Electricians...never seen a breaker like this....

[JHZR2]

I see these miniature or thin breakers on shelves all the time, other times in panels.

I was always under the impression that as long as you respect the total amperage of the panel you could stuff these type things in to your
hearts content - but I'm certainly no electrician.


View attachment 48438

I’ve seen them as well. Some panels actually give the number of circuits with and without them. Here’s a panel I just bought:

4 spaces, 8 circuits... only if you use doubles...

I only used single (normal?) size breakers.

 

[spasm3]

I wonder if there is perhaps a septic pump and alarm on the 20A, so these all mutually lock out?

Could be, that would be smart. Good idea to disable the well pump if the septic pump stops.

 

[UncleDave]

I didn’t pick up on that before. It’s like they’re all half sized breakers. So it’s pretty nice to be able to have options for subpanels and other circuits. I’d agree it’s sensible to use for a kitchen to feed a range and two kitchen circuits (could be two 20A in a MWBC for dishwasher and disposal or something else). All in a smaller package.

I’d suspect they use it for the well, well, just because.

I wonder if there is perhaps a septic pump and alarm on the 20A, so these all mutually lock out?

This might be the case - there is a septic pump and alarm on this property,

Not sure why they'd route that circuit all the way to the garage though except maybe to tie them together...??

 

[JHZR2]

This might be the case - there is a septic pump and alarm on this property,

Not sure why they'd route that circuit all the way to the garage though except maybe to tie them together...??

If it’s not a gravity septic, and the pump trips or is turned off for service, the last thing you want/need is someone taking a shower (or worse, a dump) because the water is still on...

 

[exranger06]

I see these miniature or thin breakers on shelves all the time, other times in panels.

I was always under the impression that as long as you respect the total amperage of the panel you could stuff these type things in to your
hearts content - but I'm certainly no electrician.


View attachment 48438

That's a tandem breaker. Those are used for x2 120V circuits, where each circuit has its own neutral wire. You cannot use those on 240V circuits, or on 120V multi-wire branch circuits (shared neutral). For 240V circuits, you MUST use a double pole breaker. For multi-wire branch circuits, you MUST use either a double pole breaker OR two regular single pole breakers that are handle-tied together.

There IS a limit on how many tandem breakers you can use in a panel. Many panels have bus bars designed so that a tandem will clip onto the bus bar only in certain spaces.

 

[UncleDave]

That's a tandem breaker. Those are used for x2 120V circuits, where each circuit has its own neutral wire. You cannot use those on 240V circuits, or on 120V multi-wire branch circuits (shared neutral). For 240V circuits, you MUST use a double pole breaker. For multi-wire branch circuits, you MUST use either a double pole breaker OR two regular single pole breakers that are handle-tied together.

There IS a limit on how many tandem breakers you can use in a panel. Many panels have bus bars designed so that a tandem will clip onto the bus bar only in certain spaces.

If it isnt 240 then I have 2x 120V at 50 amps- plus 2x 20 at 120V?

Never seen 50 amp 120.

 

[mk378]

It depends on how the other end of the wires are connected. If you connect the load between the two hot wires it gets 240 volts, if it is between one hot wire and a neutral wire it gets 120 volts. The breaker doesn't care, it only sees current not voltage.

Heavy loads on 120 volts require unnecessarily large wire compared to designing the system for 240 volts. It's never done either in a house or industry. Any single unit that needs more than the 2 kilowatts or so that a 20 amp 120 volt circuit can supply will be designed for 240 volts instead.

 

[exranger06]

If it isnt 240 then I have 2x 120V at 50 amps- plus 2x 20 at 120V?

Never seen 50 amp 120.

The 50A is definitely 240V. Basically any circuit that's 30A or more will be 240V 99.9% of the time. The 20A circuit is likely also something that runs on 240V, but it could be a 120V multi-wire branch circuit, which is basically two individual 120V 20A circuits.

 

[JHZR2]

The 50A is definitely 240V. Basically any circuit that's 30A or more will be 240V 99.9% of the time. The 20A circuit is likely also something that runs on 240V, but it could be a 120V multi-wire branch circuit, which is basically two individual 120V 20A circuits.

Didn’t you just say above the exact opposite?? Or did you mean you can’t make 240 from a tandem?

 

[exranger06]

Didn’t you just say above the exact opposite?? Or did you mean you can’t make 240 from a tandem?

