Ground Rod

[ajw22]

I said "0 volts relative to the main panel ground". That means is equalpotential, e.g. no voltage difference with respect to earth.

The potential of the bonding grid is not relative to the earth. Sorry, this is where you are conceptually wrong. For someone within the bonding grid the potential will be 0 relative to all that is touched within the bonding grid while it can have a potential relative to the earth. That is what keeps you safe from stray currents when you are within the bonding grid.

 

[ajw22]

To @poolman11 original question about installing a subpanel and grounding in what sounds like a separate structure.

A subpanel installed in the primary structure is always tied back to the main electrical service ground and does not have a separate ground rod.

There becomes debates among electricians and code inspectors about when another structure on the property for electrical purposes is part of the main structure and should be wired the same as a subpanel on the main structure. Or when the electrical system in a "pool shed" or "pool house" should be considered a separate structure with its own electrical feed and ground. The devil is in the details of the property, the structures on the property, local codes, and the electrical inspectors interpretation of the applicable codes. There is not an answer that can be resolved on a forum on the internet.

 

[poolman11]

I'm really sorry but I'm still not understanding. What would be the proper way to safely wire the outlet by the pool and the pool light. Would the grounds for the outlet and light be connected to the bonding grid and not the panel, or would the grounds be connected to the bonding grid as well as the panel?

 

[JamesW]

A feeder circuit supplying a separate building subpanel must include a properly sized equipment grounding conductor (EGC).

A grounding electrode system (GES) must be installed at a separate building when a subpanel is installed in the building and the subpanel is supplied by a feeder from the main house panel.

The grounding electrode system (GES) is usually one or two ground rods (grounding electrodes) that are tied together and then connected to the subpanel ground bus bar.

Check with an electrician or local inspector to verify all work complies to all local codes.

 

[poolman11]

To @poolman11 original question about installing a subpanel and grounding in what sounds like a separate structure.

A subpanel installed in the primary structure is always tied back to the main electrical service ground and does not have a separate ground rod.

There becomes debates among electricians and code inspectors about when another structure on the property for electrical purposes is part of the main structure and should be wired the same as a subpanel on the main structure. Or when the electrical system in a "pool shed" or "pool house" should be considered a separate structure with its own electrical feed and ground. The devil is in the details of the property, the structures on the property, local codes, and the electrical inspectors interpretation of the applicable codes. There is not an answer that can be resolved on a forum on the internet.

The subpanel is being installed in a detached building.

 

[JamesW]

Would it be safe to ground the new panel to the same ground rod that is grounding the pool pump, pool light, an outlet by the pool, and is bonded to the pool rails, or do I need to install a new ground rod for the new sub-panel?

I don't understand, what ground rod is connected to the pool pump and light?

I'm really sorry but I'm still not understanding. What would be the proper way to safely wire the outlet by the pool and the pool light. Would the grounds for the outlet and light be connected to the bonding grid and not the panel, or would the grounds be connected to the bonding grid as well as the panel?

In my opinion, you are really not qualified to be doing this work by yourself with no professional help.

Please contact an electrician to help you.

 

[scchan1w]

The potential of the bonding grid is not relative to the earth. Sorry, this is where you are conceptually wrong. For someone within the bonding grid the potential will be 0 relative to all that is touched within the bonding grid while it can have a potential relative to the earth. That is what keeps you safe from stray currents when you are within the bonding grid.

Sorry to belabor this point, but this isn't totally correct. The bonding grid being equal potential is a necessary but not sufficient condition to be safe. Why? Because if the bonding grid is at a potential voltage X relative to ground/earth, if one foot were on earth/ground and the other foot on the bonding grid, there will be a potential difference across your feet and current would flow across you feet. You are correct, you want the bonding grid equal potential. But you also want the bonding grid tied into the ground network as well. That guarantees it is all equipotential AND at the lowest potential. No current can flow within the grid and from the grid to anywhere else.

 

[JamesW]

In general, any equipment that comes with a bond lug gets connected to the bonding grid with a #8 bare copper wire.

Any equipment that requires a ground wire (equipment grounding conductor (EGC)) should get a ground wire that is connected to the grounding bus bar in the subpanel.

The grounds are not intentionally connected to the bonding grid, but they are both connected to the same metal frame in equipment like motors, SWG power supplies, Automation subpanel boxes, light niches etc. So, the grounding and bonding systems are connected together through the conductive metal frames of grounded and bonded equipment.

The neutral bar in a subpanel should be isolated from the subpanel metal frame and from the subpanel ground.

A subpanel should contain properly sized conductors for two hot wires, a neutral and a ground.

Breakers should be GFCI as required.

Please verify all designs with a qualified expert before doing any work and after all work is completed to verify full safety and local code compliance.

 

[JamesW]

No current can flow within the grid and from the grid to anywhere else.

The purpose of the bonding grid is to reduce the likelihood of touching two different spots that are at sufficiently different potentials as to cause serious harm.

If a live wire comes in contact with the bonding grid, current will flow through the grid into the earth and into the equipment grounding conductors that are connected to the metal frames of grounded and bonded equipment.

You can get substantial current flowing through the grid.

See this video (jump to 16:00) where Mike drops a live wire in the pool and current begins flowing at 10.35 amps.

 

[ajw22]

But you also want the bonding grid tied into the ground network as well.

I will say again that is not to code. The NEC is clear that the bonding grid wiring is not intentionally interconnected to any grounds. Due to the way many pool pumps are constructed a pump that is both bonded and grounded will cause an interconnect between the two.

 

[scchan1w]

The purpose of the bonding grid is to reduce the likelihood of touching two different spots that are at sufficiently different potentials as to cause serious harm.

