Square D Disconnect Ground

[WalkerC]

I have a Square D QO2100NRB rain-tight disconnect box I'm using to supply power for my 4-wire spa installation. I originally bought and used it as the outdoor disconnect for a mobile home. It came with a 100 amp breaker. I'm substituting a 50 amp GFIC breaker and supplying power to it from a 50 amp breaker in my home's service panel. The question I have is about the ground. The disconnect box has a neutral bar with three lugs, but no ground bar. The wiring diagram I'm looking at shows the ground wire coming from the spa control box running to a ground bar in the disconnect box, which is turn connected to the ground/neutral bar in the service panel. Since the ground/neutral bar in the service panel is connected to the ground bar in the disconnect box, what's the difference if I run the ground wire from the spa control box to the neutral bar in the disconnect box..? Looks to me like they are connected in either case. Is there a need to have the ground and the neutral separate in the disconnect box since they connect to the same ground/neutral bar in the service panel?

http://www.spadepot.com/spacyclopedia/wiring-hot-tub-spa.htm

[Roger]

I have a Square D QO2100NRB rain-tight disconnect box I'm using to supply power for my 4-wire spa installation. I originally bought and used it as the outdoor disconnect for a mobile home. It came with a 100 amp breaker. I'm substituting a 50 amp GFIC breaker and supplying power to it from a 50 amp breaker in my home's service panel. The question I have is about the ground. The disconnect box has a neutral bar with three lugs, but no ground bar. The wiring diagram I'm looking at shows the ground wire coming from the spa control box running to a ground bar in the disconnect box, which is turn connected to the ground/neutral bar in the service panel. Since the ground/neutral bar in the service panel is connected to the ground bar in the disconnect box, what's the difference if I run the ground wire from the spa control box to the neutral bar in the disconnect box..? Looks to me like they are connected in either case. Is there a need to have the ground and the neutral separate in the disconnect box since they connect to the same ground/neutral bar in the service panel?

http://www.spadepot.com/spacyclopedia/wiring-hot-tub-spa.htm

I am going to let a more qualified person answer this but, yes, keep the nuetral and ground seperate.

[Spa_Guru]

That should cover your question.

[Dr. Spa]

Code requires ground and neutral be kept separate, EXCEPT in the main panel. Additionally, if not kept seperate, the GFCI will probably never reset.

[Spa_Guru]

Code requires ground and neutral be kept separate, EXCEPT in the main panel. Additionally, if not kept seperate, the GFCI will probably never reset.

The easiest way to keep the white wire seperate is to wire-nut the white wire from the GFI to the white wire from the main panel instead of attaching it to the screw terminal.

As long as the load white wire from the sp goes to the GFI as shown, the breaker will not trip regardless of whether you keep the GFI pigtail seperate of the ground or not, but as noted, follow code, always, AND pull a permit AND have it inspected, because if you do not, and there is an accident, or fire, your homeowner's insurance will let you twist in the wind.

[WalkerC]

That image shows the red and black swapping at the bottom side of the GFI as compared to their orientation at the top of the GFI. I suppose reversing the hots is not an issue.

[Spa_Guru]

That image shows the red and black swapping at the bottom side of the GFI as compared to their orientation at the top of the GFI. I suppose reversing the hots is not an issue.

Correct, the hot leads are interchangable, the only time swapping hot leads is an issue is with three phase connections, where swapping a lead will make your pump run backwards.

You only see three phase in commercial buildings.

[WalkerC]

Code requires ground and neutral be kept separate, EXCEPT in the main panel. Additionally, if not kept seperate, the GFCI will probably never reset.

The easiest way to keep the white wire seperate is to wire-nut the white wire from the GFI to the white wire from the main panel instead of attaching it to the screw terminal.

As long as the load white wire from the sp goes to the GFI as shown, the breaker will not trip regardless of whether you keep the GFI pigtail seperate of the ground or not, but as noted, follow code, always, AND pull a permit AND have it inspected, because if you do not, and there is an accident, or fire, your homeowner's insurance will let you twist in the wind.

