I'm going to be installing a whole-house surge protector this week and I need to have it connected to at the service panel via two 20 amp breakers. Our panel has about 30 spots for breakers, about 2/3 of which are in use. Since the surge protector says it's best to keep the wires from itself to the breaker as short as possible, and since I'll be mounting the surge protector under the bottom of the service panel, I'd like to add the two new breakers at the bottom two free spots to keep them closest to the surge protector. But this will leave unused spots in between with no breakers in them.
Is there any reason NOT to do this? Is there any reason I should only use the "next available" slots for adding new breakers? Does doing this affect the surge protection negatively at all?
Something tells me that by "as short as possible" they nean "not 20' away from the panel", they're not being critical over ~1 foot difference in which breaker you use.
If you decide to stick with the lower-most slots (and there is no reason not to, electrically speaking) you will have a slightly tougher time removing the two knockouts, and by all means get a visual confirmation that the bottom two knockouts align with the lowest two usable spots on that side of the panel, sometimes they don't! You end up needing to knock out an extra hole and filling in the bottom one with a plastic filler plate.
Best is to place protector so that it creates a circuit from each AC main to earth ground rod that is shortest. That overall distance shold be less than 10 feet.
In addition, things such as sharp bends in the wire are the equivalent of adding up to another foot to wire length. Sharp bends should be avoided or minimized.
Leave leads long enough to be manuvered and manipulated. But do not bundle up a lot of excess wire in the box since those sharp bended in the extra wire only add to wire length. Run the ground wire to make a connection closest to the earth ground wire - so that maximum copper width and minimum copper length makes a connection between both. Same applies to how the wire exits to earth ground rod. It too should be as direct as possible, seperate from other non-earthing wires, no sharp bends, and short. The connection from AC main bus through surge protector, down grounding wire, to earth ground rod is best at less than 10 feet.
But install everything also to be convenient for you. The protector on the side next to where earth ground wire connects would be a better location. But installing it at the bottom of the box is just as good if that works better for you - mechanically.
Same with circuit breakers near bottom. No problem overall. But most important is how that wire c>
From my calculations, the service panel ground bus appears to be right about ten feet from the ground rod on the other side of the wall (10 feet as the cable probably runs, that is). The only problem is that I can't see all of the ground wire because it exits the concrete block near the ground outside heading down at a 45 degree angle. I hope that indicates that the original installer knew about the "no sharp bends rule" . It's possible they put bends in the wire where I can't see it.
The other disconcerting thing is that I can't find the where the main ground wire connects to the service panel's ground bus. There's a large lug at the top of the ground bus, but nothing's attached to it. On the neutral bus, there's a larger lug at the top with a large cable (#2 or #4?) wrapped in white tape connected to it. This cable and the other two #2 or #4 cables (which connect to the main "hot" bus) all exit through the back of the panel, seemingly to go outside into the meter box. I'm now wondering *how* my service panel is grounded. The ground wire that connects to the grounding rod outside looks to be a #6 solid copper wire. The problem is, I don't see that wire anywhere inside the service panel, and definitely not connected to the ground bus. The only wires connected to the ground bus are the regular #12 wires exiting the top of the box for the various circuits. Should I be concerned about this? Can you think of how they would have grounded the service panel such that I wouldn't see the ground wire entering the cabinet?
Did you get an electrician journeyman's license while in state prison for sexually assaulting that child? If not, what makes you think you have the intelligence and knowledge to give wiring advice? Alcoholic moron.
On Wed, 3 Sep 2003 12:33:49 -0400, "Vinnie Murdico" wrote (with possible editing):
I'm guessing that the ground wire is strapped to the neutral wire (white) inside the meter box. The ground bar inside the service panel and the neutral are probably bonded together (grounded to the box). If it were me, I'd want to know for sure.
Every utility company document I have read says not to earth the meter box. Earthing wire must go directly to main disconnect box. However others report their utility wants ground to meter box.
Remember, that earthing was not originally installed for surge protection. It was only installed for human safety - as required by National Electrical Code. Characteristics of wire used for human safety do not address sharp bends and passing through metallic conduit - installation that would only adversely affect same ground wire for surge protection. Earth ground wire serves multiple purposes. Most electricians only understand what the code requires. If earth ground wire was installed short with no sharp bends, that was probably more an accident than intentional.
