1、 4100 N. FAIRFAX DR., SUITE 200 ARLINGTON, VIRGINIA 22203 2005 GUIDELINE for SELECTING, SIZING, or the tilt angle is reversed, effectively stopping heat transfer. 5.1.4.4 Cold Corner Damper or Traversing Defrost. For Plate Heat Exchangers, outdoor air is prevented from entering a portion of the Air-
2、to-Air Heat Exchanger to enable the exhaust air energy to defrost that section of the component. 5.2 Condensation Removal. Means of removing condensate may be required. If so, observe applicable codes for piping and trapping of condensate drain(s). Copyright Air-Conditioning and Refrigeration Instit
3、ute Provided by IHS under license with ARINot for ResaleNo reproduction or networking permitted without license from IHS-,-,-ARI GUIDELINE W-2005 5 Section 6. System Balancing 6.1 Balancing Considerations. 6.1.1 Energy Impacts. Equal (balanced) Supply and Exhaust Airflows provide the maximum energy
4、recovery for a given AAERVE. The system should be balanced as closely as possible as long as other conditions, such as requirements for building pressurization, are met. 6.1.2 Conditions Impact. Unequal airflows will influence the conditions of the supply air. Example: Reducing the Supply Airflow as
5、 compared to the exhaust will improve the supply air psychrometric conditions, but reduce the energy recovered from the exhaust air. On the other hand, reducing the Exhaust Airflow as compared to the supply will degrade the supply air psychrometric conditions. Again, energy recovered will be reduced
6、. 6.1.3 Variable Air Flow. On systems that vary total system airflow and/or outdoor air (demand control ventilation, variable air volume, etc.) provisions should be made to control both Supply and Exhaust Airflows in concert. In no case should the airflows be lower than needed to provide the require
7、d outdoor air ventilation rate per ASHRAE standards or local codes. 6.1.4 Building or Zone Pressurization. Requirements for building or zone pressurization should be considered when designing and/or balancing the system. 6.2 Balancing Methods. Provisions should be made for adjusting the airflows to
8、required rates. The methods listed below can be used independently or in combination. 6.2.1 Dampers. Dampers may be used to balance airflows to the space to insure proper air distribution to individual zones or connected air-handling equipment. Dampers may also be used to balance AAERVE Supply and E
9、xhaust Airflows. 6.2.2 Blower Settings. Methods such as multiple speed motors, adjustments in blower sheaves, etc., may be used to adjust airflows. 6.2.3 Variable Speed. Variable frequency drives, electronically commutated motors, and similar variable speed technologies may be used to adjust airflow
10、s. 6.2.4 Unitized. Operation of the main unitary blower can impact the AAERVE Supply and Exhaust Airflows. Methods should be provided to balance these flows and unitary airflow. 6.2.5 Integrated. Operation of the main unitary blower can impact the AAERVE Supply and Exhaust Airflows. Methods should b
11、e included to balance these flows. 6.2.6 Measurement of Flows. Methods should be provided to measure Supply and Exhaust Airflows for the purpose of balancing. Methods can include static pressure across the component, conventional velocity methods in the duct, or other airflow measuring devices. 6.2.
12、7 Outdoor Air Correction Factor (OACF). Consider the impact of OACF to ensure that the correct amount of outside air is introduced to meet the ventilation requirements for the building. Example: If the outdoor air is being measured at the outside air inlet and the OACF = 1.1, the measured air volume
13、 should be 110% of the required (ventilation design) Supply Airflow. This will ensure that the specified level of outdoor air is being introduced into the building (even with the OACF impact from the Air-to-Air Heat Exchanger). 6.3 Equal and Unequal Air Flows. The amount of outside air and exhaust a
14、ir required may be the result of the building design. Many facilities have exhaust air removed from a variety of sources, other than the AAERVE. In order to maintain a proper air balance in the building, this may result in the need to exhaust less air than the outdoor air requirement. In this case,
15、Effectiveness will be increased by definition (because the percentage of energy extracted from the reduced Exhaust Airflow is increased), however, the conditions of the supply air will be less favorable and the Effectiveness of the building system will be reduced (due to induced exfiltration without
16、 benefit of energy recovery). If the exhaust air is greater than the outdoor air intake, Effectiveness would again be increased by definition; supply air conditions would improve, but again, building system Effectiveness would be reduced (in this case due to induced infiltration without benefit of e
17、nergy recovery). Copyright Air-Conditioning and Refrigeration Institute Provided by IHS under license with ARINot for ResaleNo reproduction or networking permitted without license from IHS-,-,-ARI Guideline W-2005 6 Section 7. Economizer Operation 7.1 Economizer Operation. Some applications and some