I said that a tandem can only be used for x2 120V circuits, where each circuit has its own neutral wire. In other words, a tandem will work on any 120V circuit that's NOT a multi-wire branch circuit. A multi-wire branch circuit is x2 120V circuits that share ONE neutral wire. And even though they are 120V, they work basically just like a 240V circuit, which is why they require either a double pole breaker (like a 240V circuit), OR two single pole breakers that are handle-tied together (which ensures that each breaker is on a different hot leg, like a double pole breaker. It also ensures that both legs get turned off if you were to manually shut the breaker off. You wouldn't want to disconnect a neutral wire if there's still current flowing through it because you only shut off one hot leg)

 

[JHZR2]

I said that a tandem can only be used for x2 120V circuits, where each circuit has its own neutral wire. In other words, a tandem will work on any 120V circuit that's NOT a multi-wire branch circuit. A multi-wire branch circuit is x2 120V circuits that share ONE neutral wire. And even though they are 120V, they work basically just like a 240V circuit, which is why they require either a double pole breaker (like a 240V circuit), OR two single pole breakers that are handle-tied together (which ensures that each breaker is on a different hot leg, like a double pole breaker. It also ensures that both legs get turned off if you were to manually shut the breaker off. You wouldn't want to disconnect a neutral wire if there's still current flowing through it because you only shut off one hot leg)

Yeah, agree.

 

[kschachn]

I said that a tandem can only be used for x2 120V circuits, where each circuit has its own neutral wire. In other words, a tandem will work on any 120V circuit that's NOT a multi-wire branch circuit. A multi-wire branch circuit is x2 120V circuits that share ONE neutral wire. And even though they are 120V, they work basically just like a 240V circuit, which is why they require either a double pole breaker (like a 240V circuit), OR two single pole breakers that are handle-tied together (which ensures that each breaker is on a different hot leg, like a double pole breaker. It also ensures that both legs get turned off if you were to manually shut the breaker off. You wouldn't want to disconnect a neutral wire if there's still current flowing through it because you only shut off one hot leg)

The point about each circuit protected by a standard tandem breaker having its own neutral is critical. Since a tandem breaker takes current from only one phase (leg) then each neutral can carry the full load. That's a big reason many times a tandem circuit breaker is not allowed.

 

[Job]

I see a single wire high voltage power line running on poles through a neighborhood. They drop the thin single high voltage wire to the transformers, then there are two 120 volt legs created from the transformer. Those feed the houses. Forgive my lack of knowledge but what creates the two phases or legs? I guess I could look it up on the internet and look smarter, but for some reason hate to do that. Special transformer? I think it’s very interesting how they planned and developed the electrical grid we so take for granted. I guess Tesla the man actually invented the system we use today.

 

[ironman_gq]

I see a single wire high voltage power line running on poles through a neighborhood. They drop the thin single high voltage wire to the transformers, then there are two 120 volt legs created from the transformer. Those feed the houses. Forgive my lack of knowledge but what creates the two phases or legs? I guess I could look it up on the internet and look smarter, but for some reason hate to do that. Special transformer? I think it’s very interesting how they planned and developed the electrical grid we so take for granted. I guess Tesla the man actually invented the system we use today.

It's a center tapped transformer. The output coil has 3 wires coming off of it, the ones on the ends are your 120v legs, the center one is your neutral/ground to the main panel. The legs are 120v to neutral or 240v between legs. The single wire coming in is usually 7200v and there is a neutral coming out of the transformer and grounded at the pole or to a neutral line between poles

 

[exranger06]

I see a single wire high voltage power line running on poles through a neighborhood. They drop the thin single high voltage wire to the transformers, then there are two 120 volt legs created from the transformer. Those feed the houses. Forgive my lack of knowledge but what creates the two phases or legs? I guess I could look it up on the internet and look smarter, but for some reason hate to do that. Special transformer? I think it’s very interesting how they planned and developed the electrical grid we so take for granted. I guess Tesla the man actually invented the system we use today.

There is also a neutral wire that goes from pole to pole. It's located further down the pole (It's labeled "D" in the pic below). The transformer is also connected to the neutral. It's a little hard to see in the pic, but it's labeled "H."

And here is how the transformer is wired:

You can see at the top, you just have one high voltage hot leg and the neutral. At the bottom, you have 2 hot legs with 240V between them, and (not really shown) a neutral wire, which connects to the center (X2) bushing. Since the neutral connects right to the center of the secondary windings, it basically splits the secondary voltage in half. That's how you're able to get both 120V and 240V.