts looking for somewhere to go. If it goes down the spout the lower wire will route it away from you and your “stuff”, if it heads up the spout you need a wire there to route it to earth or it can actually attract a full-fledged massive direct-hit lightening “strike” (like the ones that turn trees into tooth picks)… and in the case of a full-fledged “direct-hit” there ain’t enough grounding wire on the planet that can protect you and your "stuff".


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## jwilly (Sep 3, 2013)

How many people have their metal roofs bonded to the electrical ground?


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## philoshop (Sep 3, 2013)

We need some qualified electricians to jump in here before someone gets hurt. Please.
I do a lot of electrical work and have done so safely for many years, but have very limited knowledge when it comes directly to lightning protection. That being said...
There is a huge difference between 'grounding' and 'bonding to ground'. The electrical service panel in your house is 'grounded' via the rods pounded into the earth by the installer. Your receptacles are 'bonded' to that ground
so that you may safely use them. Trying to separately 'ground' something in or around your house is definitely a bad idea unless you know what you're doing.
If you're truly concerned about your chimney taking a lightning strike, you should contact someone who is knowledgeable about lightning protection and the proper procedures therein. 
Be safe,
Philo

Thanks Jwilly for mentioning bonding, as opposed to grounding.


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## chadihman (Sep 3, 2013)

Wouldn't a good ground attract a lightning bolt? I'm not sure of this but it seems if you ground it your asking for trouble. Your small ground wire will probably do nothing but glow or blow if your pipe gets struck. I stay clear of the wood stove in a storm just to be safe.


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## MrWhoopee (Sep 4, 2013)

Whitespider said:


> Living out in the sticks I was forced to use a dial-up internet connection for years and lost three computers in that time from lightening strikes (well, assuming lightening). All three times it came in on the phone line, taking out the computer, phones, and anything else connected to the phone line (like the satellite TV tuner)… once it even blew some of the modular connector boxes clean off the walls!! But I’ve never once had my TV antenna tower get touched… it’s likely the tallest thing for a mile radius at least, the damn phone line is underground!!.


 
I have seen the same. Living in the mountains, lightning strikes are not uncommon. I have seen several cases where a nearby lightning strike would apparently come in thru the phone line, fry the phones, the DSL modem, the ethernet adapter and, in one case, the motherboard of the computer. On a couple of machines, the damage ended at the ethernet adapter. Strange.


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## Whitespider (Sep 4, 2013)

chadihman said:


> *Wouldn't a good ground attract a lightning bolt? I'm not sure of this but it seems if you ground it your asking for trouble.*



No... it won't "attract" lightening.
There are two types of cloud-to-earth or earth-to-cloud lightening, negative and positive.

Negative lightening is the most common, it is actually the transfer of electrons from something on earth (like your chimney) to the clouds. Those electrons are the result of a static charge build-up... the ground wire(s) provide a path-to-ground for that charge before it becomes strong enough to make the "jump" into the clouds and "zap" you or your "stuff" in the process.

Positive lightening is the rarer and much more destructive type, it travels from the clouds to earth. Positive lightening blows things to smithereens, turns trees into toothpicks, takes out power grids for hours or days, starts fires and whatnot. Positive lightening is attracted to something containing a large negative charge (remember your grade school lessons, opposites attract). If you metal chimney is properly grounded it won't likely become negatively charged by static process, and therefore won't likely "attract" the rare, but highly destructive cloud-to-earth positive lightening.

Remember, in my previous post, I said lightening and grounding protection don't always follow the rules... properly grounding your chimney (or whatever) doesn't make you 100% immune to lightening, but it will greatly reduce the likelihood of a negative strike, and it will greatly reduce the severity if it does happen because there's less negative charge for it to work with (or should be less)... often reduce it enough that you won't even be aware it did happen. It nearly (I said nearly) eliminates the likelihood of a positive strike (which is already rarer)... but it can't do much to protect you from the resulting damage if it does happen.


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## Whitespider (Sep 4, 2013)

jwilly said:


> How many people have their metal roofs bonded to the electrical ground?



Your metal roof is not, or should not be directly connected to anything inside your home... much like lightening rods installed on your roof. Anything metal protruding through the roof should be insulated via a non-conductive (rubber) boot. A metal chimney, on the other hand, is connected to some sort appliance _inside_ your home... and may even have some sort of electrical service connected to it (such as a blower). You are talking about two separate things.


