Old bx wiring in 200 amp service box

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Old 06-21-11, 04:32 PM
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Old bx wiring in 200 amp service box

Okay, this goes with a older post I had here concerning adding a sub-panel. I have been realigning things since I bought a portable generator and am adding a Reliance Q310A transfer panel.
As some have already replied to that post I apologize for this question, but it is a continuation of it.
I am attempting to identify all circuits in this house (circa 1927) and have just about finished. I have come across two (2) 15 amp CB's that don't seem to control anything. I will probably disconnect, label, and cap these but I am a (as my wife and friends(?) say) a obstinate, obsesive order freak guess from my military and previous occupation leftovers.
These two non-control CB's have been traced to a BX cable that has a Red\Black\white wires. I don't see any bare but I may be missing it visually.
Now the wires are connected as follows;
- one red to a 15 amp
-the black to another 15 amp
-with white to the neutral bar.
These are the only wires connected to the individual CBs. I am sure someone here has seen this before. Any idea on this setup?
They are independent CBs and there is no bar connecting them.
The wire goes behind the mounting backing and can't be seen for visual trace. I have put a tone tracer on them and because of the metal shield the tone degrades and I lose the tone after a short distance.
Just curious as to this configuration.
 
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Old 06-21-11, 05:22 PM
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Multiwire branch circuit; two hots share common neutral.
A lot written about potential dangers of these circuits, for example:
Multiwire Branch Electrical Circuits and Split-Wired Receptacles - Electrical Wiring Safety Requirements

Useful for wiring say a garbage disposal and a dishwasher; run one cable to one outlet, energize top one with one branch (say black one) and lower outlet with the other branch (red one) with the tab that normally connects the brass screws on the outlet broken; the neutral (white) is shared (silver screw on outlet). This allows one wire to be run and two circuits to be protected at the panel.
 
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Old 06-21-11, 07:23 PM
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While there are potential dangers of multiwire circuits, millions of them are installed without any issues. Just be aware of the dangers and how to avoid them and you will be fine.
 
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Old 06-21-11, 07:30 PM
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Assuming the two circuit breakers are next to each other I agree with Bob that it is a MWBC. Dishwasher/disposal is a common use for these as could be other kitchen receptacle circuits. They are not, however only used in kitchen circuits but could be used anywhere. It is only in the latest, or perhaps next-to-latest code that a two-pole circuit breaker with tied handles has been required. My own home (built in 1986) has several MWBCs but did not have either two-pole or handle-tied circuit breakers.
 
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Old 06-21-11, 09:13 PM
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Thanks guys

Thanks guys! You may have given me a lead as to where this bloody thing goes! When we had some kitchen worked done many years ago ( I was away at the time and wifey was the overseer) We had the whole kitchen rewired and some dedicated circuits (refridge/micro/oven/stove) added. At that time there was a ancient dishwasher there that was removed, so probably this config. may have fed it and it was not capped and abandoned then.

May re-do the tone thing and see if there is a possibility I can locate it going to the kitchen. Can't find it anywhere else!

Thanks again. I guess I just found two additional empty slots in my panel
 
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Old 06-21-11, 10:10 PM
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Originally Posted by Furd View Post
Assuming the two circuit breakers are next to each other I agree with Bob that it is a MWBC. Dishwasher/disposal is a common use for these as could be other kitchen receptacle circuits. They are not, however only used in kitchen circuits but could be used anywhere. It is only in the latest, or perhaps next-to-latest code that a two-pole circuit breaker with tied handles has been required. My own home (built in 1986) has several MWBCs but did not have either two-pole or handle-tied circuit breakers.
Up until 2008, handle ties were only required on MWBCs where both circuits serve the same device (a split duplex receptacle for example). For a 'standard' MWBC, handle ties were not required, the circuits just have to land on adjacent breakers. As of NEC2008 though, all MWBCs require handle ties.

And that overblown 'hazards of MWBC' keeps getting brought up every code cycle by people who want MWBCs banned and the committee keeps rejecting it.
 
