Installation Honeywell nest E five wires

[johnsuri]

trying to install a Nest e from an old Honeywell.  Have five wires.

• top left
  • RH red for the air conditioning heating,
  • RC also red for air conditioning cooling,
• top right
  • Green for the fan 
  • W white heat,
  • Y white AC
• on the nest
  • white heat goes to wh
  • white ac goes to y1
  • green fan goes to g
• not sure what to do with the two red rc and rh

thanks in advance

[Houptee]

Do you have a separate heating system and separate AC system?

Not sure why you have 2 red wires and they are jumpered together with the metal tab.

Usually there is only 1 red power wire if you have a hot air furnace and AC

Separate systems like a hot water boiler and a AC system would have 2 red power wires coming from each system but they would not be jumpered together at the thermostat.

So can you describe the type of system you have.

Can you access the system to see where the 2 red wires are connected?

[johnsuri]

Thanks for your response.  I do have two separate systems.  Once a hot water boiler and the other is an AC.  I think I might have to transformers one for each system. I believe the two red wires are for the AC.  One is for heating and one is for cooling both for the AC. Thanks in advance. 

[Houptee]

The Nest E will not work on "dual transformer" systems.

Only one that works when you have 2 separate systems with their own transformer power is the Nest Learning Thermostat.

Or if you are good at wiring you can use the E but you need to put a relay on the boiler and change some wiring around.

[johnsuri]

I will have to look closer and confirm that I actually do have a two transformer system. Thanks for your advice.

[Houptee]

Boilers with hot water heat (raditors or baseboard) have their own power supply usually R and W coming from the boiler.

The AC air handler will have a totally separate power supply R Y G (and you need to have a C wire coming from the AC system, is there a spare color wire not connected in the one cable from the AC?).

So you never jumper the R (+) from each system together since they are from separate power transformers.

If you already have the Nest E you can buy a relay from Amazon for under $20 and it would be turned on by the Nest using the W wire but you must have a C wire connected from the AC.

https://www.amazon.com/dp/B004XS148C

Put relay near boiler and connect R and W from boiler to the pins on the relay R to #2 and W to #4 (the normally open contacts)

Then the wires that come from the Nest will be W and C and connect to relay pins W to #1 and C to #3 (the relay coil that energizes and make the relay click on).

[johnsuri]

That is awesome. Thank you so much. 

[johnsuri]

And makes a lot more sense.

[Markjosephp]

Hello folks,

I wanted to ensure that everything was covered here.

Thanks for your expertise, @Houptee.

@johnsuri, I hope you've got the answer you're looking for. If you're still in need of assistance, feel free to let us know.

Regards,

Mark

[johnsuri]

Will do thanks. 

[Markjosephp]

Hi johnsuri,

Perfect! Please keep us updated on how the installation goes, and I'd love to know the outcome.

Thanks,

Mark

[EmersonB]

Hello everyone,

@johnsuri I'm dropping by to ensure that everything is covered here. How's it going with your wiring configuration? In case you have an update or more questions, you know where to find us.

I appreciate the help, Mark and Houptee.

Regards,

Emerson

[EmersonB]

Hey johnsuri,

Just one quick final check in here since activity has slowed down. We'll be locking the thread in the next 24 hours, but if you still need help, I would be happy to keep it open. If there's more we can do, just let us know.
  
Best,
Emerson