wire to subpanel


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Old 11-26-07, 07:17 AM
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wire to subpanel

I have a subpanel that was originally a 220v feed to my electric furnace. A previous owner added some 110V circuit breakers to that subpanel for various things. When we bought the house, the inspector made them add a fourth wire (originally only one three conductor cable fed that subpanel) from the main box to the sub panel for an additional ground, neutral or some such thing needed because of the 110V circuits. I've had some furnace work done, and their electrician says it cannot be done that way. He says I must replace the two wires (big 3 conductor wire and the single added wire) with a single 4 conductor wire to meet code. Is this true? Theye want to run new 4 conductor copper cable.
 
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Old 11-26-07, 07:54 AM
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I have a subpanel that was originally a 220v feed to my electric furnace. A previous owner added some 110V circuit breakers to that subpanel for various things. When we bought the house, the inspector made them add a fourth wire (originally only one three conductor cable fed that subpanel)
Three-wire subpanels used to be legal. It depends on how long ago this subpanel was installed, but there's a decent chance that this subpanel was legal as it was and the home inspector was wrong. What type of inspector enforced this change? However, now that the feeder has been modified possibly without a permit, you may in fact be required to fix it.

He says I must replace the two wires (big 3 conductor wire and the single added wire) with a single 4 conductor wire to meet code. Is this true?
Do you know if the existing three-wire cable has all three wires insulated black-red-white or is it black-black-bare? Do you know the AWG of the wires involved? Is there any printing on the cable jacket? What is the size of the breaker feeding the subpanel?

The best solution to meet modern safety standards is to replace the existing feeder with a new four conductor cable. What I am not sure about is whether you are legally obligated to do so. Your answers to the above questions may help us determine that.
 
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Old 11-26-07, 08:14 AM
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thanks for the replies. I can see no writing on the wire. It is a large oval shaped wire with three conductors, a red, black, and bare stranded aluminum. The subpanel originally fed just the electric furnace and had a 100A breaker. When some 30A 110V breakers were added, it necessitated the addition of the extra wire, which appears to be single conductor, black insulation, copper wire about as thick as a finger. They put white tape on this wire to give it a striped appearance. I was told the main wire looked like #2 AL, but the guy was really guessing...I think. Nobody "official" actually inspected this, just the house inspector when we bought the house.
 
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Old 11-26-07, 08:28 AM
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The wire added was a neutral. The original furnace did not need a neutral, but the 120 volt circuits added do require one.

The addition of the wire was incorrectly done and is unsafe.

What 120 volt circuits were added that need 30 amp breakers?

Replace the cable. it is unsafe the way it is.
 
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Old 11-26-07, 08:43 AM
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Thanks for the reply. There are two 110v breakers in the box, one is a 15A that feeds an electrostatic precipitator (filter) on the furnace, and the other is actually a 20A breaker that feeds the lights and outlets in a small detached barn/shed/garage. I don't understand why having the wire separate makes it unsafe. It is sitting along the same path as the three conductor wire, it's just not wrapped in the same piece of plastic insulation.

Originally Posted by racraft View Post
The wire added was a neutral. The original furnace did not need a neutral, but the 120 volt circuits added do require one.

The addition of the wire was incorrectly done and is unsafe.

What 120 volt circuits were added that need 30 amp breakers?

Replace the cable. it is unsafe the way it is.
 
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Old 11-26-07, 08:49 AM
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You answered the question. "it's just not wrapped in the same piece of plastic insulation. "

If the additional wire were a ground wire, does not normally carry current, then it could be argues that it is safe (or relatively safe) and not an immediate concern.

However, this extra wire is a neutral wire, which carries current. It is not legal or safe by itself (not in conduit and not in a cable assembly).

The electrician who wants to replace the cable and wire is correct. Allow him to do it. I know it costs money, but your house is a fire and/or electrocution waiting to happen the way it is now.
 
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Old 11-26-07, 08:56 AM
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Thanks. Also, my problems started because one of the terminals at the subpanel came loose over the years, and this caused it to become red hot, melt plastic parts of the panel and breaker next to it, and stink up the house. He is suggesting I use copper wire {presently it is Al) if I am willing to spend the money. Any thought on that, or should I search the threads? Thanks again. We are talking 30' of cable here. Of course, I am also getting a new subpanel and breakers.

Originally Posted by racraft View Post
You answered the question. "it's just not wrapped in the same piece of plastic insulation. "

If the additional wire were a ground wire, does not normally carry current, then it could be argues that it is safe (or relatively safe) and not an immediate concern.

However, this extra wire is a neutral wire, which carries current. It is not legal or safe by itself (not in conduit and not in a cable assembly).

The electrician who wants to replace the cable and wire is correct. Allow him to do it. I know it costs money, but your house is a fire and/or electrocution waiting to happen the way it is now.
 
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Old 11-26-07, 09:04 AM
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The "PROS" will chime back in momentarily, But I think a "SUB PANEL FEED" would be considered a "Branch" circuit, which is no longer permitted to be aluminum. At any rate, use the copper,and be able to sleep at night.
 
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Old 11-26-07, 09:12 AM
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Since you are replacing the sub panel, you need to replace the cable. No inspector would approve a new sub panel with the cable that is presently in place.

My advice is to go with copper. Aluminum is allowed, but I prefer copper. That distance is not significant enough where I feel the cost difference between copper and aluminum is great enough to justify the aluminum..
 
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Old 11-26-07, 09:26 AM
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Thanks. They are replacing the subpanel today, and pulling the new wire tomorrow since it will involve some carpentry. They don't want me to be without heat tonight so they are temporarily wiring the new subpanel with the old wire. Tomorrow all will be well. Thanks again for the help. BTW I am going with copper wire.
 
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Old 11-26-07, 11:23 AM
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Given the added information, I believe that your electrician's assessment is correct. The subpanel feeder needs to be replaced with a new, four conductor cable. Either copper or aluminum is acceptable with appropriate terminations on each side, although over 30' the difference in price will not be substantial.

Originally Posted by UncleDiezel
But I think a "SUB PANEL FEED" would be considered a "Branch" circuit, which is no longer permitted to be aluminum.
Subpanel feeders are different than branch circuits. Feeders may be aluminum if the termination lugs are rated for aluminum (nearly all modern panels and breakers are) and you use non-oxidation grease on the bare metal.
 
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Old 11-26-07, 12:36 PM
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The subpanel was installed today and looks fine. The installer clarified that he is using copper wire to go from the subpanel to the furnace, but Aluminum to go from the main panel to the subpanel, saying that to use copper for a 100A subpanel would be way more expensive than aluminum. Is Al wire the norm for this situation? I may decide to go with Cu anyway, if it is not outrageously expensive.
 
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Old 11-26-07, 12:53 PM
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Originally Posted by hage1 View Post
Is Al wire the norm for this situation?
Yes, aluminum wire is commonly used to feed subpanels. It is legal and safe in this situation when installed by a professional.
 
 

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