Critical Environments

Critical Environments
Laboratory Control Basics and Room Control Strategies Copyright© 2006 TSI Incorporated

Copyright© 2006 TSI Incorporated
Insert Agenda slide Laboratory customers and goals Laboratory environment Safety Comfort Experiment integrity Energy efficiency Room pressurization control Constant Volume Direct pressure Flow tracking, a.k.a. “Airflow Tracking” or “Volumetric Offset” Flow tracking with pressure feedback VAV control types Temperature control Laboratory control Copyright© 2006 TSI Incorporated

Laboratory Customer Types
Universities Teaching labs Research labs High Schools/Middle Schools Hospitals Copyright© 2006 TSI Incorporated

Laboratory Goals Safety Containment Primary: fume hood containment Secondary: Directional room airflow-net negative airflow labs Ventilation (dilution) Comfort Temperature Ventilation Sound Copyright© 2006 TSI Incorporated

Laboratory Goals Experiment Integrity Protection of research Uniform airflow, reduce drafts Stable room pressurization Energy-efficiency Current energy costs (Q1,2006): $7.50/cfm; 1000 cfm hood costs $7,500/yr) Copyright© 2006 TSI Incorporated

Laboratory Environments
Use determines Requirements Animal Research Clinical labs Analytical Chemistry Teaching labs Biocontainment Forensic labs Nanotechnology Copyright© 2006 TSI Incorporated

Laboratory Environments
Ideal laboratory configuration Designed to meet specific requirements for a given application or task Chemical lab will have different needs than a pharmaceutical lab or vivarium Copyright© 2006 TSI Incorporated

See App Note LC-125 for More Information! Laboratory Safety Minimize long-term exposure to chemicals and fumes Primary Containment Fume hood Laminar flow bench BSC Snorkels Secondary Containment Laboratory itself Copyright© 2006 TSI Incorporated

Laboratory Safety Objectives of Lab Ventilation A laboratory is built to accommodate materials and processes that contaminate air which may pose a health risk to the occupants Lab exhaust devices capture contaminants Lab exhaust system removes contaminants Lab ventilation system provides dilution air 100% Outside Air (4-12 air changes per hour) No Recirculation 24 hours/day, 7 days per week See App Note LC-125 for More Information! Copyright© 2006 TSI Incorporated

Laboratory Safety Ventilation rate examples OSHA 4-12 ACPH Prudent Practices 6-12 ACPH ASHRAE Laboratory Ventilation 6-10 ACPH NFPA Minimum of 4 ACPH Typically greater than 8 ACPH when occupied See App Note LC-125 for More Information! Copyright© 2006 TSI Incorporated

Calculate Air Exchange Rate (ACPH) Air Changes Per Hour
To calculate air exchanges per hour, use the following formula: L= Length W= Width H= Height CF= Cubic Feet (of lab space) ACPH = Air Changes (or exchanges) Per Hour Measure your room and work the following equation: L’ x W’ x H’ = CF (ex: 10’ X 12’ X 8’ = 960 CF with 180 cfm) 180 cfm / 960 CF = .1875/m .1875/m x 60m/h = ACPH Copyright© 2006 TSI Incorporated

Examples of Air Changes per Hour
Lab Space ACH OA Chemistry (standard Wet Lab) 10 100% Biological (Tissue Culture, DNA) 12 Special Lab (High Odor Generation) 30 Chemical Storage & Distribution Analytical Lab (Instrument Room) Equipment Room (autoclaves, centrifuges, freezers) 15 Computer server or dry electronics lab 12 to 60 20 cfm/person Animal rooms ISO Class 4 Clean room 660 ISO Class 5 Clean room 600 ISO Class 6 Clean room 200 ISO Class 7 Clean room 70 ISO Class 8 Clean room 20 Copyright© 2006 TSI Incorporated

Laboratory Comfort Maintain space temperature More challenging with VAV Maintain ventilation Normally covered by ACPH for a given lab application Limit infiltration from sources other than HVAC system Reduce drafts or odd airflow patterns Minimize noise Copyright© 2006 TSI Incorporated

Energy-Efficiency Exhaust as little air as possible without impacting safety or comfort Using less air is the most promising tactic VAV system Occupied and unoccupied modes Recover the heat Move air more efficiently Increased initial cost Saves operating expenses in the long-term Copyright© 2006 TSI Incorporated

