GE Subpanel

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  #1  
Old 05-30-04, 02:58 AM
doingitmyself
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GE Subpanel

This is to continue the help requested in my previous thread http://forum.doityourself.com/showthread.php?t=168638

We've got a 125 amp GE PowerMark Plus Load Center serving as the subpanel in the detached garage. He installed it himself about 4 years ago. Hasn't had any problems, but I know it's not up to code and is, most probably, unsafe as all get out.

Specs on the panel door provide the following:

Type 1 Indoor Enclosure Cat. No. Surface Type/TLM812S1 MOD1
Also has a Flush Mount Number: TLM812F1 MOD1
Main Rating -
Standard: 120/240 VAC, 1 phase, 3 wire, 125 amp max.
Optional: 208Y/120 VAC, etc for 3 phase I guess.
Optional: 240VAC, 1 phase, 2-wire, 125 amp max

Here's the current situation:

Everything from the home to the subpanel looks correct (4 conductors: 2 Hots, Neutral and Ground). The main breaker on this panel is 60 amps. Heck, now that I think about it, I guess I'm gonna have to look at it again later, because I'm not sure this 60 amp breaker is the main disconnect. It is on breaker slots 2,4 and I'm not sure what that's all about. It may be serving some type of branch circuit instead of the main cutoff. Will check into this and get back.

There is just the neutral bus bar in this panel (no separate grounding bus). The neutral and the ground from the house is bonded together at the neutral bus in the sub panel (parallel circuit?). All branch circuit grounds and neutrals are bonded to the neutral bus. There is no ground rod driven for the detached garage:

1A. Q: Where am I to put the ground wires? There's no place to put them (again, there is just the neutral but no ground bus bar).

1B. Q: Is a ground rod needed for this application?

1C. Q: Why doesn't this panel have a ground bus?


Now, there is a panel bond strip which is not in physical contact with the neutral bus:

2. Q: Is this bond strip to be used for anything, or should I just leave it be?

On the door label, the following instructions are given: "Suitable for use as service equipment with main circuit breaker or when not more than six service disconnect means are provided and when not used as a lighting and appliance branch circuit board. See Article 384-14 NEC"

3. Q: Are we not to use this particular Load Center to supply lighting to the garage? Or am I missing something between the lines?

4. Does anyone have any experience with this specific model? I don't know how to upload pictures here, as I have seen others do, but I'm hoping one of you are fanmiliar with the layout of this specific model, and maybe can lend me some advise here.

I'll attempt to detail how it is laid out, from memory:

The diagram on the door shows a Line side of 3 wires: 2 Hots and a Neutral, with specs of 6/2-0 Cu-Al.

The 2 Hots (220 VAC between these) are shown as connecting to the two main lugs, and then.........

The diagram continues with the breakers arranged as two normal columns ("A" and "B" phases) of breakers.
On the left side ("A" phase [?], I assume) shows double pole breakers utilizing 1,3 - 5,7 - 9,11 - 13,15
The right side, has breaker slots 2,4 - 6,8 - 10,12 - 14,16.

Phew, I hope this isn't too much to digest. I just figure I give you all I know at the present and hopefully it's of some value.

I know I gotta check this (what I thought was a) main breaker thing.
Q: If this is not the main, where should it be located? All panels I've seen had the main disconnect right in the center between the branch circuit breakers.

Hope to hear soon, as I plan on going back tomorrow (Sunday) and figuring it out. It seems like a messed up job to me.

Thanks for the help,
Terry
 

Last edited by doingitmyself; 05-30-04 at 03:10 AM.
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  #2  
Old 05-30-04, 05:53 AM
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Sub panels are a difficult subject. Many factors come into play.

However, this setup is definitely wrong and needs to be fixed.

A straight sub-panel is fed with four wires from the main panel and must have the ground and the neutral isolated at the sub panel. The neutral buss that comes in these panels usually has a green screw. When tightened this screw connects the neutral buss to the panel itself. This is not used when it is necessary to isolate the ground and the neutral wires.

