HVAC type question

[SPIKER]

When you have your downstairs new fan switch on, the fan is always on no matter what the thermostat upstairs wants. So yes, you can leave it on too long by mistake too as tallyho8 has mentioned.

This might be what SPIKER was referring to: With your added description of what you want, there is another way you can go. You can place a new simple thermostat downstairs. Use the white wire connection point on that new thermostat and connect it to the fan (green wire on your heat pump). Then you set the temperature on that downstairs thermostat and when that room is cooler than the set point the fan runs. Note you must also connect the red wire to the red connection on that new downstairs thermostat. When your downstairs room is warm enough, the fan turns off. If you turn the new downstairs thermostat off, it's out of the picture and can't run the fan.
I did this for my Dad years ago when he had a wood stove going in part of the house, and wanted to spread the heat around to another room. Works great.

Pete

yes, use the cheap t-stat downstairs to turn on the fan only, not parallel the upstairs stat.
mark

 

[radioman]

may I ask why not K.I.S.S. it ? Most furnace I have seen without AC really only uses 3 wires. 2 for thermostat and one other for fan on override. Before we get into this further- is it really important for you to have a 3-way for fan? If not you can just run a pair of straight to furnace fan panel and connect to a simple on/off switch. Just train yourself to turn off the fan before leaving the room otherwise you will wonder why fan is on and switch looks off upstairs, otherwise if it too much of an inconvenience then go with 3-way.