Room Pressurization Control
To maintain directional airflow by controlling supply and exhaust air flows in order to pressurize or depressurize the room relative to an adjacent space and to maintain a comfortable, non-fluctuating air temperature. Primary containment Laboratory fume hoods Biological safety cabinets Snorkels Secondary containment Laboratory room itself Copyright© 2006 TSI Incorporated

Room Control Strategies
Constant Volume (CV) Control and/or balance supply & exhaust flows Monitor pressure only Constant Volume (CV) – Two Position Variable Air Volume (VAV) Control supply & exhaust flows under varying loads Monitor critical parameters NOTE: CV and VAV also used on lab hoods NOTE: Dampers and flow stations or Venturi valves can be used for either CV or VAV systems Copyright© 2006 TSI Incorporated

Constant Volume May monitor ΔP No ΔP Control Simple Read only 8635-M 8610/12,8650-MON CVV (Venturi Valve) Temp by others Requirements Closed door Low Traffic Stable reference 8635-M 8650-MON Copyright© 2006 TSI Incorporated

Constant Volume Use Constant Volume when Low hood density (large room with one hood) Low concern regarding energy usage Room ventilation rates of 10 ACPH or more Advantages Easy to design Minimizes cost of controls Few controls to maintain Disadvantages Equipment sized for full flows High initial and operating costs Difficulties arise when relocating equipment Limits future expansion Wastes energy Copyright© 2006 TSI Incorporated

Variable Air Volume (VAV)
Use a Variable Volume System when High hood density If fume hood energy usage exceeds lab ventilation or thermal requirements Advantages Reduced energy costs less air conditioned supplied and exhausted air vary depending on loads Use of unoccupied mode with reduced flows saves energy Applying diversity factors Sizing equipment based on expected flows as opposed to maximum flows Pressure-independent VAV controls adapt to system changes Maintain constant face velocity regardless of sash position Modulate supply and exhaust based on room ΔP or temperature demand Disadvantages Reduced airflows and energy usage are dependent on good hood user sash position management Increased HVAC system complexity Higher installation costs Copyright© 2006 TSI Incorporated

VAV Control Types Direct pressure Measure room pressure differential Maintain it Flow tracking Measure supply and exhaust air flows Maintain an offset between supply and exhaust flows Copyright© 2006 TSI Incorporated

VAV Control Types Flow tracking with pressure monitoring Measure supply and exhaust air flows Monitor pressure differential Maintain an offset between supply and exhaust flows Flow tracking with pressure reset (AOC) Measure pressure differential Adjust offset between supply and exhaust flows based on pressure measurement Copyright© 2006 TSI Incorporated

VAV Control Type Features
Direct Pressure Control Flow Tracking Flow Tracking with ΔP monitoring Control with ΔP feedback Measures room ΔP X Modulates supply and exhaust flows Measures supply and exhaust flows Fixed flow offset Adjusts flow offset to meet room ΔP set point Copyright© 2006 TSI Incorporated

Factors to consider in Determining Control System Strategy
Number of hoods Room volume Energy costs Room Ventilation Rates Hours of Operation (occupied/unoccupied hours) Heat generation in labs Number of researchers Type of lab work being performed Open or closed lab Tightness of constructed envelope Complexity of cleanliness requirements Speed of disturbances and response Duct conditions for flow measurement Copyright© 2006 TSI Incorporated

VAV Control Loops Direct pressure Closed loop on pressure Flow tracking Closed loop on flow Open loop on pressure Flow tracking with pressure monitoring Flow tracking with room pressure feedback Copyright© 2006 TSI Incorporated

Open Loop on Pressure – Closed Loop on Flow
Copyright© 2006 TSI Incorporated

Closed Loop on Pressure – Closed Loop on Flow

Direct Pressure Control
Model 8636 8650 Copyright© 2006 TSI Incorporated

Measure room pressure differential with thru-the-wall sensor Modulate supply and exhaust to maintain room pressure differential set point Measure the supply flow to set minimum ventilation rate and to determine ACPH Copyright© 2006 TSI Incorporated

