topic Re: Installation wiring in Nest Thermostats

Installation wiring

FastDr — Tue, 13 Dec 2022 21:05:19 GMT

Hello:

My original thermostats are Rodgers-White (Model 1F80-261). Photo attached. I successfully installed the Nest Learning Thermostat on the main floor. It works perfectly. Photo attached.

I need help with the upper level which has a master and slave configuration (I believe?). The primary/main thermostat has a Blue and Orange wire in addition to the Red, White, Green and Yellow wires. The secondary/slave thermostat has White, Yellow, and Red wires only. Both have jumper wires. I would like to replace just the primary/main with the Learning Thermostat. Photos attached.

Hoping you can help.

Original ThermostatOriginal Thermostat model numberFirst Floor Nest installationSecond Floor main thermostatSecond Floor slave thermostat

Re: Installation wiring

CoolingWizard — Tue, 13 Dec 2022 21:20:56 GMT

FastDR,

there cannot be two thermostats controlling one system. What you can have is one system as a heat pump and the second system is not a heat pump. The wire that’s connected to the O terminal is the heat pump system. The second thermostat controls and AC system with a furnace. The only other possibility is you have a zone controlled HVAC system.

Ken, The AC Cooling Wizard

Re: Installation wiring

FastDr — Tue, 13 Dec 2022 22:04:26 GMT

Thanks so much for your prompt response. We only have a single system for the entire house. The heat is an oil fired boiler. We have traditional air conditioning. The distribution is via hydro air. So does it sounds like we have a zone controlled HVAC system? If so, will the Nest work on this zone and how would I wire?

Re: Installation wiring

CoolingWizard — Tue, 13 Dec 2022 22:21:58 GMT

Some zone controllers are very compatible with thermostats and some use a proprietary communication system. The odd thing is that thermostat which has a wire on the O terminal is definitely a heat pump type system. Heat pumps use a four-way reversing valve that changes the direction of the flow of the refrigerant to make it change from air-conditioning mode to heating mode., the mode switch is controlled by the O wire when the O wire is energized with 24 V AC current, the valve switches, and it changes modes.

The only other explanation is it the HVAC tech hooked up the orange wire to the O terminal, but there is no heat pump.

Ken

Re: Installation wiring

FastDr — Wed, 14 Dec 2022 19:42:37 GMT

Here are additional photos from the main panel located in the basement air handler for the main level and basement zones and the panel on the upstairs air handler for that zone (primary/slave). Not sure they help, but hopeful.

Basement panelBasement panel_2Basement panel_3Second Floor panel

Re: Installation wiring

CoolingWizard — Wed, 14 Dec 2022 23:53:45 GMT

Hello FastDR,

yes indeed you have two separate zone controllers. The NCM 300 supports up to three zones dampers and up to three controlling thermostats. Your NCM 300 is utilizing two controller thermostats and two motor driven dampers.
The second zone controller is an EWC-ST-2E and it supports two zone dampers and 2 controlling thermostats. What I am trying to figure out is if the two are interconnected with each other.
basically, he’s on controller sits between the thermostat and the HVAC equipment and integrate the operation of dampers to open and close zones.

Since you have a single system, and there are two independent zone controllers and that is not a typical configuration. Normally the two zone controllers would be interconnected and these two are not.

Ken, The AC Cooling Wizard

Re: Installation wiring

FastDr — Fri, 16 Dec 2022 18:36:43 GMT

Hello Ken:

I so very much appreciate you putting your head on this. I had no idea these things could be so complicated. Now i know. If you come up with anything, please let me know!

Otherwise, have a happy holiday season, CoolingWizard!

FastDr

Re: Installation wiring

CoolingWizard — Fri, 16 Dec 2022 21:33:59 GMT

I am going to make some annotations on your photos and post them back here.

Ken

Re: Installation wiring

FastDr — Fri, 16 Dec 2022 21:50:32 GMT

Okay. Will be on the look out!

FastDr (AKA Ed)

Re: Installation wiring

CoolingWizard — Fri, 16 Dec 2022 22:19:33 GMT

Re: Installation wiring

FastDr — Sat, 17 Dec 2022 19:48:33 GMT

Hi Ken:

I will definitely be filing these annotated photos. It makes a lot more sense to me now. Still, hopeful I can make the Nest work, with your help of course. The blue and the orange wires need to be located on the Nest (?O/B and C).

