I was called in to provide a solution concerning a 40 ton rooftop unit. This unit was sized for a commercial building that could have up to 130 people in the conditioned area. Actual occupancy can be anywhere from 20 to 130 people.
During the summer, the humidity levels are high, due to the minimum outside air being brought in through this unit. The compressors will not run long enough to de-humidify. Minimum air was reduced to 5%, which helped a little.
The system is controlled by a Varitrac. Terminal units are VAV with a bypass damper to maintain airflow across the DX coils.
The engineer recommended a 25KW reheat coil with a return air humidistat to control. I told him that there would be a wide temperature swing, which was confirmed by Trane. In addition, the VAV boxes would not 'know' what was going on with the discharge air temperature.
My experience with DDC has been mainly with Andover 256 and Infinity systems. After some research on the Trane site, it seems possible to interface a Tracer with the Varitrac and install an I/O module in the rooftop. I would specify a humidity sensor and CO2 sensor for demand based ventilation and SCR control of the reheat coil.
Has anyone integrated a system as described above?