Minimum wire to ground rods
- Thread starter crtemp
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John120/240
Senior Member
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- Olathe, Kansas
I would use #6 bare if it was my job.
If the 30A is a feeder to a panel, then it needs a ground electrode system. The minimum wire listed in table 250.66 is #8 copper for a GEC. That size must be protected from damage by being in conduit. You you are better off running #6 and running it along the surface of the building or taking additional measures to protect it.
- Location
- Chapel Hill, NC
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- Retired Electrical Contractor
Are you installing a sub panel? If so then I would run a #6 - since I don't carry #8- from the panel to the rod.
kwired
Electron manager
- Location
- NE Nebraska
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- EC
Nothing says this conductor has to be bare, and nothing states a specific insulation color for grounding electrode conductors, though many inspectors for some reason think they need to be green.
ptonsparky
Tom
- Occupation
- EC - retired
I am lost. Why is this information relevant?
You could save $$$ with less wire size. Distance for conductor size required for V drop and motor load efficiency is not mentioned let alone what voltage is used. Size and type of pump will give reason for not needing to run 3 wire. If sub panel is used then a 3-wire w/g is required. This can help give a better answer for less wire size/cost needed. Using a 6 AWG EGC as mentioned in another reply is conjecture without line and load data.
ptonsparky
Tom
- Occupation
- EC - retired
The question is what size wire to ground rods.
For sub panel one rod is needed, if the casing is metal with proper AWG bonding, no rod needed. Without adequate data, a decent answer is not easy.
kwired
Electron manager
- Location
- NE Nebraska
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- EC
For a separate building or structure a grounding electrode system is needed at the separate building or structure. Go to 250 part III and do same thing as you did for the building with the service. If a rod is the only electrode and first one has a resistance of more than 25 ohms you need a second rod. If you can't or don't want to measure the first rod resistance drive the second rod anyway. If some other qualifying electrode other than a water pipe is present then no rod is necessary.
I wouldn't count on a well casing to be metallic beyond the first few feet on anything installed in the past 30 years, maybe even 40 years.
Thank you for making the point about non-ferrous well casings and supply pipes. That is so common in modern rural wells. Other than [250.112(M)] EGC bonding to a utilization equipment BC , would you mention the article for a two electrode requirement that would come into play at a well shed? Tx
You need a ground electrode system for the building/structure. If that electrode is a UFER or building steel, you're done. If it is a rod, plate, or pipe electrode, then a single electrode of that type must be augmented by a second one unless you can prove it is 25 ohms or less [NEC 250.56]. Installing a second rod is cheaper/easier than testing the one that is there.
kwired
Electron manager
- Location
- NE Nebraska
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- EC
I did. Art 250 part III
If you want me to be more specific, start by reading the first section in part III - 250.50 tells us each separate building or structure needs a grounding electrode. But that is just the start that tells us we need a grounding electrode, much of the rest of part III tells us all the details of how we can do it.
250.112(M) is about equipment grounding not grounding electrodes. If the well casing were to be a qualifying electrode then 250.50 tells us it must be connected to the grounding electrode system, but most of the time wells are stand alone structures so they do not need anything larger than the equipment grounding conductor of the pump circuit to bond to them.
Two ground rods would be required by 250.53(A)(2) unless the exception is met.
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
If it is a single circuit just to feed the well pump then no GES is required. (250.32 Exception)
No electrode
No electrode
Amen Wayne. You read the post correctly. I was asking about a utilization equipment BC which is common in most residential rural wells just for the water supply pump. That includes a 3-wire 1ph controller. Tx
No electrode
Amen Wayne. You read the post correctly. I was asking about a utilization equipment BC which is common in most residential rural wells just for the water supply pump. That includes a 3-wire 1ph controller. Tx
But don't most people want a light in their well house? And then an outlet? I think you could put a light on a 30A branch circuit, but not a receptacle, assuming the fastened-in-place pump was using only 50% of the circuit. But then you show them the screw in light to receptacle adapters while mentioning the common 600W limit on keyless fixtures and the light to recetpacle adapters...
Just about any building should have a panel if its got a large fastened-in-place load IMHO. People usually want a light and receptacle available. Although a multiwire branch circuit fed from handle tied 2A0 and 30A single pole breakers may we a nice way to solve that.
Just about any building should have a panel if its got a large fastened-in-place load IMHO. People usually want a light and receptacle available. Although a multiwire branch circuit fed from handle tied 2A0 and 30A single pole breakers may we a nice way to solve that.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
What qualifies something as a "large fastened in place load"?
Most domestic wells have some great significance to the people that use them, can have associated plumbing that could be considered "big", may even be a significant consumer of energy each month on the electric bill, but as far as KVA needed to be able to supply them are a rather small load compared to some other loads. Most times a 15 amp circuit is sufficient to handle the well.
A large fastened-in-place load is one that needs more than 50% of the circuit rating. That prevents you from putting lights or receptacle on the circuit. I would expect most well pumps to be in the 10 to 20 amp nameplate range at 120V or half that at 240V. But electricians tend to use the 250% rule for motors, so you end up with larger circuits than you need. Once over 20A, you can't use normal receptacles anymore. At 30A, you may only be allowed heavy duty lampholders.
The OP said a 30A circuit. The few wells I've seen had 30A circuits. Seems overkill for the typical size of a pump motor, but I haven't done any wells myself. I don't know if the OP's circuit was truely a single well pump circuit pushing the 250% breaker limit, or if a 20A circuit would work just as well plus allow regular lighting and receptacles. Depends on the size of the well pump. But I would consider a well pump to be fastened-in-place, and even a 10A pump is using up half the circuit so you can't add lights or receptacles to that circuit. A 240V pump and a 120/240V 20A multiwire circuit would probably solve the problem in many cases.
The OP said a 30A circuit. The few wells I've seen had 30A circuits. Seems overkill for the typical size of a pump motor, but I haven't done any wells myself. I don't know if the OP's circuit was truely a single well pump circuit pushing the 250% breaker limit, or if a 20A circuit would work just as well plus allow regular lighting and receptacles. Depends on the size of the well pump. But I would consider a well pump to be fastened-in-place, and even a 10A pump is using up half the circuit so you can't add lights or receptacles to that circuit. A 240V pump and a 120/240V 20A multiwire circuit would probably solve the problem in many cases.
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