Sorry to beat a dead horse with this subject but I'm a little unclear when it comes to the issue of installing additional ground rods. So here's my situation….The pool has not been installed yet but I've run an 8/2 UF-B line (not live yet) that will run about 130-140' from the house breaker panel to a 2 circuit sub-panel at the pool location. One circuit will be dedicated to the pool pump and the other circuit will be for general use since the pool is so far away from the house. My general use outlet box is connected about 6" away from the sub-panel via water-tight conduit and a GFCI outlet. The pool pump circuit will be connected with the same type conduit and GFCI outlet but will be about 6' from the sub-panel. Both outlets will be more than 5' from the edge of the pool. So, besides my question of needing an additional ground rod, if not, is the 12 gauge ground in the 8/2 line sufficient back to the house panel?
Electrical – Installing electrical sub-panel at future above-ground pool
electrical
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Yes, you can. The systematic computer programmer in me even thinks it's a good idea, allowing a "star" topology for electrical distribution.
You will need 4 wires, as others have mentioned.
Keep the ground and neutral separate in the subpanels. The only place they should be bonded is in the main panel.
You will need ground rods at the new location. Yes, it's redundant, but it's still required.
The wire feeding the new subpanel must be protected from overcurrent by an appropriately-sized breaker. It can be at either end - in the old subpanel or in the new subpanel - or at both ends. It's up to you, but if only using one, I slightly prefer the upstream location, so that I can easily kill power to the feeder wire. If using both, 1 must be sized for the conductor, and the other can be that size or larger -- convenient if you buy a panel with a 100A breaker preinstalled.
While there are wires rated for direct burial, it's good that you're planning to use conduit. Oversize the conduit for ease of pulling wires, and minimize bends. While you have the trench open, run a second conduit for future expansion (ethernet? gas? macerator?). May as well run a water line, too, so you can have a sink.
Most electric kitchen stoves are installed on 240V/50A circuits. If you're installing something like that, then I suggest a 60A subpanel. That gives you plenty of headroom to install lighting, a small point-of-use electric hot water heater, and some convenience receptacles. Those will come in handy when doing maintenance in the area.
Aluminum wire is usually much cheaper than copper, but harder to work with. It's stiffer. You must use 1 size larger than with copper. The ends must be protected from corrosion with anitoxidant goop. The lugs must be torqued correctly. Some people think you should retorque the lugs on some schedule. Last time I bought wire, I wanted 8ga copper, but 2ga aluminum was 1/2 the price, so going with Al was worth it.
I will answer your questions in turn, and then add a few notes at the end -- the code for pools is complex, partly because they are bespoke installations for the most part and partly because of how pool electrical safety evolved over time.
- You actually cannot do this -- the wire run must be in conduit as per 680.25(A)(1). You can use Schedule 80 PVC or RTRC-XW for the entire run provided the stub-up is protected from physical damage (i.e. being clobbered with a mower or whatnot -- 4x4 corner posts around the panel should do the trick, as would mounting it in a drained pump room or pit using an outdoor enclosure, provided clear working space is maintained). Otherwise, you're stuck with RMC or IMC (NOT EMT) -- likely red brass to avoid corrosion.
- That 125A number is overkill, requiring a 1/0 or 2/0 triplex in Al. I'd recommend instead using individual XHHW-2 Al conductors instead of a triplex (with an 8AWG copper THWN-2 or XHHW-2 wire for the EGC, of course) -- this will be easier to get through the conduit than a triplex, and also isn't liable to short the neutral to ground unexpectedly if you're running it in red brass. (Conductor/subpanel sizing advice is below, if you wish it.)
- You are correct -- never bond neutral and ground in a subpanel.
- Your overall plan seems sound, provided the subpanel is correctly placed (it cannot be within 5' of the nearest edge of the pool).
Additionally, given the type of pool you are dealing with, there are a few additional points to consider:
- You'll need a convenience receptacle somewhere outside 6' but within 20' of the pool -- this can be at the subpanel, attached to the lighting circuit and protected by its GFCI. (While you don't need GFCI protection on a lighting circuit that's feeding listed low-voltage ground-free luminaires -- it's cheap insurance.)
