220v Wiring Help

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  #1  
Old 05-27-13, 03:59 PM
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220v Wiring Help

Hi- This is my first post. Would appreciate any help with the following. I'm currently installing a home automation system (yes- I know there is a sub-forum for that but since my question is on wiring- I thought this would be the place to post). My plan for today was to replace the switch for a free standing 220v air conditioner. When I opened up the switch/junction box I found that my contractor seems to have taken a "shortcut": instead of using a double pole switch- he "hard wired" one leg and used a single pole switch for the other "leg". I really like electrical work and would like to educate myself. My questions:

- was the air conditioner using any current while seemingly off?

- was this wiring scheme damaging the air conditioner in any way?

- aside from the potential shock risk to anyone who may have worked on the air conditioner thinking it was off- is there any other down- side to wiring this way?

THANKS!
 
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Old 05-27-13, 04:20 PM
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Voltage is 240 not 220 for standard residential service. You only need to break one wire to stop the flow of electric but for safety if used as a service disconnect it should be double pole. Is this central AC or a window AC. Normally central ACs are connected using a double pole disconnect switch. Can you please post pictures? http://www.doityourself.com/forum/li...-pictures.html
 
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Old 05-27-13, 04:22 PM
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I take it that this was a central air conditioner unit?

If so the breaker should have been a 2 pole breaker. Both of the hots need to be disconnected at the same time. Only having one leg de-energized presented a shock hazard to anyone working on the unit.

With the switch off there was no return path for the circuit to be complete.
 
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Old 05-27-13, 08:11 PM
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- aside from the potential shock risk to anyone who may have worked on the air conditioner thinking it was off- is there any other down- side to wiring this way?
Wow....is that dangerous. It sounds like that contractor was just there. I'd call him up and ask him what the he** was thinking.
 
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Old 05-27-13, 08:22 PM
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As Ray posted, this is acceptable for control wiring, but not as a disconnecting means. Anybody servicing the unit would pull/switch the disconnect to kill power to the unit.

If this is done in/at the disconnect, then this is wrong, and PJmax's post pretty much nails it.
 
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Old 05-27-13, 11:26 PM
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Hi-
Thanks for everybody responding. The unit is a wall/window free standing air conditioner (Friedrich) (Not central air). It is rated as 240 VAC (not 220- my error); 15 A and 3600 watts. I'm happy to send pictures if my description is not clear but the setup is straight forward: I have a 240 receptacle under the unit and then a WALL switch below the receptacle (standard decora paddle). My questions pertain to the wiring of the decora paddle switch/junction box. The decora paddle switch is a single pole- it only breaks one "leg". Both the neutral and the other "leg" "pass through" the junction box. I'm not sure what is being meant by a "service disconnect" - does this refer to the breaker? (not an issue at the current time). The unit was installed 2 years ago and I haven't had any trouble with it. Ray seems to suggest that only breaking one "leg" might actually be acceptable- did I understand correctly? [with the understanding that anyone working on the A/C unit would need to pull the breaker prior to work- which any competent technician/ electrician should do anyway].
Some additional info- my intent is to add the air conditioner to my Insteon home automation system. Unfortunately- Insteon doesn't make a small 240 switch for standard applications. For this reason I was going to use an X10 switch which is compatible with Insteon. You can see the X10 switch here:

X10 XPS2 Heavy Duty 220V X10 Wall Switch - Ivory - Smarthome

The x10 protocol is not as reliable as Insteon. For this reason- if hard wiring one "leg" is acceptable- I'd much rather use this switch:
SwitchLinc On/Off - INSTEON Remote Control Switch (Dual-Band), White - Smarthome

What should I do? THANKS!
 
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Old 05-28-13, 04:29 AM
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If the A/c unit is cord connected, which it sounds like it is, it is OK to interupt one leg of the 240 volt to the receptacle. Receptacles are not required to have a disconnect.

