Mini tandem breakers

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Old 09-24-07, 07:09 AM
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Mini tandem breakers

Can inspectors fail you if you use tandem breakers on a permitted job? I assume they can if the panel wasn't designed for it, but this panel was designed for it and has plenty of room for tandems. I know its frowned upon in new construction, where your putting a new panel in, but this is a huge addition my brother is doing, and the main panel will remain the same. Its a third floor and a few extra rooms on the 2nd and 1st floor.

The reason I ask is because the electrician is charging $650 to put in a subpanel, for maybe 6 circuits. The main panel has 3 full spaces left, and according to the literature, can take about 18 or so tandem breakers. I don't think so, but maybe I'm wrong...can an inspector fail using tandem breakers?
 
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Old 09-24-07, 07:14 AM
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If the panel is designed for tandem breakers and the tandem breakers used are designed for the panel and they are installed in the proper locations in the panel and they are installed in the proper manner, then the inspector cannot fail you for using them.

However, depending on what FUTURE needs are it may be a better idea to install a sub panel. Depending on the specifics of the sub-panel proposed, $650 may be a good price.
 
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Old 09-24-07, 07:32 AM
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There arn't any future plans, my brothers wiped out as it is. But even if there where, after all this jobs breakers are installed, there would still be about 10 circuits left if using tandems.

I guess maybe its more proffesional looking using a subpanel instead of a tandems, no? If I was the electrician tho, I would be all about customer satisfaction, and that would mean keeping the price down, which means using tandems.
 
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Old 09-24-07, 07:35 AM
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Does the panel literature actually say that it takes "18 or so" tandem breakers? This level of imprecision suggests that perhaps you need to look more closely. Maybe there's some other issue. Note that panels that can take a certain number of tandem breakers can usually only take them in certain spaces, and perhaps those spaces are already in use.

I suspect that there is more to this story. Your brother should talk again to the electrician to make sure he completely understands why the electrician is going to put in the subpanel. I don't think you yet have the whole story.

But anyway, the answer to your original question is "no".
 
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Old 09-24-07, 07:45 AM
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I don't know exactly how many, I saw it took plenty more then he needed and so I didn't feel the need to count. And you would definitly have to take out some of the old breakers and gang em up with tandems. There are only three blanks spaces currently.
 
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Old 09-24-07, 11:22 AM
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Just to clarify, when you guys are talking about panels not designed for tandem breakers, are you talking about panels where you can physically install tandem breakers, but where it's not advised to do so? If so, what is the safety/code concern?

The panel in my house has a couple of tandem breakers, even though there were a few empty spots at the time of construction. Probably what the electrician had in his pocket at the time of the install, I guess. If the panel came with the house and you don't have any documentation or model number, how do you know the limit for the number of tandem breakers?
 
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Old 09-24-07, 11:37 AM
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Every panel has a manufacturer and model number. If you cannot find this information and cannot determine what it is, then you cannot safely add breakers of ANY kind.
 
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Old 09-24-07, 11:41 AM
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Modern panels will block the installation of tandem breakers in spaces that do not allow them. Some people, however, will still get out their metal file and illegally modify the panel to get around this.

The label in the panel should specify which spaces, if any, will accept tandem breakers. You can also usually get a clue by looking at the place where you label the circuits. Spaces that accept tandems often have two lines, one for each half of the space.

When in doubt, find the panel specs on the web or call the panel manufacturer.
 
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Old 09-24-07, 05:42 PM
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You didnt mention what these rooms will be used for. A subpanel may well be the only feasible alternative. Bedrooms may be required to use AFCI protection, AFCI breakers are not available as "TANDEMS" . Water related-- ie..Bathroom, laundry room convienience areas may require GFCI protection,and on dedicated lines. again , unavailable as tandem. You could very possibly "Run out of Space" well before planning is complete.
Since you mentioned whether or not an inspector would fail you, means you are for the most part "CODE CONSCIOUS". I would be more worried about what is required to pass , instaed of focusing on each piece , wondering if its ok.

The price of tandems can add up quickly, and I would rather be stuck with something that I need , Than stuck with something I cant use.

Originally Posted by biking_brian View Post
If the panel came with the house and you don't have any documentation or model number, how do you know the limit for the number of tandem breakers?
Most manufacturers ,when they limit the number , or positions of tandems.........They physically "DONT FIT" . Square D makes "NON CTL" breakers in a tandem for pre 1967 boxes. They will fit in all Square D QO boxes, but they arent approved for use. At 40 bucks each...WHY WOULD YOU?
 
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Old 09-24-07, 06:42 PM
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Usually the panel has a schematic inside the door. Regular spaces have one wire going to each space, tandems have two. Usually the bottom section is the location that holds tandems, if any. The other giveaway is standard murray/bryant/etc. panels have a notch in the center of each busbar that the breaker snaps onto. This means that the panel can legally take $10 tandem breakers. If you don't have these notches, you can put in a $20 tandem breaker that is designed to go where you can't put tandems. These breakers have deeper notches to clip onto the bus bar, almost twice as deep. I can't see how these would be legal since they go against manufacturer's instructions which definitly isn't legal. They do sell them though.
 
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Old 09-24-07, 07:08 PM
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What youre describing is a Non CTL tandem. These were used in early to mid 1960's. They are sold under the premise of "REPLACEMENT USE ONLY". While yes they do fit...They arent legal.
 
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Old 09-26-07, 10:06 AM
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I have a 100A panel with 4 spaces on the top, then the main shutoff, and then 8 spaces on the bottom. The paper schematic on the inside lid has been torn out. Is it highly likely that the panel was designed for tandem breakers on the bottom but not the top? That seems to make sense, as it would give 20 breakers for a 100A panel.
 
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Old 09-26-07, 10:23 AM
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Brian, what you described sounds like a split-bus panel. These panels aren't even legal any more for new installations. The top spaces are usually just for 240-volt loads.

Most of the time, especially with newer panels, the model number itself tells you the number of tandem breakers it accepts. Even with older panels, a google search of your model number will usually tell you want you need to know. So even if all the other information has fallen out of your panel, if you still have the model number, you can probably figure it out.
 
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Old 09-26-07, 10:50 AM
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No, it's nothing like that. I've got a photo somewhere, but I can't get to it from work.
 
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Old 09-27-07, 01:01 AM
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OK, here's the photo. It's hard to tell, but there are two open spots on top where there are no breakers.

http://www.flickr.com/photos/[email protected]/932141095/
 
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Old 09-27-07, 07:57 AM
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The buss is slotted on the top to allow tandem breakers. 100 AMP panels with 24 circuits are pretty common. Definitely not a split buss panel.
 
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Old 09-27-07, 09:19 AM
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Thanks ... I'll probably pull a breaker out from the top and the bottom and compare the busses just to be sure.
 
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