Tandem or Single Pole Breaker

[Milton]

Besides having two for one, is there a difference between a tandem breaker and a single pole? Outside of being able to add more circuits to a load center, is there a reason to use a tandem breaker over a single?

-ML

[Alectrician]

""Besides having two for one, is there a difference between a tandem breaker and a single pole?""

Cost?

The full sized breaker would logically have more ability to dissipate heat.

[George Roberts]

Both meet code. I prefer the half width breakers.

[SolarPowered]

I think it is unlikely that AFCIs will come in tandem versions. So thinking about future circuit additions, it is better to have a full-width slots available for future AFCI use. So you're better off with a panel that gives you more full-width slots, rather than one that allows a bunch of tandems.

[goldstar]

You're only permitted to have 42 circuits per panelboard. That being said most of the newer breaker panels that are made give you the ability to use tandem breakers but only in a given portion of the panel so that you cannot exceed 42 circuits. Thus, if you have an older 40 circuit breaker panel and begin using tandem breakers, technically speaking you can only use 2 tandem breakers. On the other hand, if you begin adding circuits and replace the std. breakers with tandems you will not only be in code violation but you will soon run out of neutral and ground bar space and run the risk of over-heating the panel. To make the blanket statement that tandem breakers are approved is not quite accurate. The panelboard has to be designed and approved to accept the tandems. If it weren't (and in theory) you could actually turn a 40 circuit panel into an 80 circuit panel.

[sparkyinak]

I prefer not to use tamdems except as a last resort. There is the heat disipating problem Alectrician mentioned and potential too many wires needed aplace to teminate in the panel mentioend by Goldstar. The one thing that has puzzeled me with tandems is do they count as 1 or 2 circuits when it comes to CTL rated panels? NEC states that a single pole counts as one and a 2-pole counts as two. Is a tandem considered a single or a double? Just food for thought

[George Roberts]

So much misinformation but that is to be expected.

They meet code. That is all that matters.

If you have problems with heat disipation or you put in more than a box is listed for, you have problems not the 1/2 width breakers.

[jwelectric]

I have wired many an apartment using 12/24 panels and mini breakers without any problems

[BillHartmann]

You're only permitted to have 42 circuits per panelboard. That being said most of the newer breaker panels that are made give you the ability to use tandem breakers but only in a given portion of the panel so that you cannot exceed 42 circuits. Thus, if you have an older 40 circuit breaker panel and begin using tandem breakers, technically speaking you can only use 2 tandem breakers. On the other hand, if you begin adding circuits and replace the std. breakers with tandems you will not only be in code violation but you will soon run out of neutral and ground bar space and run the risk of over-heating the panel. To make the blanket statement that tandem breakers are approved is not quite accurate. The panelboard has to be designed and approved to accept the tandems. If it weren't (and in theory) you could actually turn a 40 circuit panel into an 80 circuit panel.

Tandem breakers are only allowed in number and slots that they are aproved for. Most 40 slot panels are only approved for 40 poles.

I am looking at a SQ QO load centers with main breakers rated at 200 amps.

They have 20 slot, 40 pole panel - 20 tandems
24 slot, 24 poles, no tandems allowed.
30 slots, 30 poles, no tandems allowed.
30 slots, 40 poles, 10 tandems allowed.
40 slots, 40 poles, no tandems allowed.
42 slots, 42 poles, no tandems allowed.

[goldstar]

Bill,

You are 100% correct. The breaker panels that you cited are approved for use as described. In the case of the 30 breaker/40 circuit panel the bottom 5 slots are approved for tandem use (if desired) and thereby providing the means for making a 40 circuit panel.

Mike,

Using a 12/24 panel is OK if it is manufactured and approved for that use (but then again, you already knew that). You can probably land multiple EGC's on one terminal of the ground buss if it is marked for use in that manner. However, you can only land one neutral per terminal (but then again you already knew that also). You can also wire nut multiple EGC's and land a properly sized EGC to the terminal block providing you have the trough space inside the breaker cabinet for the splice. Can you also wire nut neutrals together and land one properly sized wire to the terminal bar ? (I'll bet you know the answer to that also). Just curious though, how did you end up with 24 circuits in an apartment ?

They meet code. That is all that matters.

George,

Making the blanket statement that "tandem breakers are approved" is not quite accurate. They are approved for use in certain panels and irrespective of whether that panel is designed for their use or not you cannot have more than 42 circuits per cabinet. Just as a side bar, can you install a multi-wire branch circuit (say a 14/3 RX cable using a common neutral) using a tandem breaker ?

The one thing that has puzzeled me with tandems is do they count as 1 or 2 circuits when it comes to CTL rated panels? NEC states that a single pole counts as one and a 2-pole counts as two. Is a tandem considered a single or a double? Just food for thought

Just to clarify, a two pole circuit breaker takes up two full breaker slots and provides circuit protection for two separate phases (240 volts in residential as an example). A tandem circuit breaker provides circuit protection for two single phase 120 volt circuits of the same phase. In some of the older panels there were two pole, tandem breakers (actually providing 4 separate s/p circuits) that were manufactured with approved handle ties. When you installed these breakers into the panel they took up two full circuit breaker spaces. Circuits 1 and 4 were one 2-pole, 240 volt circuit and circuits 2 and 3 were the other.

[campster]

Just as a side bar, can you install a multi-wire branch circuit (say a 14/3 RX cable using a common neutral) using a tandem breaker ?

I'm no professional but I would say NO. Both breakers would be fed from the same bus and you would overload the neutral.

[normel]

can you install a multi-wire branch circuit (say a 14/3 RX cable using a common neutral) using a tandem breaker ?

While not technically a tandem, the skinny (half height) breakers made by GE can be installed, in such a way in some GE panels, so that each is on a different hot leg, so yes, in certain cases , you can.

[BigB56]

While not technically a tandem, the skinny (half height) breakers made by GE can be installed, in such a way in some GE panels, so that each is on a different hot leg, so yes, in certain cases , you can.

You can also do it with standard twins. You just cannot land both sides of a multiwire on the same twin. This comes in handy in a tight panel when you have multiple multiwire circuits, you just keep all your blacks on one leg and all your reds on the other, 2 of the same color per twin.

I am not too fond of twin quads however used on heavy loads such as HVAC. I have seen them melt down more times than I can count.

[goldstar]

I'm no professional but I would say NO. Both breakers would be fed from the same bus and you would overload the neutral.

And...We have a winner !!!

Professional or not, knowing this much makes you more professional than many.

I am not too fond of twin quads however used on heavy loads such as HVAC. I have seen them melt down more times than I can count.

I'm glad you pointed that out. Next time you come across one see if they have an "HACR" label on the side.

[SolarPowered]

You can also do it with standard twins. You just cannot land both sides of a multiwire on the same twin. This comes in handy in a tight panel when you have multiple multiwire circuits, you just keep all your blacks on one leg and all your reds on the other, 2 of the same color per twin.

However, I believe the 2008 NEC requires a single throw for multiwire circuits, so what you describe will no longer be allowed when the 2008 Code takes effect.