Having said this, I would run a dedicated #4 AWG ground wire from earth ground rod directly to breaker box. Since that ground wire goes wherever, simply install a new dedicated ground wire and be done with it. Don't know what your utility wants, but code says that main disconnect box must be earthed. Additionally, shorter ground wire means more effective 'whole house' protector. Better to route through foundation rather than up through joist or rim board, then down to breaker box; less bends and shorter wire length. For surge protection, better to route that the ground wire separated from other wires.
That wire wrapped in white tape would be neutral. But there should also be another bare copper ground wire from main disconnect box to within 5 feet of where cold water pipe enters earth - on earth side of water meter. That 5 foot on cold water pipe required by code for human safety reasons. Connection can be long, because that ground is for human safety; not surge protection. But connection is required.
I installed the Intermatic IG1240RC tonight -- took all of about 10 minutes. Took another hour to run the new ground wire, though .
I left the original ground wire in place. That wire appears to be grounding at the meter (as you suggested) since it comes out of the bottom of the meter box and immediately goes into the concrete (stucco) exterior wall, then comes back out of the wall near the ground and attaches to the foundation rebar right there.
I ran a new #4 solid ground wire from the panel's ground bus through the exterior wall on an angle pointing down (to "soften" the bends) to the outside of the house, then down the outside of the house in PVC (to make it neat and protect it), then had to make a slight "soft" bend to run horizontal to the ground rod (which was closer to the service panel than the foundation rebar connection). Previously I had bonded the foundation rebar to the grounding rod with #4 solid wire as well to add additional "grounding" to the whole system. Total length of the new run from bus to rod was about 8 feet so I hope it will be a good ground path in case of a strike.
Of course _all_ meter boxes must _absolutely_ be grounded [this is usually accomplished (by default) at the factory by directly connecting the neutral lug to the meter box metal enclosure.] Perhaps you meant to say that the some electric companies do not require that the _connection_ to the system grounding electrode conductor (GEC) to be to be made _at_ the meter (as opposed to the main service disconnect?) That's just not true either. Many electric companies require that the system grounding connection be made _at_ the meter..........in this case, as evidenced by the OP's configuration.
In _fact_, NEC(2002) Section 250.24(A) allows the premises wiring system to be grounded at the meter, the service disconnecting means, or even at the weatherhead (although not practical).
Here's one :
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page 90) You'll also note that the lightning protector is installed _at_ the meter, thus, keeping the surge _outside_ the building.......where it should be.
While the NEC does not address sharp bends, it most certainly does address conditions where the GEC is installed in a metal conduit by requiring that the GEC be bonded to the metal conduit at _both_ ends..........this, in fact, is very critical and the consequences of not doing so will _not_ be evident until the system suffers a serious ground-fault or lightning surge.........in either case it will be too late.
System grounding is a _very_ misunderstood topic, not only is it misunderstood by many (mostly residential) electricians, but some engineers also....._Power_ EE's excluded. If anyone wants to really understand electric system grounding, the following book (as recommended by the International Association of Electrical Inspectors, IAEI) should be referenced:
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Changes to an existing grounding system should _never_ be made unless one knows where and how _all_ connections are made. What you are proposing to do will most likely result in a parallel (objectionable) current flow on that #4 wire.......and not permitted by NEC Section 250.6. If the neutral and the equipment grounding busbars inside the main panel are bonded together (very, very likely), there's the parallel connection.....not good. The solution is for the OP to purchase a protector that is intended to be installed at the meter...........or definitely not install that #4 wire and use what he has.........it will still be connected to grounding system via his original set up. The solution is _not_ to remove the main bonding jumper inside the main panel.
Well, he needs to find out..........chances are pretty good that if the service is grounded at the meter that the lightning arrestor should also be installed there.
What you just did was _install_ an objectionable current flow on your electric grounding system...........this is something that should be _discouraged_, not helped along. If you are a doubting Thomas (pun intended) get a clamp-on ammeter and see how much current is now on that wire.........there is now a parallel connection between the newly installed wire and the neutral. (Intentionally installed) objectionable current flow on the grounding system is not permitted by NEC Section 250.6. If you decide to remove it, turn off all power first.