Requirements Closed door with low traffic Stable reference Fluctuations in reference space will cause disturbances within the lab Supply flow measurement is required for ventilation control and to determine ACPH TSI Models 8635, 8636 Copyright© 2006 TSI Incorporated

Direct Pressure Control Sequence of Operations
If fume hood flow increases and makes space more negative, then … Controller senses an increased exhaust flow Controller gradually closes the general exhaust damper to minimum if required If ΔP set point is still not achieved … Controller gradually opens supply until ΔP set point is achieved Copyright© 2006 TSI Incorporated

If fume hood flow decreases and makes space more positive, then … Controller senses a decreased exhaust flow Controller gradually opens the general exhaust damper to maximum if required If ΔP set point is still not achieved … Controller gradually closes supply until ΔP is achieved Copyright© 2006 TSI Incorporated

If the door to the lab opens, then … Controller senses the room ΔP go toward neutral Controller quickly closes supply to minimum if required If ΔP set point is still not achieved … Controller quickly opens the general exhaust damper to maximum if required until ΔP is achieved Copyright© 2006 TSI Incorporated

If the lab temperature increases, then … Controller senses temperature increase Controller closes reheat valve If, after 3 minutes, the lab is still too warm … Controller gradually increases supply Controller senses ΔP decrease Controller increases general exhaust to meet ΔP set point Copyright© 2006 TSI Incorporated

If the lab temperature decreases, then … Controller senses temperature decrease Controller opens reheat valve If, after 3 minutes, the lab is still too cold … Controller gradually decreases supply Controller senses ΔP increase Controller decreases general exhaust to meet ΔP set point Copyright© 2006 TSI Incorporated

Direct Pressure Controller Components 8635-C, 8636
8635-C includes: Controller Output Cable, 4-cond., 25 ft. SureFlow Room Pressure Controller SureFlow Room Pressure Sensor w/ Cable VAC Transformer with Cable 8636 includes: Controller Output Cable, 4-cond., 25 ft. SureFlow Room Pressure Sensor w/ Cable VAC Transformer with Cable SureFlow Room Pressure Controller Copyright© 2006 TSI Incorporated

Flow Tracking Control Measure supply and exhaust air flows Exhaust flow is more than supply flow (negative lab) Difference is referred to as “offset” air Determine an offset between supply and total exhaust flows Total exhaust includes fume hoods, general exhaust, snorkels, plus other exhaust devices Offset value is generally listed on the room schedule Determined by the number of doors or other penetrations into the lab space If unknown, use 10% of maximum exhaust Copyright© 2006 TSI Incorporated

Flow Tracking Control Modulate supply and exhaust flows to maintain offset Once lab is completed, offset value may be adjusted to sufficiently create a negative space Measure the supply flow to set minimum ventilation rate and to determine ACPH Copyright© 2006 TSI Incorporated

Flow Tracking Control Controls flows to numerical set points Exhaust flow greater than supply flow (labs) Difference is referred to as offset Closed-Loop on Flow Measure and control supply and exhaust flows Open-Loop on Pressure Differential pressure set point not guaranteed Requirements All flows are measured Stable air flows TSI Models: 8680, 8681 & 8682 Copyright© 2006 TSI Incorporated

Flow Tracking Control, Calculating Offset Flow
Measured fume hood flows = 1400 cfm Measured snorkel flows = 150 cfm Measured general exhaust = cfm Total exhaust = 1900 cfm “Offset” requirement per schedule = cfm Supply air flow rate set to = 1700 cfm Copyright© 2006 TSI Incorporated

Flow Tracking Control The only option for open labs or labs with no suitable reference space Labs where containment is not critical Labs designed around competition Remember Doesn’t measure or guarantee room differential pressure Copyright© 2006 TSI Incorporated

Flow Tracking Control Sequence of Operations
If fume hood flow increases and makes space more negative, then … Controller senses an increased exhaust flow Controller gradually closes the general exhaust damper to minimum if required If offset is still not achieved … Controller gradually opens supply until offset is achieved Copyright© 2006 TSI Incorporated

If fume hood flow decreases and makes space more positive, then … Controller senses a decreased exhaust flow Controller gradually opens the general exhaust damper to maximum if required If offset is still not achieved … Controller gradually closes supply until offset is achieved Copyright© 2006 TSI Incorporated

