Session, April, 00 HVAC Systems Who s in Control? Basic ventilation Wall openings / Curtains Ridge vents Wall and/or pit fans Room and attic inlets s Room heat Zone heat Cooling systems Supplemental cooling fans, tunnel fans Sprinklers, drippers, evaporative pads It s convenient to use factory/installer settings, but the manager of a swine unit is ultimately responsible for the environment produced. Objectives Better understand terminology used in setting controllers Increase confidence in adjusting controller settings Improve capability to enhance pig environment and performance What kind of information does your controller need? Activation temperatures s at which stages are or de increments Changes in temperature that result in stages being or de Other information lags Minimum settings
Set-Point Set-Point s Target temperature for controller Not the average room temperature Other settings are generally based on the set-point temperature Heating season Cooling season Room and Solid Slatted Solid floor Solid Slatted Solid floor floor floor with straw floor floor with straw body weight Dry sows 9 70 Farrowing 7 8 Nursery lb. 79 8 77 8 8 79 lb. 7 7 7 7 79 7 Grow/finish Continuous fill -0 lb. 8 70 0-0 lb. 7 9-0 lb. 70 All-in - all-out Temp. Room T lb. 70 7 8 7 7 7 lb. 8 7 70 7 8 7 lb. 8 70 90 lb. 8 00 lb. 9 0 lb. 9 7 9 0 lb. 7 9 9 lb. 7 9 9 lb. 7 9 9 7 lb. 7 9 0 9 7 8 Over 00 lb. 7 9 0 9 Source (in SI/metric units): Zhang, 99. Swine Building Ventilation: A Guide for Confinement Housing in Cold Climates. Prairie Swine Centre, Inc., Saskatoon, SK, Canada. Sensor Location Setting the Set Point Sensors should be placed to represent the temperature in the pig space. The set-point temperature may need to be adjusted to account for sensor location. Not so good Much better Most controllers have the set-point temperature setting situated near the display of room temperature Dial setting Push-button sequence Room Temp. = 8. o F Room RH = 8% Set-point T =? 9 0 Enter: 8 o F Differential difference (hysteresis) allowed before activation of a stage A fan comes on or speed increases A curtain begins to drop, heater turns on, sprinklers, etc. Room T activation T Temp. Fan on Setting the Differential: Direct Method User selects the temperature increment, ΔT Set-point T = 8 o F Stage- differential =? Enter: o F Fan off Differential Controller calculates activation temperature Ex.: Stage activation Temp. = 8 o F + o F = 8 o F
Setting the Differential: Indirect Method User selects activation temperature -Stage Control with Single-Speed Speed Fans Stage Stage Set-point T = 8 o F Stage at? Enter: 8 o F Controller calculates the differential Ex.: Differential = 8 o F - 8 o F = o F Min. Vent. Continuous fan Differential Differential Differential Offset increment that is used to: Accommodate lags e.g. rooms w/large heaters Prevent systems from operating simultaneously Heating & curtains / wall fans Heating Offset Establishes a new basis for heating differentials Temp. on off on off Room T Offset Differential Setting the Offset: User selects the offset temperature increment, ΔT Set-point T = 8 o F offset =? Enter: 0. o F Heating differential =? Enter:. o F Heat output Stage Control Stage 7 Controller calculates activation and deactivation temperatures Ex.: Activation Temp.: 8 o F 0. o F. o F = 80 o F Deactivation Temp.: 8 o F 0. o F = 8. o F 8 Differential Differential Heat offset Set Point
Ramped Control Stage output varies with temperature Variable-speed fans Variable-output heaters Some curtain controllers Output commonly expressed as % of Max. output % output 00% Min. setting Max. setting The temperature increment defining the temperature range over which output is to vary. ΔT = T upper T lower Min. setting % output 00% T lower Max. setting T upper 9 0 Ramped Stage Output Primary function is to moderate output to better suit the thermal needs of the animals. Temp. Fan reaches Max. capacity Room T Fan speed increase begins Decrease begins Fan @ Min. speed Differential Control of Variable-Speed Fans Range of fan output Set indirectly Minimum & maximum % range for change to occur Set directly Differential (ramp length) Set-point T = 8 o F Minimum % =? Enter: 0 % Maximum % =? Enter: 00 % Differential/offset =? Enter: o F =? Enter:. o F Model Scenario: V-S & S-S S Fans 7 8 Stage Stage 0 9 Stage Control of Variable-Speed Fans What is being adjusted? Generally voltage Voltage affects speed which affects airflow rate (cfm) Does % value shown = voltage %? Generally no! Minimum Offset Differential Differential Set Point
s cale airflo w % Full-s 00 80 0 0 0 0 0 0 0 0 0 0 70 80 90 0 Variable-Speed Controllers Controller variable-speed setting Results from the Air Dispersion Lab, ISU 00 Actual Ideal Variable-Speed Fans: Getting Control Without adjusting a motor curve Conduct trial runs with empty room, a high fan differential/offset, and a variety of minimum %. Sense the % range over which most of the rise in output occurs. With adjustment of motor curve Select a motor curve that has a better linear fit of controller % vs. voltage. In either case, Determine an acceptable minimum setting. May want to control the fan to operate in the % range over which most of the rise in output occurs. % Full-sca ale airflow Selecting an Operating Range for Improved Control of V-S Fans 00 80 0 0 0 0 Min. % Max. % Operating range Actual Buffering of Stages When a new fan stage is, the operating variable-speed fans are dropped back to minimum speed, then slowly ramp back up Reduces shock effect of activating large fans Controller variable-speed setting 7 8 Buffered Scenario: V-S & S-S S Fans delay Stage Influenced Settings Shifting of activation temperatures occurs during certain conditions. Cold outside air temperature Extended periods at maximum ventilation Shift Stage Minimum Stage Shift Differential 9 0
Ventilation Curves Automated adjustment of activation temperatures with time [growth]. Need to establish bend points and settings Stage activation temperature Actual curve Ideal curve On/Off or Cycle rs Sometimes used to achieve a lower rate of air exchange than can be delivered by the installed fan(s) Generally not recommended for controlling fans in humid livestock environments Results in a lot of fluctuation in conditions Useful for controlling sprinklers and other events that are intended to On occur intermittently Off Off Days in room On Cooling Fan & Sprinkler Control Using a Cycle r If your controller has an adjustable cycle timer, consider using this Stage feature to counter heat waves. Questions?? Curtains start to drop Cooling fans Sprinklers @ /0 minutes Sprinklers @ / minutes Differential Differential Differential Differential