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  1. #14
    Join Date
    Aug 2009
    Location
    Jurupa Valley, CA
    Posts
    1,758
    The trend in the states (and it's a good one, I feel) is to add more and more circuits, segregating loads better throughout the house. (The average kitchen in a new construction home, for instance, may potentially have 4 different recepticle circuits in it). This results in even new construction homes using the tandem breakers. No real problem with it, unless the electrician doesn't understand what he's doing (as this one apparently didn't). Still, wouldn't be a terrible thing to fix in this case, by just swapping the bottom 'A/C' leg and the GFCI one above it, and ganging the 'A/C' breakers together (like the breaker spaces below it for 'new heat').

    Tandem breaker:

  2. #15
    Join Date
    Jun 2012
    Posts
    7
    I've seen better than half a panel done using tandems. They were using 1 space on one tandem, and 1 space on the tandem immediately below. 2 poles, and I probably shouldn't have told you that. This is VERY dangerous.

    I was called out to troubleshoot the tripping main...and they wanted to know what that "cooking" smell was. And, yuck, were those Homelines?

  3. #16
    Join Date
    Apr 2010
    Location
    Red Deer, Alberta
    Posts
    653
    Quote Originally Posted by machery View Post
    So, tandem or piggyback breakers are not allowed in canada? Is this why I've seen panels there that are available with 60 and 80 spaces whereas here in the states we were limited to 42 spaces. Supposedly here now, the code has been re-written to allow bigger panels with more spaces, but no one is selling them yet.
    Well, closer investigation on my part seems to indicate that they are legal here, but very rarely used and are sort of frowned on. Personally have never ever used one, and this thread was actually my first inkling that there was widespread use of them in the USA. I'll be in Anaheim this weekend and for curiosity's sake will check out my in-laws breaker panel...

  4. #17
    Join Date
    Aug 2009
    Location
    Jurupa Valley, CA
    Posts
    1,758
    Quote Originally Posted by enb54 View Post
    Well, closer investigation on my part seems to indicate that they are legal here, but very rarely used and are sort of frowned on. Personally have never ever used one, and this thread was actually my first inkling that there was widespread use of them in the USA. I'll be in Anaheim this weekend and for curiosity's sake will check out my in-laws breaker panel...
    Why are they frowned upon?

  5. #18
    Join Date
    Jun 2012
    Posts
    7
    Quote Originally Posted by CraziFuzzy View Post
    Why are they frowned upon?
    Tandems make it too easy to overload a panel. Overloads generate lots of heat, and sometimes a breaker just doesn't trip, causing a fire. No AHJ in my locale will allow a tandem breaker, even going so far as to fail the inspection if they see one--even if it was existing.

  6. #19
    Join Date
    Aug 2009
    Location
    Jurupa Valley, CA
    Posts
    1,758
    Quote Originally Posted by swhatIdo View Post
    Tandems make it too easy to overload a panel. Overloads generate lots of heat, and sometimes a breaker just doesn't trip, causing a fire. No AHJ in my locale will allow a tandem breaker, even going so far as to fail the inspection if they see one--even if it was existing.
    That - frankly - is a stupid argument against them. You can just as easily install a bunch of 50 amp breakers and overload a panel just as easily. The fact is, the panel is going to be feeding the number of appliances, lights, and receptacles in the house. Doesn't matter whether those receptacles are spread across 5 breakers, 20 breakers, or 40 breakers. The main breaker is the only thing that matters in preventing the panel from being overloaded.

  7. #20
    Join Date
    Jun 2012
    Posts
    7
    Quote Originally Posted by CraziFuzzy View Post
    That - frankly - is a stupid argument against them. You can just as easily install a bunch of 50 amp breakers and overload a panel just as easily. The fact is, the panel is going to be feeding the number of appliances, lights, and receptacles in the house. Doesn't matter whether those receptacles are spread across 5 breakers, 20 breakers, or 40 breakers. The main breaker is the only thing that matters in preventing the panel from being overloaded.
    That's the rationale, nonetheless. The main breaker will trip on overload, but not always. So, in order not to make a habit of testing the main, most inspectors will err on the side of avoiding the overload in the first place. The easiest, and really most common, way to do this is to prohibit the use of tandems.

