AC Watermaker trips Genset breaker on start up

[MondayNever]

Good morning folks,
I’ve got a 1995-era HRO AC water maker (16gpm 240v 50hz) that is tripping the Fischer Panda 6kw Generator breaker immediately on start up. This is a new condition - it worked fine less than a week ago.

Symptoms/testing results:
- Trip happens instantaneously upon pressing Watermaker Start button
- Trips the main GEN breaker, not the individual WM breaker. Both are B16 breakers.
- Other AC loads do not trip GEN breaker. Tested up to 5.4kw of other loads without tripping.
- Tested WM with no other AC loads running so as to isolate to WM only
- WM starts up and runs properly on Mastervolt 2.5kw Inverter. Does not trip B type 30a inverter breaker. Draws 1-1.4kw (4-6 amps).
- Attempting to switch the AC Source Selector from INV to GEN with water maker running instantly trips GEN breaker. Trying the same test with a different AC load running, like the air conditioner, does not cause the GEN breaker to trip.
- Something specific to the WM, that does not apply to any other AC load on the boat, is causing the GEN breaker to trip
- I can’t test the shore power circuit because I’m at anchor in the Exumas and all the power around here is 60hz and this is a 50hz boat


Possibly relevant info:
- GEN breaker is original 1995 era. Can old breakers fail/become too sensitive?
- INV breaker is new, from a recent professional AC re-wire that eliminated the original 1995 era Mastervolt master control panel and relay system.

Any thoughts about what could be going on here? Can breakers begin to fail? Can a big induction motor in a water maker create a different profile of power draw that can trip a sensitive breaker, which does not apply to other AC loads of similar amps/watts (water heater, air conditioner, etc)?

Thank you!

[HeywoodJ]

I’d Ohm the motor windings just for sanity (https://www.electricalengineeringtoo...gle-phase.html), would expect 40-50 on the run winding.

But yes, breakers can and do fail with old age. The more often they trip the worse it gets (so if this is the problem it will only trip faster next time). And if it lives in a high temperature environment....

Since they are both B16, how easy to swap Gen and WM breakers? If not hard then try that. If the problem follows the breaker then you know your problem.

[TheOffice]

Change the breaker. After 26 years it may be failing. Cheap enough, and worst case, will allow you to rule it out. Is the wiring corroded? That will add more resistance.