The Insteon switch should work fine, however you need to make sure you have a neutral in the switch box. What you call a neutral in the box may not really be a neutral, even though it is white. It might be just the other leg of the 240 volts. You need to confirm that it is a neutral with a meter and read between it an one hot. You should get 120 volts (be sure to set your meter to a higher voltage) Also read between it and ground, and you should get close to zero volts.

A disconnect is basically a way to disconnect power to a piece of equipment. This can be as simple as a cord connected appliance to a multi-phase switch
 
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Old 05-28-13, 02:48 PM
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The x10 protocol is not as reliable as Insteon.
Really? Haven't had any problem with X10 over the past 14 years. How much more reliable does something have to be to justify a 56% markup?

I would install the XPS2 for two reasons. Besides my comfort level with them and the significant cost difference, there's this:
The SwitchLinc installs like a traditional wall switch with the exception of requiring connection to neutral.

Source: Smarthome
Both the neutral and the other "leg" "pass through" the junction box.
There is no neutral conductor in a straight 240V circuit. There are two ungrounded conductors - i.e., two hot wires. If you only have a pair of wires going to your 240V receptacle, then you don't have neutral.

To answer your earlier question, unplugging the window/wall unit is the means of disconnect. The single-pole switch is not. That means you don't have to install a double-pole switch to replace it - but it wouldn't hurt.
 
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Old 05-29-13, 03:19 PM
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Hi- Thanks for all the feedback. I have a total of 6 wires in the switch box (3pairs).
The black pair is the one "broken" by the switch (leg 1) and the red pair is energized (leg 2). That leaves the white pair. I live in NYC and all my wiring is BX/MC. My contractor explained to me that the ground is "carried" by the box and "over" the BX/MC metal (from what I've read on the internet this seems to be correct). For this reason - I don't have separate grounds in any of my other boxes. I've since done some reading and like Nashkat 1 says- a 240v switch doesn't use a neutral. I had assumed that the white pair was my neutral but maybe my contractor decided to run a "true" ground. Whats the best way to differentiate if the white is a neutral vs true ground? Thanks!
 
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Old 05-29-13, 03:44 PM
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Your ground would not be white if the wiring is done properly. White is reserved for neutrals.

Measure between white and the box. You should read 0 volts.
 
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Old 05-29-13, 07:08 PM
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My contractor explained to me that the ground is "carried" by the box and "over" the BX/MC metal (from what I've read on the internet this seems to be correct). For this reason - I don't have separate grounds in any of my other boxes.
Sort of correct. BX/AC (Armor Clad) that has a bonding strip uses the cable armor as the grounding path. MC cable uses a separate green grounding wire in the cable. Newer MCAP (Metal Clad All Purpose) has a full sized aluminum bonding strip.

If there is no ground wire (green or bare) in the boxes, your metal wiring method is your grounding path. Any ground wire should be bonded to the metal boxes with screws or clips.

I've since done some reading and like Nashkat 1 says- a 240v switch doesn't use a neutral.
Yur A/C unit does not need a neutral, but the switch you posted in the link does.
 
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Old 05-29-13, 07:58 PM
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I've since done some reading and like Nashkat 1 says- a 240v switch doesn't use a neutral.
Please don't put words in my mouth - it isn't sanitary.

What I actually said was
There is no neutral conductor in a straight 240V circuit. There are two ungrounded conductors - i.e., two hot wires.
The switch from Smarthome requires a neutral. You don't have neutral available. The XPS2 from X10 does not require a neutral and will work with your wiring.
 
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Old 05-29-13, 09:57 PM
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Originally Posted by Nashkat1 View Post
Really? Haven't had any problem with X10 over the past 14 years. How much more reliable does something have to be to justify a 56% markup?
There's nothing wrong with X10, but larger systems can be flaky. X10 is cheaper because it is a 'dumb' system. The receivers simply listen for their control code (on/off/bright/dim/all lights on/all units off) to come over the power line and react to it when they hear it. The biggest issue with X10 is that you basically NEED a phase bridge to ensure reliability.