And would wire-nutting the grounds at the sub panel grant the same thing?

[WalkerC]

I don't doubt what I'm being told here, and I'm keeping the ground and neutral separate at the sub panel, but I still don't quite see what makes the difference. Once the neutral and the ground from the main panel are connected to neutral bar and the ground bar at the sub panel, the resistance between the neutral bar and and the ground bar at the sub panel is zero. Of course this is expected, since they are connected via the main panel ground/neutral bar... so what's the difference?

[arnspa]

I don't doubt what I'm being told here, and I'm keeping the ground and neutral separate at the sub panel, but I still don't quite see what makes the difference. Once the neutral and the ground from the main panel are connected to neutral bar and the ground bar at the sub panel, the resistance between the neutral bar and and the ground bar at the sub panel is zero. Of course this is expected, since they are connected via the main panel ground/neutral bar... so what's the difference?

Walker, IF you connect the grounding wire (Green) and the Neutral wire (White) to a common bar in the subpanel, you turn the Green wire into a parallel Neutral return. And so any short between the Hot wires (Black/Red) and the Neutral wire (White) will turn the Green wire into a hot wire because you tied the White and Green together in the subpanel.

Do NOT connect the Green and White wires together in the subpanel in any fashion.

(And certainly do not try to reduce the number of wires in your conduit by tying the Green to the White or vice versa in the subpanel)

You are right to think that once the two wires join at the common ground in the main panel it is all machs nichts, but on the way to the main panel (at the tub, in the subpanel, and in the conduit) you want these lines to be separate, not joined.

While you are making this installation, I suggest you consider adding a new additional grounding rod at the subpanel. This is not required by code but can be a good idea. NOT as a substitute for running a ground wire back to the main panel, but as additional grounding capability. And again, do NOT tie your neutral (White) to this.

Disclaimer: I am not an electrician, I'm a philosopher.

[WalkerC]

Thanks for all the help gentlemen!

[Dr. Spa]

DO NOT ADD A GROUND ROD ANYWHERE BUT AT THE MAIN PANEL. Doing so will create an electrocution hazard. DIRT is NOT a proper ground, and you risk electrifying the ground around you.

[arnspa]

DO NOT ADD A GROUND ROD ANYWHERE BUT AT THE MAIN PANEL. Doing so will create an electrocution hazard. DIRT is NOT a proper ground, and you risk electrifying the ground around you.

Dr Spa, What are you thinking? While I much admire all the work that you and other moderators put into forums such as this, I don't at all understand your thinking here.

I have before me a copy of McPartland's NEC Handbook. I find nothing that would rule against my suggestion above that there be a grounding rod at the subpanel. Indeed, I find language that suggests that a ground rod at a subpanel is permissible but not required.

I readily acknowledge that I am not an electrician. I'm a philosopher. But I can read. (And I've found that some electricians are better at that than others)

I do find that there IS a situation in which a grounding rod at a subpanel would be dangerous*. As I said above one should NOT try to use a grounding rod at a subpanel as a substitute for a Neutral (White) wire or Grounding (Green) wire return to the Main Panel. But given those two wires are in place, the NEC definitely permits, and in some cases requires an additional grounding rod at a subpanel. (In a garage, for example, a grounding rod is permitted but not required if you have a single circuit to a subpanel. With more circuits it may be required.)

But like any true philosopher I know that anyone who shows me my mistake is my friend. So, in friendship, Dr Spa (or others), I ask you to say more of what you're thinking -- or better, send us to the NEC that forbids (YOU DID USE CAPS) a grounding rod at a subpanel where the Neutral and Grounding wires are intact, returned to the Main Panel.

Else, rather than I acknowledge you as my friend you may wish to acknowledge me as yours.

DISCLAIMER: DrSpa and I have had a previous exchange on this issue. Also, I recently criticized DrSpa for what I called blatant commercial promotion here. I hope DrSpa bears no grudges. Better that we get correct advice on additional ground rods than than we win an argument.

