HE,
I'm a little bummed out at you for dribbling out the most critical info: A HISTORY OF FAILED TRIP UNITS IN THE SAME LINE-UP!!!! What's up with that? It's a ton of you-know- what that replacing the trip units should cost more than installing new breakers! Especially when one of their folks should be doing it, on site, with minimal cost to your customer. And did you press them for the exact failures in the trip units? A bad run of electrolytics? Tantalum caps in backwards? At the price you're paying, you deserve specifics! Did you happen to put your high-end analyzer on the breaker control power?

The more I think about this the more ticked off I get. You know that test isn't a real test, and that your trip unit is likely shot! You just want your customer up and running with a potentially deadly work-around. Do you think any peceived blessings from us would let you sleep any better at night if this situation broke badly? I'm sorry if I have you pegged wrong but I've been down this road before!
People leave out vital info to justify doing something that they already know they shouldn't!
Joe