Insteon is a 'smart' system, in that it not only listens for its control code and reacts to it, but it acknowledges the command to the controller. Not only that, but each module can be queried for its status by a controller/computer, so you can for example see from an Android app that the garage door is closed, the living room light is on, and the porch light is off..

Additionally, Insteon creates a Mesh network among all of its modules. Every module acts as a signal repeater so missed signals are virtually non-existent, even in the largest and noisiest of systems, even polyphase.
 
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Old 05-29-13, 10:46 PM
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Thanks Matt. The switch the OP found through them still won't work with his 240V circuit. The one from X10 is the only one I could find that will.
 
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Old 05-30-13, 06:15 AM
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The biggest issue with X10 is that you basically NEED a phase bridge to ensure reliability.
If the "biggest issue" with a system is needing to purchase one little $30 plug-in box for the whole house, that doesn't seem like a huge issue to me.

My biggest issue with X10 was that occasionally the dimmer signals would get confused with all-lights-on and I'd have lights on in obscure places for weeks without being noticed. So I was pretty much unable to use any dimmers on the remotes.

If I was setting up a system now I'd sure want 2-way communication with the devices though.

For what it's worth, I've stopped using X10 altogether only because of switch loops and CFLs. It wasn't worth me tearing up plaster walls in a 100 year old house just for neutrals.
 
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Old 05-30-13, 11:56 AM
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Originally Posted by Nashkat1 View Post
Thanks Matt. The switch the OP found through them still won't work with his 240V circuit. The one from X10 is the only one I could find that will.
Im not so sure it won't work.. I may be wrong, but the way I am reading it, the 2477S switch (the one we've been discussing) is rated up to 277V.. That means in this 240v application (if I am thinking about it right) you would hook it up with the neutral for the Insteon switch connected to the other hot leg. An actual 120v 'split phase neutral' is not needed.
 
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Old 05-30-13, 01:19 PM
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I'm currently thinking of trying the set up with the x10 switch. I had the A/C on yesterday and already started to have some trouble with other switches on my Insteon system responding. This is likely from either the AC throwing out line noise or "eating" the Insteon signal (I think line noise is more likely). I have no basis to think that the x10 switch will help filter out line noise- but I know the Insteon switches won't. I have nothing to lose by trying.... If I still have line noise - that will be a whole other project probably requiring I open the wall to add additional junction boxes and install line filters (not fun).
The line noise issue exists for both x10 AND Insteon. Insteon seems to know this and is increasingly only selling "dual band" switches that both send a line signal AND a wireless signal. BOTH x10 and Insteon require phase bridging (unless, of course, you have a very simple and small set-up all on the same phase). As the newer switches are dual band they are often larger- creating box-fill issues.
Now back to my question: for the purpose of the Insteon switch though- I still have that white wire.
Does it really matter if this is a "true" ground vs. a "true" neutral? (I know that there are differences between the "grounding" connector vs. the "grounded" connector. Could someone explain it to me a little better? I'm still a little confused as to how to differentiate the two using my multimeter. Thanks for all the help!
 
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Old 05-30-13, 03:17 PM
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for the purpose of the Insteon switch though- I still have that white wire.
Does it really matter if this is a "true" ground vs. a "true" neutral? (I know that there are differences between the "grounding" connector vs. the "grounded" connector.
If you're talking about the box with the switch for your window/wall A/C unit, only the "grounding" part applies.

A quick primer on your electrical system: You have a 120/240V electrical supply in your house. That means that the power from the utility comes in on three wires. One of those three wires is a "neutral." The other two wires are the two "hot" legs. Each of those carries 120V relative to neutral, and the two carry 240V relative to each other.

In your main distribution panel, each of the two "hot" utility wires is connected to a bus that feeds alternating rows of breakers. Bus A, let's say, feeds breaker positions 1 & 2, 5 & 6, 9 & 10, etc., and Bus B feeds breaker positions 3 & 4, 7 & 8, 11 & 12, etc. The incoming neutral is bonded to a separate bus bar and to the earth. That establishes the Grounding Electrode Conductor. That separate bus with the incoming neutral connected to it is also where the branch circuit "neutrals" and "ground wires" are terminated. Because they are bonded together, the "neutrals" and "grounds" in your house carry the same potential, although they serve different purposes.

