Reply to Thread

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...

Originally Posted by swhatIdo

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.

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.

Originally Posted by CraziFuzzy

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.

Originally Posted by swhatIdo

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.

Originally Posted by CraziFuzzy

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.

Originally Posted by enb54

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?

Originally Posted by machery

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...

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?

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:

Originally Posted by enb54

OK Folks...

I guess we are not as advanced as you in the USA, have not encountered any dual breakers that only contact one phase, one more lesson learned...

I looked at my Alberta Electrical Code, does not appear to be legal here...

Thanks for re-educating me!

P.S. And you are right, this is pretty darned dumb!!!

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.

Originally Posted by 1SikLBZ

Its hard to tell from the pic but Its only a regular size breaker so It only touches one phase or leg of power. Its a twining breaker used to free up space In a panel when your looking to add more equipment but don't want to do a service upgrade.

To clear things up It Is not a normal sized 2 pole breaker which would occupy both A and B phases or legs of the panel, It Is a twined breaker only touching one phase of power hence the reason my co worker only found 110v across the contactor when he was trouble shooting the unit.

PS: You are correct on checking power across both terminals and not to ground when checking for proper 208/230 power, Anything other then across both termials will be read as "Ghost Voltage"
Thats the hardest thing I find trying to teach new techs that come Into this trade.

OK Folks...

I guess we are not as advanced as you in the USA, have not encountered any dual breakers that only contact one phase, one more lesson learned...

I looked at my Alberta Electrical Code, does not appear to be legal here...

Thanks for re-educating me!

P.S. And you are right, this is pretty darned dumb!!!

Originally Posted by enb54

In Canada & USA, each alternate vertical position is normally opposite phase, horizontals are same phase, so that picture the OP posted should work as 240VAC unless there is something else wrong. The only thing wrong in the photo is that you need a bar so that both breakers operate as one unit, and usually 20Amp double pole breaker, but I don't do air conditioning...

On 240VAC circuits, measure across the two "hot" leads, not to ground, otherwise you will only see 120VAC...

Picture from http://homerepair.about.com/od/elect...elec_pnl_5.htm

Its hard to tell from the pic but Its only a regular size breaker so It only touches one phase or leg of power. Its a twining breaker used to free up space In a panel when your looking to add more equipment but don't want to do a service upgrade.

To clear things up It Is not a normal sized 2 pole breaker which would occupy both A and B phases or legs of the panel, It Is a twined breaker only touching one phase of power hence the reason my co worker only found 110v across the contactor when he was trouble shooting the unit.

PS: You are correct on checking power across both terminals and not to ground when checking for proper 208/230 power, Anything other then across both termials will be read as "Ghost Voltage"
Thats the hardest thing I find trying to teach new techs that come Into this trade.

Originally Posted by enb54

In Canada & USA, each alternate vertical position is normally opposite phase, horizontals are same phase, so that picture the OP posted should work as 240VAC unless there is something else wrong. The only thing wrong in the photo is that you need a bar so that both breakers operate as one unit, and usually 20Amp double pole breaker, but I don't do air conditioning...

The breakers in the OP are all tandem breakers, not normal 2 pole breakers.
The 2 switch breaker marked "AC" occupies the same amount of space in the panel as a single pole breaker normally would, and connects to only one buss bar.

Originally Posted by allan38

Both of these breakers are on the same phase (leg) of power. There is not a voltage difference between the two thus no 230vac.
The 120v don't add to each other unless they are on different phases.

In Canada & USA, each alternate vertical position is normally opposite phase, horizontals are same phase, so that picture the OP posted should work as 240VAC unless there is something else wrong. The only thing wrong in the photo is that you need a bar so that both breakers operate as one unit, and usually 20Amp double pole breaker, but I don't do air conditioning...

On 240VAC circuits, measure across the two "hot" leads, not to ground, otherwise you will only see 120VAC...

Picture from http://homerepair.about.com/od/elect...elec_pnl_5.htm

Both of these breakers are on the same phase (leg) of power. There is not a voltage difference between the two thus no 230vac.
The 120v don't add to each other unless they are on different phases.

Originally Posted by 1SikLBZ

Lol no it has never worked. Its touch only one Buss bar, 110v out of both sides of the breaker but not 220 because its not on A and B buss bars

what do u mean it is not on a and b bus bar. It just needs to be a double pole breaker.

I've seen that happen before.

Originally Posted by blitz

does it work?

Lol no it has never worked. Its touch only one Buss bar, 110v out of both sides of the breaker but not 220 because its not on A and B buss bars

Obviously. They forgot to turn the breakers back on...