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I am replacing my oven. Service at the main breaker's bus bar has neutral and ground in the same bus bar.
Since the wire to the old oven is Aluminum, I will run Aluminum wire to a sub panel and use copper wire from the breaker to the oven. Do I bond the neutral bar to the sub box?
I don't want to use the copper to aluminum wire wing nut twisters. Should I just run copper from the main? The house was built in 1995. ny pete
If it was me, yes I would run copper all the way out. Im not sure how far you have to go, but I wouldn't mix wire types. I'm not sure if it's a code violation or not. Others on this forum WILL know.
In your situation you can land your grounds and neutrals together in the sub panel and not have any problems. Since the sub is in your house and not in a detached building.
If I am wrong others will chime in and set me straight lol
Avoid using aluminum whenever possible. It takes experience to install it properly. Many electricians today do not know and understand how to properly install aluminum because it was used widely in the 60s when copper prices were high. Number one, the right material has to be rated for aluminum conductors (Usually stamped with an "AL/CU"). Two, the conductors should be prepared (lightly rubbed with emery cloth) so as there is no "oxidation" left on the bare conductor connection. Try not to "gouge the surfacing". You are merely removing the discoloration of the conductor, not digging into it. Three, watch how the insulation is stripped from the conductor with your wire strippers. Try not to "dig" into or "ring" the conductor's circumference. AC current travels on the outside perimeter of a conductor (Called "Skin effect") and if this is "butchered" it affects it's current carrying capacity and creates a "hot spot". And four, some anti-oxidant should be applied to the prepared conductor to assure no oxidation build up happens after the conductors are terminated. The primary reason for this is, "Aluminum oxide" is not a conductor of electricity and "copper oxide" is a conductor. Copper is far more forgiving. If it is not prepared properly, it creates "hot spots" at the connection as loads are applied. Improperly installed aluminum conductors have been the culprit of many house fires due to this reason. If you cannot avoid aluminum conductors heed the advise above and proceed with your plan. To answer the original question, the neutral is connected to the ground at its source only. In a house, this would be your main panel. A subpanel is not considered its source therefore any jumpers between ground and neutral bus need to be removed.
Mr 500 needs to be set straight.
Neutral and ground are bonded together in the main panel ONLY.
Neutral MUST be isolated in any subpanel. There is a way of doing this, but you may have to purchase a ground bar kit for the sub panel. Neutral and ground will connect to different busses in the sub-panel.
The sub-panel can be of a main lug type (no disconnect) or you can use a standard panel as the sub-panel and use whatever breaker it came with for the disconnect. The feed to the sub will be protected by the breaker feeding it from the main panel.
Use copper all the way. You can use NM-B cable (Romex).
And you did LOL> I was under the impression that the grounds/neutral could be together as long as the sub was NOT in a detached building with no path between the two structures.Quote:
Originally Posted by KeepItSimpleStupid
So kiss your saying that ANY sub no matter where it is located HAS to have a separate Equipment ground and be isolated from neutral? AND the only place they can land together is at the MAIN panel. Just to clear all the air on this. Electricity 101. Least I was OK saying use copper all way out :D :D
If the sub is in a detached building then a ground rod must also be used at the sub panel.
The point is that ALL the electrical systems have to have a "zero reference" and it must occur in only one place. That zero reference is at the first disconnect which does not technically have to be in the main panel.
Telephone and cable should share this same reference point.
Never bond the neutral and ground at a sub panel. Bonding should only be made at the main breaker and in your case it sounds like the main breaker and branch distribution are within the same panel. Using 3 wires to a sub panel and then going from the subpanel to your receptacle with 4 wires would defeat the purpose of a 4 wire system unless you properly isolated the neutral and added a grounding conductor to the subpanel. If you were going to add wire to the subpanel why not just pull an additional insullated wire (assuming the third wire presently there is a bare grounding conductor) of the same size and type to the existing receptacle box and avoid using the subpanel all together.
Read the installation manual and see what it says is required for your installation. There may be alternate methods for installing it with a 3 wire plug instead of 4 if the appliance has a bonding option. I'm not sure if the new code applies only to new construction or applies to the installation of a new appliance in an existing home. Perhaps one of the electrical guru's here could chime in and let you know the details of the most recent code, but if I'm not mistaken it only applies to new construction or homes built after the rule went into effect, but don't quote me on that!
The major issues with stranded aluminum wire is joining it with other metals; oxidation (so be sure to use an antioxident liberally on the exposed aluminum when terminating it); and making sure that the receptacles, breakers, and panels used are capable of handling aluminum. These will be marked CU/AL for most breakers and panels or CO/ALR for most receptacles. These days it is most common that they are rated for both metals but be sure to verify that before using aluminum on them. The issues that gave aluminum wire a bad name was the use of solid conductor aluminum wiring in the 60's and 70's on smaller branch circuits where problems arose with thermal expansion, oxidation, galvanic reactions when joined or spliced with other metals, and improper terminations. Other problems such as receptacles that were not intended for being used with aluminum and even some that were rated as being okay for aluminum when in fact they weren't, were problems associated with galvanic reactions because of the dissimilar metals and the aluminum reacting with the base metal in the receptacle and the rates of expansions being different for each of the metals used.
The stranded aluminum wire is less expensive than copper, easier to bend and work with and when installed properly is perfectly fine for use in larger amperage applications. Check the manual and see if there are provisional options for use with a 3 prong plug and be sure to check and see if it meets NEC and local code.
Home Inspector, all good advice, however, a few years too late.
Please refrain from answering questions older than a few months.
Thread is closed.
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