Wiring an older 220 volt machine into a new junction box, I found that the junction box had 4 wires --Black --Red --White --bare copper
In the sub panel, the neutral (white) and the ground (bare or green) were not bonded together. Separate ground and neutral wires are run back to the main panel (service entrance) where they are bonded together.
The wiring of the machine has phases 1 and 2 as blue and brown wires, and the ground wire is yellow with green. Inside the machine the yellow with green wire is connected to the machine frame.
Question; when connecting the machine to the junction box is it best to:
A -- Connect the machine ground wire to the neutral, white, wire in the junction box
B -- Connect the machine ground wire to the ground, bare, wire in the junction box
C -- Connect the machine ground wire to both the neutral and ground wires in the junction box
D -- Doesn't matter
E -- Tear the machine all apart and isolate the neutral and ground and add a separate ground wire to the machine.
F -- Other
Note, this junction box is wired like code now requires for kitchen ranges etc. which is how mobile homes have been done for decades with separate neutral and ground wires.
Ground vs. Neutral -- the same but different.
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440roadrunner
- Posts: 27
- Joined: Sun Sep 23, 2007 3:00 pm
- Location: N Idaho
Your post is a little confusing.
You say
"I found that the junction box had 4 wires --Black --Red --White --bare copper"
Do I understand that you are referring to the power source, I.E. the j box "on the wall?"
Do I understand the machine has only three wires, one of which is green and connected to the machine frame?
If so, the answer is easy. Hook up the "two hots" and hook the machine green to GROUND at the source, NOT neutral
DO NOT EVER tie a separate neutral to ground. Your sub panel sounds like it's wired correctly--the neutral should be separated on an insulated block. I believe that the box should be tied to ground (not neutral) and MAYBE there should be a separate ground rod tied to the sub panel.
Now, there may be some complications, here. Does the machine have any 120V circuits, and of course these would be hooked to the frame, if it's an older machine? If so, then yes, you'd need to tear into the machine, and
either isolate the ground return to those circuits into a dedicated neutral, or...
install a 240-120 isolation transformer, and hook the 120V circuits to that.
You say
"I found that the junction box had 4 wires --Black --Red --White --bare copper"
Do I understand that you are referring to the power source, I.E. the j box "on the wall?"
Do I understand the machine has only three wires, one of which is green and connected to the machine frame?
If so, the answer is easy. Hook up the "two hots" and hook the machine green to GROUND at the source, NOT neutral
DO NOT EVER tie a separate neutral to ground. Your sub panel sounds like it's wired correctly--the neutral should be separated on an insulated block. I believe that the box should be tied to ground (not neutral) and MAYBE there should be a separate ground rod tied to the sub panel.
Now, there may be some complications, here. Does the machine have any 120V circuits, and of course these would be hooked to the frame, if it's an older machine? If so, then yes, you'd need to tear into the machine, and
either isolate the ground return to those circuits into a dedicated neutral, or...
install a 240-120 isolation transformer, and hook the 120V circuits to that.
Last edited by 440roadrunner on Thu Nov 08, 2007 12:39 am, edited 1 time in total.
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JHenriksen
- Posts: 286
- Joined: Mon Jan 06, 2003 8:39 pm
- Location: Roscoe, Illinois
There are three types of wires in branch circuits.
1) "hot" wires, which carry load current
2) "grounded conductor" or "neutral", which carries load current also.
3) "grounding" conductors, which carry ONLY fault current.
NEVER connect "grounded" conductors to "grounding" conductors except at ONE place in the service box ("bonding").
machine frames , electrical boxes, etc connect to the "grounding" conductor ONLY.
1) "hot" wires, which carry load current
2) "grounded conductor" or "neutral", which carries load current also.
3) "grounding" conductors, which carry ONLY fault current.
NEVER connect "grounded" conductors to "grounding" conductors except at ONE place in the service box ("bonding").
machine frames , electrical boxes, etc connect to the "grounding" conductor ONLY.
