Help Wiring Nest Thermostat

[BCyph]

Currently have a Honeywell ProSeries thermostat that uses 8 wires. I have a single zone heat pump that is dual fuel (electric and propane) which is what I believe drives up the wire count. The Nest base only has 6 locations for wire install so I am unsure how to configure it. The site claims the Nest is compatible with this type of heat pump but I cannot find a good source of installation instructions, specifically the wiring. 

I am attaching a picture of my current wiring for reference.

 

[CoolingWizard · Accepted solution]

BCyph,

let me see if I can try and help you understand what you have there.  
The two wires attached to the two “S” terminals are remote temperature sensors. These will not be used with the NEST.

The remaining wires are typical HVAC control wires. 
R - has a red wire attached, this is system control power and is approximately 24 Volts AC 

W2 - has a white wire attached,  this is the wire that calls for the Propane heating. Basically “auxiliary heat”
O/B - an orange wire attached, this goes to the heat pump and switches the reversing valve from cooling to heating or from heating to cooling. 
Y - has a yellow wire attached, this calls for the heat pump compressor to start. 
G - has a green wire attached, this wire is used to turn the blower Fan on.  
C - has a black wire attached, this is the COMMON wire.  

I hope this helps to clarify things,

- Ken, The AC Cooling Wizard. 

[BCyph]

That was very helpful yea, thank you. 

A couple follow up questions if you don't mind...

If the S wires are not used for temperature sensors, then how is this function replaced with the Nest? 

Also, if the two S wires are not used with the Nest....what do I do with them? 

Other than that, the other wires seem pretty straight forward.

Thanks again for reaching out and offering the info and help!

[CoolingWizard]

What us HVAC technicians normally do, any unused wires we just wrap them around the brown insulation around the wires and keep them out of the way. As for the nest thermostat it has internal thermal thermistors that measure the indoor air temperature and when connected to the Internet the nest thermostat uses Google information concerning the outdoor weather at the location that it’s installed. Therefore it will not need those external sensors.

Ken, The AC Cooling Wizard

[BCyph]

So should I wrap the exposed ends in electrical tape? And then it sounds like you just wrap them around the main bundle of wiring coming out of the wall to get it out of the way. Or find some other way to route them away. 

Doesn't sound like those S wires should be of any concern for shorting anything out is that correct?

[EdwardT]

Hi folks,

@CoolingWizard, thanks for the help!

@BCyph, how's it going with your Nest Thermostat? Still need our help?

Thanks,

Edward

[EdwardT]

Hi BCyph,

It's me again. I wanted to check back in to see if you have other questions and concerns. Feel free to let me know if you do. 

Thanks,

Edward

[BCyph]

I was waiting for a trim piece I ordered to arrive. That was delivered yesterday so I may try to install today. I just had one additional question about properly retiring and storing the unused S wires that I asked to @CoolingWizard 

[CoolingWizard]

What you can do is just wrap the unused wire around the cable as you thought.  no need for tape. If you want it to look “neater” just cut off the bare wire part. 

Ken, The AC Cooling Wizard 

[BCyph]

I installed my Nest today...went smooth from what I can tell. Now I think it's just about learning about it's operation and finding the right set points. Thanks again for all of the help!

[Jeff]

Hey BCyph,

I'm happy to hear you got things all set up and working. That's great news. Before I mark this as resolved, I just wanted to check in and see if you needed anything else or to see if you're all set for now.

Thanks,
Jeff

[Jeff]

Hi all,

As we got our resolution here, I'm going to mark this one as resolved in the next 24 hours. Thanks to all who helped and contributed. If anyone has any other needs, please feel free to let me know before the lock.

Thanks,
Jeff