Note: When I asked my California Licensed Electrician to add a grounding rod at the subpanel (50 feet from the main panel), he said OK but it's not required. He also said you can't have too much ground when you get lightning or giant surge from the main line.

* That dangerous situation: Suppose you have a Hot wire short to a conductor in your tub (VERY unlikely) or to your subpanel (could happen). IF/IF you do not have a true Neutral (White wire) and Ground (Green wire) connected to the Main Panel to trip the circuit breaker, then a grounding rod (depending on soil humidity and distance) COULD act to send the electric wave through the earth/dirt to the grounding rod at your Main Panel. This could travel up to the Grounding bar in the Main panel where your Neutral wires connect. If efficient enough this would kick off the circuit breaker, BUT because, as Dr Spa says, Dirt is not a very good conductor, it may not kick off, but just create a hot circuit waiting for anyone to touch a conductive surface. So, when you or loved one touches the subpanel box or conduit, POW!

But as I said in my post above, a grounding rod must NOT be used as a way to reduce wires back to the main panel.

[Spa_Guru]

Well, I AM a licenced electrician, and I can tell you the use of a grounding rod in addition to a correctly wired ground and neutral is not required by the NEC book, but it never hurts to have extra grounding, a grounding rod is typically copper coated and 10-16 ft long, driven deep into the soil, now it varies from state to state how far they are required to go in.

If, however, you have a crazy idea that you want to run a ground rod instead of a proper curcuit, especially in a tub with both 120v and 240v curcuits, you probably should not be trusted alone with peanut butter.

[reeffreak]

Well, I AM a licenced electrician, and I can tell you the use of a grounding rod in addition to a correctly wired ground and neutral is not required by the NEC book, but it never hurts to have extra grounding, a grounding rod is typically copper coated and 10-16 ft long, driven deep into the soil, now it varies from state to state how far they are required to go in.

If, however, you have a crazy idea that you want to run a ground rod instead of a proper curcuit, especially in a tub with both 120v and 240v curcuits, you probably should not be trusted alone with peanut butter.

I think this has been debated a lot over on mike holt. The consensus (and I thought nec) was one ground rod per structure. More than that and you can create a grounding differential issue. So for a sub panel on the house, home run the ground. For a separate structure (eg detached garage) a new rod is required.

Now, for the OP's question.. The answer is simple- squared sells a ground bus kit for that panel I believe. Check the depot. $5.

[WalkerC]

I'm sure I'm wrong for having done so, but I picked up a Cutler Hammer ground bar and securely bolted it in my Square D sub panel/disconnect box. Before I connected the ground wire to it, I used an ohm meter to make sure it's electrically open between the neutral bar and the ground bar.

Also, my sub panel is on the house, right next to the main panel (but outside of course), connected by about two feet of wire. (Yes, four #6 wires.) The ground rod is right below the meter which is right outside of the main panel. So if I wanted to, I could easily run another ground wire from the sub panel ground bar to the ground rod already in place. Also, I happen to have a couple of ground rods that I was going to use for some electric fence just sitting in the shed.

So I'd love for you gentlemen to give me your preference on these options:

1) Leave as is, with ground bus in sub panel connected to ground/neutral bar in main panel only.

2) Add a ground wire from the sub panel to the existing ground rod.

3) Add another ground rod below the sub panel, and connect the ground bar in the sub panel to it.

This is fun! Thanks!

Walker

[Dr. Spa]

A grounding rod doesn't provide a low-impedance fault-current path to clear ground faults (translation: "lower" voltages [under 600 volts] don't travel well, or freely, through the surface of the earth).

What a secondary grounding rod could do is potentially electrify the dirt around the spa, and has the potential of ELECTROCUTING you. If you were to be standing on the ground and touch something that IS properly grounded you could be fatally electrocuted (electricity in the electrified dirt travels up through you and out to what your touching, which is properly grounded). There's actually a documented case of this happen at a fish farm in the UK. The little fishies were periodically being electrocuted from an improperly grounded/bonded power line TWO MILES AWAY. There have also been incidences of utility companies having voltage leaks from transformers into the dirt, and traveling back up secondary grounding rods, causing havoc on these peoples electrical systems (I've personally seen this and dealt with the utility company on it).

