| How it Works
A Smart Stat can be used to control a 4 Pipe Fan coil using the wiring schematic below and pairing as a 4 Pipe Fan Coil. The unit will operate as follows under standard conditions (standard conditions are often adjustable):
Heating or Cooling? The central plant will dictate whether hot or cold water is being supplied to the FCU. The Smart Stat will recognize whether central plant is heating or cooling based on supply water temp (SWT). The plant will be said to be heating if SWT > 85 and will be said to be cooling when SWT < 65 default.
Cooling: When there is a call for cooling from the space and the SWT < 65 then the fan and valve will energize until the desired temperature is achieved. When there is a call for cooling in the space and the SWT > 65 then the valve will close and the fan will be set to user defined setting or will be off if set to auto.
Heating: When there is a call for heat from the space and the SWT > 85 then the fan and valve will energize until desired temperature is achieved. When there is a call for heating in the space and the SWT < 85 then the valve will close and fan will be set to user defined setting or will be off if set to auto.
Fan Staging: You have the ability to control 3 stages of fan. There are 5 modes for fan control; Off, Auto, Fan Low, Fan Medium, and Fan High. If you choose Low, Medium, or High the fan will run at that level all the time during occupied hours. Auto fan will run Fan low whenever the space temp is 1 degree off from desired, Fan medium will run when space temp is 2 degrees from desired, and Fan high and all speeds will run when space temp is more than 3 degrees from setpoint.
As a further explanation of the cooling control you can see from the example in the diagram below, there is a desired cooling setpoint of 74F, with a 2 degree deadband and a .5 degree hysteresis. As the zone warms past the Cooling Deadband (desired setpoint), the cooling valve will open and first stage fan will engage. If the zone temperature rises another 2 degrees, second stage fan will engage. When the zone temperature starts declining, second stage fan will disengage once it reaches Cooling Deadband (74F in this example). The zone will continue to cool to the hysteresis value (73.5F in this example), at which point, the fan will disengage and the cooling valve with shut."
The diagram below shows the application of the Hysteresis Band and its role:
Once you've paired the Smart Node as a 4 Pipe Fan Coil profile, you will need to select a few specific configuration parameters that define the physical characteristics of your box.
Fan Medium Speed - Activated when space temp is 2 degrees from setpoint
Fan High Speed - Fan high and all speeds will run when space temp is more than 3 degrees from setpoint.
Fan Low Speed - Activated whenever the space temp is 1 degree off from setpoint.
Water Valve - Energize in Heating - Activated when the central plant is in cooling, but this particular zone is below setpoint.
Water Valve - Energize in Cooling - Controls the water valve to keep the zone close to setpoint.
Airflow Temperature Sensor - Only select If using an airflow sensor. These are helpful for troubleshooting.
Supply Water Sensor - Required for gauging the supply water temp.
Enable Occupancy Setting - Select if you would like to use the Occupancy Setting for setpoint control.
Use External 10k Temp Sensor - Only select if you are using an external 10k sensor for room temperature detection. This will disable the temperature sensor mounted in the Smart Stat and only use the remote sensor.