Often you must purchase a grounding bar for a subpanel as an additional item. They are sold for a few dollars and attach to the panel.

One question you did not answer. Are there any other wires going from the house to the garage? I am referring to telephone, cable TV, intercom. The answer to this question is important.
 
  #3  
Old 05-30-04, 08:01 AM
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1A. Buy and install a grounding bar kit.
1B. Yes.
1C. Because nobody installed one.

2A. Depends. What does it connect to what?
3A. I don't know. Have you read the cited section of the NEC?
 
  #4  
Old 05-30-04, 01:01 PM
doingitmyself
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Originally Posted by racraft
The neutral buss that comes in these panels usually has a green screw. When tightened this screw connects the neutral buss to the panel itself.
Originally Posted by John N
2A. Depends. What does it connect to what?
Racraft: I seen no evidence of the green bonding screw.

John: I'm thinking that the "bonding strap" I mentioned does this job. Not sure though

Originally Posted by racraft
One question you did not answer. Are there any other wires going from the house to the garage? I am referring to telephone, cable TV, intercom. The answer to this question is important.
Nothing else is going to the garage.

-Terry
 
  #5  
Old 05-30-04, 06:34 PM
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The answer to the "other wires" question is not important since you already ran a grounding wire between buildings. If the bonding strap connects the neutral to the panel cabinet, disconnect and discard it.
 
  #6  
Old 05-31-04, 05:18 AM
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While your current situation is _not_ to code, and needs to be fixed, it is probably not 'unsafe as all getout'. Your ground and neutral are operating in parallel as a single conductor, and as we discussed in the previous thread on grounding, this means current flowing in the grounding system. But because this is in a detached structure, there is very little path for 'objectionable current flow' outside of the incorrectly wired EGC conductor.

In fact, I would argue that your situation is approximately as safe as any residence, with proper single point grounding, which shares a transformer with any other residence, where the other residence is also properly grounded.

I am not suggesting that you should _not_ fix your problem; it is not up to code, and IMHO you should get the proper grounding bus and install it in the subpanel, install properly sized ground rods and run the ground rod conductor to the (newly installed) grounding bus in the subpanel, properly separate grounds and neutrals, etc. But IMHO your installation is 'safe enough' that you don't need to _rush_ into the project as if the house will burn down tomorrow if you don't fix this flaw. Gather all the materials that you need ahead of time, and then shut down power and make the changes.

To expand John's answers to 1A and 1C: most panels sold for residential use are expected to be used as the main panel, and have a single combined ground/neutral bus. For subpanel applications, it is expected that you will buy an additional bus that gets installed in the panel. This is just a strip with screw terminal holes that you mount somewhere in the panel. The installation of these kits will depend upon the kit itself and the panel in question. Of critical importance: make sure that you remove paint that might prevent a good electrical connection between this grounding bus kit and the panel metal. Depending upon your panel, you may install this grounding bus kit in a location that lets the ground bus strap reach the new bus.

As you have described your system, something strikes me as an immediate hazard. The subpanel neutral bus should have some sort of bonding strap or screw, something that is used to connect the neutral bus to the metal case of the panel in order to ground the panel when it is a main panel. You have said that this strap is not connected. This means that your panel is not grounded at all, either properly or improperly. If this is the case, then I would upgrade the urgency of making these repairs.

-Jon
 
  #7  
Old 05-31-04, 11:53 PM
doingitmyself
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Originally Posted by winnie
As you have described your system, something strikes me as an immediate hazard. The subpanel neutral bus should have some sort of bonding strap or screw, something that is used to connect the neutral bus to the metal case of the panel in order to ground the panel when it is a main panel. You have said that this strap is not connected. This means that your panel is not grounded at all, either properly or improperly. If this is the case, then I would upgrade the urgency of making these repairs.
The bonding strap that I referred to looks to be just for this purpose: to bond the neutral bus to the metal case. The strap is connected to the metal case, near the neutral bus, and can be swung around to make contact with the neutral bus. It is not currently making contact. However, both neutral and ground service entrance wires are connected to the neutral bus. Though, since I suppose that the neutral bus is isolated from the metal cabinet, perhaps, indeed, the cabinet isn't grounded at all "either properly or improperly".

