TEC Controller Terminal Box (VAV) - Parallel Fan Powered with Hot Water Reheat, Application 2027 Application Note 140-1056 2015-10-05 Building Technologies
Table of Contents Overview ............................................................................................................................. 4 Hardware Inputs .................................................................................................................. 6 Hardware Outputs ................................................................................................................ 6 Ordering Notes .............................................................................
Overview Hardware Inputs Overview In Application 2027, the controller modulates the supply air damper of the terminal box for cooling and modulates a hot water valve for heating. When in heating, the terminal box either maintains minimum airflow or modulates the supply air damper. Application 2027 has a parallel fan that re-circulates the room air. In order for the terminal box to work properly, the central air-handling unit must provide supply air.
Overview Hardware Inputs Application 2027 Control Schedule with Minimum Supply Air in Heating Mode. NOTES: 1. See Control Temperature Setpoints. 2. See Heating/Cooling Switchover. 3. The reheat valve is modulated. 4. (Optional) The airflow is shown at minimum in the entire heating mode (default setting, with FLOW START and FLOW END = 0). The airflow can operate sequenced, parallel, or overlapping with the reheat coil. See Sequencing Logic.
Overview Hardware Inputs NOTES: 1. See Control Temperature Setpoints. 2. See Heating/Cooling Switchover. 3. The reheat valve is modulated. 4. (Optional) The airflow is shown modulating in the entire heating mode. The airflow can operate sequenced, parallel, or overlapping with the reheat valve. See Sequencing Logic.
Sequence of Operation Control Temperature Setpoints Sequence of Operation The following paragraphs present the sequence of operation for Application 2027, VAV with Hot Water Heat and Parallel Fan. Control Temperature Setpoints This application has a number of different room temperature setpoints (DAY HTG STPT, NGT CLG STPT, RM STPT DIAL, and so on.). The application actually controls using the CTL STPT.
Sequence of Operation Room Temperature and CTL TEMP CTL STPT is calculated as follows: With Deadband disabled: CTL STPT = Dial value With Deadband enabled in Heat Mode: CTL STPT = Dial value – 0.5 ∗ Deadband (limited between the value of RM STPT MIN and RM STPT MAX) With Deadband enabled in Cool Mode: CTL STPT = Dial value + 0.5 ∗ Deadband (limited between the value of RM STPT MIN and RM STPT MAX) NOTE: If RM STPT DIAL is failed, it maintains the last known value.
Sequence of Operation Day and Night Modes Day and Night Modes The day/night status of the space is determined by the status of DAY.NGT. The control of this point differs depending on whether the controller is monitoring the status of a wall switch or if the controller is connected to a field panel.
Sequence of Operation Modulating Damper During Heating Mode (Optional) Digital Room Units (2200/2300 Series) The digital room unit will display a graphical bar indicating the number of steps above or below the current operating temperature setpoint. When the controller switches modes (heating to cooling) the span adjustment set will be applied to the new heating/cooling mode center value.
Sequence of Operation Control Loops FLOW STPT and FLOW % are relative to MIN and MAX STPTS of corresponding heating or cooling mode. Example If CLG FLOW MIN = 200 cfm, and CLG FLOW MAX = 1000 cfm, the minimum flow setpoint is (200 cfm/000 cfm) × 100% flow = 20%. When CLG LOOPOUT is 0%, FLOW STPT = 20% flow. [0% × (100% – 20%)] + 20% = 20% This ensures that the airflow out of the terminal box is no less than CLG FLOW MIN. When CLG LOOPOUT is 50%, FLOW STPT = 60% flow.
Sequence of Operation Flow Control in Night Mode HTG LOOPOUT adjusts the value of FLOW STPT differently depending on which flow loop setup is chosen. However, the following rule applies no matter what setup is chosen. In heating mode, FLOW STPT is never set below (CTL FLOW MIN/HTG FLOW MAX) × 100% flow or above 100% flow. In heating mode, CTL FLOW MIN is equal to HTG FLOW MIN. Flow Loop – The flow loop maintains FLOW STPT by modulating the supply air damper, DMPR COMD.
Sequence of Operation Hot Water Coil – Terminal Unit Hot Water Coil – Terminal Unit CAUTION The parallel fan and heating flow setpoints should be configured to provide the required airflow across the heating coil. When the heating coil is located outside of the air terminal unit (for example, as a perimeter heating coil or a heating ceiling) supply airflow is not required. The heating loop modulates the heating valve to warm up the room. When the controller is in cooling mode, the heating valve is closed.
