I recently installed two new programmable thermostats in my house, one for the upstairs unit, one for the downstairs unit. The upstairs functions great. It's a bit different on the first floor...

I programmed the unit to keep the heat at 62 during the night and bring it up to 68 at 6am. The unit kicks on at 6am (as it should) and runs for about 30 minutes and then shuts off.

I thought it wasn't getting enough air and changed the filter - same issue occurs. There is also no water in the condensate pump. If I turn the unit off and turn it back on from the breaker it fires up. I've checked the wiring on the thermostat and it sure looks correct.

In the unit I can see the second LED light flashing. (Pressure valve?? )

I can't imagine the unit is overheating and is shutting itself off for safety. I'm in Atlanta and it doesn't get all that cold here. Any advice would be greatly appreciated.