Thermostat wiring question

[Jrizzo003]

Trying to figure out is the Nest 3G thermostat will work with my system shown in picture. I do plan to install a nest c wire adapter - but cant figure out how to wire the Nest thermostat. I have a white wire going to “O” - and a jumper wire from Y to W - pretty confusing. Any help is appreciated. 

[CoolingWizard]

@Jrizzo003 ,

You have a Heat Pump being controlled by a thermostat that is not full heat pump supportive.  The green jumper wire going from W to Y can be ignored.  The white wire attached to O is your heat pump reversing valve and that will be OB on the Nest.  Your Nest G3 wiring will be:

Red to RC

White to OB

Yellow to Y1

Green to G

AC Cooling Wizard

[Jrizzo003]

Do you think this will work without a c wire or c wire adapter?

[CoolingWizard]

@Jrizzo003 ,

The first step is to check to see if there is any unconnected wire tucked into the wall behind the thermostat. In any case, an Nest Power Adaptor will work with your system.

AC Cooling Wizard