I am installing a spa at casa de Rick. I have someone doing the electrical work for me. He ran a dedicated 50A circuit w/GFI breaker for the spa. Two hots and a neutral. The inspector came out and looked at it and said that no, it has to be two hots and a ground.
I said that I don’t have a problem with this, but since the ground and neutral are tied together at the main panel aren’t they the same electrically?
No was his response, a ground is a ground and a neutral is a neutral.
I have no problem having my guy rewire the spa; I want it to be right. My question is that if the neutral and ground are tied at the box, then in essence isn’t the neutral a ground? What the hell am I missing here? (Obviously something) Can somebody ‘splain it to me? In short sentences with simple words? 
Damnit when you get above 12V DC this stuff gets hard.
Without getting into the aspects of article 250 which would make you crazy, there’s a simple yet delicate difference between a neutral and a ground conductor. Some appliances (resistance heating) have no differential flow, e.g. the current on each leg of the supply is equal. Appliances such as electric ranges, clothes dryers, and spas may use 240 for heating circuits, and also use 120 for control circuitry, lighting, and so forth. In those cases, the neutral is needed to complete those circuits. The equipment ground is there for safety reasons-should any malfunction occur within the device or appliance which energizes the frame of said appliance, the ground conductor is there to provide a low impedance path back to the panelboard where the overcurrent protective device (breaker or fuse) will open the circuit.
ouryL’s linked article is correct but a little involved. I’m quite sure that what the inspector was talking about was a safety ground connected to all of the metal parts of the spa. By code this is a green wire running from the ground at the breaker panel to the spa. If your electrician will run this green wire to the spa from the panel via the GFI and make sure it is connected to the metal on the spa and that all of the metal parts are connected together I’ll bet it will pass the inspection.
The way it was explained to me, the neutral line is a current carrying conductor, it’s the return path for the hot line. The ground line is there for safety, and under normal circumstances, shouldn’t be carrying any current. Even though the neutral is bonded to ground at the service entrance, the fact that the neutral wire has non-zero resistance and there is a significant amount of current flow, there can be a significant potential difference between neutral and ground. This is bad if someone connects the chassis ground on a piece of equipment to neutral instead of ground.
I’m not an electrician, so corrections are welcome.
I’ve seen equipment chassis floating at high AC voltages, creating a shock hazard, when someone miswired the ground and neutral in the breaker box. This is often discovered when someone has one hand on a piece of hardware on a miswired AC circuit and the other hand on a piece of hardware on a properly wired AC circuit.
Rick:
Does the spa require 240 VAC and 120 VAC? Or just 240 VAC?
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If the spa requires 240 VAC and 120 VAC, you must have 4 conductors: hot 1, hot 2, neutral, and ground.
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If the spa requires only 240 VAC, you must have 3 conductors: hot 1, hot 2, and ground.
If #2 is true, then you’re good to go… just use the third conductor as your ground. If #1 is true, then you need to run a 4-conductor cable. This is because a conductor is not allowed to do “double duty” as a neutral and earth ground connection - the neutral and ground must be separate conductors. If you want an explanation of why this is true, just let me know. I explained it in an old thread, and I can dig it up.
The short, one sentence description of the difference between nuetral and ground is this: The neutral carries current and the ground doesn’t.
In other words, the neutral is part of the circuit that does the work, and the ground is a safety device. You want all exposed bits of metal or anything that is conductive to be connected to ground. You never ever connect anything exposed to a neutral.
Since the neutral carries current, there’s going to be a voltage drop along the wire. Parts of the neutral will not be at true earth ground potential. The voltage difference between ground and neutral is going to be pretty small, but it’s not zero. Even a small voltage can shock you though, especially when you have water (like a spa) involved.
If you have a two wire system, here’s the possible faults:
Fault on “hot” wire - no big deal, the thing just stops working.
Fault on “neutral/ground” wire - case becomes hot (VERY BAD!)
If you have three wire system (seperate protective ground) here are your possible faults:
Fault on “hot” wire - no big deal, the thing just stops working.
Fault on “neutral” wire - no big deal, the thing just stops working.
Fault on “ground” wire - case is no longer protected, but is not hot unless you get a second fault that shorts the hot to the case.
