220 V Wiring

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  #1  
Old 09-07-11, 01:31 PM
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220 V Wiring

Hi there,
I have a electric range that is connected from a 50A breaker in the electric panel.
I am separating my range into a gas cooktop and a wall oven.

So, this means that I will reroute the range line to the new wall location.

I turned off the breaker, then checked for voltage in the 220V outlet, then removed the wires from the gang box.

Questions:
1) It's a 3 wire setup: 2 blacks and 1 ground. I am confused by this-I expected a 1-black, 1-red and ground. The new wall oven's instructions are straight-forward: black to black, red to red, ground-ground.

So, which is black and which is red in my oven line?

2) The new oven calls for a 40Amp breaker. If I swap out the existing 50-Amp breaker for a 40 Amp breaker, will that be fine?

Thanks
 
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  #2  
Old 09-07-11, 01:47 PM
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The colors red and black are interchangeable. Yes, you should change to a 40 amp breaker.* How did you plan to extend it?

*Assumes a minimum of #8 copper/#6 aluminum.
 
  #3  
Old 09-07-11, 04:11 PM
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If Aluminum, you also need noalox grease or something similar.
 
  #4  
Old 09-08-11, 02:50 AM
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Thanks.
The existing lines are all aluminum.

Extension - At this time, it appears that the existing length will be enough to take it to the new location.
However, assuming that that is not the case, what is involved in extending it?

I have read elsewhere on this forum that a 220 line can be extended via a junction box.
The oven does not come with a male plug, it's meant to be hard-wired.

So, here's my plan for the extension (if necessary):
1) Disconnect/remove 50 Amp breaker
2) Pigtail oven to a new appropriate wire (aluminum or copper?) (use conducting grease as Justin mentions)
3) Connect other end of new wire to existing wire in a junction box (again, use conducting grease)
4) Connect other end of existing wire (pop in new 40 Amp circuit breaker)
5) Bake that lasagna kids have been asking for since the oven has been down!

Please advise if I am missing something.
 
  #5  
Old 09-08-11, 06:32 AM
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I have read elsewhere on this forum that a 220 line can be extended via a junction box.
The oven does not come with a male plug, it's meant to be hard-wired.
That is correct except the nominal voltage is actually 240v in most homes. The junction box must remain accessible. You would probably use 8-3 copper NM-b so special connectors would be needed to join to the existing aluminum cable. Same thing if the whip on the oven is not rated cu/al and you don't move the existing cable. Anti-oxidant grease isn't enough. The connectors must also be rated cu/al.
 
  #6  
Old 09-08-11, 09:52 AM
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The oven is here and the wires are aluminum.
Here's a picture:
Left - Line from the electric panel
Right - Oven wires (these are a lot thinner than the wires from the panel!)



So, if I use al wires for the extension between the 2 sets of wires shown in the image, there should be no al/cu issues, correct? Should I stick with al/cu rated connectors or anything else, now that everything is al?

Thanks
Alex
 
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Old 09-08-11, 09:59 AM
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Oven wires are probably tined coper not aluminum. Use Noalox or equivalent on the connections and a connector rated for aluminum not a regular wire nut.
 
  #8  
Old 09-08-11, 11:12 AM
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Since you have FOUR wires on your new oven it appears that it requires a 240/120 volt supply. IF you do not move the existing three-wire supply you can use it PROVIDING you use the proper aluminum-to-copper connectors. If you DO move the existing cable then you will need to replace the old cable with a new four-conductor cable all the way back to the circuit breaker panel.

If you can use the old cable then you need to carefully read the instruction manual for the oven to see how to connect the four oven wires to a three-wire cable.
 
  #9  
Old 09-08-11, 11:23 AM
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Ray,
Just to be sure, you are suggesting that I use a connector rated for al, not al/cu. Correct?
 
  #10  
Old 09-08-11, 11:55 AM
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Alex, the wires on your new oven are NOT aluminum, they are tinned copper. Proper connectors will be rated for CU/ALR.
 
  #11  
Old 09-08-11, 11:59 AM
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You will need to replace the aluminum wire anyways because theres no neutral.
 
  #12  
Old 09-08-11, 12:01 PM
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Justin, IF he is able to connect the new oven without moving or adding to the existing cable then it is a grandfathered installation. If it IS necessary to add to or move the existing cable then he needs a new cable.
 
  #13  
Old 09-08-11, 12:07 PM
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Originally Posted by Furd View Post
Since you have FOUR wires on your new oven it appears that it requires a 240/120 volt supply. IF you do not move the existing three-wire supply you can use it PROVIDING you use the proper aluminum-to-copper connectors. If you DO move the existing cable then you will need to replace the old cable with a new four-conductor cable all the way back to the circuit breaker panel.