Do a search for NEC 250.4(A)(5) and 250.45((4)

[arnspa]

A grounding rod doesn't provide a low-impedance fault-current path to clear ground faults (translation: "lower" voltages [under 600 volts] don't travel well, or freely, through the surface of the earth).

What a secondary grounding rod could do is potentially electrify the dirt around the spa, and has the potential of ELECTROCUTING you. If you were to be standing on the ground and touch something that IS properly grounded you could be fatally electrocuted (electricity in the electrified dirt travels up through you and out to what your touching, which is properly grounded). There's actually a documented case of this happen at a fish farm in the UK. The little fishies were periodically being electrocuted from an improperly grounded/bonded power line TWO MILES AWAY. There have also been incidences of utility companies having voltage leaks from transformers into the dirt, and traveling back up secondary grounding rods, causing havoc on these peoples electrical systems (I've personally seen this and dealt with the utility company on it).

Do a search for NEC 250.4(A)(5) and 250.45((4)

Please forgive me Dr Spa, but this is pure Alarmism.

I have described above a situation where using a secondary ground rod to eliminate a Neutral return or a Ground return to the main panel is NEC prohibited and I explained why.

You tell us about little fishes? The problem there was not a second grounding rod. Indeed, by that reasoning it seems like we shouldn't have ANY grounding elements at all (if 'electrified' earth can get us from 2 miles away).

IFF we have a short that causes a second ground rod to 'electrify' the earth, what would happen if you did not have the second ground rod? Given that you had proper returns for Neutral and Ground to the main panel, any short that would cause the second rod to 'electrify' the earth would also cause the primary earth ground to 'electrify' the earth.

More, MANY houses already have a second grounding element. My house has a ground to the metal water supply (NEC required) and to the metal gas supply (Local code required at the water heater). The primary grounding element is the rod at the main panel. That's three ground elements plus the one I have at my spa panel (50 feet from the main panel). On your reasoning it looks like I should, for safety sake and to save my little fishes, disconnect ALL of these.

Notice that if I had a horse barn or other outbuilding with livestock, NEC requires a second grounding rod/element at the subpanel in that building. Or if I put a lot of shop tools in my garage. Indeed a ground to the rebar may be required in a swimming pool. May I please say again, as affirmed by licensed electrician above, a grounding rod at the spa/tub subpanel is not NEC required but may be prudent.

(I'm reminded that laws protecting animals were adopted long before laws protecting children.)

We should note in this confab that the NEC prescribes a test for effective ground: 25 ohms. That is, the conductivity from your main panel ground rod to earth must be less than 25 ohms. IF it is not, Code requires addition of more effective ground. That is, Code can require addition of a second grounding rod.

So, THE way to determine whether you need or do not need a second grounding rod (or a third), is to do a test (as described in the Code). You will need to have several tests over the course of a year, as the earth humidity and temperature changes. (Where I live there is drought, zero rain, May to November, then lots of rain. My friend in Cincinnati was told she should water her foundation this summer to avoid cracks)

After a great expense and trouble for testing it may be determined that you do or do not need a secondary grounding element. In some locales, electricians use two grounding rods without question and without testing. Testing is expensive and can take a year. Rods are cheap.

To return to OP's latest question: Because the subpanel is so close to the main panel I would think a separate ground for the subpanel not needed. BUT because rods are so cheap, unless the ground is moist year round, I would be tempted to add a second rod tied to the MAIN grounding rod (not at the subpanel). Or he could do testing to determine he didn't need this. My reason for saying this is that we should recognize the inherent danger of electricity and water. NEC thinking on this has evolved. We now need GFCIs in baths, outside, garage. We can't be too careful inthe tub.

