Chiller VariPro - Controller Overview; Introduction of the Controller; Operating Principle of the Controller

To Next Page

To Previous Page

3 Controller overview

3.1 Introduction of the controller

Chiller’s VariPro is a bus-based room controller designed for adjusting room

temperature. It is used to control GRAND VariPro, BOX VariPro and STUDIO

VariPro fan coils that are based on EC technology and equipped with a VariPro

control card.

The VariPro room controller has two RS-485 interfaces, and it can be connected

to any building management system based on the Modbus RTU protocol.

3.2 Operating principle of the controller

Using the VariPro room controller you can set the temperature of a room with 0,5

°C precision. The in-built temperature sensor of the controller continually

measures the temperature of a room with 0,1 °C precision. The required cooling

power control for the fan coil unit is calculated by the temperature differential

between the measured and set room temperatures. The method of control is PI

control. First, the power is increased by the amount calculated from the

differential (relative control P). After this, power increase continues

automatically, until the differential decreases (integrative part I). This means that

the temperature in the room is decreasing. When the set temperature is

reached, the relative control part P is reset. The accumulated integrative part I

stays as a constant while the room temperature is at the set temperature. If the

room temperature continues to decrease, the integrative part is decreased. If the

room temperature continues to increase, the integrative part is increased.

The functioning of the control algorithm aims to keep a balance where the

cooling power in the room and the heating load annul each other. Because of

different and variable heating loads, the balance is reached with different cooling

power levels even if the set temperature remains the same. In terms of the

control algorithm, changes in the set temperature and the heating load

correspond to each other. A change in either one starts the control, and a new

balance is sought. The same operating principle applies for the heating mode,

only the control directions are reversed.

9 (37)

N03104128 Rev. A VariPro Room controller – Installation and Operation Manual