Replacing a battery- operated thermostat with a EcoBee thermostat

tomsloancamp

I am looking for advice. I am replacing a thermostat that is battery operated and is connected to a central air unit in my attic. The wires currently used are Rc,G,Y,W on the thermostat. In the attic, the thermostat Red is connected to the R on the Air Handler ( RH1P3017STANAA), thermostat Green to Green on the AH, and thermostat Yellow to an Aquaguard Pan Sensor via Grey wire. The thermostat White and Blue are not connected any any wires. The Air Handler has a Brown wire connected to a Red wire from the AC Compressor (RA1318AJ1NA). The Sensor has a Purple wire connected to the White wire coming from the Compressor, a Red connected to the other 2 Red wires, and a Grey connected to the Thermostat’s Yellow wire.  My question is where should I connect the Blue ( or White) wire? I assume it needs to connect somehow to the Brown “Common” wire from the Air Handler for power.

Steamhead

Are there any unused wires in the cable between the AHU and the thermostat?

109A_5

Hello @tomsloancamp,
Since that unit appears to be cooling only (No Heat or Heat Pump) you probably don't need the White, the Blue could be used for the Common. The EcoBee thermostat may appreciate having the C wire connected. Here is a modified wiring diagram from the manual and other info.
Found here https://cdn.globalimageserver.com/FetchDocument.aspx?ID=C87180FE-DC30-45C5-B253-6C36B460A68C

I did not include the Pan sensor wires, I was not 100% sure of your description. It may just interrupt the Y from the thermostat to shut down the cooling, it may have power to it also.

HVACNUT

The Brown wire at the air handler (the one that has the Red to the condenser) is Common and connects to C on the thermostat. 
Use the spare Blue wire as White is typically used for heat. 

tomsloancamp

@Steamhead (in transit)the White wire is connected to the W terminal on the thermostat but unconnected at the air handler and the Blue wire is completely unused.

HVACNUT

tomsloancamp said:

@Steamhead (in transit)the White wire is connected to the W terminal on the thermostat but unconnected at the air handler and the Blue wire is completely unused.

Then you must have a separate heat thermostat. 

tomsloancamp

@HVACNUT the installer tried to talk me into adding heat to the unit and I believe had the electrician wire the thermostat with the heat but I don’t understand why the blue or white are not connected at the AH? Mostly I need power to the ecobee and wasn’t sure where to connect the common wire.

HVACNUT

tomsloancamp said:

@HVACNUT the installer tried to talk me into adding heat to the unit and I believe had the electrician wire the thermostat with the heat but I don’t understand why the blue or white are not connected at the AH? Mostly I need power to the ecobee and wasn’t sure where to connect the common wire.

If that's the only thermostat, then something must be connected to Rh and W.

tomsloancamp

the Rh has a jumper to the Rc and is connected to the R to the AH.

109A_5

For clarity of all, with this model RH1P3017STANAA, 115 VAC power, no heat from the factory so connecting the white wire at either end or both ends may have no benefit. I do not believe it would hurt anything if connected. I suspect the heat in the building (if any) is accomplished with other equipment with its own thermostat.

tomsloancamp

@109A_5 you are correct. There is a gas boiler /steam heat system with its own thermostat. The installer proposed adding heat to air handler. It wasn’t in the budget so the unit is cooling only.

HVACNUT

tomsloancamp said:

@109A_5 you are correct. There is a gas boiler /steam heat system with its own thermostat. The installer proposed adding heat to air handler. It wasn’t in the budget so the unit is cooling only.

How did the installer propose to add heat to the air handler, heat pump? 

109A_5

Maybe a field installed add on kit or maybe the purchase of a unit that includes heat.

Looks like it could do both or either resistive or heat pump.

tomsloancamp

@109A_5 @HVACNUT I believe it was a hydronic handler that would be heated with a tankless water heater.

Jamie Hall

tomsloancamp said:

@109A_5 @HVACNUT I believe it was a hydronic handler that would be heated with a tankless water heater.

