Heat Pumps and Electric Heating - Thermostat Y2

My old thermostat has 5 wires including Y2 with a blue wire running to it. The new thermostat does not have a Y2 but does have a B. From what I've read so far I think I need to take the new one back and get one with a Y2 (which is apparently for 2 stage cooling -- what ever that is)! Anyone know about this stuff?????

Thanks, Rick

Do you have a heat pump there?
If so, find out if the outdoor unit has either a 2-speed compressor or perhaps 2 compressors. If you don't have either, then...
On that old thermostat, the "Y1" could very well have been there for the purpose of energizing the reversing valve coil (a reverse-on-cooling strategy), while the "Y2" to juice up the compressor contactor. On that new t-stat, in addition to the "B" terminal there should be an "O" terminal.
The wire that was connected to the "Y1" in the old t-stat should be connected to the "O" in the new t-stat and the wire connected to the "Y2" in the old, should be hooked up to the only "Y" terminal in the new.

Your posting begs for more information.
Outdoor and indoor units' MFR and M/N?
old and new t-stats' MFR and M/N?
it's hard to give you precise assistance with what's been posted so far.

some pics would not be a bad idea either.

If you are changing just the thermostat and nothing is different about the system and the last person hooked it up right then you have two stage cooling and your thermostat is not compatible with your system

Like Pflor said, we need more info to help you out.

We'll wait till you post back with info before we can help you out to see if for sure you have two stage cooling... or heat pump..