thermo-couple

so, ever since we moved into the house, we've only ever been able to control the (one) heating furnace by the thermostat in the downstairs apartment. there was a thermostat mounted on the wall of the second floor apartment, but it has never worked. i tested the thermostat itself and it was functioning, so that wasn't the problem. for two years i've been ruminating as to how to be able to have the furnace controlled by both apartments.

my three options were:
1. thermostat control in front hall, while thermostat temperature sensor was located in 1st floor apartment (naturally colder than 2nd floor apartment). however, i couldn't find such a two-piece thermostat.
2. thermostat in communal area, such that 1st or 2nd floor occupants could adjust. however, front and back hallways are both too cold for this to work halfway efficiently.
3. remote-controlled thermostat. these do exist. we would locate the thermostat in the 1st floor apartment and give the 2nd floor apartment the remote control. however, this just seemed like it could lead to thermostat wars...

finally, when we were having the furnace serviced this year, i asked the tech what my options were. he said simply to have each apartment thermostat hooked up to the furnace, and the higher setting would trigger the furnace. well, d'oh. so, i rummage around the wiring in the basement and find the existing 2nd floor thermostat wiring... with one of the wires knocked out of the wire nut... double d'oh. so, all along, the system had basically been in place. anyway, i'm just pleased it was a relatively easy solution (and that i had the foresight not to rip out the 2nd floor thermostat wiring when hanging the new drywall, just in case...).

so, now we have the best solution without any major modifications for a two-apartment, one-furnace set up.