Overloading netural wire?

I have a 20Amp tandem breaker. They installed it using 12-3 romex wire. The black wire is on one circuit and the red wire is on the other circuit. Is it ok that these two wires share one neutral wire?

 

Yes provided that the breaker is double wide and you measure 208-240 volts between the two breaker terminals where the red and black wires are connected respectively.

In other words you may not use the 3 conductor cable and share the neutral here if you measure 0 volts red to black (and 120 volts red to neutral and 120 volts black to neutral).

To meet the latest code the two breaker handles in question need to be linked together with an approved fastening so that if one trips, the other is flipped off.

 

Allan gave a good description. If you need to read up on it further, google "multi-wire branch circuit". They are very common.

 

The breaker isn't a double wide. It only takes up one slot. I'm not currently at my house, but Ill have to check it out. I currently have 3 tandem breakers two 15AMP and one 20AMP breaker. They are all hooked up with 12-3 wire so I was just wondering if this was a problem or not.

 

This one is a long shot because you might not find one that fits your panel.

You could use a quad tandem breaker that is double wide, using breakers 1 and 4 for one of the 3 conductor cables and using breakers 2 and 3 for another 3 conductor cable. There would need to be provison for handle ties that connect the respective handle combinations.

 

When you have a true tandem breaker that uses one slot of the panel, you have two single pole circuits operating from the same leg powering the panel (or the same stab). If you connect both the red and black conductors from a 12-3 or 14-3 NM cable wired as a multiwire branch circuit, both circuits are drawing power from the same leg and yes, the neutral will be overloaded. From your description the wires were connected incorrectly. A quad breaker is something slightly different and draws power from both legs powering the panel as it uses two adjacent slots in the panel.

 

If this is a GE panel a twin will work if it is placed right but this is a tandem in most other panels as stated it is unsafe. Ask the people who did the work to come back and correct it on their dime.

 

The model # of the panel is BR2040BC200. Unfortunately I would contact the people that built the house, but they went bankrupt.

Is there a reason why they decided to use 12-3 wiring for this type of circuit? I have explained my situation to a Lowes employee and he said it wasn't a big deal. The only reason it caught my eye was a ran a new circuit in the basement for a treadmill.

So what is the proper way to wire a single wire tandem breaker? I ask this because I want the fridge and the over the range microwave on there own 20AMP dedicated circuit.

Since I have 3 tandem breakers installed incorrectly with 12-3 wire would it be ok to tie in the two 15AMP tandem breakers to the quad breaker? Then the remaining 20AMP tandem breaker can be replaced with a double pole breaker?

 

Sounds like,e it may be time for a sub panel to make room for the new circuits and straighten the other one out.

 

That is a Cutler-Hammer 200 amp 20 space, 40 circuit main breaker panel with copper bus. Each of the 20 spaces has a notched stab and a tandem or quad breaker can be used anywhere in the panel.

This is a multiwire branch circuit, they are used many times to reduce labor.

You asked a less than informed employee. It's unfortuneate the big box stores have employees like this who don't have a clue about code or electrical safety.

A 20 amp tandem breaker is intended for two separate 20 amp, 120 volt circuits, each with their own neutral conductor (two 12-2 NM B cables). Your multiwire branch circuit should be fed from a 20 amp 2 pole breaker (or two 20A 1 pole breakers with a handle tie like a BR120); the BR220 breaker takes two full spaces in the panel. This is why I don't like the cramped panels that double the number of circuits by using tandem and quad breakers. If your panel is full, you can remove two adjacent 20 amp tandem breakers and replace it with a quad like this which provides you with two 20 amp 2 pole breakers in two panel spaces. This will accomodate two 20 amp multiwire branch circuits. The catalog number is BQ220220.

Shop Eaton Type BR 20-Amp Quad Circuit Breaker at Lowes.com

Some electricians and builders use the 20-40 panel for savings, but my opinion is that the added cost of tandem and quad breakers washes out any savings and just creates a cramped panel.

 

Do you mean that you have two half-inch high breakers, one above the other, in a standard one-inch breaker space? Or are you describing a breaker with two handles side by side?

Two 120V circuits that share a neutral are known as a multiwire branch circuit. It must be wired so that the two hot wires are fed by the two different legs of your single-phase 120/240V service. That's not possible with a side-by-side handle pair, and is tricky to do properly with two half-high breakers.

The same as any other single-pole breaker: with a 3-wire, 2-conductor cable, terminating the black wire to the breaker and the white wire to the neutral bus.

Why? Neither should require more than 15A if on their own. Alternatively, the refrigerator may be supplied from one of your two 20A countertop small appliance circuits, usually before the GFCI protection is added.

This is a common misconception. The two breakers supplying a multiwire branch circuit must have their handles linked together to provide a common disconnect. A common trip is not required.

 

Here is a picture for a better understanding of what Im talking about.

Here is a run down of what items are on these tandem circuits.

20A
-master bath and guest bath(GFCI)
-3 outlets around stove(GFCI)

15A
-Fridge (draws 8.5A)
- GD (4A), Dishwasher (8.1A)

The other 15A tandem just powers on a few lights and bath room exhaust fans. I'm more worried about the breaker with the fridge, GD and Dishwasher. My plan was to remove the circuit from the fridge so the GD and the dishwasher would be on there own circuits.

Would it be ok to buy a 15A quad breaker to tie in the two 15A tandem breakers?

 

I see one 15 amp tandem and one 20 amp tandem. I'd use a quad breaker that combines a 2 pole 15A and 2 pole 20A in one unit. I'm looking for a picture and am pretty sure Cutler-Hammer makes on in the BR series. I'll add the picture when I find one.

OK, couldn't find a picture, but the catalog number would be BQ215220. The center two poles are 20A with a handle tie and the outer two poles are 15A with a handle tie. Finally found a picture, check this out. This will replace the 20 amp tandem and the 15 amp tandem breakers in the picture.

https://www.platt.com/platt-electric...px?zpid=652295

 

Its not the greatest picture, but there is another 15A tandem breaker below it.

 

I have been reading your thread to learn a little.
There seems to be one extra wire in there, or is it just the angle of the photograph?

Thank you,

 

Its just a bad angled shot.

 

There are quad breakers available in different configurations to do whatever you need. You could even remove the 30A 2P breaker and replace with a quad in those 2 spaces for a 30A 2P and a 20A 2P. Instead of Lowes, you may need to go to a supply house with a catalog so they can find you the proper configuration.

 

When you mix different Amp breakers on a quad breaker does it reduce the load? For example, if I tied in a 20A and a 15A in a quad breaker?

Im just trying to save space in my panel as I only have one slot left. Basement will be finished eventually. Id rather not install a sub-panel if possible.

Also, where is a good place to find cheap 12-2 NM romex cable?

Ok just want to make sure I get the correct breaker. I can use this to tie in the two 15A tandem breakers I have, correct?

Eaton 15 Amp 2 Poles BR Type Breaker, BQC Quad Breaker-BQC215215 at The Home Depot

 

Load is determined by what is connected to the circuit, not the breaker.

The big box stores are usually pretty competitive, I doubt you'll find it cheap anywhere.

From what I remember, you had both circuits from a multiwre branch circuit connected to the two legs of each single tandem breaker. Yes, use the quad you linked two for two multiwire branch circuits.