Carnegie Mellon University Website Home Page
 

Control and Data Acquisition

A comprehensive set of instruments has been installed for both system control and performance monitoring. Both control and data acquisition of the system are accomplished through WebCTRL, as illustrated in Figure 15.

Data Acquisition and Control
Figure 15 Data Acquisition and Control of SEMCO REV 2250 and FVR 2000

External adjustments of the control system include:

  • system on/off.
  • supply air (or space) temperature and humidity through control set points.
  • supply air flowrate through a control set point.
  • outside air and exhaust air flowrates through dampers.
  • heating source: heat pump or gas.
  • bypass damper around the desiccant wheel

Internal adjustments include:

  • supply fan variable frequency drive, VFD.
  • compressor VFD.
  • condenser fan VFD.
  • desiccant wheel VFD.
  • regeneration fan VFD.
  • regeneration natural gas valve.
  • heat pump in heating or cooling mode.
  • switch from heat pump to gas heating.

Once the external adjustments are set by the user, the internal adjustments are made based on the control algorithms programmed in WebCTRL in order to achieve user specified settings.  The supply air flowrate controls the supply fan frequency; the temperature, the compressor frequency; the supply air humidity, the gas flow. Other internal adjustments are controlled directly by the operator.  Defrost and equipment safety modes are separately programmed.

Measurements from the sensors as well as indications of various control signals are recorded at user specified time intervals. The data are stored in the control server and can be traced back at anytime. As an example, Figure 16 shows the outside, supply and return air temperature on 25 February 2007. These data can also be reported in spreadsheets to facilitate data analysis.
 

Data Sample
Figure 16 Data Sample of SEMCO REV 2250 and FVR 2000