Hi,
J Tiers is right, but code varies depending where you are. Here in Ontario, the white or neutral wire is grounded in the main panel but nowhere else. If you join the two together elsewhere you will get ground currents because the neutral is a current carrying conductor & will have voltage drops over its length so this will cause the ground wire to carry current as well which is a No-No. Ground wires are meant to carry fault currents only. That is why they can be undersized (and also not insulated). In other jurisdictions, the neutral may not be grounded, so you need to check & see what is required where you are.
Also, you only have one phase in this case; you get 120 volts between either red or black & the neutral and you get 240 volts between red & black. The neutral is the center tap on the step down transformer out on the street. In all cases, the phase of each possible circuit is the same.
Also, remember this is North American practice. Code is different in other parts of the world & some of it may appear strange to us & vice-versa. At the bottom, in any jurisdiction, the whole idea is to get an installation that is safe & won't kill anyone.
Perhaps this helps?
Richard Trounce.
J Tiers is right, but code varies depending where you are. Here in Ontario, the white or neutral wire is grounded in the main panel but nowhere else. If you join the two together elsewhere you will get ground currents because the neutral is a current carrying conductor & will have voltage drops over its length so this will cause the ground wire to carry current as well which is a No-No. Ground wires are meant to carry fault currents only. That is why they can be undersized (and also not insulated). In other jurisdictions, the neutral may not be grounded, so you need to check & see what is required where you are.
Also, you only have one phase in this case; you get 120 volts between either red or black & the neutral and you get 240 volts between red & black. The neutral is the center tap on the step down transformer out on the street. In all cases, the phase of each possible circuit is the same.
Also, remember this is North American practice. Code is different in other parts of the world & some of it may appear strange to us & vice-versa. At the bottom, in any jurisdiction, the whole idea is to get an installation that is safe & won't kill anyone.
Perhaps this helps?
Richard Trounce.
Hello,
Just curiuos as to what you are up to as in previous posts you are inquiring about 3 phase wiring and a 3 phase junction box and now in this post you are asking about single phase wiring and junction box connections.
Is this for two different machines?
Is your service single or three phase?
PLEASE MAKE SURE YOU UNDERSTAND what you are doing so you don't get hurt!!! (or fry something!!)
Glenn
Just curiuos as to what you are up to as in previous posts you are inquiring about 3 phase wiring and a 3 phase junction box and now in this post you are asking about single phase wiring and junction box connections.
Is this for two different machines?
Is your service single or three phase?
PLEASE MAKE SURE YOU UNDERSTAND what you are doing so you don't get hurt!!! (or fry something!!)
Glenn
Yes I have some 110 v some 220 v and one 3 phase 220vGlenn Wegman wrote: Just curiuos as to what you are up to ...
... Is this for two different machines?
Single phase, I have to use a rotary converter for 3 phase.Glenn Wegman wrote: Is your service single or three phase?
That's why I am asking !Glenn Wegman wrote: PLEASE MAKE SURE YOU UNDERSTAND what you are doing so you don't get hurt!!! (or fry something!!)
I have been using my ohm meter to verify that the ground wire of the machine is really ground and not being used as neutral.
440 road runner picked up on something that is a key concerns in this wire color issue.
My chinese lathe uses a complex motor starting relay set that prevents just checking the for hot wire connections to ground with the ohm meter and I don't trust the chinese wiring diagram either440roadrunner wrote: ... Now, there may be some complications, here. Does the machine have any 120V circuits, and of course these would be hooked to the frame, if it's an older machine? ...
IF the relays are 110, then they would likely be using the machine frame as ground There is at least one transformer which powers the indicator lights and maybe the relays. All of this stuff is packed into a small box which cannot be circuit diagrammed without disassembling.
I am open to suggestions as to how to verify just what the situation is with this Chinese lathe.