Which would be a perfectly horrible way to do it.

tomsloancamp

Here is the wiring setup…
1. Old thermostat wiring (note:installer connected the white wire at the thermostat but is not connected to handler or anything else. Blue wire not connected at all.)


2. The control board on the air handler. There wire, Red, Brown (common), Green.


3.The wiring connecting thermostat to air handler. White and Blue disconnected, Red to Red, Green to Green, Yellow is connected to Grey wire from a Sensor which shuts off system when condensation pan overflows (product is called Aquaguard) The manufacturer states the wiring should be “red to transformer, purple to thermostat, black to common, and white is for option alarm.” The red wire from the sensor is attached to the red Thermostat/Air handler connection, purple is connected to white white coming from the outdoor condenser unit, and the black is connected to the Brown ( Common - Air Handler) and Red from the outdoor condenser unit. That wiring is in the second photo.

HVACNUT

tomsloancamp said:

@109A_5 @HVACNUT I believe it was a hydronic handler that would be heated with a tankless water heater.

I 100% agree with @Jamie Hall. When you already have (hopefully) comfy steam heat? That's just about the most ridiculous thing I've ever heard. I could see maybe a high efficiency heat pump for the shoulder seasons, but a hydro coil off of a water heater? Ludicrous. 

109A_5

Hello @tomsloancamp,
So you are not operational yet ?

The manual gave me the impression that it was screw terminals, not wire pigtails with some missing. Anyway connect the Blue to the C at the thermostat and connect the Blue to the Brown under the wire nut.

The old thermostat ran off a battery the EcoBee most likely wants to get power from the Red and the Common. The Blue wire will give the Common a path to the thermostat. The Blue is at the thermostat in the wall, or did they cut it off ? I don't see the Blue in the thermostat mount plate picture.

In your case the White is unused (no heat), unless it need to be a substitute for a cut off Blue. Then connect the White to the C at the thermostat and connect the White to the Brown under the wire nut.

tomsloancamp

@109A_5 the blue wire is shoved back into the wall behind the base plate of the old thermostat. I figured it needed to connect to common but just was confused by the addition of the wiring from the condenser overflow sensor.

109A_5

Hello @tomsloancamp,
Looks to me like the pan sensor uses the Red and the Black for power (24 VAC), and the Gray and Purple just interrupts the Yellow wire functionality, compressor control (White out to the compressor) so if the drain is plugged up the compressor gets shut off before the pan overflows.

So you are up and running ?

tomsloancamp

@109A_5 I am still using the old thermostat. Unfortunately in order to get to the attic, I need to completely empty the closet and remove some shelves. I hope to accomplish that tomorrow. thank you for your assistance!!!

tomsloancamp

@109A_5 Finally hooked up the Ecobee. Blue wire to brown under the nut. I got power! Now there is one problem. The the fan must be turned on for the condenser to work. Initially I turned the temperature down and nothing was running. I turned the fan from auto to on and it then started working. 

tomsloancamp

@109A_5 here are all the connections from
left to right.
1. Purple from sensor to white from condenser
2. Blue (thermostat) red (condenser) brown/common (handler) black ( sensor)
3. Red (sensor) red (thermostat) red (handler)
4. Yellow (thermostat) grey (sensor)
5. Green (thermostat  green (handler)

109A_5

Hello @tomsloancamp,
Since it worked with the old thermostat (the G wire), assuming it is connected to the EcoBee correctly since it works in the 'ON' position. The EcoBee 'Auto' function may have a programming setting that needs to be changed to also energize the G wire. I don't think that is a wiring issue.

HVACNUT

Agree with @109A_5. If the thermostat is wired,
Red to R
Blue to C
Green to G
Yellow to Y,
then it's in the thermostat. I've only installed a few Eco Bee thermostats within that past year, but I've never had that issue. G should always be powered through the thermostat with a call for cooling along with Y.
I don't recall even seeing anything in the setup that would allow G not to close along with Y.

109A_5

It does seem odd, maybe the G was not properly detected / recognized with the initial setup, maybe run the setup process again.