If a live wire comes in contact with the bonding grid, current will flow through the grid into the earth and into the equipment grounding conductors that are connected to the metal frames of grounded and bonded equipment.

You can get substantial current flowing through the grid.

See this video (jump to 16:00) where Mike drops a live wire in the pool and current begins flowing at 10.35 amps.

You're correct, I shouldn't have said no current can flow. It would flow from the source of higher potential and be sinking current from that higher potential. You're safe so long as no potential difference exists across you.

 

[JamesW]

You're safe so long as no potential difference exists across you.

Any time that current is flowing, there will be a potential difference between any two different points depending on the amount of impedance (resistance). Assuming low impedance (resistance), the potential difference should be low enough to be safe.

Current follows every available path. If you touch two different points while current is flowing, some current will flow through you and some through the other available paths. The amount that flows through you depends on your resistance compared to all other available paths the current can take.

As shown in the video, a live wire in the pool caused 10.35 amps of current to flow and there was a dangerous potential difference between different points in the pool due to the resistance of the water even though the water is all electrically connected together.

 

[jseyfert3]

I strongly suggest you stop installing this panel yourself and hire it out to a licensed electrician familiar with the pool section of the NEC and get it inspected by a local inspector, if that inspection is not automatically triggered by the electrician pulling a permit (as it would be where I live).

Electricity is one of best ways of transporting and using energy, and when done properly one of the safest as well. Done improperly it can be extremely hazardous and deadly. Please make sure this is done properly by hiring an electrician and getting an inspection.

 

[JamesW]

Note for clarification.

The pool bonding grid is in substantial contact with the ground, especially if the bonding grid is connected to the rebar in a gunite pool shell or the galvanized steel walls of a vinyl liner pool.

The bonding grid will be connected to the grounding wires of any equipment that is bonded and grounded through the metal frames of the equipment. So, even though it is unintentional, the bonding grid is effectively equivalent to a grounding electrode system (GES).

For example, the Easytouch automation box with subpanel is a metal box with a ground bar inside and a bond lug outside. The ground and bond are in contact through the metal frame of the enclosure/box.

So, this is functionally equivalent to having a separate ground rod/grounding electrode system (GES) for the subpanel.

A terminal bar is located inside the supply terminal box. To reduce the risk of electric shock, this terminal must be connected to the grounding means provided in the electric supply service panel with a continuous copper wire equivalent in size to the circuit conductors supplying this equipment (no smaller than 12 AWG or 3.3 mm).

The bonding lug(s) provided on this unit are intended to connect a minimum of one No. 8 AWG for US installation and two No. 6 AWG for Canadian installations solid copper conductor between this unit and any metal equipment, metal enclosures or electrical equipment, metal water pipe, or conduit within 5 feet (1.52 m) of the unit.

https://www.pentair.com/content/dam/extranet/pentair-pool/residential/manuals/automation/easytouch/easytouch-control-system-pl4-psl4-installation-guide.pdf

A separate ground rod/grounding electrode system (GES) is only required if the subpanel is in or on a separate building from the main building.

 

[poolman11]

At sub panels grounds and neutrals are separate. If I wire the pump motor wouldn't that effectively combine the two because ground and neutral are combined at the main panel? How do I wire the pump correctly without that happening?

 

[JamesW]

You should have a breaker like in the picture below (Assumes the pump is 240 volts). Since this is a new installation, I am assuming that the pump is 240 volts, correct?

A variable speed pump gets connected directly to a GFCI breaker.

Siemens 20 Amp Double Pole Type QPF2 GFCI Circuit Breaker US2:QF220AP - The Home Depot

Prevent a ground fault in construction applications like spas, hot tubs, kitchens or bathrooms with this Siemens Double Pole Type QPF GFCI Circuit Breaker.

www.homedepot.com

Pentair Breaker 20a Dbl Pole W/gfi - PA220GF - INYOPools.com

Pentair Water Pool and Spa® announces an affordable selection of 1-and-2-Pole GFCIs, available in 15 and 20 amp versions.

www.inyopools.com

The breaker has load terminals for both hot lines. It has a load terminal for a neutral (center terminal), but you won’t need that. The two hot lines connect to the load hot terminals.

The breaker comes with a white pigtail that connects to the neutral bus bar.

The ground wire from the pump connects to the ground bus bar in the subpanel.

If you are using a single speed pump, you will have a double pole single throw timer, switch or relay between the breaker and the pump that will control the pump On/Off.

What pump do you have?

 

[poolman11]

The outlet is within 5 feet of the pool and it is a gfci outlet. Does it need to be bonded to the bonding grid. If it does how would I do that?

 

[ajw22]

The outlet is within 5 feet of the pool and it is a gfci outlet. Does it need to be bonded to the bonding grid. If it does how would I do that?

The NEC requires a 120V outlet to be no closer than 6 feet away if they are GFCI protected. On in-ground pools, there MUST be at least one GFCI protected convenience outlet located between 6 feet and 20 feet from the edge of the pool.

 

[eh1159]

There are two discussions here: equipotential bonding and “Grounding Electrode” requirements for subpanels on separate structures.

I’m a Master Electrician and strongly recommend you hire an electrical contractor based on the scope of work. Reference NEC 250.32(A) to make sure they install a grounding electrode (ground rod or concrete encased electrode in the buildings slab). The pool shouldn’t have a ground rod so they may be able to utilize the one there.
Have them inspect your pools equipotential bond while they are there!

 

[CrystalRiver]

This is life and death, and you clearly do not have the knowledge base to do the work yourself in a safe and legal manner. Hire a professional.