After punching the tubes one of our chillers had a high temp AFD alarm. The alarm was reset and did not return. The chiller was run as normal, with no alarms for about 10 minutes before an arc jumped from two of the phases to the box and shut down the chillers. No fuses were blown but two of the main breakers were tripped.
After a little inspection it was found that the system that circulated the water cooling the AFD / bus bar was plugged and likely the main cause of the overheating. It seems that punching the tubes just before was probably just a coincidence. We have since fixed the circulating system.
Our facility has engineers and HVAC technicians but no 100% qualified technicians to work on the chillers so we have outside contractors do major repairs with our assistance. I am a mechanical engineer and hvac tech and have been taking classes to become a competent chiller tech, so I'm just looking for more insight into what happened. Our electricians think that the panel heated up, ionized the air, which allowed the arc to the panel. It sounds like a reasonable explanation. Anyone else have ideas? We have not tried to run the chiller since, nor are we going to until we have our contractor come, repair if needed, and start it up.