If you can use the old cable then you need to carefully read the instruction manual for the oven to see how to connect the four oven wires to a three-wire cable.
Furd,
Thanks for bringing it up. I read the manual and it says that connections to 3-wire and 4-wire circuits are possible.
For connection to 3-wire circuit, it says:
1. Connect the oven ground (green) wire and neutral
(white) wire to the branch circuit neutral (white or
gray in color) wire, using a wire nut.
2. Connect the oven red wire to the branch circuit red
(L2) wire in accordance with local codes, using a
wire nut.
3. Connect the oven black wire to the branch circuit
black (L1) wire in accordance with local codes,
using a wire nut. If the residence red, black or white
wires are aluminum conductors, see WARNING on
page 8.
4. Install the junction box cover.
As mentioned before and can be seen in the image below, the branch circuit has 2 black wires and one bare wire.
So, in step 1: branch circuit neutral means the bare wire? (It says white or gray, but I have only bare)
Step 2: branch circuit red wire means one black wire
Step 3: branch circuit black wire means the other black wire
 
  #14  
Old 09-08-11, 12:13 PM
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The warning in step 3 is as follows:
Improper connection of aluminum
house wiring to copper leads can
result in an electrical hazard or fire.
Use only connectors designed for
joining copper to aluminum and
follow the manufacturer’s
recommended procedure closely.
 
  #15  
Old 09-08-11, 12:16 PM
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That is correct. Understand that the three-wire connection, while grandfathered, is NOT as safe as the now required four-wire circuit.

Yes, you need connectors that are rated for both aluminum and copper wire.
 
  #16  
Old 09-08-11, 12:21 PM
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Can he use the 3 wire cable as the 3rd (bare) wire is ground and it sounds like he needs 120 for part of the oven and the ground wire would now be acting as the neutral?
 
  #17  
Old 09-08-11, 12:46 PM
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Yes, as long as the existing cable is not moved or extended it is grandfathered. Any extension, no matter the length, would void that grandfather clause and require a new four-conductor (three insulated plus bare equipment ground) cable. The same holds true for merely relocating the existing cable.
 
  #18  
Old 09-08-11, 12:50 PM
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Most manufacturers design appliances to be compliant with either three- or four-wire circuits so they are compatible with pre-1996 circuits. The new type is safer, but the old ones can still be used as-is.

To join the copper to aluminum you need to get connectors which are rated for use with both metals. It should be marked Cu/Al. Polaris is one brand of this type of connector, but I don't recall off the top of my head if they make one small enough for range wiring. A good Cu-Al joint needs to be mechanically fastened (screw, bolt), not a friction fit connection like a wirenut.
 
  #19  
Old 09-08-11, 01:11 PM
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Curiosity questions:
1) In my branch circuit with 2 insulated wires and a bare wire, it is said that there is no neutral. Then, where did the neutral go? Is it connected to the bare wire back at the panel?

2) When the manufacturer instructs to connect the white and green on the oven to the "neutral" on the branch, do they mean to the bare wire on my branch?

From all these wordings, it seems that the neutral and the ground are the same in my branch circuit and that this is the bare wire. Is this correct?
 
  #20  
Old 09-08-11, 01:24 PM
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Many decades ago, some state it was for conserving copper for the (WWII) war effort, the code allowed for a combined neutral and equipment grounding conductor for certain appliances. I think it was about fifteen or twenty years ago that this practice was finally changed in the code. However, because there was/is such a huge number of homes that were wired under the old standard the code has allowed that previously acceptable installations can remain in use PROVIDED they are still in serviceable condition AND are not mover or extended.

Yes, in this instance the equipment ground and neutral are the same conductor and in your case that would be the bare wire in your existing cable.
 
  #21  
Old 09-08-11, 02:04 PM
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Thanks for the clarification.
Even though I did not need an extension, I will have to move it. So, I am going to rewire all the way to the panel with new wires. Better safe than ...

Now, I need to finalize the breaker amperage and wire gauges. Please scratch my earlier mention of a 40Amp breaker requirement. On reading the manual, here's what I find:

Mine is a single wall oven. The manual says:

A single wall oven can consume up to 4,100W at 240VAC.
A 30Amp circuit breaker with wire gauge at least #14 AWG must be used.
Then, the oven specs say the following:
Broiler Element: 2500W Inner/1500W Outer
Bake Element: 2500 W
Convection Element: 2500W
I guess the bake and broil elements may not be on at the same time, but the convection can be on while either baking or boiling. Hence, at full capacity, that's 5000W. So, I am not sure how the manual can say "A single wall oven can consume up to 4,100W at 240VAC."

So:
1) What should be the breaker rating?
2) What should be the wire gauge?
3) Should the wire be copper?
 
  #22  
Old 09-08-11, 02:12 PM
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Use a 30A double-pole breaker, #10-3/g NM-B cable, copper.

Or if you want some room for future expansion to a bigger oven use #8-3/g NM-B copper cable, but leave the breaker at 30A.
 
  #23  
Old 09-08-11, 02:15 PM
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Your 30 amp circuit for the oven would require #10, not #14 as the instruction mistakenly call for. You would use a 2 pole 30 amp breaker. You just need to tell if the oven is 240 or 120/240. If 120/240 you need a 10-3 cable with ground.
 
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Old 09-08-11, 02:26 PM
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Let me clarify my own answers. In your first post you stated:
The new wall oven's instructions are straight-forward: black to black, red to red, ground-ground
No mention of a neutral. Then you wrote:
The new oven calls for a 40Amp breaker.
Was that a different oven? My comments were based on those statements.
 
