I can take a pic later tonight, but I don't think it'll help nearly as much as the picture in the back of the aprilaire install manual.
I can walk you through that pretty easily - have you gotten it to work with your furnace yet?
OK, we have power. Using the single stage Furnace and AC diagram, we were missing the connection between RC and R. Now to program the thermostat.
Thanks,
Ruben
I can take a pic later tonight, but I don't think it'll help nearly as much as the picture in the back of the aprilaire install manual.
I can walk you through that pretty easily - have you gotten it to work with your furnace yet?
[snip]...Old wiring...[snip]
RC ------- Cooling Power -------------------------------------------------------------------- Red
R ----------Heating Power ------/
Y ----------Compressor contactor ----------------------------------------------------------- Yellow
C ----------Common wire from secondary side of cooling system transformer --------- Blue
O/B -------Changeover valve for heat pumps --------------------------------------------- Orange
G ----------Fan Relay ------------------------------------------------------------------------- Green
Aux -------Auxiliary heat relay -------------------------------------------------------------- White
Here is my guess:
Old Thermostat ----------------- 8870
RC and R ------------------- RH and RC
Y ------------------------ ???????
C ------------------------- C
O/B ------------------------ split wire to O and to B???????
G --------------------------- G
Aux ------------------------ W1??????
[snip]...Old wiring...[snip]
RC ------- Cooling Power -------------------------------------------------------------------- Red
R ----------Heating Power ------/
Y ----------Compressor contactor ----------------------------------------------------------- Yellow
C ----------Common wire from secondary side of cooling system transformer --------- Blue
O/B -------Changeover valve for heat pumps --------------------------------------------- Orange
G ----------Fan Relay ------------------------------------------------------------------------- Green
Aux -------Auxiliary heat relay -------------------------------------------------------------- White
Here is my guess:
Old Thermostat ----------------- 8870
RC and R ------------------- RH and RC
Y ------------------------ ???????
C ------------------------- C
O/B ------------------------ split wire to O and to B???????
G --------------------------- G
Aux ------------------------ W1??????
This is pretty general but it may help some other folks also: Disclaimer: the below terminals/colors are for the above poster's application! NOT ALL UNITS ARE THE SAME! Always consult the wiring diagram that is inside your heat pump air exchanger or the thermostat itself.
On a normal HVAC system, the Y's are for various COOL stages of the compressor; on a heat pump the first Y is for cooling AND heating. Remember the same compressor is used for both roles on a heat pump. Y -to- Y1
On a normal HVAC system, the W's are for various stages, different types, or speeds of HEAT (ie W1 may be gas, W2 is geothermal, etc); on a heat pump the first W terminal is always the Emerg./Aux Heat (also 'defrost', but you don't have to worry with this). Aux -to- W1
G is easy, Blower. G -to- G
The O/B: your existing thermo can go two ways: it either energizes for for cool or energized for heat. Your heat pump obviously only has one reversing valve: give it power for cool. FYI some heat pumps use two: this is why the 8870 splits it into two terminals. Anyways you likely need O -to- O. If the thermostat works in reverse (cools when it should be heating) then simply swith your Orange wire to B then.
On your old thermostat, was there a jumper between RC and R?
R -to- RC & RH
!!! For 8870 standalone operation you will need C (usually 'B') from the heatpump to C on the 8870. Also a jumper from RC/RH to R on the 8870. This is to provide power to the actual front panel thermostat electronics.
!!! For 8870 automated operation remove the above jumpers going to C and R. Your RS484 wiring will now provide power (from the Arpilare distro panel).
PLEASE verify this: I am researching the connection of an 8870 to my own heat pump and the above is very close to mine (terminals are a little different because it's a Trane unit).
IVB: nice. This is my first delve into HVAC controls, and from what I can tell it's a zoo when it comes to wiring. It seems although there are some 'general' standards for wiring, it's really a crap-shoot when you get down to it. Like a mini-mystery every time you pull off a thermostat front panel... In some twisted kinda way I wish my house had something a little more advanced. Now the mystery is over.![]()
[snip]...Old wiring...[snip]
RC ------- Cooling Power -------------------------------------------------------------------- Red
R ----------Heating Power ------/
Y ----------Compressor contactor ----------------------------------------------------------- Yellow
C ----------Common wire from secondary side of cooling system transformer --------- Blue
O/B -------Changeover valve for heat pumps --------------------------------------------- Orange
G ----------Fan Relay ------------------------------------------------------------------------- Green
Aux -------Auxiliary heat relay -------------------------------------------------------------- White
Here is my guess:
Old Thermostat ----------------- 8870
RC and R ------------------- RH and RC
Y ------------------------ ???????
C ------------------------- C
O/B ------------------------ split wire to O and to B???????
G --------------------------- G
Aux ------------------------ W1??????
This is pretty general but it may help some other folks also: Disclaimer: the below terminals/colors are for the above poster's application! NOT ALL UNITS ARE THE SAME! Always consult the wiring diagram that is inside your heat pump air exchanger or the thermostat itself.
On a normal HVAC system, the Y's are for various COOL stages of the compressor; on a heat pump the first Y is for cooling AND heating. Remember the same compressor is used for both roles on a heat pump. Y -to- Y1
On a normal HVAC system, the W's are for various stages, different types, or speeds of HEAT (ie W1 may be gas, W2 is geothermal, etc); on a heat pump the first W terminal is always the Emerg./Aux Heat (also 'defrost', but you don't have to worry with this). Aux -to- W1
G is easy, Blower. G -to- G
The O/B: your existing thermo can go two ways: it either energizes for for cool or energized for heat. Your heat pump obviously only has one reversing valve: give it power for cool. FYI some heat pumps use two: this is why the 8870 splits it into two terminals. Anyways you likely need O -to- O. If the thermostat works in reverse (cools when it should be heating) then simply swith your Orange wire to B then.
On your old thermostat, was there a jumper between RC and R?
R -to- RC & RH
!!! For 8870 standalone operation you will need C (usually 'B') from the heatpump to C on the 8870. Also a jumper from RC/RH to R on the 8870. This is to provide power to the actual front panel thermostat electronics.
!!! For 8870 automated operation remove the above jumpers going to C and R. Your RS484 wiring will now provide power (from the Arpilare distro panel).
PLEASE verify this: I am researching the connection of an 8870 to my own heat pump and the above is very close to mine (terminals are a little different because it's a Trane unit).
It is strange but very cool and satisfying to control your HVAC system from 100 miles away. Now to find a practical purpose!