Please look at:
http://www.geindustrial.com/products...mg-drawing.pdf.

Our panel is the one listed as on Drawing Page 17 (it starts at page 5/25 and continues to page 7/25 in the adobe reader). The model number listed in this .pdf drawing is TLM812U2, although the number on the panel itself is: TLM812S1. Please let me know if you're able to figure out anything from this drawing. If you could find a link that would give a photo of the inside of the panel, I would appreciate seeing it and comparing it with you. I think there was a production modification to the one listed as opposed to the one I actually have, but it is close. The one I have is a "PowerMark Plus". The one listed is a PowerMark Gold, I believe.

I appreciate your help, Jon. I've searched the internet for actual photos of the inside of my model, but I just can't find any.

-Terry
 
  #8  
Old 06-01-04, 05:14 AM
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Well, the GE link tell you what you need to get. You need to buy a TGK12 equipment ground kit, and install it according to the directions.

With the ground kit installed, you should land all of the EGC wires on it, and keep all of the neutral wires on the current neutral bus. As a detached structure, you should drive a ground rod and run the ground conductor to the new grounding kit as well.

Once all of these changes are made, the ground bond strap that you describe will either not be connected at all, or will be connected to the new ground bus (this depends upon the installation instructions...the new ground bus needs to be connected to the panel is some fashion, but this might be independent of the ground strap).

At the present time, with that ground strap disconnected, the panel is either not grounded at all, or grounded through a device (eg. if you have a metal raceway and a grounded outlet, the panel is grounded through that raceway, then through the device yoke, then through the ground screw, to the (very undersized for this application) ground wire at the receptacle. Either way this is an immediate hazard and should be fixed. If the bonding strap _were_ connected, then the panel would have been (improperly) grounded to the neutral, with 5 years of correct function saying that this was probably okay in this case. But since the bonding strap is not connected, I would not connect it now, but would instead do the proper fix.

-Jon
 
  #9  
Old 06-01-04, 11:39 AM
doingitmyself
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ground rod and conductor size

Originally Posted by winnie
At the present time, with that ground strap disconnected, the panel is either not grounded at all, or grounded through a device (eg. if you have a metal raceway and a grounded outlet, the panel is grounded through that raceway, then through the device yoke, then through the ground screw, to the (very undersized for this application) ground wire at the receptacle. Either way this is an immediate hazard and should be fixed. If the bonding strap _were_ connected, then the panel would have been (improperly) grounded to the neutral, with 5 years of correct function saying that this was probably okay in this case. But since the bonding strap is not connected, I would not connect it now, but would instead do the proper fix.
Jon, The grounding conductor from the main panel in the house is connected to the neutral bar, as is the neutral conductor. So, I guess there's a path for ground back to the ground rod provided for the main panel in the house. But, I don't see how the subpanel metal case is bonded.

On another point:

Just to be sure about the grounding conductor and rod; I plan on #4 with 8'x5/8" ground rod. Is this correct? Also, and I asked this earlier, but I think it was overlooked: Should the grounding conductor from the main panel in the house remain connected at the subpanel?

I'm still collecting information on parts, etc. and I hope to get this done this weekend. He's not in any big hurry as I don't think he understands the urgency since it has been running for 5 years with no problems. Although he has just recently (within the past month) installed a 240-V Air Compressor.

This is turning into a headache cause the Compressor circuit is going to have to be evaluated as well. Nah, it's still fun

-Terry
 
  #10  
Old 06-01-04, 03:20 PM
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There is clearly a path from the subpanel circuits back to ground via both the neutral and the ground conductor. The problem is that the case of the panel is _isolated_ from this, so there is not path to ground from the case of the panel. As you noted, the subpanel case is _not_ bonded, unless by a haphazard path (eg. a ground wire to a receptacle and then back to the panel through some conduit). If a hot wire touches the case, then it might become energized. This is a significant hazard.

