Carrier AquaEdge 19XRV series Operation, Maintenance And Installation Manual

Also see for AquaEdge 19XRV series: Start-up, operation and maintenance instructions Start-up and service instructions Installation instructions Start-up, operation and maintenance instructions Start-up and service instructions

Contents

45and below the CONTROL POINT. The CONTROL POINT set-ting range is 0.5 to 2° F. If temperature control is satisfactoryand the guide vanes are stable, do not change the setting.When very close temperature control is required, as forsome process applications, the deadband may be reduced.When constant small load changes occur in a system andthe vanes will not stabilize, increase the size of the deadband.The deadband must always be smaller than the allowable driftin leaving water temperature.PROPORTIONAL BANDS — The proportional bands con-trol how far the guide vanes will move in response to a specificchange in leaving water temperature. Increasing the propor-tional band increases the amount that the water temperaturemust move away from the control point in order to move theguide vanes a specific amount. Decreasing the proportionalband allows the vanes to move the same amount with a smallerchange in water temperature.If the proportional band is too large, the leaving water tem-perature will increase or decrease slowly enough that the tem-perature moves away from the control point by an unaccept-able amount. A proportional band set too low will cause theleaving temperature to overshoot the control point and causethe guide vanes to “hunt.”The PIC controls have separate proportional bands for in-creasing and decreasing capacity. The PROPORTIONAL IN-CREASE BAND should be set as described above. The PRO-PORTIONAL DECREASE BAND should be set at a typicallysmaller value than the increasing band so that the guide vanescan close quickly enough on a sudden drop in load to prevent alow temperature safety trip.Proportional Entering Chilled Water Gain — When EnteringChilled Water Control is enabled the controls are resetting theLeaving Chilled Water (LCW) control point every 10 secondsin order to keep the ENTERING CHILLED WATER TEMP atthe ENTERING CHILLED WATER (ECW) SETPOINT.The ECW GAIN affects the size of the LCW CONTROLPOINT change in proportion to the difference between theECW SETPOINT and ECW TEMPERATURE.NOTE: Before enabling the ENTERING CHILLED WATERCONTROL and before tuning the ECW GAIN, the LCWPROPORTIONAL BANDS and LCW DEADBAND should beadjusted satisfactorily.Increase the ECW GAIN if the ENT CHILLED WATERTEMP drifts away from the ECW SETPOINT. Reduce theECW GAIN if the ENT CHILLED WATER TEMP swingsabove and below the ECW SETPOINT. Because the water musttravel around the entire loop before the controls receive feed-back on the effect of the LCW CONTROL POINT, the chilledwater loop should be given the opportunity to stabilize beforethe gain is adjusted. The following example shows how the En-tering Chilled Water Control works to move the vanes based onthe rate of change of the ENT CHILLED WATER TEMP aswell as the by the difference between ENT CHILLED WATERTEMP and ECW SETPOINT.Effect of Proportional Entering Chilled Water Band (ECWGain) (See Fig. 25)Error = the contribution of the ECW control to the total er-ror that inputs to the guide vane control. Positive error drivesthe vanes open. Negative error drives the vanes closed.ECW set point = 47 FECW = Entering Chilled WaterECW-10 = Entering Chilled Water 10 seconds previousExample 1 — The first section of Fig. 25 shows the enteringwater dropping with a constant rate. The ECW algorithm isreducing its effort to open the guide vanes. After the enteringwater temperature drops below the set point the error dropsbelow zero and thus is trying to close the vanes.Example 2 — The second section shows the water temperaturedropping but at a decreasing rate as shown by the reduction inthe difference between ECW and ECW-10. The error value isleveling at zero but takes a dip because the entering water tem-perature drops below the set point.Example 3 — The third section of Fig. 25 shows the enteringchilled water temperature increasing. Again the error starts tolevel off or drop as the temperature change over 10 secondsbecomes smaller.-1-0.500.511.522.5346.446.646.8SET POINT = 4747.247.447.647.84848.2TOTAL ERROR°FEXAMPLE 1E C W (°F )E C W -10 secE rror, G ain = 1E rror, G ain = 3EXAMPLE 2 EXAMPLE 3XXXXX XXXXXX XMPLE 1XX XXXXXX XXX XXX XXXXXX Fig. 25 — Transient Example of ECW Gaina19-1957