I removed the cover of a 2 gang electrical box to replace some switches. The metal box inside is a 2 gang box, but it seems to have an extra pair of mounting tabs. Most of the 2G metal junction boxes have mounting tabs at opposite corners to mount mud rings. 2G switch boxes have two pairs along two edges for direct mounting of switches or receptacles. Yet this box has two tabs at the corners, and next to those each tab there is an additional tab. Here is a picture of the box. As you can see, there is a flat 2G mud ring over it, secured by screws into the corner tabs. The last picture shows that clearly. Yet there is an additional tab below the upper right corner, and above the lower left corner. What are those for? With those tabs in the way, I cannot use a bulkier dimmer switch.

Greetings, (2) unrelated questions, for a common cause: I'm going to be ordering one of those TED energy monitors for my house, with the ability to check current on individual branch circuits. I guess they use little inductance coils that clamp around the hots where they connect to the breakers. Question #1: They say I only need a single coil to monitor a 240V circuit (the readings from one of the legs is doubled in the software program), but only IF the loads are balanced. I'd be monitoring the A/C and maybe the electric clothes dryer. Do these typically present balanced loads? I know any electronic circuit boards would likely be stepped down from one of the 120V legs, but that would be only a tiny difference. But what about, for example, the dryer's drum motor. That might be significant if it runs from a 120V leg. I'm pretty sure that with the A/C, the condenser fan motor is likely 240V, so probably no imbalance there. Question #2: Also monitored will be several "shared neutral" branch 120V circuits. I will ask the manufacturer if the readings might be off as result of shared neutral, as it has to do with their product, but for y'all, just generally, this is where a wire comes into the breaker box containing a ground, a neutral, a red and a black, with the red and black breakers side by side, so they connect to opposite 110V legs. My house was built in 1984. Is this acceptable practice nowadays? Seems I read somewhere that it could lead to current on the neutral, for good or bad, don't know. I have (3) " shared neutral pairs in the panel. Thank You!