Here's a slick Canadian subpanel with a "generator interlock". It is a normal 2-pole panel, just like common USA panels, and it's Square D QO, which is common as dirt in the USA. However for the generator interlock, it uses 3-pole breakers (this series of panel is also made in a 3-phase version, so the 3-pole breakers are also common). The third pole switches neutral.

We often have applications here in the US where someone needs a generator interlock/transfer switch, and there are loads of things like this on the US market, but they are only 2-pole (no neutral). That won't cut it, because they are coming off an inlet from a portable generator, and most portable generators have neutral-ground bonds, which means neutral must be switched. (the consumer can't be counted on to install and remove the N-G bond every time he uses the generator).

This thing is both CSA and UL listed (CSA is a US Nationally Recognized Testing Lab) and actually made in the USA. So could I just pop across the Friendship Bridge, buy one in Home Depot.CA, and use it in Virginia? Or is that statutorially disallowed, and if so, by which Code cite?

  • The correct question to ask is: What does MY LOCAL CODE require/permit? Even "Virginia" is not specific enough since your local jurisdiction may have requirements different from other parts of the state. The fact that it's CSA is, in my opinion, irrelevant. It is, UL listed but that doesn't make it compliant with your local codes. For that, you'll need to consult the codes themselves and ensure that you are compliant with the application.
    – jwh20
    Commented May 27, 2019 at 16:48
  • @jwh20 this is under the purview of 110.3 re: listing and labeling -- inspectors generally defer to the UL listing on a listed/labeled product such as a panelboard, as trying to field verify compliance to UL 50 practically requires UL to bring their truck o' gear out... Commented May 27, 2019 at 16:53
  • Can you get me the UL file number off of one? The drawing Schneider Canada provides only lists the CSA file number, and I don't think it's cCSAus, although I can see if I can access their database... Commented May 27, 2019 at 16:54
  • Yeah, I can't find it either nor do I see the C/US device on the CSA mark. Photos aren't focusing on that. I'd love to go check one out, but I don't want to get 50 lashes with a wet noodle for reentering the US without proper papers... Commented May 27, 2019 at 16:58
  • @ThreePhaseEel My point was that UL listing in and of itself is not the final determining factor as to whether or not a specific piece of equipment is legal in a particular use or locality. There are plenty of UL listed components that, when used or installed incorrectly, are dangerous and illegal.
    – jwh20
    Commented May 27, 2019 at 17:16

1 Answer 1


In your specific case, no, because the labeling is wrong (or you just can't get what you want)

Looking at the photos on HD.ca, it is clear enough that the panel is not labeled for service in the US, as it would either need a cCSAus mark, or a UL mark alongside the CSA mark, in order to be usable in the US as well as Canada.

Generally speaking? I'm not sure

I am not certain if one could make a binational loadcenter assembly that was listed and labeled cULus or cCSAus; it depends on how harmonized UL 67 (the UL standard for panelboards) is with its Canadian counterpart.

As it turns out, there is an easy way to do this after all, so you can get what you need

Fortunately for us, there is a way out of this while staying within the QO loadcenter line. The split-bus QO generator loadcenter (aka the QO122X26M200PC) has its backfed/interlocked breakers about halfway down the panel, which isn't compatible with the traditional QO backfeed retainers that attach to the main interior mounting screw located just above the branch stabs. So, Square-D had to develop a different retainer kit for that panel, the QOCGKX, which attaches to the accessory mount points on the right side of the interior (one screw, one clip). Fortunately for us, while the accessory mount point configuration on QO loadcenter interiors varies, there are other QO interiors that provide a configuration compatible with the QOCGKX, with a screw and clip combination open on the right side of the loadcenter.