If I’m reading your description right, you essentially used the neutral as a protective ground. Since your neutral in this case wouldn’t be carrying current, it would effectively function as a protective ground. You didn’t make an unsafe situation. All you did was basically used the wrong color wire for your safety ground.
Follow David’s recommendations for how to fix it and you should be ok.
I wasn’t fully clear in my OP.
The spa is 240V only** no separate 120V Circuit. Three wires. Hot 1 Hot 2 and Ground. BTW I read the manual tonight. It calls for a bonded ground within 5 feet of the spa. So among my other questions, what is a bonded ground? I understand the need for a neutral in a 120V circuit. This is a 240V circuit. If I understand correctly in theory all I need to run a 240 appliance is the two hots. The ground is a safety.
From ouryl’s link
That is what I am thinking also…
But my spa does not call for a neutral, only a 2 hots and a ground. In a 120V circuit I understand what he is saying. But in my spa what difference does it make if I run the wire to the neutral lug or the ground lug inside the box? BTW in case I have not made it clear this is a dedicated circuit, no shared neutral, GFI breaker.
Now about voltage drops, I understand those. I understand that if there is a voltage drop along the wire back to the box, the chassis of the spa will be at a non-zero voltage potential. I understand this is a bad thing.
My question is, isn’t just as likely that you could also get a voltage drop if I have a green wire wired to the ground lug, as if I use a white wire wired straight to the neutral rail, that is wired to the ground lug? Yes the neutral has an extra connection or two, but assuming (and I know what assume means) that the connections are clean good and tight, then electrically aren’t the ground and the neutral at the same potential?
I can help but equate this to the electrical system in a car. (Cause that’s what I know) The ground in the car is the (-) terminal of the battery. The negative terminal is wired to the body of the car. Everything is grounded to the body of the car. We see no problems with this. In my 15 watt brain the body of the car is like the neutral in the circuit in my spa.
David That is what the inspector said to do, and this is what we will do. I am trying to wrap my 15-watt brain around why we need to do it this way. IOW I am trying to fight my own ignorance.
Your spa doesn’t send any current back on the neutral. Electrically, in your spa, there’s no difference between a ground and a neutral since neither one would be carrying current. All you are really guilty of is using the wrong color wire.
In many appliances, though, the neutral is carrying current. The control circuitry on many 240 V appliances will often run off of 120 V. In this case there is a difference between the ground and neutral connection.
There are two main differences between houses and cars that are important here. One is that cars very rarely have appliances in them with big metal boxes. The second difference is that you can grab the hot and ground in a car with your hands and not have anything terribly bad happen. The three wire protective ground system is used in homes to prevent faults from becoming fatal. The same type of fault in a car would not be fatal because the voltage is lower and it’s much more difficult to find a large piece of ungrounded metal.
Your oven can become ungrounded if just one wire breaks. Most cars have very little exposed metal, but let’s say you’ve got an old 1960’s car that has a metal dash. You’d have to break a lot of bolts before the dash became ungrounded. Even if you did manage to get the dash at 12 V potential, it wouldn’t hurt you if you touched the dash and the door at the same time.
If your oven becomes ungrounded and a wire shorts to the case, then if you touch the case and touch your sink (let’s say your grabbing the tea pot to wash it) you’d get a full 120 VAC shock going across your chest, which is one of the most fatal possible scenarios for a home shock.
The protective ground in a home is mostly for metal cases, like the outside of your oven, fridge, computer, metal cased power tools, etc.
While this is true, this is not the *primary * reason of why a neutral cannot also be used as a safety ground.
Bingo! They *primary * reason a neutral cannot *also * be used as a safety ground is because the chassis will become hot if there’s a break anywhere in the neutral line. Now you might be thinking, “Yea, I understand what you’re saying. But is this really a serious issue? I mean, how often is there a break in the neutral line?” Here’s the answer:
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If the device is permanently wired to AC (via conduit or whatever), then there’s only a small chance a break will ever occur on the neutral line. Still, it could happen.
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If the device is a 120 VAC receptacle, a break in the neutral occurs all the time. How? Think about it… every time you plug or unplug an appliance into a 120 VAC receptacle, there’s a 50/50 chance the hot will make contact before the neutral. Which means there will be a short amount of time when there’s a break in the neutral. So for a 120 VAC receptacle, neutral breaks are happening all the time! This means that - for a 120 VAC receptacle - it is *extremely * important for the neutral and ground conductors to remain separate.
