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I want to add an additional 120 volt circuit to a bedroom. My house was built in 1979 and originaly had a heat-pump in the attic. This was powered from a sub-panel in the attic that was controlled from a 125 amp breaker in the main panel. Later I had the heat-pump removed and a gas furnace put in, so the installer disconnected a 60 amp breaker in the attic sub-panel and added a 30 amp breaker for the gas furnace. The sub-panel box uses Zinsco type breakers which I found were obsolete. So I want to use the now empty 60 amp breaker to connect a new sub-panel nearby, where I could install a 15 amp breaker for the new bedroom circuit. My question concerns the attic sub-panel. It is connected to the main panel by an AL Type SE Cable Type XHHW 3 CDRS 600 Volts. There are 2 hot leads connected to the sub-panel and then some bare wires that are twisted together and connected to a neutral bar (in 2 places) in the sub-panel. This neutral bar appears to be connected with a screw to the metal sub-panel box. Is this old sub-panel wired properly so that I can use it to feed the new sub-panel and have a properly working ground connection etc.?
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By code, at least the newer ones, any sub panel needs to have the neutral isolated above ground and an auxillary ground bar installed.
The feeder to this panel needs a four wire cable - two hots, a neutral and a earth ground wire. Hots go to a back fed breaker OR a set of MAIN lugs, white neutral to neutral and the wrapped bare ground to the aux bar. The bonding screw is NOT used.
So I guess in your case - run a four wire to the new sub. Red/Black to the main lugs, red/black to the 60 amp breaker, Neutral and wrapped ground to the neutral in the OLD panel. In the new panel, neutral to the neutral bus, add an aux bar and put the wrapped ground here.
Don't use the bonding screw or jumper.
The romex you connect for your circuit, black to the breaker, white to the neutral bus and the bare to the aux ground bar. When you install the aux ground, scrape the paint off so it makes intimate contact with the box metal.
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HayZee,
Thanks for the information and I think I will use a GFCI breaker or receptacle for added safety on the new circuit.
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Hayzee is correct. The only problem I see is that the neutral, by NEC, is required to be run in the same cable as the 2 hots. You can't use the bare wire that is in the cable for a neutral 'cause that is also a NEC violation. You may want to re-identify one of the hot wires as the neutral with white tape at both ends and just feed 120 volts to your subpanel, then you can use the existing cable & not have to put in another wire. By NEC, if your new circuit is for a bedroom it needs to be protected by an arc-fault circuit breaker. Just my 2 cents worth.
DanchargerComment
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Misuse of color code of wire
Dancharger, You suggest to use a black or red wire as a neutral. Black and red are reserved to indicate 'hot'. I believe it's a NEC violation also. Don't use a black or red wire to indicate a neutral. BUT, it is OK to identify a neutral as a 'hot'(as in 'White marked Black' for a switch leg).Comment
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Dan and Steve Mc. read my post again. I specified to use a four wire cable, an SER cable all current carrying conductors, a white neutral and a wrapped bare ground are enclosed within a jacket.Comment
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neutral conductor ID prob
HayZee518, I just joined this forum and saw Danchargers comment on re-identifying the white neutral to black or red. I was just here to clarify for future work. Color-coded wire is for safety also.Comment
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doesn't matter the op is five years old.Comment
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question on outdoor, old blade-type disconnect, Buss-fused sub panel
Hi HayZee 518, I live in CA. I have a project: to change-out this old fuse-type sub panel to a outdoor 100 amp SQ D HOMELINE 6 spaces sub panel(for future lighting). QUESTION: Is this disconnect a 3-phase type being used as a 2 phase? The inside has 3 conductors from the masthead going to 3-25amp Buss fuses on the line side. Ground is properly hooked-up. A small red crimp-like flag is on the middle conductor. I'm not familiar with this marking, except that for 240V, any two 120V conductors can make 240V, usually a black conductor marked with red tape. The way it is in this sub panel: the 2 black conductors are: 1 on the left and 1 on the right, line side of the fuse holder. The middle red-flagged conductor is connected to the middle line side fuse holder but no conductor is on the load side. I would like to know if this was originally the proper way of marking a black conductor red. BTW,this feeds a 240V well pump motor. The amperage note is missing(not clear) on the label. I'm going by the existing fuses(25amp each) to buy the right size CB for the water pump: a two-pole 50 amp CB. I also want to add a 100 amp Main shut-off. Right now the electric company must come out and shut the power off to work on it. I didn't know how to add photo. Sorry to be so lengthy.Comment
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grab a voltmeter and check each line side wire to earth ground. mark down whatever voltage you read and post them here. a black wire with a flag might indicate a 120/208 service three phase.Comment
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sub panel question
HayZee518, Thank you. I have to leave to the job site right now. It's 250mi away and no internet until I have the ISP provider redo the setup on Monday. I will let you know in about a week what I found.Comment
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the 120/208 is indicative of a three phase wye connection. the midpoint of all three phases will give you 120 volts to each leg. across any two phases you'll get 208 volts. another variation is a delta secondary with a midpoint tap to generate a neutral. the stinger leg will give you approx 190 volts to this midpoint tap.Comment
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