For this approach, you'll need:

  • A QO124L125PGC loadcenter (if you need more spaces for standby circuits, you can use a 42- or 54-space, 225A, main lug loadcenter instead)
  • A QO350SWN breaker for the utility feed into the panel
  • A QO1xx to serve as a mechanical adapter (the amp rating doesn't matter)
  • A QO330SWN or QO350SWN (depending on the size of your generator/inlet/wiring) for the generator feed into the panel
  • A QOCGKX interlock/retainer kit (you'll need to order this from a supply house that stocks Square-D parts)
  • Some white wire of the appropriate size and matching wirenuts or crimp (compression) splices to extend neutral pigtails with
  • And a QO3HT handle tie

The trick here is that the retainer mounts to the bottom right accessory mount points in the QO124L125PG's interior. Since the standard QO2DTI interlock requires a single pole breaker on the left in order to interlock with a 3 pole breaker on the right, we have to mount the breakers with one of the QO3xxSWN breakers in the far bottom right 3 spaces, followed by the QO1xx directly above it, and finally the other QO3xxSWN directly above the QO1xx. Once this is done, the interlock piece can go on the upper QO3xxSWN breaker so that it interlocks that breaker with the single pole breaker below it. That single pole breaker is then handle tied to the lower QO3xxSWN breaker using the QO3HT tie, allowing the interlock to operate on the combination of the lower QO3xxSWN and the QO1xx as if they were a single breaker with a single handle in the appropriate position. Next, the QOCGKX's retainer is mounted in the lower right accessory position, as per the instructions provided with it. This makes sure you can't pull the backfed breakers out (or the mechanical adapter-breaker for that matter).

Now that all the mechanical details are taken care of, we can handle wiring this setup. The neutral pigtails on the QO3xxSWN breakers are extended (if necessary) using splices and appropriately sized white wires, then landed on branch neutral terminals in the panel interior while the main lugs on this panel are left open to be used as expansion subfeeds. From there, this is wired as a normal subpanel with the utility hots and neutral going into one QO3xxSWN, the generator hots and neutral going into the other QO3xxSWN, and branch circuits wired as you would from any other subpanel; you can even use QO plug-on neutral breakers here if you wish, as the panel supports them. The grounds, of course, land on separate ground bars; the QO124L125PGC is supplied with a ground bar, but it may still have to be field-fitted.

If you can't get a QOCGKX...

The good news is that it's possible to do this, even if you can't get a QOCGKX; the bad news is that you need to use unit mount breakers (and a few jumper wires) to do this in that case because QO loadcenter interiors do not support retaining backfed breakers in arbitrary positions (even the QOCGKX is quite limited both in positioning and compatibility).

In this case, you'll need:

  • Two QOU3xx breakers (you can go up to 70A for the generator and up to 125A for the utility, wire bending space permitting)
  • A QOU1xx breaker to serve as a "dummy" pole (if the utility breaker is 70A or less)
  • A QO3HT handle tie (if the QOU1xx is necessary)
  • A QO2DTILA interlock kit
  • QOUMFS1 threaded mounting feet, two per breaker pole
  • 8-32x3/8" mounting screws, two per breaker pole
  • Insulated three-port mechanical splice connectors (three) and suitably sized jumper wires (six) to connect the load-side hots and neutrals together
  • And a box to wrap this all up in (the box and trim from a QO816L100xx loadcenter should do the trick quite beautifully, just yank out the loadcenter interior, take care of the twistouts, drill some holes in the trim for the 8-32 breaker mounting screws, and fit a ground bar to the box)

What you want to do here is flush mount the breakers to the enclosure cover (trim) in a 3-1-3 configuration (or 3-3 with the utility on the left if using a >60A breaker on the utility side), then mount the QO2DTILA to the left side of the rightmost breaker. Finally, if the dummy breaker is being used, it needs to be handle-tied to the leftmost breaker in this configuration.

Wiring-wise, one side of one 3-pole breaker goes to the utility (hots + neutral), while that side of the other 3-pole breaker goes to the generator. The opposite side of the 3-pole breakers gets wired in parallel using suitably sized jumper wires and splice connectors, and then that can get wired onward to another enclosure (or a loadcenter interior in that enclosure if you're doing more extensive enclosure modifications) to distribute standby power to wherever it needs to go.

As to the 1-pole breaker, if present? It simply is left unwired; its sole purpose in life is to serve as a mechanical adapter between the handle-tie going onward to the left-hand 3-pole breaker and the QO2DTILA interlock as the interlock may slide under a handle-tie space that doesn't have a handle behind it.

  • Note that it might be possible to hack a setup together that achieves what you want here, but it's going to be a terrible hack due to the way the QO interlock kit and backfeed retainers work (spoiler: retaining backfed breakers is not the QO's strong suit...) Commented May 30, 2019 at 0:40

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