Why Does My Furnace Have Two Breakers?
Breakers are an important safety feature of air handlers or furnaces. Circuit breakers are not just a switch to turn a furnace on and off. They protect the wire that feeds the power to your furnace in case of an overload such as a shorted motor or heating element.
The amount of current or electricity that a furnace uses is a “load” on the circuit or wire that feeds the furnace. If the load is large enough it makes sense to divide that load into two or more circuits using a breaker for each circuit.
DISCLAIMER: This is not a guide. This article is about why furnaces have two breakers. Wire sizes can vary by local codes, wire length, type of wire, and temperature. The wire sizes mentioned here are for explanation purposes only.
A larger load requires a larger wire. Copper wire can be expensive and depending on several extenuating circumstances from both the manufacturer to the installer, a decision has to be made as to the number of circuits and the wire size.
Most electric furnaces or air handlers in my area have two breakers, the most common load being 15KW. One breaker being a 30 amp which takes care of 5KW and the other a 60 amp which takes care of the remaining 10KW. The combination of the two creates a 15KW furnace.
For most installations of a reasonable length a 30 amp breaker can be fed with number 10 copper wire and a 60 amp breaker with a number 4 copper wire. Using aluminum wire is a whole other story not discussed here.
What If There Are Two Breakers In My Furnace And Only One In My Panel?
Sounds confusing maybe but it’s a real thing. You’re looking frantically for the second breaker in your panel to shut of the air handler but all you can find is one. It’s a single conductor or wire in a main electrical panel that is feeding two breakers in a furnace.
If you are confident, willing, and able to look inside your furnaces control panel your would see what is called a single point connection. Similar to the one pictured below.
Which by the way is a link to this product on Amazon in case you have a need for one or simply want to know about what they cost. In my opinion they are way too much for what they are.
Single point connectors allow a single conductor (two hot leads and a ground wire) to be run from the main panel to the air handler. Looking at the image above, notice the two lugs at the bottom.
The wire from the panel connects to these lugs and then the red and black wires on top connect to the two breakers in your furnace. Essentially they are split or divided in two to feed two breakers. The image below shows a single point demand wiring kit installed in a furnace.
Who knows what the price of copper has to be to decide to run a single conductor to a two breaker furnace. That’s about 90 amps for the example given earlier of 15KW. The 30 amp and the 60 amp breakers.
That’s getting into some heavy copper wire, somewhere in the area of keep your doors locked or copper thieves will find you and strip the wire out of your walls. Don’t get paranoid.
Another example of how one conductor can feed two breakers. Notice how the conductors on the right connect to the breakers. The wire on the right connects to each breaker on the top. The wire on the left connects to each breaker on the bottom feeding 240 volts to each breaker.
What Is A Piggyback Breaker?
Could be called a tandem breaker. Not likely to be found inside a furnace or air handler. It’s used to make room in a main power panel. Piggyback breakers have several names like twin or slim or wafer. Sometimes a panel can fill up fast, especially after years of remodel and additions.
It’s customary and even allowable under certain conditions to wafer up a panel to allow more circuits. Overloading the panel is one of those certain conditions. Only your electrician knows. Well, maybe you do also.
Keep in mind that there are generally two types of breakers in a panel. Not speaking of brands, but sizes. Sizes in relation to voltage. There are single circuit breakers that feed your lights and receptacles (the plugins on the wall).
And there are double circuits, they are the wider switches. If you look close you can notice that the switch or toggle on a double breaker connects to what sort of looks like two single breakers.
Double breakers feed appliances like your air conditioner, electric range, dryer, electric water heater, etc.
I hope you feel that this is all good to know stuff. I have a lot of customers who have no clue and this is important to your safety and the serviceability of your home.
You need to know what circuit breaker go to what circuits or appliances. It’s always a little too late when you need to shut off an appliance and you can’t determine which breaker is the right one to switch and make the kill.
Conclusion
Knowledge is power.
I have 2 breakers on my heat strips 50 amp & 25 amp, the existing stranded copper wire is 6-2 w/ground, the 50 amp breaker on the heat strip goes to a 50 amp breaker on the service panel, but the 25 amp breaker is being fed by a 60 amp breaker, should I change the 60 amp breaker at the panel to a 25 amp breaker ? Also can I use the existing 6-2 wire by using 2 junction boxes and use 10-2 wire to go to the two 25 amp breakers?
