Okay, a few caveats first.
The two single phase circuit breakers are to be identical in the following aspects:
- Ampacity (30A, 40A, etc)
- Approximate age
- Known good
- Same size on all faces
Furthermore, I believe the following should be observed:
- The circuit breakers being joined must not be adjacent to empty slots (the tie bar may try to slip / fall out) in the breaker panel.
- Similarly, if this temporary repair cannot be made with absolute certainty that the breakers will not be allowed to separate during installation/ removal or during their temporary installation than this temporary repair should not be made. I was able to securely join my breakers together with electrical tape thus prohibiting any separation.
Finally, the following must be understood clearly:
- This is a temporary repair. It is likely not code compliant and may result in loss of life, property or severe injury if not done correctly.
- This repair is made in lieu of simply installing two breakers with matching ampacity because of the need to simultaneous disconnection of both phases on 230 / 240 volt equipment. Leaving one phase energized on a 230 / 240 volt circuit can be dangerous to life and property!
- Always verify disconnection of service to any breaker before attempting to replace it. Failure to do so may result in injury or death!
- This is a temporary repair!!! A suitable replacement two pole breaker must be installed at the next available opportunity!
Now to answer my question...
Yes, if done carefully this is suitable temporary repair... if the above criteria are met.
While there is an internal mechanical linkage tying together a two pole breaker (see below)
preliminary results indicate that the tie bar will indeed sufficiently disengage (not trip!) the second breaker thus having the effect of simultaneously disconnecting both phases to the load.
My only concern is that 'sufficiently disengaged' may not preclude current passing by arcing. I am sure that is the reason for the internal linkage on a two pole breaker. However, this repair is being made on the service for the heat pump which will likely not go long after tripping before being noticed and reset / disconnected.