Specifically I am looking at a QOTO2020:

![enter image description here

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?

  • Would the holes be used for safety locks while someone is working on the system? It is common in the UK to for each worker to be able to lock off the part of the system they are working on with a lock they only have the key for.
    – Walker
    Oct 8 '19 at 18:24

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.

  • Specific and common example, thanks! Oct 8 '19 at 2:08

It's to make what are called "quad" breakers, where you have two twins side-by-side, creating 2 two-pole breakers out of 2 slots instead of 4 (or, as in the photo below, one 2 pole + two 1 pole). YOU cannot do this on you own, you would have to buy them AS quad breakers, but when they make the twins, they make them all the same.

enter image description here

  • QO quadplex breakers come "some assembly required" (i.e. as a kit containing two QO tandems and a handle tie, such as in the QO20303020) Oct 8 '19 at 0:20

The question isn't whether the breakers are able to accept a connecting pin. The question is whether the manufacturer makes a UL-listed handle tie for those pins. I would bet they do not.

There might be a reason to handle-tie the inner breakers of two adjacent duplex breakers; i.e. In an A1 A2 B1 B2 arrangement, tying A2 to B1. That would be for the normal uses of handle-ties, e.g. Multi-wire branch circuits and 240V-only loads.

Also keep in mind, handle ties do not assure common trip; multi-pole breakers have an internal mechanism which does that. (Which also means a multi-pole breaker is much more than two singles bolted together). The purpose of handle ties is common maintenance shutoff, needed for 240V loads (which can have each leg separately fused), MWBCs (so you don't get nailed by the other leg), and 2 circuits on 1 yoke (ditto).

  • I will have to check if such a tie is available... clever design whether they mean to assemble them themselves that way, or actually do provide for the installer to do so. Thanks Oct 8 '19 at 2:09
  • @DaveInCaz I am quite sure they would never factory handle-tie the two breakers of a duplex, for reasons I gather you are well familiar. Oct 8 '19 at 3:19

if you put it next to another similar breaker you can have a 240V circuit where they abut.

That is, you can join one handle to the neighbor breakers handle to make a two pole breaker

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