Nest compatible with Daikin AC

[Memopvh]

I have had 3 Nest Thermostats for over 10 years. I just had to change a 5 ton Carrier unit with a Daikin unit and it has not been working properly. The first night the ac would not cool, the second night it would not stop and kept on getting colder and colder. The installer tells me that the Nest Thermostat is not compatible with this new Daikin unit. Does this make sense?

Do they need to install it differently for it to work?

thanks

[CoolingWizard]

This depends on the control interface of the Daikin.  Get me the model numbers if your Daikin indoor and outdoor units. We can help you to ensure they set it up correctly. The conventional control uses a 24VAC system. The newer systems also have a digital 2-wire control system.  In the conventional control system the R terminal is the 24VAC power sent to the thermostat.  The Y or Y1 controls the compressor relay.  If you have Y2 this is stage 2 Cooling.  The G controls the Blower Fan relay. The W/W1 controls the Heating. And if you have a W2 this this Stage 2 Heat.

This all changes of you have a heat pump for heat,  then the  OB, controls the Heat Pump reversing valve. With heat pumps the W2 is Auxiliary heat. and W1 is not used unless you have Duel Fuel system ie., Gas Furnace with a Heat Pump.

If you get me the model number of the indoor and outdoor units, I can look at the installation manual. 

AC Cooling Wizard 

[Memopvh]

THE MODEL OUTSIDE  IS A DX5SEA601AA FROM DAIKIN. 

THE INSIDE IS AMST60DU14001AA

THANKS IN ADVANCE FOR YOUR HELP IN GETTING MY NEST BACK TO WORK

[CoolingWizard]

@Memopvh , Your outdoor unit is a single stage air conditioner that uses a standard conventional HVAC 24VAC control system. This system is fully compatible with any conventional thermostat including the Nest Thermostats. 
Your Diakin system uses the following wiring standards

R terminal is for 24VAC power (Line) into the thermostat. 
Y terminal is Compressor Relay

G terminal is Blower Fan relay

W terminal is Heating Control

C terminal 24VAC Power (Neutral)

When your thermostat is calling for cooling, it internally connects R to Y and G.  This signals the indoor unit to turn on the Blower Fan and it Turns on the outdoor Air Conditioning unit.  
Unless your HVAC installation company changed the wiring, all should be good.  You should have wires only on R/Rc, Y/Y1, G, C, and W/W1 in your Nest Backplate. That is only 5 wires. 
Carefully remove the nest display, take a picture of the backplate so I can see the wires attached. 

 Now your indoor air handler unit can be upgraded with Electric Heat Strips. According to your model number, no heat strips were installed during manufacturing. If you have heat strips, your HVAC contractor would of had to install them. When the Nest thermostat calls for heating, It connect R internally to W/W1.  The furnace control board sees the W/W1 power and starts the heating cycle.  
Now, if you have a duel fuel type of a system, you will have a a Gas Furnace in which case you would not have needed the full air handler you purchased.  So, the real questions is, what type of heating system do you have?

AC Cooling Wizard

AC Cooling Wizard

[Memopvh]

thanks we are in Florida so we really don't need the heat, but on my other units if I wished I could turn it up to heat. 

will follow these instructions to see if my nest can get up and running. would this help in controlling humidity? 

[CoolingWizard]

@Memopvh In Florida to control humidity the key is to slightly lower the air flow over the evaporator coil. Here in  the dessert we use 400CFM and in higher humidity we lower it to 350CFM per ton of cooling. If your system has multiple blower fan speeds, it is possible to  set up your Nest to control this.  Now this all depends on how your contractor  set up your air handler and capabilities of the air handler. 
AC Cooling Wizard

[Memopvh]

will give all of this a try and let you know how it worked. Thanks

[Jenelyn_O]

Hi folks,

Thanks for reaching out. I just want to check if you were able to proceed with the instructions provided above. How does it go? Please keep us posted.

I appreciate the help, @CoolingWizard.

Best,

Jenelyn

[Jenelyn_O]

Hi Memopvh,

Checking if you still need help. Please let us know, as we'll be willing to assist you further. 

Thanks,

Jenelyn

[Jenelyn_O]

Hi there,

We haven't heard from you in a while so we'll be locking this thread if there is no update within 24 hours. If you need assistance or want to discuss topics, feel free to start a new thread.

Regards,

Jenelyn