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## Whitespider (Sep 4, 2013)

philoshop said:


> *We need some qualified electricians to jump in here before someone gets hurt...
> There is a huge difference between 'grounding' and 'bonding to ground'. The electrical service panel in your house is 'grounded'... Your receptacles are 'bonded' to that ground so that you may safely use them...
> ...you should contact someone who is knowledgeable about lightning protection...*



Why would you ask an electrician about lightening protection for a metal chimney??
My home is over 100-years old... not one single outlet is "bonded" to ground, and we've "safely" used them for over 20 years. There isn't any third "ground" wire running to anything in my home unless I've personally installed the line myself since moving here.

Sometime when you're feeling frisky try this experiment...

Disconnect the "bonded" ground wire from the neutral bar in your service panel.
Next, turn off one of the breakers, disconnect the line running from it and connect a jumper from the breaker to the "bonded" ground wire.
Now turn on the breaker. Guess what? It won't snap into "open" state... heck, it won't even "pop" a 10-amp fuse!!!
What do you think would happen if you now touched that jumper wire with one hand and touched the neutral bar with the other hand??? Even though that jumper wire is directly "bonded" to ground, you're still gonna' get the-shock-of-your-life (until the breaker snaps to open state).

That "bonded" ground outlet doesn't offer you the "safety" you think it does unless a "ground fault interrupter" outlet is installed... which is a common misconception. It does serve a purpose, but not what you're thinking (another topic, for another thread). By-the-way, a "ground fault interrupter" outlet will work without the third "ground" wire if installed properly and offers more protection than the third "ground" wire ever could.


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## Deprime (Sep 5, 2013)

First off I will say that I am not an electrical engineer (my degree is in mechanical engineering) but I am an amateur radio operator and have thoroughly researched grounding for the purpose of lightning protection so I will throw my 2 cents into the discussion.

Just make sure any ground wires meant to provide a path to earth ground for the purpose of direct strike lightning protection are ran outside of your house. A few sources stated that 6ga wire is the minimum gauge wire to be used but most recommended 4ga or larger. I went with 4ga myself. Make sure that there are no tight radius bends in the wire when it is routed down the roof and over the side. Any sharp bends will greatly increase the chance that the wire will blow out before the energy of the lightning strike has been fully disapated into the ground. (The tight bends increase the resistance in the wire when large amounts of current are moving through and with a lightning strike we are talking about moving a lot of power in just a few milliseconds)

The ground wire should be connected to it's own copper clad ground rod which is 12ft or more away from the service ground. Two ground clamps should be utilized on this ground to increase the contact surface area between the rod and the wire. The ground rod should also be bonded to the service ground with a recommended 4ga solid copper wire to prevent differences in electrical potential between the two.

This is how I set up my antenna which is mounted on a tripod on the peak of my roof. It protrudes about 14 ft above the roof peak and is grounded just as described above.


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## Whitespider (Sep 5, 2013)

*Deprime*,
The reason for the separate ground rod and then bonding it to the service ground is to reduce the “resistance to ground”… that’s also the reason for it to be some distance from the service ground, to increase the dissipation area. The National Electrical Code specifies “_not more than 25 ohms of resistance_” to earth ground… which is too high for most sensitive radio equipment antenna connections, but more than sufficient for a chimney. It wouldn’t hurt anything to install an additional ground rod for a chimney… but as you state, it *must* be bonded to the service ground.

This isn't about lightening, but for reference, if the exact resistance to ground is known you can determine how many amps the service ground will draw if a ground fault happens in your electrical system.
Volts/Resistance = Amps
So if we figure a 120 volt ground fault to a 20 ohm earth ground (likely a generous number for most homes)…
120/20 = 6 amps
That’s why a direct short-to-ground at your outlet won’t pop the 15/20 amp breaker or fuse… you would need something less than 6 ohms to pop a 20 amp fuse/breaker. Unless you’re very, very lucky and live were the soil conditions are perfect (yeah, where is that?)… you’d need to drive a 150 foot ground rod into the water table to achieve that sort of low resistance.

addendum; I should clarify... a direct short to ground at your outlet will pop the breaker as long as the service neutral is intact, because the "third" ground wire at the outlet is bonded to the neutral bar along with the ground at the service panel (i.e. you would have 0 ohms resistance). But... the main purpose of the _combination_ of service ground/third ground wire at the outlet is to route voltage in the unlikely (double) event the service neutral becomes disconnected and a short to ground occurs (well, that and lightening).