You guys are over-analyzing this. All the electrician has to do is put green tape on the neutral (to id it as a grounding conductor) and make sure it’s secured under the proper screw (green) in the hot tub control box and at the panel.
If this hot tub didn’t require a neutral conductor then there is no place in the control box to land that wire, not sure what the electrcician connected it to…
In this case the neutral wire can be used as the ground wire as long as you identify that wire with some green tape.
The neutral in a typical circuit is designed to carry the unbalanced current from the load(s), and the ground is designed to make sure no metal parts of the appliance become energized by creating a ‘short’ between the hot and the grounded metal case (of the appliance) thereby making the breaker trip or the fuse blow.
Rick, in your electrical panel the nuetral and the ground lugs are the same. They are both bonded to each other and to the panel itself so they are one in the same. One may be green or copper in color and the other may be silver. If it’ll make the inspector happy, bond the ground to the green or copper colored bar. :rolleyes:
The bonded ground within 5 feet of the spa is refering any metal that is not part of the spa or directly connected to the spa. All and any metal within 5 feet of the spa must be (electrically) bonded to the spa. Reason is that you want all metal objects that swimmers can come into contact with to be at the same ground potential so the risk of shock is eliminated. Things like pipes, gutters, fences, metal railings, etc. should be bonded to the same ground wire that grounds the hot tub.
There are several ways to bond these items and your electrician should know how to do this.
I might be wrong, but I thought plugs and receptacles were designed to make sure the neutral made contact first and broke last. A loose plug-outlet connection could result in a hot only make. I thought this was designed out a long time ago.
It’ss the safety ground that makes first and breaks last. On the plug the roundish thing that sticks out is the safety ground and it is longer than the two circuit blades. On plugs that don’t have the safety ground, the neutral blade, these days, is wider than the hot blade so that the plug can’t be inserted backwards. On devices with a transformer input this isn’t necessarily true but that’s going deeper into the matter than is needed for this thread.
This is what I thought. The inspector is actually pretty cool, but I doubt he has anywhere near the knowledge of the dope. 
OK, that is easy enough to understand, and comply with since there will be no other metal with in 5 feet of the spa.
Thanks to all you for helping a guy that understands DC handle AC
It does seem that he’s being excessively technical, but making sure it’s hot-hot-ground will prevent someone down the road from tapping into it for a regular outlet, and turning the ground wire into a current carrying neutral.
One thing not mentioned thus far:
You said you have a GFI breaker on this circuit.
It would be possible to design a 230V 4 wire GFI breaker such that it allowed current on a dedicated neutral line (connected through the GFI breaker) in addition to the current on the two hots…the algebraic sum of the current in the THREE wires would have to remain zero. That would be a good idea if you had a 4 wire appliance in an outdoor location.
That would be bad in your case, as it would defeat the purpose of the GFI. You want it to trip if the current in the two hots is not exactly equal and opposite.
I am told they exist, but I have never actually seen a 230V GFI breaker so consider that in relation to my response.
The rounded pluggy thing is what again?
Just kidding. I think that what you describe is obvious to everyone, but what I was sublimely referring to was i thought that the receptacle was designed to recieve the neutral first. This could be accomplished by making the neutral side of the receptacle’s mating material (inside the receptacle) closer to the surface, if you know what I mean.
Ah yes. What you describe is entirely possible on the new recepticles that are polarized. I’ll have to look at one and see.
Well, I just looked at a recepticle and I can’t tell. The difference would only need to be 1/16" or so and that difficult to see without taking the thing apart. And, dammit, I didn’t say the “rounded pluggy thing.” I said “roundish thing that sticks out.” I put it that way because their shapes range from round to U shaped. Harrumph. :<│
I’m pretty sure receptacles are not designed to ensure the neutral makes contact first. Even if they were, the NEC would never allow a conductor to serve as a neutral and earth ground. Though such a receptacle would be a great improvement in terms of safety (if a conductor served as a neutral and earth ground), the NEC would still be concerned about breaks in the neutral at any other location.