TEC Controller Terminal Box Controller (VAV) Parallel Fan Powered with Hot Water Reheat, Application 2027 Application Note 140-1056 2014-05-01 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. 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 valve (optional). See Sequencing Logic.
Overview Hardware Inputs NOTES: 1. See Control Temperature Setpoints. 2. See Heating/Cooling Switchover. 3. The reheat valve is modulated. 4. The airflow is shown modulating in the entire heating mode. The airflow can operate sequenced, parallel, or overlapping with the reheat valve (optional). 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, etc.). 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 If ROOM TEMP has a status of Failed the last known good value of ROOM TEMP will be used to determine the value of CTL TEMP. If CTL TEMP is overridden then: CTL TEMP equals its overridden value and ROOM TEMP has no effect on the value of CTL TEMP. Day and Night Modes The day/night status of the space is determined by the status of DAY.NGT.
Sequence of Operation Modulating Damper During Heating Mode (Optional) If the following conditions are met for the length of time set in SWITCH TIME, the controller switches from cooling to heating mode by setting HEAT.COOL to HEAT: CLG LOOPOUT < SWITCH LIMIT. CTL TEMP < CTL STPT by at least the value set SWITCH DBAND. CTL TEMP < the appropriate (defined in Control Temperature Setpoints section) heating setpoint plus SWITCH DBAND.
Sequence of Operation Control Loops appropriate range of values determined by flow minimum (CLG FLOW MIN) and flow maximum (CLG FLOW MAX). As described in the following figure, the flow setpoint is calculated by: FLOW STPT = [CLG LOOPOUT × (100% – % minimum setpoint)] + % minimum setpoint. Where percent minimum setpoint is: % minimum setpoint = (CLG FLOW MIN / CLG FLOW MAX) x 100 % FLOW STPT and FLOW % are relative to MIN and MAX STPTS of corresponding heating or cooling mode.
Sequence of Operation Control Loops Option 2: Operate in sequence with the reheat. Option 3: Operate parallel with the reheat. Option 4: Have its operation overlap with the operation of the electric reheat. If the option 1 is chosen, HTG LOOPOUT will control the electric reheat in order to maintain the room temperature. If option 2, 3, or 4 is chosen, HTG LOOPOUT will control both the flow loop setpoint (FLOW STPT) and the electric reheat in order to maintain the room temperature.
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 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%, will equal 0% open. When HTG LOOPOUT = 50%, will equal 50% open. When HTG LOOPOUT = 100%, will equal 100% open.
Sequence of Operation Calibration 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%, will equal 0% open. When HTG LOOPOUT = 50%, will equal 50% open. When HTG LOOPOUT = 100%, will equal 100% open.
Sequence of Operation Fail Mode Operation The airflow out of the supply duct, FLOW, is greater than the value stored in PARALLEL OFF. (This means that there is enough airflow out of the supply duct to allow the heat from the hot water valve to get into the room.) If the conditions have not been satisfied to turn the fan either ON or OFF, the state of the fan will remain unchanged. (If the fan is ON, it will remain ON if the fan is OFF, it will remain OFF.
Sequence of Operation Wiring Diagram Wiring Diagram CAUTION 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 2014-05-01 © 2014 Copyright Siemens Industry, Inc. Technical specifications and availability subject to change without notice.