Any single breaker in your panel can supply 120V when combined with a connection to neutral. Any two breakers that are fed by the two different legs of the service will supply 240V. That'y why 240V breakers are 2-pole breakers that occupy two vertically adjacent spaces.

The proper name for the "hot" supply is "ungrounded potential."
The proper name for the "neutral" supply is "grounded potential."
The proper name for a "ground wire" is "an equipment grounding conductor."

In general in residential systems, ungrounded potential is carried on conductors with black or red insulation, grounded potential is carried on conductors with white insulation, and equipment grounding conductors are bare wire.

The major exception to this is when a 240V circuit is wired using 3-conductor, 2-wire cable with one black, one white and one bare wire in it. In that case, most jurisdictions allow the white wire in that cable to be used as the second ungrounded conductor. That wire is supposed to be marked, or tagged, with black or red (or any color except green or gray) electrical tape at every termination or splice to show that it has been re-purposed and is carrying ungrounded potential.

In the wiring supplying your A/C unit, the white wire is carrying the same potential as the black wire - 120V relative to neutral or ground. It should have been marked or tagged in the switch box to designate its different function, but it wasn't.

The bottom line is that a neutral conductor must always be white or gray, a white wire may not be functioning as a grounded, or neutral, conductor.

You don't have a neutral in that switch box, nor anywhere in that circuit. You have two ungrounded conductors, or "hots," and one grounding conductor, or "ground." That's why a switch that requires a neutral connection for its internal functions can't be used there.

If you plan to continue doing work that involves parts of your electrical system, you should buy and read Wiring Simplified. You may be able to find it in the electrical aisle at a big box store.

Wiring Simplified is authoritative, inexpensive and readable. It explains why, as well as how, residential electrical systems are put together. It is, in a word, the text for our little online seminar.
 
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Old 05-30-13, 04:58 PM
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Originally Posted by Nashkat1 View Post
You don't have a neutral in that switch box, nor anywhere in that circuit. You have two ungrounded conductors, or "hots," and one grounding conductor, or "ground." That's why a switch that requires a neutral connection for its internal functions can't be used there.
I guess you missed my post earlier.. This switch is rated for 120-277v.. Considering there would be no fundamental difference between 240v line-to-line and 277v line-to-neutral as far as powering the switch's circuitry goes, the 'neutral' wire from the switch could simply be connected to the other hot leg.
 
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Old 05-30-13, 10:37 PM
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I guess you missed my post earlier.. This switch is rated for 120-277v.. Considering there would be no fundamental difference between 240v line-to-line and 277v line-to-neutral as far as powering the switch's circuitry goes, the 'neutral' wire from the switch could simply be connected to the other hot leg.
Yes. If I had seen it I would have questioned it. Here's why:

Wires
Line (Hot) - black, 12 AWG
Neutral - white, 18 AWG
Load - red, 12 AWG
Ground - bare copper, 12 AWG
Source: SMARTHOME
Nothing tells me that an 18 gauge wire built into a device for connecting to grounded potential can simply be connected to the other ungrounded potential.

Here's the part I missed:
Both the neutral and the other "leg" "pass through" the junction box... I have a total of 6 wires in the switch box (3pairs).
The black pair is the one "broken" by the switch (leg 1) and the red pair is energized (leg 2). That leaves the white pair. I live in NYC and all my wiring is BX/MC. My contractor explained to me that the ground is "carried" by the box and "over" the BX/MC metal...
Biglarmd, I apologize for the lecture about electrical systems. Use a multimeter to verify that the white wires are, in fact, neutral. If they are, you can install the switch from SMARTHOME and connect its white wire to the white wire splice in the box.

 
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