Neurorad
Senior Member

Page 3 of the P212s instructions show 2 jumper locations on the board, JP1 and across 'Neg' and 'M' ('Important'), for M1 Data Bus Mode operation (vs 'Stand-Alone mode').
Again, for posterity's sake, when you enrolled the P212s, did you define it as a 'Power Supervisory Zone', and set type to '0, EOL Supervised'?
(Stupid question, but did you un-enroll the P212s?)
Are any devices on the bus grounded? Does the garage have a dedicated ground that isn't bonded to the house? Does the garage have a separate electrical service? From what I gather, currently, everything is powered from the house, from the M1 control board and the Altronix. Are the garage or house devices in a metal enclosure that might be grounded? Did you add an outlet to any metal enclosures? Are you using standoffs?
Did you bond the Altronix and M1 control negative common terminals, in the house, or just at the garage DBH?
A couple times now, searching old posts, I've read DEL's mention of problems using Altronix with the Elk M1, and a resultant Elk white paper. Did you look into that?
http://cocoontech.com/forums/topic/22475-altronix-power-supply-weirdness/?p=183757
I did read this whole thread last night, and I don't recall DEL mentioning that potential issue; I'm guessing it's a particular line of Altronix PS - he offered to let you try some of his Altronix hardware.
I've learned a great deal from this thread, Mike. Thanks!