Will a 240v compressor run without a ground?

[dtbingle]

Not saying that anyone should do this, but a couple coworkers and I were debating this.

The original argument was that a neutral line was needed as a return path for current. The counter argument was that my 240v compressor only requires the two hot leads. Each of these leads essentially act as 120v and -120v due to the split phasing to create a 240v potential for the motor. When in operation one lead is the "supply" and the other is the "return", if you're trying to think of current flow. No current should go through ground under normal operating conditions.

So that leads to: 1) Is the above correct? and 2) Do 240v AC compressor motors actually use and need the ground wire as a reference voltage potential? In other words, would the motor still work if the ground was removed?

 

[sld961]

1. Yes, it will still work. 2. No, they don't need the ground. The ground is to return voltage to the panel in case of a short. It is for safety.

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[joe_padavano]

Not saying that anyone should do this, but a couple coworkers and I were debating this.

A dedicated 240 circuit doesn't even have a neutral. It DOES have a ground, which is a different wire for fault protection. The motor only has two hot wires and a ground, no neutral.

 

[larry_g]

No ground needed for NORMAL operation. As said the ground wire is for fault protection.

lg
no neat sig line

 

[n20junkie]

For the welders, I equate it to MIG.

120v is a push system.

240v is a push-pull system.

 

[wyliesdiesels]

Not saying that anyone should do this, but a couple coworkers and I were debating this.

The original argument was that a neutral line was needed as a return path for current. The counter argument was that my 240v compressor only requires the two hot leads. Each of these leads essentially act as 120v and -120v due to the split phasing to create a 240v potential for the motor. When in operation one lead is the "supply" and the other is the "return", if you're trying to think of current flow. No current should go through ground under normal operating conditions.

So that leads to: 1) Is the above correct? and 2) Do 240v AC compressor motors actually use and need the ground wire as a reference voltage potential? In other words, would the motor still work if the ground was removed?

Whoever said that needs to take electrical 101.

 

[AntonLargiader]

The original argument was that a neutral line was needed as a return path for current.

That would describe two separate 120V circuits rather than a 240V circuit, since the neutral is not 240V away from anything.

 

[sdwalter]

1. Yes, it will still work. 2. No, they don't need the ground. The ground is to return voltage to the panel in case of a short. It is for safety.

Sent from my SM-G930V using Tapatalk

Ditto

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[TractorJeff]

Was Beer involved?

 

[LX-Markham]

^^^exactly.
and did nobody have a smartphone?

Google has ended pretty much EVERY bar argument. Used to be able to "debate" a subject for hours! Now somebody just pulls out a phone and finds the true answer. Argument over. Crickets.

 

[cgrutt]

Agree with what others have said but will add that you should ground your compressor not only for path in event of fault but compressed air can also be a source of static electricity. My compressor wiring has ground that goes back to box but I also ran a separate ground wire from the tank directly to cold water pipe as an extra precaution.

 

[Trey T]

OP: the neutral wire that's commonly seen in homes across US are for appliances that uses both 120v and 240v. Perhaps that's where the confusion.

I would run an induction motor w/o ground, but I wouldn't run it w/o overload protection (built into the motor or on a magnetic starter). If you want to follow code, I'm sure it would recommend you to use ground. BTW, I use ground on my 5hp compressor motor.

I've given you the choice - just pick!

 

[zmaxmotorsports]

Whoever said that needs to take electrical 101.

 

[LS6 Tommy]

Regardless of voltage rating or whether a Neutral is used, all alternating current devices are "push-pull". That's why it's called ALTERNATING current


Tommy

 

[EOC_Jason]

No ground needed for NORMAL operation. As said the ground wire is for fault protection.

^^ What he said. I've tested out a few 240v motors with just the hot leads and no ground connected.

Here's a nifty chart if you want to see what 240v looks like, they are essentially 180 degrees out of phase from each other. Ignore the orange & blue lines, that's for 3-phase (high leg delta)...

 

[Weird Tolkienish Figure]

^^ What he said. I've tested out a few 240v motors with just the hot leads and no ground connected.

Here's a nifty chart if you want to see what 240v looks like, they are essentially 180 degrees out of phase from each other. Ignore the orange & blue lines, that's for 3-phase (high leg delta)...

I believe this is why a "hanging neutral" can fry 110v electronics devices, without a neutral the hot wires become 220v as they will carry both legs, rather than just one.

I could be wrong of course.

 

[wyliesdiesels]

For the welders, I equate it to MIG.

120v is a push system.

240v is a push-pull system.

AC alternates back and forth 60 times a second.

the voltage doesnt matter.

I believe this is why a "hanging neutral" can fry 110v electronics devices, without a neutral the hot wires become 220v as they will carry both legs, rather than just one.

I could be wrong of course.

Yes thats true for MWBC- multiwire branch circuits. The service drop to houses is a multi-wire branch circuit.

 

[forAK]

So that leads to: 1) Is the above correct? and 2) Do 240v AC compressor motors actually use and need the ground wire as a reference voltage potential? In other words, would the motor still work if the ground was removed?

Yes. No ground is needed be it 120 or 240.