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## steved (Sep 5, 2013)

Whitespider said:


> Why would you ask an electrician about lightening protection for a metal chimney??





Because they have to follow the national electric code (NEC), which actually has a section on bonding and grounding for lightning protection. 

If I remember correctly, my 2005 or 2008 copy of the NEC states that all that is needed for an antenna (like a satellite dish) is a 14 gauge (stranded?) ground wire ran from the antenna to an electrical ground. As someone noted, its not to protect from a direct hit, but to bleed off any static electricity that could potentially build up and attract a strike. If you look at the coax cable used to hook up a satellite dish, it likely has the ground wire as part of it.

While an antenna and a stove are not exactly the same, it can be applied to things like this. Its better than nothing at all. In my case, my chimney is grounded because I have an electric blower, and the entire stove and chimney are grounded via the blower to the electric panel.


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## Whitespider (Sep 5, 2013)

steved said:


> *Because they have to follow the national electric code (NEC), which actually has a section on bonding and grounding for lightning protection.
> If I remember correctly, my 2005 or 2008 copy of the NEC states that all that is needed for an antenna (like a satellite dish) is a 14 gauge (stranded?) ground wire ran from the antenna to an electrical ground.*



Not quite... they have to follow local code, which may, or may not, be portions of, or entirely the NEC (likely it is, or even more specific). In any event, electricians are not the only people who must adhere to those codes (or portions of them). Typically, electricians do not install chimneys or radio and communications equipment like satellite dishes (but I install communication towers, antennas and equipment, and I am required to follow code when doing so). Yeah, 14 gauge stranded may be specified in the NEC handbook, but if manufacturer installation instructions specify something greater... _code_ requires I follow manufacturer installation instructions.

Also, specific grounding requirements for communications equipment can not be applied, or compared to any other thing... including metal chimneys.
If you read carefully in the NEC manual you'll find this...


> *Chapter 8 - Communications Systems*
> Chapter 8 is not subject to the requirements of of Chapters 1 through 7 (which, by-the-way, is the whole rest of the code) except where the requirements are specifically referenced in Chapter 8.


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## philoshop (Sep 5, 2013)

Whitespider you are, as usual, correct.
In my earlier post, my concern was that someone without any experience with lightning protection might try a DIY solution to a problem that may or may not exist, and in the process create a potentially hazardous condition.
My recommendation to consult an electrician with the proper experience was given to hopefully help someone avoid that situation.
Best regards,
Philo


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## Whitespider (Sep 5, 2013)

And, *philoshop*, your concerns were well founded.
Improper, DIY grounding solutions will in fact likely “_create a potentially hazardous condition_” and likely increase the resulting damage from a lightning strike or some sort of electrical fault.
If you’re lucky, they may simply be wholly ineffective… if you’re lucky.


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## CWME (Sep 5, 2013)

I have nothing productive to add to the conversation other than to say this is a very interesting thread.


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## bayard (Sep 5, 2013)

*doing it wrong*

you might be on to something, about grounding it wrong. lightning has hit around my house many times.i mean very close.trees 20 feet away the backyard etc.now my metal boiler pipe is the highest point on the roof .we have never had a house strike? so maybe leave it be.k


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## Deprime (Sep 5, 2013)

Just to clarify, my previous post was just in relation to protection for the structure (i.e. house) from direct strikes. Some of the other grounding that has been discussed provides for dissipation of induced currents. For safety sake, I wanted to make sure that no one was running ground wires through the structure of their home for the sole purpose of direct strike lightning protection. The idea of that is to keep the energy created from a direct strike outside of the structure so as to prevent your house from catching on fire. Consequently, this also provides for dissipation of induced voltages as well.



Whitespider said:


> *Deprime*,
> The reason for the separate ground rod and then bonding it to the service ground is to reduce the “resistance to ground”… that’s also the reason for it to be some distance from the service ground, to increase the dissipation area. The National Electrical Code specifies “_not more than 25 ohms of resistance_” to earth ground… which is too high for most sensitive radio equipment antenna connections, but more than sufficient for a chimney. It wouldn’t hurt anything to install an additional ground rod for a chimney… but as you state, it *must* be bonded to the service ground.



