tandem breakers in new panel installation

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Ken 6789

Senior Member
Are tandem breakers ok to install in new panels. I only need to install one tandem. I can't find anything in the NEC prohibiting their use in new boxes nor in the local electrical code. I try to use tandems in existing boxes only. I'm assuming the AHJ cannot red flag me on this. Thanks
 

480sparky

Senior Member
Location
Iowegia
The panel label should tell you. If not, use the model number to go to the manufacturer's website or Google it.

Sometimes, the model number alone will tell you. For instance, Square D uses numbers like 2020 and 3030 and 3040. If the first two and the last two digits are the same, that means it's only made for xx number of spaces, xx numbers of circuits. If they're different, then the bottom 5 bus bars will accept tandems.
 

Jim W in Tampa

Senior Member
Location
Tampa Florida
Maybe at the original install, but putting tandems in a 25-year old 30/40 panel?
I understand doing it under conditions like that but have worked for companies that used them on new houses with GE panels. Just says cheap cheap cheap to me. I have same situation on one of my own sub panels
 

480sparky

Senior Member
Location
Iowegia
I understand doing it under conditions like that but have worked for companies that used them on new houses with GE panels. Just says cheap cheap cheap to me. I have same situation on one of my own sub panels

I don't think in all my own new installs, I've ever put in a 20- or 30-space panel. A 40-space is what, $5 or 10 more? I think it's more than worth it. I might not be the one coming back in 25 years to add a half-dozen circuits, but it sure is nice to have the spaces available.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
If space is limited a 30/40 panel will be smaller than a 40 circuit panel. GE panels really don't use tandems, they just use 1/2" breakers.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Electrical Contractor
I agree with Ken I rarely use anything other than a straight 40 circuit panel esp. with the requirement for afci. I hate those 20/40 installs on new homes- god awful
 

PetrosA

Senior Member
I had a boss who would continuously buy undersized panels out of some inborn cheapness. I explained to him a number of times that once we used 2 twins the costs were higher than if he had just bought the larger panel to begin with. It didn't help.
 
Location
Central NJ
NEC vs. manufacturers installation requirements and guidelines.

NEC vs. manufacturers installation requirements and guidelines.

Are tandem breakers ok to install in new panels. I only need to install one tandem. I can't find anything in the NEC prohibiting their use in new boxes nor in the local electrical code. I try to use tandems in existing boxes only. I'm assuming the AHJ cannot red flag me on this. Thanks
NEC vs. manufacturers installation requirements and guidelines.

An excellent (and often asked) question!

The easiest way to answer this is, the NEC is not the only source for installation details. As a matter of fact, the NEC has very few installation details to begin with. To sum it up the NEC makes a very simple reference... "As per manufacturers installation guidelines". The is a mouthful!!! By making this 5 word statement the NEC pushes the responsibility of installation detail onto the manufacturer.

As far as answering your question, you have to look at the small panel detail graphic (usually on the inside of the panel). This and the wording on the label will explain what type of breakers can be installed in the panel, if tandems are allowed and if so where they would be positioned in the panel.

CTL vs. NON-CTL (Ant discussion about tandems has to touch on this)
I can type all day to explain the difference in tandem circuit breakers but I have a lot to do today so here's a Wiki link...

http://en.wikipedia.org/wiki/Circuit_Total_Limitation

This will help eliminate the old wives tale of "If it fits in the panel, it's code compliant".

Surprisingly (sadly) many inspectors don't know too much about this.

Just my 2-cents (0.00012 cents after adjusting for inflation)

Cheers,
Ken C.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Ken C., gesundheit! :)

Ken the OP, as said above, as long as the panel and tandems are suitable, I don't have any problem with using them. From what I've read, they use the same guts as full-sized ones.

I don't use them unless I need to. When I do use them, I do my best to use them on the lowest-rated circuits I can. 50/30 quads (tandem two-poles), for example, make me a bit uneasy.
 

hurk27

Senior Member
Manufactured homes have been using them for years, I think they have a line on them because lately I been seeing them in panels with plenty of extra spaces but still every breaker in the panel is a tandem, yes including the two poles (quads) they must have a low cost place to get them because our cost is $25.00 to as high as $48.00 for the 20/30 quads they use, even in a new install I can understand where the new home buyer adds more circuits like for electric floor heating, and adding all electric cooking and dryer, in that case the cost of changing out the panel would allow the cost of tandems, but not for a planed system just because of the cost it adds, like others we changed to 20/30 panels on 100 amp services (rare), and 30/40 or straight 40 space panels on 200 amp services, but with upgrades it depends upon the amount of space you have to install the replacement panel.
 
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