Implementing Demand Controlled Ventilation to Meet ASHRAE Standard 62.1 - 2010 - PowerPoint Presentation

Implementing Demand Controlled Ventilation to Meet ASHRAE Standard 62.1 - 2010 By Klas C. Haglid, P.E., R.A., CEM 1

Klas C. Haglid, P.E., R.A., CEM - Bio ASHRAE Distinguished Service Award2011 ASHRAE Handbook, HVAC Applications and Management, Chapter 37,– Author, Klas C. Haglid P.E. R.A. ASHRAE Standard 189.1, Corresponding MemberGPC 32P - Sustainable, High Performance Operations & Maintenance, Voting Member, Contributing, Co-Author Technical Committee 5.5 - Air-To-Air Energy Recovery, Handbook Subcommittee Chairman, Past ChairmanTechnical Committee 7.6 - System Energy Utilization, Voting MemberTechnical Committee 7.8 - Owning and Operating Costs of Commercial Buildings, Past ChairmanASHRAE Standard 84-1991R, Voting MemberReviewed draft of ASHRAE Standard 84-1991R and provided engineering details for efficiency calculations. 2

ObjectivesComplying with ASHRAE Std. 62.1-2010 to improve IAQ while increasing energy efficiency ASHRAE Std. 90.1 can be accomplished with: Displacement VentilationDemand Controlled VentilationEnergy Recovery VentilatorsVariable Speed Drives 3

ASHRAE Std. 62.1-2010Ventilation for Acceptable Indoor Air QualityHow to determine minimum prescriptive ventilation rates How to use Demand Side Ventilation to meet ASHRAE Standard 62.1-2010 4

Definitions “acceptable indoor air quality: air in which there are no known contaminants at harmful concentrations as determined by cognizant authorities and with which a substantial majority (80% or more) of the people exposed do not express dissatisfaction .” –ASHRAE Standard 62.1-2010 pg. 3 5

Definitions Demand Control Ventilation (DCV): any means by which the breathing zone (Vbz) can be varied to the occupied space or spaces based on the actual or estimated number of occupants and/or ventilation requirements of the occupied zone –ASHRAE Standard 62.1-2010 pg. 4 6

6.1.1 Ventilation Rate ProcedureThe following procedure for determining the minimum prescriptive ventilation rates can be used on any zone type. 6.1.1 Takes into consideration:Space typeNumber of OccupantsFloor AreaTypical contaminant sources and source strength 7

Ventilation Rate Procedure Breathing Zone ( bz) Outdoor Airflow (OA) V bz = RpPz + RaAz where: R p = outdoor airflow rate required per person as determined from Table 6-1*. P z = zone population R a = outdoor airflow rate required per unit area as determined from Table 6-1*. A z = zone floor area *Table 6-1 from ASHRAE Standard 62.1-2010 8

Two Parts to the Formula How many people? Type and size of space?

First Part of the Equation 10 ASHRAE Std. 62.1 2010

Second Part 11

Combined 12 Breathing Zone Outdoor Airflow

Office Example V bz = (5x12) + (.06 x 1500) = 60 + 90 = 150 cfm What is the prescriptive design for outdoor air (cfm) of a 1500 square foot office with 12 occupants? Eq 6-1 : V bz = R p P z + R a A z Design inputs for office space: Pz = 12 people Az = 1,500 square feet of floor area 13

School Example Vbz = (10 x 30) + (.12 x 1100) = 300 + 132 = 432 cfm What is the prescriptive design for outdoor air ( cfm ) of a 1100 square foot classroom with 30 students?Eq 6-1 : Vbz = RpPz + R a A z From Table 6-1: R p = 10 cfm /person R a = 0.12 cfm /ft 2 Design inputs from school classroom project for ventilation: P z = 30 peopleAz = 1100 square feet 14