    Because 15A and 20A circuits are what we use most, and what we add the most, these become the biggest culprit in overloads. No one really has a need to fill a panel with 2pole 50's--there isn't that much consumer equip that requires that kind of connection. Extra 15A and 20A ckts are another matter. We have TVs in every room now, computers, phone chargers, Playstations, DVD players, fans, heaters, hairdryers...it all adds up quick.

    We used to say that no one ever utilizes all ckts to max rating at the same time, so we didn't worry that our 100A panel had a 50 for the dryer, a 50 for the A/C, a 20 for the fridge and 6 15A general ckts, far exceeding 100A by fuse rating, but we are becoming less and less able to say that.

    They know we'll use the hell out of them and might burn our houses down in the event that main doesn't trip(some breakers were notorious for this--FPE). Hence tandems are frowned upon.

    Don't get me wrong, if you put in a pool and your panel was full, I'd install a tandem, maybe even 2, but after that I'll suggest a small subpanel.

  8. #21
    Join Date
    Apr 2010
    Location
    East of Lyndon's
    Posts
    525
    The foolish thing about using tandems is the cost. Why use a smaller panel with tandem breakers when it would be cheaper to just install a larger panel?? The other foolish thing is why do they call a panel a 16 space panel when it only has eight spaces. The only way you can get 16 is to fill it with tandem breakers. Some of the panels won't except the regular tandems. Square D is marketing a panel with more than 40 space in it but it is cheaper to install a 40 space and than branch off with a 20 space ML panel.
    If you can't fix it with a hammer, you've got an electrical problem.

  9. #22
    Join Date
    Jul 2008
    Location
    Poestenkill, NY
    Posts
    769
    Quote Originally Posted by swhatIdo View Post
    That's the rationale, nonetheless. The main breaker will trip on overload, but not always. So, in order not to make a habit of testing the main, most inspectors will err on the side of avoiding the overload in the first place. The easiest, and really most common, way to do this is to prohibit the use of tandems.

    Because 15A and 20A circuits are what we use most, and what we add the most, these become the biggest culprit in overloads. No one really has a need to fill a panel with 2pole 50's--there isn't that much consumer equip that requires that kind of connection. Extra 15A and 20A ckts are another matter. We have TVs in every room now, computers, phone chargers, Playstations, DVD players, fans, heaters, hairdryers...it all adds up quick.

    We used to say that no one ever utilizes all ckts to max rating at the same time, so we didn't worry that our 100A panel had a 50 for the dryer, a 50 for the A/C, a 20 for the fridge and 6 15A general ckts, far exceeding 100A by fuse rating, but we are becoming less and less able to say that.

    They know we'll use the hell out of them and might burn our houses down in the event that main doesn't trip(some breakers were notorious for this--FPE). Hence tandems are frowned upon.

    Don't get me wrong, if you put in a pool and your panel was full, I'd install a tandem, maybe even 2, but after that I'll suggest a small subpanel.
    Fuzzy logic. If a sub-panel is added to avoid the "evil" tandem breakers the whole load still goes thru the service panel and service entrance. Shoot, you can put two (three, four, etc, etc) 60 Amp sub-panels on a 100 Amp service.

    The amp load rating and the circuit capacity rating of a panel are two different things. You can have a 200 Amp 42 slot panel that is only allowed to have 60 circuits. Fill it with tandems and you are breaking code. This is the only "frowning" that should occur - when the code is violated. Using tandem breakers itself does not allow the home owner to overload the main any more than adding a sub-panel or loading every 20 amp circuit to the max with space heaters while running the electric dryer, electric range, and an electric water heater etc, consecutively.

    Circuit diversity alone has little to do with total amp draw. In general, more circuits are better. I agree with what CraziFuzzy said 100%. In fact, "disallowing" tandems in some way actually promotes overloaded branch circuits, if you think about it. The uneducated are going to use what they are going to use, and if this means splitters in receptacles until the cows come home that's exactly what Joe Public will do.

  10. #23
    Join Date
    Apr 2010
    Location
    Red Deer, Alberta
    Posts
    653
    Well, the relatives in Anaheim have them, I'm going over to the local electrical wholesaler this week and see if they carry them, just curious...

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