Modulation Of Variable Capacity Compressors (Vcc); Vcc-Analog; Vcc-Digital - Full Gauge Controls RCK-862 plus Manual

Quick start manual (3 pages)

Table of Contents

14.SUCTION CONTROLS

14.3 Modulation of Variable Capacity Compressors (VCC):

Variable Capacity Compressors (VCC) are compressors controlled by means of an analog output (VCC-Analog) or by means of fast-acting digital

outputs (VCC-Digital).

Only compressor 1 of each suction pressure switch can be configured as VCC and when operating together with ON / OFF compressors it is the first to

be actuated and the last to be shutdown.

14.3.1 VCC-Analog:

To control an analog variable capacity compressor, a 0-10V analog output and optionally a digital Start/Stop output are used. The analog output

selected in function 1.2.x.36 is configured in menu 1.10 according to the characteristics of the device to the controlled (frequency inverter or digital

control module). The start of modulation of the output (compressor start) occurs when the difference between the measured pressure and the setpoint is

equivalent to or greater than the configured minimum value. If a starting value of the analog output (1.10.x.3) is configured, the RCK-862 plus

applies this value during the starting time (1.2.x.67)

14.3.2 VCC-Digital:

To control a compressor of the VCC-Digital type, it is necessary to configure a digital output for motor activation and one or more fast-acting outputs

(SSR) for actuation of capacity modulation valves. During compressor operation, only one valve is modulated while the others remain on or off. The

choice of which valve should be modulated is made automatically considering the smallest number of actuations between the valves of the same

compressor, thus increasing the life span of the assembly.

The compressor starts when the required capacity is greater than the value configured in VCC-Digital: Minimum capacity (1.2.x.69) and remains

operating without load during the time configured in VCC: Starting time (1.2.x.67).

The Algorithm present in the RCK-862 plus automatically determines when the auxiliary outputs are to be actuated. If it is of interest to carry out the

control of the valves at fixed time intervals, select the desired period in the parameter VCC-Digital: Control period (1.2.x.70).

Each digital compressor manufacturer determines limitations for the mininum activation time of the modulation valves, which can be configured in VCC-

Digital: Minimum valve activation time (1.2.x.71).

The maximum time that the compressor can operate without load can be configured in VCC-Digital: Maximum time without load (1.2.x.72), when this

time elapses the compressor actuates one of its modulation valves (increasing the flow of refrigerant in the compressor) for the same time configured in

(1.2.x.72). A compressor start time can be configured, according to:

Note: Re-balance a shorter starting time than the maximum time without a load (1.2.x.72).

The RCK-862 plus allows the control of several variations of digital compressors, allowing the modulation of compressors from one to three auxiliary

control valves. For the correct selection, it is necessary to evaluate which configuration meets the compressor characteristics, according to:

VCC-Digital 10-100 1V: One main output for compressor activation and one digital output (SSR) for modulation of auxiliary valves. The main output is

considered to represent 0% of the compressor capacity.

VCC-Digital 10-100 2V: One main output for compressor activation and two digital outputs (SSR) for modulation of two auxiliary valves. The main output is

considered to represent 0% of the compressor capacity.

VCC-Digital 10-100 3V: One main output for compressor activation and three digital outputs (SSR) for modulation of three auxiliary valves. The main output

is considered to represent 0% of the compressor capacity.

VCC-Digital 33-100 1V: One main output for compressor activation and one digital output (SSR) for modulation of auxiliary valves. The main output is

considered to represent 33% of the compressor capacity.

VCC-Digital 33-100 2V: One main output for compressor activation and two digital outputs (SSR) for modulation of two auxiliary valves. The main output is

considered to represent 33% of the compressor capacity.

VCC-Digital 50-100 1V: One main output for compressor activation and one digital output (SSR) for modulation of auxiliary valves. The main output is

considered to represent 50% of the compressor capacity.

The following table illustrates the behavior of the outputs in relation to the capacity required by the compressor without considering the rotation of the outputs

Modulation VCC-Digital 10-100 1V

Capacity

Main

Aux 1

Off

10-100%

>100%

Modulation VCC-Digital 10-100 2V

Capacity

Main

Aux 1

Off