If the lab temperature increases, then … Controller senses temperature increase Controller closes reheat valve If, after 3 minutes, the lab is still too warm … Controller gradually increases supply Controller gradually increases general exhaust to offset ΔP unknown Copyright© 2006 TSI Incorporated

If the lab temperature decreases, then … Controller senses temperature decrease Controller opens reheat valve If, after 3 minutes, the lab is still too cold … Controller gradually decreases supply Controller gradually decreases general exhaust to offset ΔP unknown Copyright© 2006 TSI Incorporated

Flow Tracking Controller Components 8681-NS, 8682-NS
8681-NS includes: VAC Transformer with Cable SureFlow Adaptive Offset Controller 8682-NS includes: VAC Transformer with Cable TYPE 1 NEMA Hinged Box DIM COMM cable, shielded 2-wire, 25 ft. SureFlow Digital Interface Module SUREFLOW DDC CNTL W/O LON Note: All damper/actuators and flow stations must be added separately. Adaptive offset and flow tracking controllers require the addition of factory start-up. Copyright© 2006 TSI Incorporated

Flow Tracking with Pressure Monitoring
Measure supply and exhaust air flows Maintain an offset between supply and exhaust flows Monitor pressure differential Differential pressure may vary Copyright© 2006 TSI Incorporated

Flow Tracking with Room Pressure Feedback

Formerly referred by TSI as Adaptive Offset Control (AOC) Combines Direct Pressure and Flow Tracking controls Measures supply and exhaust air flows Measures room pressure differential Maintains an offset between supply and exhaust flows, more exhaust than supply Adjust offset between supply and exhaust flows to ensure differential pressure set point Copyright© 2006 TSI Incorporated

Closed loop on Flow Measures and controls supply and exhaust flows Closed loop on Pressure Measures room differential pressure Differential pressure measurement is used to adjust offset to maintain room pressure set point Models: 8680, 8681, 8682 Copyright© 2006 TSI Incorporated

Safety of direct pressure with stability of flow tracking Requires suitable reference pressure Maximum offset limits configurable Not used for Open labs Labs without suitable reference space NOTE: Controls on flow first Pressure is slow reset back to set point Copyright© 2006 TSI Incorporated

Flow Tracking with Room Pressure Feedback Sequence of Operations
If fume hood flow increases and makes space more negative, then … Controller senses an increased exhaust flow Controller gradually closes the general exhaust damper to minimum if required If offset is still not achieved … Controller gradually opens supply until offset is achieved Controller adjusts offset to meet ΔP set point Copyright© 2006 TSI Incorporated

If fume hood flow decreases and makes space more positive, then … Controller senses a decreased exhaust flow Controller gradually opens the general exhaust damper to maximum if required If offset is still not achieved … Controller gradually closes supply until offset is achieved Controller adjusts offset to meet ΔP set point Copyright© 2006 TSI Incorporated

If the door to the lab opens, then … Controller senses low ΔP Increases offset to meet ΔP set point Controller gradually opens the general exhaust damper to maximum if required Controller gradually closes supply to minimum if required Copyright© 2006 TSI Incorporated

If the lab temperature decreases, then … Controller senses temperature decrease Controller opens reheat valve If, after 3 minutes, the lab is still too cold … Controller gradually decreases supply Controller gradually decreases general exhaust to offset Controller adjusts offset to meet ΔP set point Copyright© 2006 TSI Incorporated

If the lab temperature increases, then … Controller senses temperature increase Controller closes reheat valve If, after 3 minutes, the lab is still too warm … Controller gradually increases supply Controller gradually increases general exhaust to offset Controller adjusts offset to meet ΔP set point Copyright© 2006 TSI Incorporated

Temperature Control To meet comfort demands in a lab environment, integral temperature control is a standard feature on Models 8636, 8681 and 8682 controllers which feature adjustable: Temperature dead band range Temperature set point throttling range Temperature set point integral value Reheat valve control direction See App Note LC-129 for More Information! Copyright© 2006 TSI Incorporated

Temperature Control Temperature Dead Band (TEMP DB, ±0.1° - 1.0°F) Defines how sensitive controller needs to be regarding space temperature above and below temp set point If the TEMP DB is set to its maximum value (±1.0°F), the controller will not react to changes unless the space temperature rises above or below the set point by 1.0°F. If the TEMP DB is set to its minimum value (±0.1°F), the controller will react to space temperature changes 0.1°F above or below set point. See App Note LC-129 for More Information! Copyright© 2006 TSI Incorporated

