circuit breakerelectrical
Specifically I am looking at a QOTO2020:
You can see what seem to be holes in the handles for a connection pin.
On a single pole breaker I can't think of an application where you would want both independent circuits to switch off in the event of a fault on one of them. Unlike a 2 pole (USA) breaker where you would want both legs to go off in unison.
What use would be pinning the two handles together? Or are those holes not for that purpose?
It sounds like you may be mistaken as to how this is wired, or that perhaps I'm just not understanding your explanation. As others have mentioned, it's not possible to get 240 volts from a single pole in a 120/240V split phase system. Each tandem breaker provides 2 120 V circuits, this is true. However, if you measure between the terminals on a single tandem breaker, you'll get 0 volts. This is because the terminals are both powered from the same leg, and so are at the same voltage potential. If you measure from a terminal on the top tandem breaker to a terminal on the bottom one, then you'll measure 240 volts. This is because each breaker is connected to a different leg, which are each one half of a 240 volt circuit.
With all that said. For this setup to work, one appliance would have to be connected to both breaker. Something like this...
Notice that each appliance circuit has one wire connected to each of the tandem breakers. In this situation, you'd need a device like Speedy Petey shows.
Which ties the breaker handles together, to provide common trip characteristics.
Notice how the inner handles are tied together, and that the outer handles are also tied to each other. This way if either trip (or are turned off by the user), the entire circuit is shut off.
If this is wired the way you've explained, where the dryer is connected to the top tandem and the heater is connected to the bottom. Then there's some magic going on in those breakers.
Addressing your points in turn:
1) Handle ties do not make a BR breaker pair common trip (2-pole BR breakers have an internal common trip mechanism) -- see footnote 2 on page 84 of Eaton's catalog.
2) Common trips are generally used in 240VAC circuits -- while what the previous installer did with the pump circuit is not wrong as per the 2014 NEC 240.15(B)(2):
Grounded Single-Phase Alternating-Current Circuits. In grounded systems, individual single-pole circuit breakers rated 120/240 volts ac, with identified handle ties, shall be permitted as the protection for each ungrounded conductor for line-to-line connected loads for single-phase circuits.
common trips are generally used on all 240VAC circuits (it's hard to get a non-common-trip 240VAC breaker in a typical form factor), and are needed in mixed 120/240VAC circuits for the reason you observed, as per NEC 240.15(B):
Circuit Breaker as Overcurrent Device. Circuit breakers shall open all ungrounded conductors of the circuit both manually and automatically unless otherwise permitted in 240.15(B)(1), (8)(2), (B)(3), and (B)(4).
(The exemption in (B)(1) is for multiwire branch circuits serving only 120VAC loads, while (B)(3) and (B)(4) are irrelevant to residential practice.)
3) You are correct -- this is documented pictorially in the table headings on page 82 of the Eaton catalog, so it's easy to miss.
Best Answer
You need to tie breakers together in certain scenarios.
One common scenario was 15 amp kitchen plugs in certain jurisdictions where on a single device you have severed the outlet tie and have two circuits powering the single device. When working on the outlet you want to flip the breaker and not be able to have half of the device live.