Thanks again for all your help with this install!!

Re: Installation wiring

CoolingWizard — Sat, 17 Dec 2022 21:51:08 GMT

From the standpoint of a thermostat, it does not know that there are zone controllers in the system. All the thermostat does is provide the function of either calling for heat or calling for cooling depending on your settings within your thermostat. So as long as your nest is wired the same way as your old thermostat was wired, colored wire to the same color and label screw for example it will work just fine.

Re: Installation wiring

FastDr — Sun, 18 Dec 2022 14:46:15 GMT

Great! However, I am still confused about where to place the orange and blue wires. I am not sure which of these two is to be placed on the "C" terminal of the Nest thermostat.

Re: Installation wiring

CoolingWizard — Sun, 18 Dec 2022 16:36:07 GMT

Since you, as you stated, you do not have a Heat Pump system, you will not need to connect the Orange wire on O nor the wire connected to B. Your thermostat is manufactured by White Rogers and it uses the O and B for heat pumps only. You currently do not have a common wire at either thermostat as well.
Ken, The AC Cooling Wizard

Re: Installation wiring

FastDr — Mon, 19 Dec 2022 15:24:00 GMT

Got it! Thanks a million Ken!!

Best,

Re: Installation wiring

FastDr — Tue, 20 Dec 2022 19:44:32 GMT

Hello again Ken:

I connected the thermostat attaching just the four wires (red, yellow, green, and white). Unfortunately, it works initially as I was able to complete set up, but get an error message after a few minutes regarding power (E15 within an orange circle on the thermostat screen) and a suggested online link (nest.com/e80). I disconnected and charged it up with a USB cable, but the same problem occurs after a few minutes after remounting it. Any ideas? External power source?

Thanks as always!

Re: Installation wiring

CoolingWizard — Tue, 20 Dec 2022 19:58:18 GMT

Your thermostat connects to the digital control board, and as a result, it cannot use the so-called back door charging method that the Nest third generation can do. What you need to do is check to see if behind the wall you have an extra wire not connected at your thermostat. If you do, we will connect it to the common side of the transformer and we able to charge your thermostat that way.

Ken

Re: Installation wiring

FastDr — Wed, 21 Dec 2022 18:32:26 GMT

Yes, there are two free wires that run between the thermostat and control panel.

Re: Installation wiring

CoolingWizard — Wed, 21 Dec 2022 20:46:27 GMT

FastDR,

do you need to pick one of the two free wires, hopefully blue is one of them, and then attach it to the seat terminal of the thermostat. Then you need to go to the other end of the cable and find it the same color, blue for example, and you need to attach it to the common side of the power transformer. How to do this you’re going to have to do a little work, if you look at the orange and blue wire cable that comes into the zone controller, that goes to your main unit power transformer you need to follow that cable open that panel and take a look. And here comes the tricky part. One of the two wires coming off of the transformer is going to be routed to all the devices inside that HVAC air handler. And one wire is only connected. Going out of the unit on a cable. The one that is attached from the transformer to all the other devices is indeed the common one and that’s where you attach your blue wire , so one of the two wires coming from there the orange in the blue is going to be the common and that’s where you will put your blue common. I hope this makes sense.

Ken, The AC Cooling Wizard

Re: Installation wiring

FastDr — Wed, 21 Dec 2022 22:41:41 GMT

Hello Ken:

Well, the good news is the Nest is connected, getting power, and passed the tests performed by it. I was able to program it and all is well there. The bad news is now I cannot seem to get the other thermostat (labeled thermostat 2) connected to the second floor panel (EWC-ST-2E) to work. You were crystal clear about the non function/need for the blue and orange wires (no heat pump) so they are not connected to the Nest. I did not use either of those two for the common connection either. As you saw in my original photos those wires were connected to the main controlling thermostat (labeled thermostat 1). I have two other wires (tan and black), one of which I used for the common connection and left the blue and orange wires alone. You're response was a little confusing, so I may have missed something along the way.