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Discussion Starter #1
Yesterday evening I cut off the main power to check if a Siemens tandem 20A single pole breaker was going to fit my Siemens 200A panel in preparation for making a 10-3 UF run to my shed. The bottom two left slots are open. No wires were hooked up, the new breaker switches were in the off position. It fit fine, snapped in tight and easy in the next to bottom left open slot. I left it there and turned the main power back on. This morning I noticed my shower was not real hot. I checked the panel and the double 30A hot water heater breaker (bottom right) was off an the 20A above that was off too. I switched them back on. They didn't trip when I cut them back on. I don't remember cutting them off last night...guess i could have but had no reason to touch them. When I get home today, I am going to check them first thing to see if they are still on. Given the above situation, is there any explanation that would cause the other breakers to trip?
 

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Master Electrician
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Assuming you put the cover back on when you were done, maybe they got bumped? I'd take the cover back off and double check that they are fully seated, and monitor them for a couple days.
 

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Discussion Starter #3
That makes perfect sense. I did have a little difficulty in lining up the screw holes last night...I remember. I will continue to monitor. Thanks.
 

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Master Electrician
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Yesterday evening I cut off the main power to check if a Siemens tandem 20A single pole breaker was going to fit my Siemens 200A panel in preparation for making a 10-3 UF run to my shed. The bottom two left slots are open. No wires were hooked up, the new breaker switches were in the off position. It fit fine, snapped in tight and easy in the next to bottom left open slot. I left it there and turned the main power back on. This morning I noticed my shower was not real hot. I checked the panel and the double 30A hot water heater breaker (bottom right) was off an the 20A above that was off too. I switched them back on. They didn't trip when I cut them back on. I don't remember cutting them off last night...guess i could have but had no reason to touch them. When I get home today, I am going to check them first thing to see if they are still on. Given the above situation, is there any explanation that would cause the other breakers to trip?
If you are trying to get 240 volts or a MWBC on the 10-3 a tandem breaker will not work.
 

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licensed electrician
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This has happened to me a million times when putting the panel board cover back on :D some breakers go off on the slightest pressure, easy to do without realizing it.
 

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This has happened to me a million times when putting the panel board cover back on :D some breakers go off on the slightest pressure, easy to do without realizing it.
And don't forget that breakers do not last forever, so if you have a doubt swap it out.
 

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Discussion Starter #8
Got it. I just need the 2x120v circuits. About the cut-off HW breaker...they do flip easy. The panel cover has a thin center divider and unless you place it straight on it wil touch a toggle. I did it again yesterday.
 

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Sparky
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Got it. I just need the 2x120v circuits. About the cut-off HW breaker...they do flip easy. The panel cover has a thin center divider and unless you place it straight on it wil touch a toggle. I did it again yesterday.

you cant get 2 120v circuits with 1 neutral, off a tandem breaker.

Panel is run L1,L2,L1,L2(assuming 'single phase') all the way down.

to use one neutral for two circuits the two hots must be on opposite 'Lines', ie 1 L1, and 1 L2. If you dont do this the neutral could potentially have a much larger load than it's rated for(using 2 20A circuits, if both fully loaded, neutral would be carrying 40A)


you'll either need a 'quad' tandem, 2 standard single pole breakers (and a handle tie, if using 2008 NEC or newer), or a standard factory 2 pole breaker
 

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Discussion Starter #10
I'm planning on going to a subpanel at the shed with the two hots going to the two poles, neutral to neutral bar, and ground to ground. I'm grounding the box to two 8' copper rods 6 ft. apart. 20A circuit #1 will feed 8A (max) fridge and 4A (max) worth of lights. 20A circuit #2 will feed a circular saw or a 5000 btu AC (not at the same time).
 

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Sparky
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a 2x20A Siemens Type QT tandem breaker only hits one 'pole' or 'line', you cannot feed a subpanel with one., a 'quad' breaker ( 4 poles, 2 1" spaces) will connect to both 'poles' or 'lines'
 

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Discussion Starter #12
Dagnabit! Well, what good is a tandem breaker if you can't use it to fill one slot on one pole and attach to the two hots on 10-3? The 10-3 only has one neutral...right? I guess I'll go buy the twin 20A breakers and fill both my empty slots (I had wanted to save that for a future back porch project). Can I use the 2x20A tandem I own for the shed panel? Seems to me somewhere or another one neutral wire in the 10-3 is gonna cause the same problem whether at the house sub or the shedsub. Now i got 30 inches of SIP foam to get through from the top of the house panel to the attic and i have to eat up two slots for 40A. Rats.
 
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