Temperature Control If TEMP DB is set to 1.0°F, and the TEMP SETP is set to 70.0°F, the controller will not take corrective action unless the space temperature is below 69.0°F or above 71.0°F. See App Note LC-129 for More Information! Copyright© 2006 TSI Incorporated

Temperature Control Temperature Throttling Range (TEMP TR, ±2.0°-20.0°F) The temperature range in which the controller fully opens or closes the reheat valve Defines reheat valve movement Smaller TEMP TR range provides more precise control Larger TEMP TR range provides more stable control See App Note LC-129 for More Information! Copyright© 2006 TSI Incorporated

Temperature Control If TEMP TR is set to ±3.0°F, and the TEMP SETP is set to 70.0°F, the reheat valve will be fully open when the space temperature is 67°F. Similarly, the reheat valve will be fully closed when the space temperature is 73.0°F. See App Note LC-129 for More Information! Copyright© 2006 TSI Incorporated

Temperature Control Temperature Set Point Integral Value (TEMP Ti VAL) Manually changes the temperature control PI integral control loop variable Increasing TEMP Ti VAL will slow the control system which will increase stability Decreasing TEMP Ti VAL will speed up the control system which may cause system instability See App Note LC-129 for More Information! Copyright© 2006 TSI Incorporated

Temperature Control Reheat Control Direction (REHEAT DIR) Determines the temperature control signal’s output direction can be set to DIRECT or REVERSE if the control system closes the reheat valve instead of opening the valve, this option will reverse the control signal to now open the valve. See App Note LC-129 for More Information! Copyright© 2006 TSI Incorporated

Laboratory Control How Does This All Work? A Model 8636, Model 8681 or Model 8682 controller receives a temperature input from a temperature sensor (1000 Ω Platinum RTD). The controller maintains temperature control by: Controlling supply and general exhaust for ventilation and cooling Controlling the reheat coil for heating Copyright© 2006 TSI Incorporated

Laboratory Control The controllers have three configurable supply flow minimum set points. The ventilation set point (VENT MIN SET) is the minimum flow volume required to meet ventilation needs of the laboratory (ACPH). The temperature supply set point (COOLING FLOW) is the theoretical minimum flow required to meet cooling flow needs of the laboratory. The unoccupied set point (UNOCC SETP) is the minimum flow required when the lab is not occupied. the supply flow will not be modulated for space cooling when in UNOCC SETP mode; space temperature control will be maintained by modulating the reheat coil. Copyright© 2006 TSI Incorporated

Laboratory Control The controller continuously compares the temperature set point to the actual space temperature. If set point is being maintained, no changes are made. If the space temperature is rising above set point: The controller will first modulate the reheat valve closed. Once the reheat valve has been fully closed for three minutes, the controller will then gradually begin increasing the supply volume by 1 CFM/second up to the COOLING FLOW set point. Copyright© 2006 TSI Incorporated

Laboratory Control If the space temperature decreases below the set point: The controller will first reduce the supply volume. Once the supply volume reaches its minimum (VENT MIN SET), the controller will then start a 3 minute time period. If, after 3 minutes the supply flow is still at the VENT MIN SET flow rate, the controller will begin modulating the reheat coil open to meet the heating demand. Copyright© 2006 TSI Incorporated

Capabilities Model 8635-M 8635-C 8636 8680 8681 8682 Room pressure monitor x Room pressure controller Flow tracking controller Flow tracking controller with room pressure feedback Low alarm relay High alarm relay Alarm relay Switch input (occupied/unoccupied) Analog output (pressure) Supply flow input 1 2 4 Supply control Exhaust flow input Exhaust control Temperature input (0 - 10V) Temperature input (RTD) Temperature control Hood flow input 7 Copyright© 2006 TSI Incorporated

TSI’s Position Full-featured controls Local support Choice of laboratory control method Fully digital controls – easy to configure & calibrate Software specials Tailor made to meet specific requirements Integration into BAS via: LON BacNet (currently via gateway) Modbus N2 Copyright© 2006 TSI Incorporated

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