Sequence of Operation Sequencing Logic Example 2 (Airflow and Heat Sequenced Together) Assume that your system has a hot water valve that is to operate in parallel with the flow loop. If: FLOW START = 0% FLOW END = 100% REHEAT START = 0% REHEAT END = 100% then, When HTG LOOPOUT = 0%, FLOW STPT will equal 0% flow. When HTG LOOPOUT = 50%, FLOW STPT will equal 50% flow. When HTG LOOPOUT = 100%, FLOW STPT will equal 100% flow. When HTG LOOPOUT = 0%, VLV COMD will equal 0% open.
Sequence of Operation Calibration FLOW END = 0% (or/and HTG FLOW MIN = HTG FLOW MAX) REHEAT START = 0% REHEAT END = 100% then, When HTG LOOPOUT = 0%, FLOW STPT will equal (170 cfm/1000 cfm) × 100% flow = 17% flow. This will cause the flow loop to maintain airflow of 170 cfm out of the terminal box. When HTG LOOPOUT = 50%, FLOW STPT will equal 17% flow. When HTG LOOPOUT = 100%, FLOW STPT will equal 17% flow. When HTG LOOPOUT = 0%, VLV COMD will equal 0% open.
Sequence of Operation Fail Mode Operation If the conditions have not been satisfied to turn the fan either ON or OFF, the state of the fan remains unchanged. (If the fan is ON, it will remain ON if the fan is OFF, it will remain OFF.) When the fan is configured to be controlled as varied (FAN MODE = VARIED); The fan turns ON only when the following two conditions have been met: The airflow out of the supply duct, FLOW, is less than PARALLEL ON. The heating demand, HTG LOOPOUT is greater than FAN ON.
Sequence of Operation Wiring Diagram Wiring Diagram NOTE: The controller’s DOs control 24 Vac loads only. The maximum rating is 12 VA for each DO.
Application 2027 Point Database Application 2027 Point Database Point Number Descriptor Factory Default (SI Units)2 Eng Units (SI Units) Slope (SI Units) Intercept (SI Units) On Text Off Text 1 CTLR ADDRESS 99 -- 1 0 -- -- 2 APPLICATION 2091 -- 1 0 -- -- {04} ROOM TEMP 74.0 (23.44888) DEG F (DEG C) 0.25 (0.14) 48.0 (8.88888) -- -- {05} HEAT.COOL COOL -- -- -- HEAT COOL 6 DAY CLG STPT 74.0 (23.44888) DEG F (DEG C) 0.25 (0.14) 48.0 (8.
Application 2027 Point Database Point Number Descriptor Factory Default (SI Units)2 Eng Units (SI Units) Slope (SI Units) Intercept (SI Units) On Text Off Text 32 CLG FLOW MAX 2200 (1038.18) CFM ( LPS) 4 (1.8876) 0 -- -- 33 HTG FLOW MIN 220 (103.818) CFM ( LPS) 4 (1.8876) 0 -- -- 34 HTG FLOW MAX 2200 (1038.18) CFM ( LPS) 4 (1.8876) 0 -- -- {35} AIR VOLUME 0 (0.0) CFM ( LPS) 4 (1.8876) 0 -- -- 36 FLOW COEFF 1 -- 0.
Application 2027 Point Database Point Number Descriptor Factory Default (SI Units)2 Eng Units (SI Units) Slope (SI Units) Intercept (SI Units) On Text Off Text {76} CTL FLOW MIN 220 (103.818) CFM ( LPS) 4 (1.8876) 0 -- -- {77} CTL FLOW MAX 2200 (1038.18) CFM ( LPS) 4 (1.8876) 0 -- -- {78} CTL TEMP 74.0 (23.44888) DEG F (DEG C) 0.25 (0.14) 48.0 (8.88888) -- -- {79} CLG LOOPOUT 0 PCT 0.4 0 -- -- {80} HTG LOOPOUT 0 PCT 0.4 0 -- -- 83 STAGE FAN 10 PCT 0.
Issued by Siemens Industry, Inc. Building Technologies Division 1000 Deerfield Pkwy Buffalo Grove IL 60089 Tel. +1 847-215-1000 Document ID 140-1056 Edition 2015-10-05 © Siemens Industry, Inc., 2015 Technical specifications and availability subject to change without notice.
