Seimens tandem breakers.

[Greg1707]

What is the difference between these two products? They are on the shelve side beside at HD and Lowes. I have never noticed this before. One product has a label on the side: "For replacement use only not for CTL assemblies."


http://www.homedepot.com/p/Siemens-...cuit-Breaker-Q2020NC/100158567#specifications

http://www.homedepot.com/p/Siemens-...-Single-Pole-Circuit-Breaker-Q2020U/100016494

 

[GoldDigger]

If I am reading it correctly, one is twice the width of the other.
(Even though the pictures look similar... )

 

[Smart $]

The difference is the NC at the end of the model number, which means Non-CTL version. CTL refers to a panel manufactured with a rejection feature in spaces not designed or intended for tandem use.

 

[GerryB]

If you look at the back you will see the slot on the $11 one is not as deep and it will not fit into many panels.

 

[PetrosA]

CTL stands for "circuit total limitation". It's how modern panels are designed for 8, 12, 16, 20, 24, 30, 40, 42 etc. circuits. On a 30/40 space panel, 5 of the bus stabs will allow twin or tandem breakers to be installed which gives you the 40 circuit rating. The non-CTL breakers fit on any bus tab which IIRC pretty much voids the UL listing of a panel since you could put 40 non-CTL twins into a 40 circuit panel and have 80 circuits total.

 

[norcal]

The non-CTL twin breakers are for panels manufactured prior to 1968 that do not have the notched bus stabs that later ones have.

 

[kwired]

The non-CTL twin breakers are for panels manufactured prior to 1968 that do not have the notched bus stabs that later ones have.

and anyone that wants to cheat and use in a newer panel:happyyes:

You find similar situations with other brands of breakers as well - and the Non-CTL are usually at least double the price of the CTL rated ones.