As the name suggests, a 4-pipe fan coil unit comprises 4 pipes, supporting two different coils. One favors the heating allowing a hot water supply into the heating coil, and the other favors the cooling, allowing a chilled water supply into the cooling coil. Along with the coils, a fan to run air over.
A fan runs air over the coil to convert it to conditioned air. The thermostat has control over whether to turn on the fan and at what speed and also which coil supply valve to turn on.
| How it Works.
The 75F SmartStat 4 Pipe Fan Coil unit is a unique profile, that provides both heating and cooling conditioning with,
- 3 Stage Fan Speed Control
- Heating Valve Control
- Cooling Valve Control
- 2 Thermistor inputs connecting to Airflow Temperature Sensor & Supply Water Temperature
- Occupancy Sensing Control
Based on the conditioning and fan modes the system is in, and the temperature of the supply water from the chiller, the heating, and cooling operations are triggered, and the corresponding actions and conditioning are achieved.
Additionally, it also supports the Auto Force Occupied and Auto-Away occupancy-based controls.
| Application of Deadband and Hysteresis
The diagrams below show the application of the Deadband and Hysteresis Band and their role:
| Wiring Diagram
- Select the SmartStat option from the device screen.
- Select 4 Pipe FCU from the module type.
The pairing options are displayed on the screen which provides the steps to successfully pair the device.
- Click Pair to start the pairing.
- Select the displayed Bluetooth address.
- Enter the PIN displayed on the device and press Pair.
You can see the configuration screen for the 4 PIPE FCU with the following options available for configuration.
| Configuration Parameters
Once the SmartStat is paired as a 4 Pipe Fan Coil profile, you will need to enable the required configuration parameters as below, which define the physical characteristics of the device.
|Fan Medium Speed
|Activated when space temp is 2 degrees less or 2 degrees more from the heating or cooling desired setpoint respectively.
|Fan High Speed
|Activated when space temp is 3 degrees less or 3 degrees more from the heating or cooling desired setpoint respectively.
|Fan Low Speed
|Activated when space temp is 1 degree less or 1 degree more from the heating or cooling desired setpoint respectively.
|Water Valve - Energize in Heating
|Activated when the central plant is in cooling, the zone demands heating.
|Water Valve - Energize in Cooling
|Controls the water valve to keep for the cooling coil input from the central plant.
|Airflow Temperature Sensor
|Enabled when an airflow temp sensor is used for the profile.
|Supply Water Sensor (as an External 10k Temp Sensor)
|Used to connect the supply water temperature sensor.
|Enable Occupancy Setting
|Select if you would like to use the Occupancy-based setpoint control.
- Enable the required parameters as below.
- Click Set to confirm the parameters configured.
| Post Configuration
The zones paired with 4PIPE FCU profile is displayed in the CCU as below.
Below are widgets configured in the heatmap pages in the portals.
| Fan Modes
4 Pipe FCU profile supports the following fan and conditioning modes.
- Fan Low Current Occupied Period [From hardware changed]
- Fan Low Occupied Period
- Fan Low All Times
- Fan Medium Current Occupied Period [From hardware changed]
- Fan Medium Occupied Period
- Fan Medium All Times
- Fan High Current Occupied Period [From hardware changed]
- Fan High Occupied Period
- Fan High All Times
Note: The SmartStat hardware supports only the following fan modes at its end.
And when a change is made, it would translate to the following in the CCU.
- Auto------ Auto
- Low------Fan Low Current Occupied Period
- Medium-------Fan Medium Current Occupied Period
- High-------Fan High Current Occupied Period
| Conditioning Modes
- Cool Only
- Heat Only
| Modes of Operation Based on User Intents
Let us consider the multiple working modes of operation available under the 2 Pipe FCU Profile.
|All relays associated with multiple inputs will be non-functional and set OFF
|Heat Only Operation
|Cool Only Operation
During the setback mode the temperature drifts further away from the setpoint to save energy
information in the tool.