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Old 06-22-11, 12:32 AM
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MWBCs are not hazardous to people that understand them. The problems arise when unknowledgeable people start re-arranging circuit breakers in a panel, usually to get two adjacent open slots to allow for a two-pole breaker for a sub-panel and end up putting both "hot" leads on the same leg. Or, someone starts taking apart wires without opening BOTH circuit breakers and then when opening the neutral they end up with an unbalanced circuit which then causes the voltages on different loads to rise or fall from the "standard" 120 volts.

Since I know about and understand MWBCs they are no problem to me as long as I know that the circuit I am working on IS a MWBC and that is not always easy to see UNLESS a person first removes the cover on the circuit breaker panel and discovers the cable to the branch circuit has multiple wires connected to adjacent circuit breakers. Since there are many DIYers with limited knowledge of anything electrical, let alone MWBCs, that monkey around with their residential circuits AND the plain fact that in most residential construction the labor and materials saved by using MWBCs is minimal I DO feel that MWBCs should not be allowed in residential construction.

In my own home I have made a detailed panel schedule that identifies all MWBCs and I have also installed handle ties on all circuit breakers feeding MWBCs that are not fed from a two-pole circuit breaker.
 
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Old 06-22-11, 11:38 AM
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I especially like them because I can change the receptacle with a nema 14-20 or a nema 6-20 at a later point if needed.
 
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Old 06-22-11, 12:20 PM
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Originally Posted by Bob M View Post
May re-do the tone thing and see if there is a possibility I can locate it going to the kitchen. Can't find it anywhere else!
Any chance it powers an outbuilding like a garage, shed, pool shed or well house? Maybe even a demolished one that might still have some wiring to a post or pad? If you have a septic system there might be lift pump.
 
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Old 06-22-11, 03:35 PM
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Also, look for an old monkey's face around your outside as this was a common way to feed an outbuilding in my area. There may also would have been an insulator rack next to it at the time, too.
 
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Old 06-22-11, 03:48 PM
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Justin wrote:
Also, look for an old monkey's face around your outside
Justin, as has been said before it would be more helpful if you used terms a poster is likely to be familiar with. Myself, I don't have a clue what a "monkey face" is.
 
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Old 06-22-11, 04:03 PM
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I've been living almost as long as Ray and I too have no idea of what the term "monkey face" is in reference to.
 
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Old 06-22-11, 06:07 PM
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Also, look for an old monkey's face around your outside as this was a common way to feed an outbuilding in my area.
Justin, how many old monkeys are running around your area without a face?
 
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Old 06-22-11, 07:41 PM
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Old Electrical Parts - ECN Electrical Forums

This is the only picture I could find of one, and monkey face is the only term I know for it. If you know another name for it, please tell me. You can expect to find one of these on every old farm in my area. It will be hanging out of the wall with a short length of bx, then transistioned to individual conductors suported by porcelain or glass insulators. I have seen lots of them.
 
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Old 06-22-11, 09:08 PM
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Interesting. Thanks for the education.
 
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Old 06-23-11, 06:40 AM
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That thread link you posted mentions a few names for the monkey face. If you dig deep into it, someone says that it is "known as an "A-Head" in old catalogs."
 
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Old 06-23-11, 08:45 AM
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That thread link you posted mentions a few names for the monkey face. If you dig deep into it, someone says that it is "known as an "A-Head" in old catalogs."
I googled old electrical monkey face and I clicked on it and the pic was on the top. After I posted, I read that about the A-Head. Sometime, when I have a camera with me, I will take some pics of some and post them somewhere.
 
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Old 06-27-11, 06:49 PM
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Thanks guys and I will go in order. There are no "Out" buildings of any kind on the property and never has been. I have some of the original architectual renderings of the building and none are shown. As to "Monkey faces, et al" I have not found any (yet!) did find some newspapers used as insulation dating to Dec 8th 1941! Unfortunately they crumbled before I could humidify them to spread out. Did read as much as I could between the creases.
I have turned off the two breakers and NOTHING seems to be inoperable. I really do believe that this was for the OLD electric range that was removed and had the replacement cooktop has a dedicated wire. Sure wish the guy had did some labeling of the circuits as he took them apart/reassembled!
 
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Old 06-28-11, 10:10 AM
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Looks like you did your homework pretty well on tracing these down. Seems safe to disconnect the old wiring and reuse the breaker slots if you need them or just label them unused.
 
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