What is the difference between a Munchkin Boiler model# T80M & model# 80M. The house that I'm installing it on has cast iron radiators & no zoning is wanted or needed, but i will need it to have outdoor reset with primary & secondary pumps. Do i need to install the vision 1 kit also or can i just buy the outdoor sensor & a relay pack separate. I think the T80M is a wall mount & the 80M is a floor mount. Are both Boilers the same efficiency & modulation rate? The thing that i don't understand is the venting in the installation instructions. They're both 80,000 BTU's modulating boilers, but the T80M calls for 2" venting while the 80M calls for 3". does anybody know why?