The size of your 'grounding electrode conductor' for the 60A panel is only required to be #8 (possibly even #10, depending upon your supply conductors), however such a small conductor will need to be protected by conduit. #4 only requires protection if exposed to 'severe physical damage', and is good because it is nice and sturdy and lets you simply direct bury up to your rods.

If you have no way to _test_ your ground rods, then you will be required to place two of them, spaced at least 6 feet apart. Ideally, place these ground rods near the building, but just outside of the eaves area, so that they are in ground that gets wet. Because testing is difficult and time consuming, most electricians simply make sure there are two ground electrodes rather than try to get away with one.

Make sure that you use connections for your ground rods that are rated for direct burial, or use 'exothermic weld' devices (these are fun to play with . In the ideal case, you put the ground rod under a little cover that provides access for inspection, but prevents a tripping hazard.

In answer to your question about the ground conductor from the main panel, all the ground connections, including the ground conductor from the main panel, the conductor to the ground rods, the equipment grounding conductors, as well as any additional bonding conductors (eg. bonding to structural steel if this is a metal building), should be connected to the ground bus that you install.

-Jon
 
  #11  
Old 06-02-04, 03:17 AM
doingitmyself
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grnd conductor and Main Breaker Kit

Originally Posted by winnie
The size of your 'grounding electrode conductor' for the 60A panel is only required to be #8.....
Jon,

This is a 125 amp panel, not a 60 amp, so am I correct in using #4 GEC?

Two more questions before I put this to rest awhile:

1). I was reading that a subpanel doesn't need a main breaker. This one does not have one. Can I go ahead without installing a main, or is this required? Was just thinking that in a detached bldg, a way of disconnecting the whole service would be desirable. But, I would like to know whether or not it's required by NEC.

2). Along the lines of #1, I believe that the service to the subpanel from the main is off of a 60 amp breaker. Can/Should I install a main breaker equal in size to that of the one from the house? Could I install a 125 amp breaker in the sub even though the on supplying the service is of lesser ampacity?

Thanks,
-Terry
 
  #12  
Old 06-02-04, 03:44 AM
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For sizing the GEC, the amp rating of the _panel_ is not the question. Rather the question is the amp rating of the circuit feeding the panel. I was under the impression that this was a 60A feed. Be that as it may, there is no problem using a larger GEC than required, and as I stated above, the larger GEC doesn't require as much protection as the smaller GEC. If you were to use a #8 GEC, you would have to install it in conduit, and I would recommend that you use the #4 GEC even if not required. What is the size of the EGC conductor from the house?

As far as main breakers on the subpanel are concerned, a subpanel does not require a main breaker if the feeder which supplies it is protected at the source. However a detached structure _requires_ disconnecting means, and a main breaker does a good job of this. In your case, either a main breaker or some other sort of disconnect switch would be required. (There is an exception: if you have fewer than 6 circuit breakers in the panel, then this counts as the 'main disconnect'...with a 125A panel, this is probably not the case.)

You have confirmed that the panel does not have a main breaker? What is the rating of the breaker feeding the panel at the house? What does the 60A double pole breaker in the subpanel supply? For what its worth, it is possible that the 60A double pole breaker is being used as a main breaker even though it is in a 'load' position on the panel; this is called back-feeding, and gives something else to double check: was a 'back-feed' kit installed? This is generally a extra screw or bolt that holds down the back-fed breaker much more securely than normal, and is required when breakers are back-fed because the risk of shock or arc is much greater when a back-fed breaker pops out by accident.

-Jon
 
  #13  
Old 06-04-04, 07:54 AM
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Hi,

The way you edited the first post to add the additional questions got this lost in the shuffle. Your PM was the only reason that I saw it.

