Correcting Improper Wiring

[bayfarmer]

I recently purchased a duplex. Two main power panels (breakers) are in the basement. Wiring then goes to a master panel in either the upper or lower unit. For the upper unit, a sub-panel with one breaker comes off the main and feeds the air conditioning unit for the upper unit.

I found out that the line that goes to the air conditioner also powers the furnace, lights, and sump pump in basement. The 220 line that feeds the air conditioner was split with half feeding the furnace and the other half feeding the lights and sump pump.

I removed the fuse breakers and installed a 70 amp sub-panel. Questions?
Is it all right to leave it this way?
Should the A/C sub-panel and line feed only the A/C?
If they should be separated should the feed to the 70 amp sub-panel for the furnace and lights come off the main, the sub panel, or doesn't it matter.

Thanks for your help.

[pushkins]

The AC must be on it's own dedicated breaker....no exceptions to the rule.
If you installed a 70 amp sub (that's a fairly small sub) What size cables did you use ?
Feed the AC from the 70 amp sub on a dedicated circuit and then feed your furnace from an outlet circuit from this panel same for your sump They could both be on the same line but for the best practice I'd separate them.
The lights should be on their own circuit from the main especially since you will have a sump motor and the furnace motor on this 70 amp sub panel.

[HayZee518]

I'm trying to visualize what you are saying. In the basement you have two main breaker panels only? From here you have a line going to a distribution panelbox in each apartment. if this is so then these apartment panelboxes are to be treated as a sub panel and require a four wire feeder to each apartment.

[bayfarmer]

Clarification

Thanks for your replies. I think it is clear that the AC must be on its own dedicated circuit. Let me provide more information about the rest of the wiring and my continuing concern.

The house is a duplex. The wiring for each unit is totally separated. Each has a 100 amp service. I will only talk about the upper unit. The service comes into the basement to a 100 amp breaker. Wiring for the upper unit, except for the AC, furnace, sump pump, and basement lights, go to a service panel in the upper unit. At this time, I am only concerned with these appliances that are not served by the panel in the upper unit.

In the basement, a 70 amp single circuit breaker comes off of the main. (The following is the area of my concern) A #8 2-wire line (B,W,G) comes from that breaker and crosses the basement to an electrical box. In this box, the line is connected via wire nuts to an older line going to the AC. A #12 2-wire (B, W, G) is also connected to the #8 wire black to black and white & ground to the ground wire. This used to run to a 60 amp fuse box. I remove the fuse box and installed a 70 amp breaker box with four circuits providing individual 20 amp circuits for the furnace, sump pump, lights, and outlets. Everything works.

My assumption at this time is that I should remove the wire feeding the 70 amp sub panel and dedicate the AC line only to the AC.

So, here is my question. If I do that, should I run a #12 wire from the main directly to the 70 amp sub panel that I installed? If not, what else do I need to do.

I hope this explains it in greater detail. Thanks for your help.

[HayZee518]

a 70 amp breaker is too big for an 8-2 wire. #8 is good for 40 amps. 2ndly, a 12 wire spliced onto the 8 is a definitine no-no. you got 70 amps available on a wire that can only tolerate 20 amps!

[HayZee518]

Wiring

Original poster: this diagram is written/drawn using microsoft paint. Open it up and make any changes that accurately reflect your predicament and re-post it here in the electrical forum. Speedy or Myself will look it over and make suggestions.

[bayfarmer]

Diagram

I am using a Mac and do not have Microsoft Paint. Attached is a drawing using a program called Paintbrush. If you can't open it, I will scan a picture in.

My assumption at this time is that I remove the #12 line that feeds the 70 panel from the AC line. I am further assuming that i reinstall that line directly from the 100 amp service.

Let me know if this is correct.

[HayZee518]

from a main breaker, sub panels are usually fed slightly lower in amps than the main. reason is false tripping of the main. I will work out another diagram to give you some idea

[HayZee518]

wiring

take a look at this drawing - is this something like what you described?

[bayfarmer]

Reply To Drawing

Yes, the drawing is correct.

You ask two questions: 1) 12 gage? The wiring from the 40 amp sub-panel to the box and from the box to the AC is #8 2W+G. The wiring from the box to the 70 amp sub-panel is #12 3W+G. This provides 2 feeds to the 70 amp sub-panel. Each feed serves two 20 amp breakers. 2) Protection? The 70 amp sub-panel has four 20 amp breakers one each for the furnace, sump pump, lights, and outlets.

My thought at this time is to disconnect the 70 amp sub-panel from the AC line at the Box. Install two 40 amp breakers in the main panel to feed the breakers in the 70 amp sub-panel. This is redundant but is easier than removing the 70 amp sub-panel from the system.

Do you see any problems with this?

[HayZee518]

Yes BIG problems. to begin a 12/3 will never carry 40 amps - it will burn up. Better way is to eliminate the junction box completely. Take a length of 8/4 and go from the 40 amp breaker panel to the 70 amp panel and feed its breaker unless it is a panel without a main breaker [called a MAIN LUG] panel. All panels AFTER your main disconnect are sub panels and require a four wire to feed them. Send me your email address and I'll contact you directly with diagrams.

[HayZee518]

improper wiring

take a look at this diagram. it's different than the previous one. I eliminated the junction box

[pushkins]

I'm confused, how is a 70 amp sub fed from a 40 amp sub ?

[HayZee518]

the backfed 70 is just a means for connecting up the wires as a main panel does not have sub-lugs. the 70 will never trip

[HayZee518]

sub panel pictures - main lug

sub panel pix - main lugs only. if the user needed a sub panel but didn't have the sub lugs the he'd backfeed a breaker on the stabs which would energize the panel stabs