General Manufacturing Example (Excludes Heavy Industrial and processes using chemicals) V bz = (10 x 20) + (.18 x 50000) = 200 + 9,000= 9,200 cfm What is the prescriptive design for outdoor air (cfm) of a 50,000 square foot coat hanger production facility with 20 machinists?Eq 6-1 : Vbz = R p P z + R a A z From Table 6-1: R p = 10 cfm /person R a = 0.18 cfm/ft2Production facility input data:Pz = 20 peopleAz = 50,000 square feet of floor area Notice the Area outdoor air rate (Ra) increased for a manufacturing facility. Increase 15

Ventilation Rate Procedure – Zone Outdoor Airflow Voz = V bz/Ez (Ez) The zone air distribution effectiveness shall be determined using ASHRAE Std. 62.1-2010, Table 6-2. ( Partial Table ) 16

Methods of Providing Outdoor Air to Zone Dilution Ventilation Displacement Ventilation 17

Dilution Ventilation It’s important to design ventilation system to have maximum air distribution. This will help eliminate dead space and short circuiting of air flow Poor distribution of air across classroom breathing zone 18

Dilution VentilationTypical in U.S. construction Outdoor air is brought into space and dilutes contaminant concentrations in the space. Adequate air mixing 19

Air Mass Exchange Diagram shows good air circulation providing fresh air on one end of room and exhaust pulling air out on the other end to maximize removing contaminant concentrations by displacing room temperature air across a Breathing Zone 20

Displacement Ventilation (DV) Uses natural convection to provide “Buoyancy-assisted forced ventilation”Effectively removes contaminants from people and objects locallyASHRAE Std. 62.1-2010 Table 6-2 recognizes DV to be 1.2 times more effective than traditional dilution ventilation Some applications measured DV to be 2 to 2.5 more effective than traditional dilution ventilation 21

Displacement VentilationUsing displacement ventilation and then measuring air quality of the space is an effective way to improve IAQ Often times, balancing airflow according to how effective the displacement ventilation system is can reduce required airflow by 50%This saves energy and reduces latent loadsCan be achieved with Variable Speed Drives (VSD) 22

Demand Controlled Ventilation (DCV) “any means by which the breathing zone outdoor airflow (Vbz) can be varied to the occupied space or spaces based on the actual or estimated number of occupants and/or ventilation requirements of the occupied zone.” – ASHRAE Std. 62.1-2010 pg. 4 23

Example of DCV Methods ERV CO2 Sensor comes on over 700 ppm and turns off under 600 pp m SOA EA People Fan Relays 24 ERV- Energy Recovery Ventilator EA- Exhaust Air SOA- Supply Outside Air

DCVCO2 concentrations in outdoor air generally range from 300 to 500 ppmASHRAE std. 62.1 2007 and 2010 recognize 700 ppm of CO2 above outdoor ambient levels or 1000 to 1200 ppm to be acceptable air quality for an indoor space. Reference page 37 of Appendix C Displacement Ventilation with CO 2 Demand Controlled Ventilation properly engineered and installed will keep CO2 levels well below 1000 ppmDCV can reduce runtime from 168 hours per week to 30 hours per week for a classroom. That is an 82% reduction in runtime. 25

Summary of Ventilation Rates Determine prescriptive design ventilation rate for zone by using Ventilation Rate ProcedureDetermine Method of VentilationDilutionDisplacement – up to 2.5 times more effective Choose appropriate method to control the ventilation system and monitor the contaminants of concern CO2 sensor VSD – Variable Speed Drive to reduce fan speed to balance and optimize ERV efficiency26

Fan Affinity LawsAssuming fan diameter and air density are constant Eq (1) : Eq (2) : Eq (3) :   27

Fan Affinity Laws Eq (1) :   28 100 cfm @ 100 rpm 200 cfm @ 200 rpm

Fan Affinity Laws Eq (2) :   29 100 cfm @ 100 rpm 200 cfm @ 200 rpm 0.3 WC @ 100 rpm 0.9 WC @ 200 rpm Pressure is squared

