Going back to the OP topic. Have a M55 Cast Insert.. and have tripped the flashing #4 high temp switch about 5 times in the past 2 weeks. Seems to trip with the stove kicks on to heat level 3 (I have it on a hi/lo stat). Called the dealer he said it may be a airflow problem and he was going to replace the cap on the chimney. Also, when the installed the stove originally back a few months they had the damper fully closed. So the first couple days before I called the dealer back the burn was very very dirty. He thinks that might have clogged up some stuff. Overall he seems to think it is an airflow issue. I read back through all the posts here.. I'm not seeing if there was a determination made for what is causing the high limit switch to trip.. or what Enviro or the Dealers did to help the issue. Any updates from anyone that I could bring to the dealer when he comes to service the machine would be helpful. Thanks!