McQuay MicroTech II Operation & Maintenance

OM 750 Page 21 of 32
PI Loop Feedback
PI Loops
Type
Setpoint
(Controlled Variable)
Output
PI-1 SpaceTemperature
Effective Heating or Cooling
Space Temperature
Calculated Discharge Air Temperature
Temperature Setpoint Setpoint Output
PI-2
Primary Cooling Calculated Discharge Air
Discharge Air Temperature Position the OA Damper
(Economizer) Cascaded Temperature Setpoint Output
PI-3 Secondary Cooling
Calculated Discharge Air
Discharge Air Temperature Operate the Compressor
Temperature Setpoint Output
PI-4 Primary Heating
Calculated Discharge Air
Discharge Air Temperature Operate Electric Heat
Temperature Setpoint Output
PI-5 CO
2
(optional) Single Effective CO
2
Setpoint Space CO
2
Position the OA Damper
PI-6 Low Limit Single
Calculated Discharge Air
Discharge Air Temperature Position the OA Damper
Temperature Setpoint Output
PI Control Loops
The MicroTech II UVC uses PI-loop control for heating, cooling and
ventilation processes within the unit ventilator. As many as six PI
algorithms may be used for software model 04, dependent upon the unit
Table 15. PI Loop List
Figure 17. PI Loop Graphic for CO
2
Figure 18. Cascading PI Loop Graphic 1 (Primary Heat)
Figure 19. Cascading PI Loop Graphic 2 (Primary Cool – Economizer)
DISCHARGE AIR TEMPERATURE CONTROL
The UVC uses two “cascaded” PI loops to aid in providing very stable
space temperature control. The Space Temperature PI-loop is used to
calculate the Discharge Air Temperature Setpoint Output required to
meet the Effective Setpoint Output, a second PI-loop (Primary Cooling,
ventilator configuration. The UVC uses “single” and “cascading” PI
loops where needed.
Secondary Cooling, or Primary Heating) is then activated to control the
heating or cooling device required to achieve the calculated Discharge
Air Temperature Setpoint Output. The second PI-loop used is dependent
upon unit mode (i.e. Heat or Cool).

McQuay MicroTech II Specifications

General

Brand	McQuay
Model	MicroTech II
Category	Controller
Language	English