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440roadrunner
- Posts: 27
- Joined: Sun Sep 23, 2007 3:00 pm
- Location: N Idaho
Probably the fastest way is if you have an "amprobe" type meter---an inductively coupled ammeter--put the meter in the GROUND lead and see if there's any current draw with the machine operating. If so, You've got 120V circuits that are trying to use the ground as a neutral, or worse---unwanted current leakage to ground. A properly wired, properly operating machine should have NO current on the "ground" (green) conductor
In either case, the leakage needs to be stopped, and/ or you need to find and isolate the return to ground on the 120V cirucuits, and route "them" to a neutral
An example of an Amprobe type meter:
In either case, the leakage needs to be stopped, and/ or you need to find and isolate the return to ground on the 120V cirucuits, and route "them" to a neutral
An example of an Amprobe type meter:
dgoddard,
Thanks for the clarification!
440roadrunner,
I would agree with you on the neutral, however I have numerous 220v single and 3 phase machines with 110v controls, controllers, lights, or coolant pumps that came with the machine, are shown on the schematics, and have no provision for a nuetral!
How does all that work as far as electrical codes?
Glenn
Thanks for the clarification!
440roadrunner,
I would agree with you on the neutral, however I have numerous 220v single and 3 phase machines with 110v controls, controllers, lights, or coolant pumps that came with the machine, are shown on the schematics, and have no provision for a nuetral!
How does all that work as far as electrical codes?
Glenn
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440roadrunner
- Posts: 27
- Joined: Sun Sep 23, 2007 3:00 pm
- Location: N Idaho
Well, it is no longer "code." Years ago, such things as kitchen ranges were wired with a 3 wire hookup--even though the range MAY have had some 120V circuits--the clock, an extra on-the-range electrical outlet, lights, etc.
This is no longer code. I'm no expert on the ramifications, because "supposedly" the ground is tied to the main box, anyhow, but---
Some older commercial buildings depended on the metal (EMT) conduit for a ground--risky at best
The ground conductor is liable to undersized in such a case, and--
I believe it may affect some ground fault devices.
The REALLY REALLY big risk of this is, what happens if the ground opens up? Let's say you have a piece of shop equipment with 120V circuits--maybe even something simple like a lamp--tied to the machine ground, tied to electrical ground, and depending on this safety ground for a neutral return.
NOW if that ground opens up, what you have is 120V sitting right there on the metal machine body, assuming the machine "can't find" another path, like a piece of conduit, etc.
This situation is VERY risky, I can't emphasize that enough. I've screwed with enough older equipment to have come across this problem.
In the case of my parents house where I grew up--with older wiring, no 3 wire outlets, the Range/ground/neutral developed a problem, and was tied to the house piping--which was ABOVE ground because the house metal piping connected to plastic on the way to the well.
EVERY FAUCET in the house along with the range became a "shocker". I was young then, and my father could not understand the problem. After it was finally fixed, even I could see the problem--at 12 or 13 years of age or so.
This is no longer code. I'm no expert on the ramifications, because "supposedly" the ground is tied to the main box, anyhow, but---
Some older commercial buildings depended on the metal (EMT) conduit for a ground--risky at best
The ground conductor is liable to undersized in such a case, and--
I believe it may affect some ground fault devices.
The REALLY REALLY big risk of this is, what happens if the ground opens up? Let's say you have a piece of shop equipment with 120V circuits--maybe even something simple like a lamp--tied to the machine ground, tied to electrical ground, and depending on this safety ground for a neutral return.
NOW if that ground opens up, what you have is 120V sitting right there on the metal machine body, assuming the machine "can't find" another path, like a piece of conduit, etc.
This situation is VERY risky, I can't emphasize that enough. I've screwed with enough older equipment to have come across this problem.
In the case of my parents house where I grew up--with older wiring, no 3 wire outlets, the Range/ground/neutral developed a problem, and was tied to the house piping--which was ABOVE ground because the house metal piping connected to plastic on the way to the well.
EVERY FAUCET in the house along with the range became a "shocker". I was young then, and my father could not understand the problem. After it was finally fixed, even I could see the problem--at 12 or 13 years of age or so.
There is NO requirement for a "neutral" to be pulled in the US.
