Sq D makes a 'Handle Interlock' , or commonly refered 'Transfere Clip', part # QO2DT1 ( sorry, i could not find a link....)

This is a simple little piece of metal that acts in a see-saw manner when mounted between two 2-P breakers.

Both the latter can not be on @ the same time due to said 'Clip'.

As one of the two breakers may be 'backfed', there is a 'breaker hold down bracket' which is required. I noticed this mentioned inside a SQ D cover's sticker.

Now this entire arrangement might top $15 in parts & seems to be kosher...
The simplicity and $$$ blows me away...

But I don't see a whole lot of these, as compared to the average T-switch, or Gen-Tran, nor have i installed one....

So i'd like to ask here, are there applicable codes,listings, concerns, etc that i've missed?

Is this a setup simply more common than i've seen?

Unfuzz me please...

The Mechanical Interlock Attachment you describe (SQD #QO2DTI) is intended as a means of preventing two loads from being connected at the same time not as a transfer switch.

However if you use the interlock with (2) breaker retaining clips then it is UL Listed as a manual transfer switch in "dual power supply applications". But only when installed in a SQD #QO816L100 load center.

You can also buy it in kit form (SQD PK4DTIM4xx) for use in newer series main lug only loadcenters.

All of this information is from Square D's Digest #172 page 1-9.

I think you would have to concern yourself about making sure one breaker disconnects its load before the next one connects.."break before make". I don't think the device you talked about does that.

Elzappr;
actually it does, but it's a God awful little piece of tin to depend on....

JBD;
thanks, i see the 1-9 accessory page. But I am because it would seem to be a T-switch for a 8-16 circuit panel only.

The NEC falls short of a definition of a T-switch, and i really can't stand on 700 or 701, as the application is residential, not an 'emergency' or 'legally required' criterion.
Should i seek a 'listing' answer here?

Sparky, look further doewn the page at Manual Transfer Equipment Kit.

This little piece of tin is the same device SQD uses in their UL Listed Generator panel shown on page 1-8.

JBD,
my cat is a 97', but i'l take your word for it, thanks.