Again, Let's all be friends. You tell me my errors and I will tell you yours.

[Dr. Spa]

Do a search for

NEC 250.4(A)(5) and 250.45(b )(4)

My error was in my wording, making it appear that my experience was with fish. Is was in fact with people that were getting shocked when exiting their spa, and there was NOTHING wrong with the spa.

[SpaMaybe]

I have a Square D QO2100NRB rain-tight disconnect box I'm using to supply power for my 4-wire spa installation. I originally bought and used it as the outdoor disconnect for a mobile home. It came with a 100 amp breaker. I'm substituting a 50 amp GFIC breaker and supplying power to it from a 50 amp breaker in my home's service panel. The question I have is about the ground. The disconnect box has a neutral bar with three lugs, but no ground bar. The wiring diagram I'm looking at shows the ground wire coming from the spa control box running to a ground bar in the disconnect box, which is turn connected to the ground/neutral bar in the service panel. Since the ground/neutral bar in the service panel is connected to the ground bar in the disconnect box, what's the difference if I run the ground wire from the spa control box to the neutral bar in the disconnect box..? Looks to me like they are connected in either case. Is there a need to have the ground and the neutral separate in the disconnect box since they connect to the same ground/neutral bar in the service panel?

http://www.spadepot.com/spacyclopedia/wiring-hot-tub-spa.htm

Be Very Careful. Only do this work if you are qualified.

The neutral conductor (it is a current conductor and not an equipment ground) is only bonded (permanently electrically connected) to the ground system at the service entrance, usually your main breaker panel. NEC 250.24(A)

Do not connect the neutral to the equipment ground anywhere else. NEC 250.24(A)(5)

It sounds like your breaker enclosure was configured as the service entrance main disconnect for your mobile home with the neutral bonded to ground but...

Isolate the Neutral Assembly from ground by removing the bonding connector. Torque correct fasteners.

Field Install the Equipment Grounding Bar, part number PK-O-GTA-2. Torque correct fasteners.

Install a suitable breaker (Amp Rating and AIC Rating). Torque correct fasteners.

Verify all this information youself at SquareD http://www.schneider-electric.us/products-services/products/square-d-products/

These may help start you:

http://static.schneider-electric.us/docs/Electrical%20Distribution/Load%20Centers/Accessories-QO-LK-PK-QO-QON/3043.pdf

http://www.schneider-electric.us/?LinkServID=62F0C4F8-215E-545B-E0274975405F02B9&showMeta=0

http://static.schneider-electric.us/docs/Electrical%20Distribution/Load%20Centers/Circuit%20Breaker%20Enclosures%20Load%20Centers/1131DB0501.pdf

http://stevenengineering.com/tech_support/PDFs/45CBQ2.pdf

[SpaMaybe]

A metal underground water pipe is typically used for a residential Grounding Electrode NEC250.52(A)(1) but it must have a Supplementary Grounding Electrode which can be a metal rod in the earth. Both the metal underground water pipe ground electrode and the metal rod ground electrode are bonded with the service neutral only at the service entrance NEC 250.24(A) and no where else on the customer side NEC 250.24(A)(5). A gas pipe is not permitted as a Ground Electrode NEC250.52 but must be bonded to the grounding system NEC250.104, usually at the residential service panel. The gas pipe is being grounded rather than the gas pipe being the ground.

"...earth shall not be considered an effective ground-fault current path." NEC250.4(A)(5)

In a ground-fault condition, the current flows back to the service panel on the equipment ground wire where equipment ground meets the neutral conductor. The service neutral then returns the current safely back to the source (transformer in most cases) on a low impedance path. If a separate ground rod is used alone at the spa, there is no bonded low impedance path back to the source transformer which is potentially dangerous.

However, a supplementary ground electrode (metal rod) is permitted to be connected to the equipment grounding conductors but the earth shall not be used as an effective ground-fault current path. NEC250.54. So install the spa ground rod if you like and connect it to the equipment but the service panel equipment ground wire must also be connected to the equipment.