You are correct in that a lower resistance to ground is required for protection of sensitive electronics. Most HF setups utilize ground radials to decrease this resistance. My current setup is VHF/UHF and I have not provided a high level of protection for the equipment. My setup is just for the protection of the structure in the event of a strike since I have a 14ft metal pole sticking up on the top of my roof.

Side Note: I know someone who has received a good jolt after coming into contact with two separate grounding circuits (connected to two separate ground rods) that were not bonded to each other. This was due to the difference in electrical potential between the two circuits. Make sure everything is bonded to each other in any grounding circuits as Whitespider has stated!


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## Whitespider (Sep 5, 2013)

Deprime said:


> *Side Note: I know someone who has received a good jolt after coming into contact with two separate grounding circuits (connected to two separate ground rods) that were not bonded to each other.*



LOL
That ain't the first time that's happened... and a perfect illustration of what can happen when improper, DIY grounding solutions are used. Your friend (I'm assuming friend) is lucky it was just a jolt, it could have been much worse. Another common one is using the water pipes as a ground for something such as the phone line... and then they get a cordless system that requires the base to be plugged into a 120v outlet... and then every time the phone rings and their hand is on a water faucet they receive a discomforting tickle... LOL


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## Whitespider (Sep 6, 2013)

bayard said:


> *...now my metal boiler pipe is the highest point on the roof...*


Are we talking a wood boiler, or some other "in-building" boiler??

Lightning protection for in-building boilers and boiler stacks may be... well... tricky when it comes to lightning protection. Typically a boiler has some sort of sensitive electronics critical to operation... and a malfunctioning boiler can be darn dangerous, not only to you and your home, but the whole neighborhood. I won't even pretend that I know what is correct, but I have seen lightning protection on boilers and boiler stacks. I suspect that basic grounding wouldn't be enough (and may even be dangerous??), more likely a protection system employing surge/lightning suppressors/arresters would be appropriate... but, again, I do not know. If you did decide to do something I would, in this case, definitely recommend you consult an electrician, maybe even the boiler/boiler electronics manufacturer, and possibly check local code and your insurance company. You may even find out that surge/lightning protection was installed with the boiler, or included in its design and installation.




Deprime said:


> *You are correct in that a lower resistance to ground is required for protection of sensitive electronics. ... My setup is just for the protection of the structure in the event of a strike since I have a 14ft metal pole sticking up on the top of my roof.*


Even so, you did lower resistance to earth ground with the additional ground point (rod). You can look at each ground point as a separate resistor (as long as they are enough distance apart), and whenever you have two or more resistors in parallel (bonding them together makes them parallel) total resistance will be something less than the value of the lowest single resistor. The formula for that looks like this...
r = 1/[(1/r1)+(1/r2)]
So, for example, if your service ground was 20 ohms, and your additional ground rod has, say 40 ohms resistance...

r = 1/[(1/20)+(1/40)]
r = 1/(.05+.025)
r = 1/.075
r = 13.33 ohms of earth ground resistance
Of course we have no idea what the resistance is at your additional ground point, it may be 500 ohms (likely much, much lower), making the total 19.23 ohms... which would hardly be worth the effort.


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## bayard (Sep 6, 2013)

*old wood boiler, northland*

i have an old wood oil boiler .been there since 1974,no fancy elec. stuff.just a water stat valve.k


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## steved (Sep 6, 2013)

I'm just going to put this little tidbit out there...grounding does not mean you won't get hit.

Further, my folks' chimney was hit back in the late 80s; blew the top three feet right off the chimney. Luckily it didn't get into the house electric service (must have just traveled down the chimney to the basement and ultimately "ground"). You want to know the interesting part of that strike? That was a masonry chimney with a clay tile liner. Not a single piece of "metal" in the entire thing down to the point the stove was hooked in. And the electric pole in the front yard is at least 20 feet higher, complete with a transformer. The insurance paid to have the top rebuilt, and a stainless liner installed...they have not been hit since. 

Lightning is unpredictable, and grounding helps; it but does not guarantee a strike won't hit.


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