Aprilaire 8870 Setup
- Thread starter rmercado
- Start date
I'm beta testing the "Text Messaging" feature on these 8870s that ELK rules can take advantage of. Look out for this production feature in the next release.
-=*Sharby*=-
ctwilliams
Active Member
Can I take you (or anyone) up on your offer for help?
I am trying to integrate the 8870 into my system and am confused. I have a heat pump that has one stage cooling and one stage heating with aux/emergency heat. The thermostat I am taking off the wall is wired as follows (descriptions are from the user manual for that thermostat):
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
In looking at the aprilaire manual (A copy is here) I am not sure which diagram I am supposed to follow.
Do I just follow Diagram 5 for single stage heat pump? If so, how do I translate what wires I have over to what they now need to be for the 8870?
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??????
Any ideas?
Thanks,
CT
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).
ctwilliams
Active Member
That worked! Thank you slipnfall, your check is in the mail. I was able to hook it up to the distribution unit and use the 24v AC off of that instead of from the HVAC unit itself.
The elk is reading the 8870 with no problem and I have homeseer reading it via the Elk.
The HVAC on my main level is a dual stage cooling and heat + emergency/strip heat. I have not taken off that thermostat yet, but hopefully I will be able to figure out the extra wires. I will have to work on that one next weekend.....
Thanks for your help!
IVB
Senior Member
Ah, I love it when someone quotes me, asks me for help, and the situation is resolved before I get back to the forums and I have yet to lift a finger 
Sorry, was at the Zoo for 5 hours with the kids. Wife went to the mall, I decided me & the kids would much rather chill with the elephants than shop with the gazelles...
Sorry, was at the Zoo for 5 hours with the kids. Wife went to the mall, I decided me & the kids would much rather chill with the elephants than shop with the gazelles...
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.
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.
UPDATE:
I've been testing a beta fw file on ELK where "Text Messages" appear on the 8870s. A few bugs exist so I'm continuing to issue feedback to offer/expand on all the features of the Aprilaires.
-=*Sharby*=-
ctwilliams
Active Member
A follow up on this if you do not mind. I have looked at the wiring for the floor that has a two stage heat pump. I am not sure of all of the specifics, but a first stage will start at a relatively low speed (and lower energy use) and if the difference in between the actual temperature and what you have is greater than a specific value, then the second stage will kick in.
That is how it works with the cooling and heating, but with the heating there are "emergency" electric heat strips also (a third stage?).
When I looked at the wiring for the floor with the two stage, there was only one wire added and it was placed in Y2. I assume from your above post that since Y is cooling (first stage), then Y2 is cooling (second stage).
There is no wire for W2, which I assume would be heating for some stage? If W1 is the "emergency" strips, then do I need a wire for W2? Or, since it is a heat pump, the wires on the Y side suffice for control of the compressor?
This may be all theoretical since I wired it up as you suggested (with the addition of the Y2 wire) and it seems to work fine.
It is strange but very cool and satisfying to control your HVAC system from 100 miles away. Now to find a practical purpose!
Thanks,
CT
IVB
Senior Member
The wife & I dug being able to crank the heat from the car 10mins from home in the winter. Nice to come home to a warm house.
Sorry, I hijacked this thread because I STILL can't get my 8870 to display anything. I am SO glad I waited for neutral weather to undertake this conversion.
My original t-stat wires are really simple red, green, white, yellow. Follow the 8870 diagrams, it looks straight forward...
white......W1
green......G
yellow.....Y1
red..........RC and RH
I have jumped the RC/RH to R also.
I have the pins on the 8870 switched ON to master, fossil, single. Not sure what to do about the 4th pin...HT pump or H/C?
The cat5 wires are screwed into the 8870 per diagram, but not connected on the other end yet. One step at a time.
I put the original t-stat back on...No problems. It works.
I put the 8870 (tried all 3 that I have) on. No display as if no power.
Please help with any insights and suggestions. HA is like a mistress...exciting, but the agony when it doesn't work. ughhhh.
Thank you !!!!
My original t-stat wires are really simple red, green, white, yellow. Follow the 8870 diagrams, it looks straight forward...
white......W1
green......G
yellow.....Y1
red..........RC and RH
I have jumped the RC/RH to R also.
I have the pins on the 8870 switched ON to master, fossil, single. Not sure what to do about the 4th pin...HT pump or H/C?
The cat5 wires are screwed into the 8870 per diagram, but not connected on the other end yet. One step at a time.
I put the original t-stat back on...No problems. It works.
I put the 8870 (tried all 3 that I have) on. No display as if no power.
Please help with any insights and suggestions. HA is like a mistress...exciting, but the agony when it doesn't work. ughhhh.
Thank you !!!!