  #25  
Old 09-08-11, 03:04 PM
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Ray,
My apologies.
The oven calls for it's white and green to be connected together (to branch's neutral) when going into a 3 wire mode.
The 40Amp breaker info was from searching the internet.

I did not have much information earlier in the day. Later, the oven arrived and I have better info now (I think).
Alex
 
  #26  
Old 09-08-11, 03:08 PM
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Originally Posted by pcboss View Post
You just need to tell if the oven is 240 or 120/240. If 120/240 you need a 10-3 cable with ground.
Power Source says: 120/240 VAC, 120/208 VAC
 
  #27  
Old 09-08-11, 03:17 PM
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Originally Posted by AlexWoods View Post
Power Source says: 120/240 VAC, 120/208 VAC
You need a 10-3 with ground if the circuit calls for 30 amps.
 
  #28  
Old 09-08-11, 04:09 PM
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All right! It is now established that I will run new 10-3 copper wires from the oven to the electric panel.

Now, regarding the electric panel itself - it's about 20 feet of cable between the oven and the panel and has to run through some tricky routes. Not a big deal, if I have to.

However, there is a sub panel much closer by, about 10 feet away. The previous owner must have put it in for a workshop. It's has no breakers on it at this point. It is a Homeline Load Center product that is rated for 100A. I need to find out which breaker on the main panel supplies the power to this sub panel. So I will update later.

If it is controlled by a breaker rated > 30A, can I use this?
 
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Old 09-08-11, 04:30 PM
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If it is controlled by a breaker rated > 30A, can I use this?
30a or greater. You would put a 30a 240v breaker in the subpanel. It would be very unusual to have a subpanel fed by less then 30a.
 
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Old 09-08-11, 04:35 PM
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That's good to know. Saves me a lot of time and wire.
I am sure that it's atleast 30A, I will confirm the exact breaker amp later.
 
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Old 09-08-11, 05:48 PM
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Be sure it is fed by two hots a neutral and a ground. If it is metal conduit all the way back to the main panel the conduit can serve as ground.
 
  #32  
Old 09-09-11, 10:32 AM
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Just curious - What is this need to hard wire the oven wires to the branch circuit? Does this not mean that the only way to disconnect the oven is to turn off the breaker at the panel in the basement? Would I be violating code if I put in a male plug on the oven and a receptacle on the branch at the wall and simply plug the oven into the receptacle?
 
  #33  
Old 09-09-11, 11:28 AM
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You could but the whip is not rated for use with a plug. You would have to remove the whip and install a cord set. The question is if the whip terminates in to a junction box on the oven and can easily be replaced or is integrated into the oven wiring. Not an appliance guy so I don't know.
 
  #34  
Old 09-09-11, 11:53 AM
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Originally Posted by AlexWoods View Post
What is this need to hard wire the oven wires to the branch circuit?
It's generally assumed that built-ins will rarely if ever be moved so might as well hardwire it. You could possibly replace the whip with a 14-30 cord (the type you use for a dryer) and add a 14-30R receptacle to the junction box, but that just adds an unnecessary $40 to the project.

Does this not mean that the only way to disconnect the oven is to turn off the breaker at the panel in the basement?
Correct. Some jurisdictions do require a breaker lock because it is not within line-of-sight of the oven, but that is only about $1 if it's even required in your area (not typical for residential).
 
  #35  
Old 09-09-11, 12:24 PM
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Sounds good. Looks like my weekend is taken care off with this little project. I'll get started first thing tomorrow morning and post here if I run into any issues. I can't thank you all enough for all the advice.
Alex
 
  #36  
Old 09-10-11, 07:50 AM
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The junction box that goes on the wall behind the oven where the hardwiring is done between the oven and the house wires: Should this be a metal box?
 
  #37  
Old 09-10-11, 07:59 AM
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As long as you don't use metallic cable either is OK. I'd use a metal box because the whip is metallic cable. If your going to surface mount I'd suggest a 4X4 metal box so there is plenty of room to work. If metal box grounds need to be tied together and pigtailed to the box. If you flush mount be sure you can get a blank cover with a knock-out to fit the whip cable clamp.
 
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Old 09-10-11, 08:56 AM
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The box also must remain permanently accessible.
 
  #39  
Old 09-10-11, 08:58 AM
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I am running into a minor issue here.
The oven has a cavity at the back top right corner just for placing the junction box.
The area on the wall where the junction box can be mounted is a generous 9"x6".
However, an air vent runs behind the wall in most of this area. There is a 3.5" space available before I hit the stud on the left.

This leaves me with a 3.5"x6" area to work with. This is still plenty, but a 4x4 box will not work. I will look around, but a 2x6 work will easily work in that gap (if I can get one).
Any ideas welcome.
 
  #40  
Old 09-11-11, 02:50 AM
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I mounted a box on the drywall. It snow sits in the cutout space provided on the back of the oven.

Originally Posted by Justin Smith View Post
The box also must remain permanently accessible.
The only way to access the box is after sliding the oven out of the cabinet. Is this considered permanently accessible?
 
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