 

[Trey T]

Whoever said that needs to take electrical 101.

come on guys, educate people ... stop being a downer...

 

[Dr Stan]

come on guys, educate people ... stop being a downer...

OK the OP can start here: http://www.how-to-wire-it.com/

A simple Google search will reveal many many more sites with electrical training/information.

 

[sberry]

That is really good, I need to study that. I still have trouble with those as I am not a natural electrician. I really don't understand circuits all that well, my skillset is really as a basic installer and with service entrance and simple supply circuits.

 

[wyliesdiesels]

come on guys, educate people ... stop being a downer...

The posts previous to mine already did the educating...

 

[Advan]

There are three wires coming into your house, -120V, 0V, and +120V. if you cross the -120V and +120V lines, you get 240V. If you cross the 0V line with either one of the 120V lines, you only have 120 Volts. Some circuits, like the one for your electric range will include all three wires (plus the ground), because that particular appliance uses both 120 and 240V.

 

[Marctrees]

For the welders, I equate it to MIG.

120v is a push system.

240v is a push-pull system.

??????????????

It's AC in either case.

What does MIG have to do with this simple question ??

Don't confuse the poor guy.

The Grounding conductor NEVER has ANY current flow, unless there is a fault to Ground.

Like the motor "fries" and power has a path to the housing.

NOT to be confused w a "Grounded conductor", that his compressor does not need.

Need to understand the TOTAL difference between "Grounded",("Neutral") and "Grounding" (connected from frame to Earth, almost always Green color, but sometimes bare uninsulated.)

They ARE the n"same", hooked together at the service dissconect, but then branch off, not be be connected down the line.

Now I'm confusing the guy, TMI.

Dtbingle - You must supply a Ground to the frame of the compressor, OR, IF, it should "Fault to ground", and you lean on it, YOU will highly possibly end up 6' in the dirt Ground.

But no, it does NOT need a Ground or Neutral to work.

Marc

 

[dtbingle]

Thanks all for the responses and info. For what it's worth, I actually have an EE degree and mainly needed "third-party" responses in the debate to prove my argument of how a 240v motor works

An additional part of the debate left out was that he said his compressor has a neutral line and won't run if either the a) neutral, or b) ground was disconnected. I don't remember much about the different types of 240v ac motors, but don't recall if there is any type requiring a neutral. I don't think any would actually NEED a ground to run though - safety concerns aside.

 

[The Cobbler]

probably the controls are 120v,thus requiring the neutral. my lathe runs on 220 but the switching is done with 120v, yes it requires a neutral

 

[wyliesdiesels]

Thanks all for the responses and info. For what it's worth, I actually have an EE degree and mainly needed "third-party" responses in the debate to prove my argument of how a 240v motor works

An additional part of the debate left out was that he said his compressor has a neutral line and won't run if either the a) neutral, or b) ground was disconnected. I don't remember much about the different types of 240v ac motors, but don't recall if there is any type requiring a neutral. I don't think any would actually NEED a ground to run though - safety concerns aside.

A 240v motor wouldn't NEED a neutral because it is 240v

U cant get 240v with a hot and neutral.

This guy either doesnt know what hes talking about and is confused or is pulling your chain.

 

[nadogail]

IMHO, your compressor motor will most probably work fine and run a long time with out a Grounded Conductor, commonly referred to as a Neutral.

However, any body who insists you do not need an equipment grounding conductor may well have intentions of consoling your widow in a manner that would be unacceptable to you.

 

[larry_g]

IMHO, your compressor motor will most probably work fine and run a long time with out a Grounded Conductor, commonly referred to as a Neutral.

However, any body who insists you do not need an equipment grounding conductor may well have intentions of consoling your widow in a manner that would be unacceptable to you.

I'm real curious where YOU connect this Neutral and what color it might be? This is not an area for opinions, if you don't have the training and facts then you should be quietly listening.

lg
no neat sig line

 

[wyliesdiesels]

I'm real curious where YOU connect this Neutral and what color it might be? This is not an area for opinions, if you don't have the training and facts then you should be quietly listening.

lg
no neat sig line

Im hoping he was being sarcastic about the neutral. Otherwise i agree with u.

 

[6PTsocket]

For the welders, I equate it to MIG.

120v is a push system.

240v is a push-pull system.

Actually it is push push/ pull pull. Rekative to neutral the hots are 180 degrees out of phase. They are pulling in opposite directions. That is how two 120's produce 240.. Then they come towards each other until they hit zero. Repeat as necessary.

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[6PTsocket]

IMHO, your compressor motor will most probably work fine and run a long time with out a Grounded Conductor, commonly referred to as a Neutral.

However, any body who insists you do not need an equipment grounding conductor may well have intentions of consoling your widow in a manner that would be unacceptable to you.

That is the point many are making. Neutral and ground are not the same thing, even if they are tied at the service panel. Neutral is a power leg used in 120 volt circuits. Ground is a parh for current that accidentally got out of the insulation to follow rather than passing through you.

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[checkthisout]

Reactive power.

Put that in your push-pull circuit and smoke it.