- Your branch circuits will need to be run in conduit as well -- either red brass RMC or IMC, or Schedule 80 PVC or RTRC-XW if you wish to use nonmetallic conduit. In any case, you must run an insulated EGC with the branch circuit.
- EQUIPOTENTIAL BOND ALL THE THINGS. If it is conductive, not a hot or a neutral, and is within 5' of the pool, don't take a chance -- just hook it up to the equipotential grid. In your case, since your pool is vinyl-lined, you do not need to run the grid under the pool, just as part of the perimeter paving -- 12" O.C. 8AWG bare copper is used for at least 3' beyond the sides of the pool, with cadwelded (i.e. exothermically welded) or otherwise listed connections. You'll also need to hook this grid up to the pool pump motor's ground wire (which is where it'll tie into the electrical system's equipment grounding system -- for a double-insulated pool pump, just run an EGC down to the pump's j-box as normal and tie the equipotential bond wire to it there), and to an underwater equipotential bonding electrode made from corrosion-resistant materials that has a minimum of 9 in^2 of surface area and can't be damaged by pool activity if there is no bonded metal in contact with the pool water. Also, I recommend running another bare wire from the grid to the subpanel itself, directly -- this is insurance against the EGC connection at the pump motor getting undone.
As to that forum that told you not to bond the equipotential grid to the house grounding system, whoever was posting that there is full of baloney, to put it extremely mildly. NEC 680.26(B)(6)(a) explains it most clearly (strong emphasis mine):
(a) Double-Insulated Water Pump Motors. Where a double-insulated water pump motor is installed under the provisions of this rule, a solid 8 AWG copper conductor of sufficient length to make a bonding connection to a replacement motor shall be extended from the bonding grid to an accessible point in the vicinity of the pool pump motor. Where there is no connection between the swimming pool bonding grid and the equipment grounding system for the premises, this bonding conductor shall be connected to the equipment grounding conductor of the motor circuit.
Finally, as to that 125A number, it's hooey -- the pool pump motor is 8FLA@240V as per Table 430.248 and uses a 20A breaker from table 430.52, not the whopping 60A fib that you were told. In fact, that 60A number that they're giving you just for the pump is enough to leave 1200VA (600 per leg) for lighting and convenience receptacle loads after the 10A max load from the pool pump and the 40A number given for the heat pump -- which is well over three times the 180VA/outlet the Code tells you to allocate to general receptacles and outlets that aren't covered by other loads.
With that information in hand, we can run 4 6AWG THWNs for the feeder, just as you propose, and 14AWG for the pool pump as 430.22 specifies a conductor rating of 125% of FLA, or 10A in your case. (You can also use 14AWG for the receptacle/lighting circuit -- nothing says it has to be 20A.)
Related Topic
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- Electrical – Updating Sub Panel in Shed: Steps and Tips
- Electrical – Wiring Pool Subpanel for Pump and Receptacles
- Electrical – Options for Installing Sub-Panel
- Electrical – Is Sub-panel Ground and Neutral Connected to Main Ground and Neutral Bar?
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Best Answer
This gets seemingly odd because of the Article 680 rules specific to pools and other water features.
First off, pool feeders are not allowed to be direct buried as per 680.25 and the Exception thereto which AFAICT doesn't apply to outdoor cabling, so unless your AHJ disagrees with me and applies the exception, you'll have to dig up the existing UF and re-run it in conduit (either red brass RMC or IMC, or Schedule 80 PVC or RTRC-XW IF you protect the aboveground portions from physical damage).
Second, your pool will have an equipotential grid of some type associated with it (at least for the pool surround, if not under the pool itself) -- this is a Code requirement to avoid hazardous step potentials in the pool area. All conductive things directly associated with the pool (i.e. within 5' of it or part of the water circulating system) must be bonded to this grid as per 680.26 -- this includes the pool pump motor. From there, the pool equipotential grid is connected to the regular bonding system by the pool pump motor's EGC. While the AHJ can't make you put a direct link between the equipotential grid and the subpanel ground bus in, it's a good idea to do so, using the same 8AWG that's used for the equipotential grid.
Last but not least, your 8/2 should have a 10AWG ground -- 12AWG copper ground wires are only good for 20A circuits, max.