Fan Affinity Laws Eq (3) :   30 0.3” WC @ 100 rpm 0.9” WC @ 200 rpm Energy E xpended is Cubed 0.3” WC @ 1 BHP 0.9” WC @ 8 BHP

ExampleWhat is the percent difference in BHP required to run a ventilation system if alternative 2 has a 50% increase in static pressure from alternative 1? Alternative 1 Conditions:CFM = 8,000SP = 1” in wgBHP = 5 RPM = 1000 31

Example Continued Rearranging Eq (2):RPM 2 = x RPM1RPM2 = x 1000 = 1225 Eq (3): BHP 2 = BHP 1 x ( RPM 2 /RPM 1 ) 3 BHP 2 = 5 x ( 1225/1000)3 = 9.2 BHP9.2-5/5 = 84% Increase A 50% increase in static pressure results in an 84% increase in power consumption   32

Not All ERVs Are the SameERV Features to Compare: Airflow ArrangementThermal EffectivenessPressure DropFan EfficiencyMaintenanceSound Levels Cross Contamination 33

Heat Exchanger Airflow Arrangement ASHRAE states: Counter-flow heat exchangers are theoretically capable of achieving 100% Sensible Effectiveness* Parallel Flow heat exchangers: 50% (Max) Cross-flow heat exchangers and Enthalpy Wheels: 50-75% (Max) *Note: Source: 2012 ASHRAE Handbook – HVAC Systems and Equipment, Chapter 26: Air-to-Air Energy Recovery Equipment. 34

High Efficiency FansTypical fan efficiency can range from 5 to 10 W/ cfmA high efficiency fan can be expected to be approximately 0.2 W/cfm The EER of an ERV’s performance is formulated by the BTUs recovered divided by the watts of power consumed from the fan energy. BTUs Recovered Watts of Fan PowerEER = 35

Thermal Efficiency vs.Overall Efficiency Combining premium Efficiency fans with High efficiency ERVs and a low static pressure system can yield great energy savingsTypical ERV has an EER of around 11. High efficiency ERV can be well above 120.36

Efficiency = Payback A short term savings in build cost is outweighed by sustainable gains over present consumption . 37

Maintenance Costs are Essential There’s more to a product than its initial costs and efficiency – Maintenance and efficiency equal long term and continuous ROICorrosion resistant equipment Minimal moving parts Low static pressure Appropriate filters and sizeEfficient fansLocation/Operation38

Tools to Meet ASHRAE Std. 62.1 and Improve IAQ While Increasing Energy Efficiency, ASHRAE Std. 90.1Displacement Ventilation Demand Controlled VentilationCO2 controls or other contaminant monitoring sensorsERVCounter flow heat exchangerLow Pressure Drops High efficiency fans Variable Speed Drives Air balancingBetter control 39

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Questions 44 Acceptable IAQ indoor air quality is defined as:Air in which there are no known contaminants at harmful concentrations . Conditions determined ASHRAE 62.1 Air with which a substantial majority (80% or more) of the people exposed do not express dissatisfaction .” All of the Above.

Questions 45Compliance with ASHRAE Standard 62.1 and an Increase in energy efficiency ASHRAE Std.90.1 can be obtained with: Displacement VentilationVariable Speed Drives Demand Control Ventilation All of the Above.

Questions 46The procedure for determining the minimum prescriptive ventilation rates that can be used in any zone type takes into consideration which of the following? The number of Occupants in the spaceAir Class defined by ASHRAE Linear Feet of Wall space Both A and B

Questions 47Displacement Ventilation can best be described as : Outdoor air that is brought into a space in lieu of contaminantsAn Improvement of Air Classification The removal of contaminants with limited air mixing None of the Above

Questions 48Which calculation best represents the efficiency of an ERV? Cfm exhaust versus cfm Intake Apparent Thermal Efficiency Fan Curve and Efficiency None of the Above