From your description, it sounds like the subpanel does not have a main breaker. When you say "The 2 Hots (220 VAC between these) are shown as connecting to the two main lugs, and then.........", that pretty much says that the feed wire are going right to the panel bus bars, without a main breaker. You should look inside the panel, and locate the main feed wires coming in from the house. If they go to terminal lugs sitting directly on the bus bars, then this panel does not have a main breaker. If they go to what appears to be a normal 'load' breaker sitting at the side, then this 'load' breaker is being 'backfed' as the main breaker. This _may_ be legal, however it depends upon the panel listing, and at a minimum requires a special bolting kit to hold the 'backfed' breaker down on the bus.

As stated above, a subpanel does not require a main breaker if the feed to the subpanel has a breaker that limits the current to less than the panel rating. If this subpanel is fed with a 60A breaker at the house, then the subpanel will not require a main breaker. However.... A detached structure requires a 'main disconnect'. This is a single location where you can turn off all power to the structure with no more than 'six throws of the hand'. Generally, the main breaker on a panel will serve as the 'main disconnect'. So as I read your situation, the _panel_ does not require a main breaker, but the _building_ requires a main disconnect, which would be served by a main breaker. You should find out if a main breaker kit is available, or if the panel is fed through a backfed breaker.

If you do not have a main breaker, and wish to add one, you can pretty much select any breaker you want, since protection is provided by the breaker in the house. If you select a breaker that is smaller than the house breaker, then you get what is known as 'coordination', where the breaker closest to the load will trip first. This is good design practice, but not required in this case, and it would essentially waste some cable capacity. If you install a larger breaker, then it essentially becomes a switch, with its circuit breaking capabilities essentially unused, which is entirely fine as a main disconnect.

-Jon
 
  #14  
Old 06-04-04, 10:52 PM
doingitmyself
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There is not a main breaker in this panel. The 60 amp breaker is being used for what looks like either a 30 amp Dryer or 50 amp range receptacle (it has 3 slots, so I guess it's a dryer receptacle?). There's alot to get reworked in this garage. I haven't been able to spend enough time over there to determine everything that's going on, including the actual wire size going to that receptacle. He's probably got #10 running to the receptacle being protected by a 60 amp breaker

Advice on Ground Rods:

It's my understanding that I need two 8' rods and that they need to be completly under the earth (not sticking up, to avoid trip hazards, etc)

1). Does Home Depot, Lowes, etc sell these and what's the average cost?
2). Any tips to actually driving these huge things 8' into the earth?
3). Does the code require that they be separated at least 6' apart? May I go even farther apart, if necessary?

Terry
 

Last edited by doingitmyself; 06-05-04 at 12:50 AM.
  #15  
Old 06-05-04, 02:18 AM
doingitmyself
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ps

ps to the ground rod: I plan on installing the rods at the perimeters of the bldg (near the gutter spouts, so that rain water can help moisten the soil, and get a better ground). What are the chances of damaging already installed services, such as gas lines, water pipes, etc? Hopefully, I won't have to call the various utilities to tell me where not to dig. Are there usually minimum distances that water pipes and gas lines are buried, so as to not interefere in this type of installation?
 
  #16  
Old 06-05-04, 03:58 AM
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Code doesn't require that _all_ ground rods be separated by a minimum of six feet. Instead code requires that when a _second_ ground rod is added in order to meet the requirement for not testing ground resistance, that _it_ be at least six feed away from the first ground rod. The ground rods can be further apart if you wish. The reason is that when ground rods are close together, the 'look' electrically like a single ground rod.

I have no advice to give on best driving methods or how much ground rods currently cost, sorry.

You don't want to create a trip hazard with the ground rod, but you also need to leave the connection to the conductor 'accessible', so that you can inspect that the wire is still properly clamped. You can use a 'exothermic weld', in which case you don't have a clamp that needs inspection, but these are hard to come by.

Usually ground rods are simply placed close to the structure, so that if they stick out of the ground a couple of inches, there is no trip hazard. This is technically a violation, since the rod must be buried to a depth of 8', and is only 8' long...but most people don't worry about these couple of inches.

