Programing question for A/C fan

Hi,
 
I have two thermostats and two seperate gas furnaces in my home. (One heats and cools the upstairs (call it UNIT1), and the other heats the main floor and basement (UNIT 2)).
 
UNIT1 has Air Conditioning, UNIT2 does not.
 
I would like to program the board so that whenever UNIT1 is activly COOLING, the FAN on UNIT2 turns on to circulate air. When UNIT1 stops COOLING, the fan on UNIT2 turns off.
 
What would the automation code look like for this?
 
Thanks.

Try this
 
EVERY MINUTE
AND IF UNIT1 SYSTEM MODE IS COOL
AND IF UNIT2 FAN MODE IS OFF
THEN UNIT2 FAN ON
 
EVERY MINUTE
AND IF UNIT1 SYSTEM MODE IS OFF
AND IF UNIT2 FAN MODE IS ON
THEN UNIT2 FAN OFF

Fan modes can only be Auto, On or Cycle
And I don't think you need to check the condition of Unit 2 for the effect the OP is looking for.
There shouldn't be any harm in constantly sending the serial commands to the T-stat turn the fan on or off.
 
I prefer not to use the Every timer trigger if I can help it. 
I think there a bit kludgy trying to detect a condition that doesn't occur most of the time.
 
You could trigger off the Outdoor Temperature going NOT READY based on your setpoint (use one only for the hot side, make the low setpoint 0)
Depends on how you have your system setup to run your HVAC program.
I use Occupancy Mode.
Do you use Heat and Cool or Auto?
 
If using the Every trigger, in this situation I'd use 5 or 10 minutes instead of every minute.
 
WHEN Every 10 Minutes
AND IF Unit 1 SYSTEM MODE IS COOL
THEN Unit 2 FAN ON
 
WHEN Every 10 Minutes
AND IF Unit 1 SYSTEM MODE IS OFF
THEN Unit 2 FAN AUTO

I think you can also do it the old fashioned way with wires.
Use a relay to keep from crossing the 24vac power supplies in each unit.
 
24vac coil relay.
Connect unit1's cool (typically yellow) and common (typically black) to the coil.
Connect unit2's fan (typically green) and power (typically red) to the terminals (Com and NO)
 
Run an 18/2 tstat cable from unit1 to unit2 and mount the relay in unit2.
Inside each unit is a control board where the tstat cable is landed.
 
When unit1's tstat calls for cooling, it sends 24vac on the cool(yellow) wire.
This activates the relay.
The relay acts like the "fan" switch on the tstat sending 24vac on the fan(green) wire.

I am doing something similar. I have 4 RIB RIBMN24C connected to thermostat and 24vac transformer to "monitor" the thermostat functions back to my Elk panel. I have a RCS TR-16 connected to the elk but it does not report or you have no way of knowing when the system is running. Just the ordered mode and setpoints. I had the system blow a fuse and AC died while I was out of town. Did not know it was not working as Elk system still had the last temp received still being reported to Homeseer and Elk M1 app on my phone. Actually the system was not running and temps were hot during my absence. Now i can monitor the 24 vac control voltage and call for fan, compressor and heat 24vac lines.

Using the RIBMN24C you could easily connect the two unit fans as sda suggets.

Thanks for the replys and sorry it took so long to get back on.
 
I had not thought of using the EVERY command, and I have to agree, I don't like the idea of running a code every few minutes when it is not on most of the time.
 
I made a few changes (below).
 
WHEN Every 5 Minutes
AND IF Unit 1 SYSTEM STATUS IS COOLING
THEN Unit 2 FAN ON
 
WHEN Every 5 Minutes
AND IF Unit 1 SYSTEM STATUS IS NOT COOLING
THEN Unit 2 FAN AUTO
 
You will notice I changed system mode to system status. Also, I changed the "turn fan back to AUTO" command to if system status is not cooling.
 
I figured it should really be the status that it's checking and not the mode.
 
If anyone else can figure out a way to do this as more of a "trigger" so that it just comes on when the COOLING begins and goes off when the COOLING ends please let me know. But for know this is a great workaround.
 
Thanks!

torque said:

Thanks for the replys and sorry it took so long to get back on.
 
I had not thought of using the EVERY command, and I have to agree, I don't like the idea of running a code every few minutes when it is not on most of the time.
 
I made a few changes (below).
 
WHEN Every 5 Minutes
AND IF Unit 1 SYSTEM STATUS IS COOLING
THEN Unit 2 FAN ON
 
WHEN Every 5 Minutes
AND IF Unit 1 SYSTEM STATUS IS NOT COOLING
THEN Unit 2 FAN AUTO
 
You will notice I changed system mode to system status. Also, I changed the "turn fan back to AUTO" command to if system status is not cooling.
 
I figured it should really be the status that it's checking and not the mode.
 
If anyone else can figure out a way to do this as more of a "trigger" so that it just comes on when the COOLING begins and goes off when the COOLING ends please let me know. But for know this is a great workaround.
 
Thanks!

Click to expand...

There is no way to trigger, but you can test every minute.  Doing that isn't really a problem.