Modulating RTU Control

75F's system profile for modulating scroll compressors, blower VFDs, and modulating furnaces is highly configurable and works with nearly all units that accept a modulating analog voltage input. Using the Central Control Unit, CCU you can control these devices using 3 separate 0-10Vdc (or other analog) outputs on the CCU - 1 each for heating, cooling, and fan speed. There is also a fourth output that can be used to map the heating and cooling modulation into a single signal. This is useful for integrating with pneumatic controls. 

To configure this profile you simply change the System profile to what has been termed Modulating Unit Control. All calculations are load based and will modulate the furnace, compressors, and fan to compensate for the zone load. If there are 20 VAVs on the unit being controlled the algorithm will intelligently determine the optimal load in the building to determine what output signal is appropriate. 

Below is an example of the profile working on a cool only unit. See as the average space temperature (purple line) rises above the average desired (black line) then the cooling analog output (blue line) also rises. This profile is highly configurable, so do not let the simplicity of the example below fool you.