Tom, I have run across this same issue before and had to ask my electrician buddy about having a larger breaker in the panel and he told me it was okay, everything was protected by the 25A breaker. I’m afraid I’m lost in your second question, don’t understand. Chad
I have been told that my furnace has two breakers 60 amps and 30 amps. A recent yearly furnace check indicated that the heater kit breaker is only receiving 11 bolts from the main breaker. I have been told I need a new breaker. My concern is that there is not an increase in amps when changing the breaker.
Joan, I’m curious why they didn’t change the breaker while there? If you don’t have the proper voltage at the furnace then it has to be addressed by finding the loss of power between there and the panel or in the panel. Changing the breaker will not increase the amps. It’s something you should have repaired soon. Chad
Hi Chad, I’m trying to power my new Bryant propane furnace. I ran 10/2 Romex. Black wire into the breaker, I grounded Both the white neutral and the bare copper on the ground bar in the panel. On the furnace end I ran ran green to green, black to black and white to white and spliced all 3 to a single pole grounded switch on the furnace. When I hit the switch to the ON position it trips the breaker.
Jordan, I think I’d disconnect the furnace and power something else with the circuit. If that something else runs the you have a short in your furnace. If not then maybe you have a bad breaker. Hope you find it. Chad
My aunt lives by herself , husband just passed . Anyways in her kitchen there is a breaker box above the heater unit , the left side was on but right side was off .is one for the air and the other for the heat , how do I know if the heater turns on what do I set it on . I need some help .
Janet, The only way I know how to help you without meters or special tools is to have you check the temperature of the air with the fan on. Turn on the other breaker and see if the temperature rises. If it does you’re good to go. If the temperature does not rise then there’s not way to know without a technician. Chad
I have an old Rheem electric furnace Model UBHA21J15SHCAI. A couple of days ago, my power went out due to the freeze here in Louisiana and I attempted to run the furnace on my portable generator which has a 30 amp breaker, which tripped so I was unable to run the furnace. The furnace has two breakers, both 60 amp, on the front panel and I am assuming one breaker for each heat strip. If I turn off one of the breakers would that shut off half the amperage, allowing the furnace to run on one heating element and possibly my generator being able to handle the load? I didn’t want to try this during the power outage because I was afraid I would damage the unit but I thought maybe you could give me some insight. Thanks.
Bob, Your furnace probably has 4 elements. Each element draws approximately 20 amps. You would have to connect to one breaker and disable one element to operate the furnace. You would have to make sure you don’t disable the low voltage transformer. Running one element would produce a small amount of heat. I wish you well down there. -Chad
I’ve got an older Carrier unit that has a double breaker in the unit. The left breaker keeps tripping (3 times today) but the unit seems to be working ok. The house is as warm as it normally is and it is cycling normally. I’m not sure how long it’s been tripped but I just discovered it today. Any suggestions?
Jeremy, something is shorting inside the unit or the breaker could be a bad one. Sometimes the elements sag and short out. I really would suggest a service call. Fortunately you still have heat. – Chad
Hello, my furnace has two breakers right on the unit but it seems to be operating just fine with just one breaker activated. Is it more energy efficient to just have one breaker on or should both breakers be on all the time?
Dan, that’s a great question. The breaker that’s on, it’s operating the low voltage (thermostat and controls) and an element or two depending on the size of your furnace. The other breaker just powers heating elements. Whether or not it is more efficient depends on a lot of things. Is it running all the time to keep the house warm? If it cycles off, you may be good. I like to turn on enough heat to get the job done and get the furnace cycled off. Not enough electric heat that is running all the time can be real expensive. I couldn’t give you any numbers as to how efficient one or the other is. You just have to watch your electric bill and make some judgements. – Chad
I have a double breaker in my main electric panel and also one inside the HVAC closet. I was labeling the main electric panel and now my heat is blowing cool air and constantly running. It was working fine before. Do I reset the unit by turning off the breaker in the closet or is that for something else?
Jessica, there wouldn’t be any harm in resetting the breakers, but if the fan is running it’s probably something else the matter. Don’t you just hate coincidences.
Two breakers 240 each or 110 each?
Kind of a combination of that. Hope this is clear enough. A electric furnace with with one or more breakers would have 240 volt circuit fed to each breaker. One wire connected to
each of the two terminals on each breaker. Measuring across the two connections would be 240 volts. Measuring from each connection to a ground would be 120 volts.
Another way of saying that would be that a double breaker is fed with 240 volts and a single breaker is fed with 110 volts.
Hope that works.
Chad