Environment: Virtual $($TinkerCad$)/$ Real Life

The Setup:

In a given space, an HVAC system is in operation. It comprises a single Fan$-$Coil unit connected within a two$-$plpe framework. This system transports either hot water from the Boiler or Chilled water from the chiller. A $12$ V servo motor regulates the water flow. Inside the space, a circulating fan redistributes air, capable of either recirculating indoor air or allowing $100\%$ external air for cooling. This fan is powered by a $9$ V DC motor, functioning solely in an ON$/$OFF capacity without speed control.

For ventilation, there exist two dampers, each capable of OPEN$/$CLOSE actions, facilitating the intake of external air into the room and expelling hot air through the exhaust damper. Both dampers are managed by $12$ V servo motors.

The Guldeline of operation is as follows:

The temperature of the spate is expected to be within $19C($lower value, $T_4)$ to $244C($higher value, $T_4)$:

The indoor temperature is measured by a temperature sensor$.$

The outdoor temperature is measured by anether temperature sensor$.$

If the outdoor temperature is dropped below $19C,$ the boiler provides hot water to the fan coll unit. The opening of the value is $15\%+1\%$ for each degree of drop and will be operated by Servo Motor$-1.$

If the outdoor temperature rises above $24C,$ the chiller provides chilled water to the fan coil unit. The opening of the vale is $15\%+1\%$ for each degree of rise.

The fan starts automatically as soon as the valve opens. Fan will remail ON until the indoor Temperature reaches the desired value.

The system will operate and will bring the semperature at above the lower range$)$ in winter and below the upper range$)$ in the summer time.

When the indoor temperature reaches the desined range, the value closes, fan turns off, display updates accordingly.

If the indoor temperature is above the higher value, $T_H$ and outdoor temperature is below the lower value, $T_4,$ then the water control valve will not open rather another Servo Motor will open the outside air damper by $100\%($by Servo Motor$-2)$ and an exhaust damper $100\%($by Servo Motor$-3)$ and will allow the outside air to be circulated through the space.

The indoor and outdoor temperature does not change by itself in Tinkercad, You need to do the change and create different scenarios to observe if the system is working properly.

The LCD panel will display:

Scenario $1(9$ummer$)$ : Indoor Temperature is $26C.$ Outdoor Tempis $35C.$ Water value will open to allow Chiled water, Circulating Fan is ON and Free Cooling is OFF.

Scenarig $2($winter$)$ : Indoor Temperature is $16C.$ Outdoor Temp is $12C.$ Water valve will open to allow Hot water, Cirtulating Fan is ON and Free Cooling is OFF.

Scenario $3($free coplingl$)$ : Instoor Temperature is $28C.$ Outdsor Temp is ${12}^{\text{'}\text{'}}C.$ Water valve is None. Circulatizg Fan is ON and Free Cooling is ON$.$

Scenario $4($No operation$).$ Ifdsor Temperatune is $21C.$ Dutdoor Tempis $12C.$ Water valve is None. Urculating Fas is OFF and Iree Cooling is OFF,

Legend:

$0$T$-$O$.$atdoor Temperature

If $-$ indosr Temperiature

V$-$Water Vive Controller Servo Nenone. Hihat, CrCool

FA $-$ Creculating Fan

FC $-$ Free Cooling

$ON-Op$ rating ON

OF $-$ Turned OFF