3-pole beaker feeds single phase panel
The use of one or two poles off of a three pole breakers for single phase circuits is permissible by the UL standard #489, but it does have a voltage limitation of 120 volts to ground.
The UL white book states the following:
?Multi-ploe common trip circuit breakers rated 120/240 V ac are suitable for use in a single-phase mulit-wire circuit, with-out the neutral connected to the load, where the voltage to ground does not exceed 120v.?
Which is taken of UL 489 section 6.1.5.1 and reads as follows:
?A multipole circuit breaker shall be constructed so that all poles will make and break simultaneously when operated manually or automatically in the intended manner; except that in a 2- or 3-pole circuit breaker rated at 125/250 V or less and having two operating poles intended for use on the outside (ungrounded) wires of a 3-wire, dc or single-phase ac system, the automatic tripping of either pole shall be permitted to be independent of the other if the independent tripping is indicated.?