A 220 device may not use any 110V and so won't need it. In the US neither 220 line is at ground (neutral) potential, although they are ALWAYS referenced to ground by bonding what WOULD be the neutral to ground at the service box. That means that the "220" line is really two 110V lines of opposite polarity, both referenced to ground.
That 220 circuit causes a lot of confusion among our foreign friends who recoil in horror at such "incredibly dangerous" wiring, which in reality is perfectly safe.
A 3 phase circuit may not have a neutral pulled, and it isn't necessary there either unless the 'star" voltage is used by control circuits, etc.
The only place on earth that I am aware of where "neutral" isn't grounded at the service box (main power inlet to building) is Norway. I understand that it isn't/wasn't code to do that there.
There are certain issues with hospital equipment also, that affect how grounds etc on specially marked outlets in hospitals are wired.
Aside from those, I think it is perfectly fair to say that a neutral (groundED conductor) is grounded one place, and bonded to the green ground wire (groundING conductor there.
It is also fair to say that there SHOULD NEVER be any current in the green/bare groundING conductor, at least within the building wiring. Any interconnection of the white and green wires (grounded and grounding conductors) Will cause a current in the green wire.
You should make certain that each piece of equipment has a proper wiring and that NO current flows in the green (or bare) groundING conductor.
One exception..... If you check your actual main groundING wire, the large one that goes to the pipes and ground stake from the service box, you MAY find currents.
This is due to current splitting between your "neutral" in the power drop wires and the path back through your water pipe to your neighbor;'s pipes and "neutrals" in THEIR drop wires. I usually find 1 to 5 amps flowing in the pipes and grounding wire in most houses with iron or copper water pipes.
I would advise NEVER relying on ANY piece of chinese equipment being correctly wired as-received...... Even the UL/CSA/CE/C-tick marks may be forgeries, and any part inside may actually be a sub-standard counterfeit.
Counterfeit or wrong is often cheaper to make, and we have taught them that cheaper is better, and that low price makes bad quality acceptable.
A 220 device may not use any 110V and so won't need it. In the US neither 220 line is at ground (neutral) potential, although they are ALWAYS referenced to ground by bonding what WOULD be the neutral to ground at the service box. That means that the "220" line is really two 110V lines of opposite polarity, both referenced to ground.
That 220 circuit causes a lot of confusion among our foreign friends who recoil in horror at such "incredibly dangerous" wiring, which in reality is perfectly safe.
A 3 phase circuit may not have a neutral pulled, and it isn't necessary there either unless the 'star" voltage is used by control circuits, etc.
The only place on earth that I am aware of where "neutral" isn't grounded at the service box (main power inlet to building) is Norway. I understand that it isn't/wasn't code to do that there.
There are certain issues with hospital equipment also, that affect how grounds etc on specially marked outlets in hospitals are wired.
Aside from those, I think it is perfectly fair to say that a neutral (groundED conductor) is grounded one place, and bonded to the green ground wire (groundING conductor there.
It is also fair to say that there SHOULD NEVER be any current in the green/bare groundING conductor, at least within the building wiring. Any interconnection of the white and green wires (grounded and grounding conductors) Will cause a current in the green wire.
You should make certain that each piece of equipment has a proper wiring and that NO current flows in the green (or bare) groundING conductor.
One exception..... If you check your actual main groundING wire, the large one that goes to the pipes and ground stake from the service box, you MAY find currents.
This is due to current splitting between your "neutral" in the power drop wires and the path back through your water pipe to your neighbor;'s pipes and "neutrals" in THEIR drop wires. I usually find 1 to 5 amps flowing in the pipes and grounding wire in most houses with iron or copper water pipes.
I would advise NEVER relying on ANY piece of chinese equipment being correctly wired as-received...... Even the UL/CSA/CE/C-tick marks may be forgeries, and any part inside may actually be a sub-standard counterfeit.
Counterfeit or wrong is often cheaper to make, and we have taught them that cheaper is better, and that low price makes bad quality acceptable.