You (supposedly) get a better ground if the rod is away from the wall, past the eaves line where rain falls; but then you need to do extra work like putting in a 'box' that provides access to the top of the ground rod so that you can inspect the clamp. Installers choice as to how much work is appropriate for these ground rods; you will have a _legal_ ground electrode system with two rods spaced at least 6 feet apart.

A small nit: the conductor to these _required_ electrodes must be continuous and un-spliced, so you end up threading the conductor through the 'middle' ground rod clamp, connecting back to the panel at one end, and to the second ground rod at the other end.

There are required minimum burial depths for underground services, however an 8' ground rod will go right past these; use the 'call before you dig' numbers in your area and the utilities will tell you if there is a problem with any 'mains'. If there is plumbing or gas from the main house to the detached garage, you will need to make some educated guesses about where it is located. Luckily you can usually see where these services enter a building, and just avoid that area.

-Jon
 
  #17  
Old 06-06-04, 05:18 AM
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Hi,

I received an e-mail saying that you posted more questions, but they do not appear on the forum.

-Jon
 
  #18  
Old 06-09-04, 12:37 AM
doingitmyself
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job completed, I think

The job is completed, and thanks, Jon, for all your help.

We simply bought a grounding lug and installed it, and separated all the neutrals and grounds. I also put in one 5/8" x 8' grounding rod (he didn't want the expense, and I couldn't make him understand the importance, of the second rod - hopefully the resistance is at or near 25 ohms), and used an acorn clamp suitable for burying. 10' of #4 EGC done the job.

No main disconnect was installed, as there are just 4 branch circuits, and that should be good for the "6 throws of the hand" rule. The sub panel is, indeed, fed from the main house by a 60 amp breaker, utilizing #6 (4 conductors: Hot, Hot, Neutral, Ground) - this breaker in the house should provide overcurrent protection.

In addition, a fused disconnect switch (with 2 15 amp fuses) is being used for the 240-V 15-amp Air Compressor (this does provide a disconnect for the AC). This installation (the AC circuit) is a bit odd, though, and maybe you have a thought or two on it. The situation is as follows:

A 50 amp 3 prong receptacle is being fed by #6 from a 60 amp breaker in the subpanel. An appliance cord is plugged into this receptacle, and is hard-wired to the line side of the fused disconnect switch. From the load side, the AC is hard-wired with 12/2 with ground.

The oddity of it, in my mind, is why he didn't simply run a 220-V, 15 or 20 amp branch circuit to the fused disconnect, bypassing the receptacle. He could have ran this off a 15 or 20 amp breaker to the disconnect switch, and the switch, being protected w/ 15 amp fuses, should have provided protection, no? I think he has ideas of using this receptical for his 40 amp welder, as well. When not using the AC, he would simply unplug the appliance cord, and the receptacle would be used for the welder. I hope this works ok and safely!!!! Actually, I can't visualize a safety hazard in this setup, it just seems odd.

All in all, I think/HOPE that everything will be okay.

One clarification to the subpanel bonding of neutral/ground: I've read that in a detached bldg., with a three wire feed (Hot, Hot, Neutral - no ground being ran from the house to the detached bldg., and no other metallic materials between the two bldgs.), the neutral/ground MUST be bonded. In my case, could I have simply disconnected the ground feeder from the house, thereby making this a 3-wire service? In that case, everything would have been fine with no need to purchase a ground lug, and ground rod; is that a correct assumption?

Again, I appreciate all of your help and patience, and if you could offer some soothing to my mind for the above described finshed (?) installation, or even some constructive chastisement, I would be most appreciative.

Thank you to all who helped,

-Terry
 

Last edited by doingitmyself; 06-09-04 at 12:54 AM.
  #19  
Old 06-09-04, 07:07 AM
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You could have eliminated the $5 cost of a grounding bar by sacrificing a superior installation. Not a good tradeoff in my opinion.

But you would have needed the grounding rod anyway.
 
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