Jim, Since a simple thermostat is just a switch once it's contacts are closed both sides are at the same potential so it would only be "safer" on the one side when the contacts were open.

My house is on a zoned system (9 zones) and I have 8 complex programmable thermostats. Several of the zones have simpler but still not plain old fashioned heat activated switch type thermostats mounted next to the more complex ones. Some of the zones have either in ceiling or in floor hydronic heat and all zones have forced hot or cold air. Some zones have hydronic control only thermostats and some have hot/cold air only and of course several have both.

The electricians who wired a thermostat in our sitting room installed the wrong stat. It was to control a fan in a duct to draw hot air from the sitting room ceiling and blow it into the master suite entry area. This was to help prevent overheating of the sitting room while running a decorative propane fired gas log parlor stove. (Sitting room is all ICF construction walls and can be heated with a candle and cooled with an ice cube.) They got a nice Honeywell stat that went open on heat rise instead of what was needed, one to give contact closure on heat rise.

I installed another Honeywell stat in the sun room to control the exhaust fan. I wired it with a center off double throw switch so the fan can be on thermostat control, forced to run no matter what, or turned off no matter what. When I get caught up a bit on projects I'd like to put an electrically controlled 2 position damper on the outlet of that exhaust fan. One position would exhaust the hot air into the attic near the ridge vent (current configuration) and the other position would route the exhausted air into the great room which would let me use the solar heated air of the sun room to help warm the house.

Now I have enclosed the open side of a shed to make a metal working/welding shop on the side of my garage/wood working shop and will be extending the HVAC out into that area. More electrically controlled dampers and stats to install.

Pat