Thanks for this info. I checked the grounding wire I installed and indeed it said there was about 200 mA on it (don't know if that's normal or problematic). I've gone ahead and disconnected the ground wire I installed and left everything as it was installed originally (except of course the new surge supressor is still installed at the panel).
I guess the only question now is whether or not the utility's ground wire from the meter runs a straight path from the meter into the wall, and down to the foundation rebar connection. Since I can only see where it exits the meter and enters the concrete block wall as well as where it exits the wall and connects to the rebar, I don't really know how it travels (especially since this is a concrete block wall).
Less desirable earthing connection is typically to meter. That was acceptable in some places - more a legacy of old practices. Many electric companies have now, with a brochure to electricians, banned earthing to meter box and demanded earthing to distribution box. Some have recently also demanded a connection to gas pipe where pipe enters building. IOW some utilities demand requirements in excess of NEC. Earthing the distribution box - the single point ground - is considered a better method even though both are permitted by code.
Code permits earthing either to meter box (once common) or to distribution box (more standard with every decade). But surge protection is enhanced when that earthing is into main disconnect box; not to meter box. A single point ground is preferred.
volts500 is correct about a potential undesirable ground loop. If the neutral breaks between distribution box and meter, then undesirable and unacceptable currents flow through both two ground wires. That could be a human safety problem.
Meter box ground is now known to exist - which was not known before. BTW, that 200 ma may still exist even if one ground is removed. Given a selection between two grounds, the distribution box ground is a better choice. If no earthing is suspected, then better to install new earthing, as you did, even if that connection, unknowingly, makes a second earthing connection. Earthing is that much more important compared to any danger created by two earth ground connection.
Grounding is for human safety (the code and volts500 understands) and for transistor safety. Good grounding principles dictate that all grounds meet at a common point. That common point where AC electric grounds meet - from water pipe, from earth ground, from meter box neutral, to all outlet safety ground, and to all receptacle neutrals - is the distribution box ground. Distribution box grounding makes even the AC electric earth grounds meet at one point since water pipe and GEC wires meet at same point in breaker box.
Best ground> Thanks for this info. I checked the grounding wire I installed and indeed
So let's assume that my meter box is the source of the main AC system ground wire (which is certainly how it appears at this time). Since there's no wire from the ground bus in the service panel connecting to the meter ground or directly to earth, how (most likely) is my service panel connected to the meter's ground wire? (I realize you can't see my setup, but I'm just wondering what would be the most likely scenario for this "connection").
The only connections I can think of are the neutral (which is bonded to the ground bar in the service panel) and travels out of the service panel and back into the meter, and/or the case of the service panel itself which is grounded to the ground bar and possibly connected to the meter by some metallic condiut passing through the wall behind it to the outside metallic meter box (maybe).
If the neutral exiting the service panel is the "ground connection" to the meter, which then continues to earth via the ground wire, does the surge supressor actually shunt a surge to the ground bar in the service panel, which then sends the surge over the neutral back to the meter where somehow the surge goes from the neutral to the grounding wire and then down to earth? Is the ground wire at the meter possibly connected to the neutral? Or, am I completely confused?
Thanks again to everyone for all your input. This disucssion has been very educational!
The neutral wire from breaker box to meter box would be path for a surge to find earth ground. Yes, the surge protector would still have an earth ground, just longer according to how it was described.
If it becomes all too complex, then just leave the meter box ground and don't use the new breaker box ground. However the important point is you do have a short connection to earth ground that provides earthing for human safety and earthing for surge protector (transistor safety).
Grounding that is beyond scope of 'whole house' protector but mentioned the grounding system is being examined:
Again, that breaker box ground must connect to cold water pipe as described earlier. This only for human safety reasons to remove electric currents from that pipe.
Because plastic pipe replaces sewer pipes, then some jurisdictions also require steel bathtubs to have a dedicated ground connection from that bathtub to breaker box ground. This appears not to be a widespread practice, but can be a good human safety feature.
Gas pipe ground - is required, by some gas companies, even if incoming pipe is plastic. Ground connection is not to earth breaker box via buried gas pipe. Ground is to remove electric currents from gas pipe - and if, necessary trip the corresponding circuit breaker.
V> So let's assume that my meter box is the source of the main AC system ground
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