18、 codes may require that Economizer operation be provided in conjunction with AAERVE. Note: Full Economizer requires up to 100% of the air-conditioning system airflow. 7.1.1 Bypass Economizer. 7.1.1.1 Unitized and Integrated Systems. Outdoor air is brought into the conditioned space without crossing
19、the component, thus not recovering energy. This can be accomplished by utilizing dampers, bypass duct and dampers, or by moving the Air-to-Air Heat Exchanger out of the outdoor airstream. 7.1.1.2 Coupled Systems. A system is added to introduce outdoor air into the conditioned space without crossing
20、the Air-to-Air Heat Exchanger which utilizes the Economizer on the air-conditioning unit. 7.1.2 Wheel Economizer. A System that introduces outdoor air into the conditioned space while crossing a Rotary Heat Exchanger without energy recovery. The component is stopped during the economizer period when
21、 energy recovery is not desired. All of the outdoor air crosses the component, thus limiting the outdoor air amount to the components airflow capacity at the application static pressure. Typically, full 100% outside air economizer function can be provided with this method only for 100% outdoor air s
22、ystems. 7.2 Modulation. All the above methods can be controlled to provide partial or modulated economizer function. 7.3 Exhaust Air Relief. Barometric relief or power exhaust is often provided in conjunction with Economizers. The exhaust fan in the AAERVE may be able to provide or assist with this
23、function. This should be considered in the design. Section 8. Design Considerations and Air-Conditioning Equipment Selection 8.1 General. The following should be considered when selecting and applying an AAERVE: a. Building design b. Building codes c. Building locale (climate consideration) d. Build
24、ing operation e. Building air-conditioning system f. Building outdoor air requirements g. Building outdoor air intake location h. Building inside air conditions i. Building structure limitations 8.1.1 Building Design. The type of building will determine the type of AAERVE required for the applicatio
25、n. The design may require that the AAERVE be utilized in a mechanical room application, a rooftop application, a through-the-wall application, or a combination. 8.1.2 Building Codes. The authority having jurisdiction will require that the system adhere to all applicable codes. 8.1.3 Climate. The loc
26、ation of the building may determine the type of AAERVE required. The temperature and humidity conditions should be considered when determining the system to be used. 8.1.4 Building Operation. Controls should be provided to operate the system as required. 8.1.5 Building Air-Conditioning System. The a
27、ir-conditioning system type utilized in the building structure will influence which AAERVE system will be easiest to install and maintain. 8.1.6 Building Outdoor Air Requirements. The required amount of outside air will affect the size and design of the AAERVE. Copyright Air-Conditioning and Refrige
28、ration Institute Provided by IHS under license with ARINot for ResaleNo reproduction or networking permitted without license from IHS-,-,-ARI GUIDELINE W-2005 7 8.1.7 Building Outdoor Air Intake Location. The location of the outdoor air intake should be considered. Never use outdoor air from an area
29、 that generates contaminated air. Examples of this are (1) areas where idling cars, trucks, or buses are abundant, (2) a processing facility that produces odors, and (3) restaurants kitchen (grease) exhaust areas. 8.1.8 Building Inside Air Conditions. The quality of the air inside the building may b
30、e important to the selection and design of the AAERVE. If the quality of the exhaust air is objectionable, the EATR should be evaluated. The EATR may be minimized through technology selection, mechanical purge, and/or pressure management. Separate spaces that must remain absolutely separated due to
31、concerns for smoking odor transfer, for example, should be treated with different systems. When exhaust air presents a safety hazard and is not acceptable for recirculation in any amount, the use of AAERVE may not be advisable. Table 1 provides a summary of classes of air as they are treated in ANSI
32、/ASHRAE Standard 62.1. Table 1: Classes of Air and Energy Recovery Ventilation Applications Classification of Exhaust Air and Dilution Limits (Refer to ANSI/ASHRAE 62.1 Addendum y) Recommendations Class 1 Air - General Space Conditioning Re-circulation permitted. Use EATR and OACF to calculate adjus
33、ted intake rates and insure that proper outside air ventilation is provided. Class 2 Air - Toilet Exhaust, etc. Supply air is acceptable when no more than 10% is class 2 air. Minimize EATR to reduce re-circulation of exhaust air. Most devices will require no special measures to achieve this level of
34、 dilution. System design, including multiple exhaust points from a variety of spaces can increase dilution performance. Class 3 Air - Education Lab, Dry Cleaning, etc. Supply air is acceptable when no more than 5% is class 3 air. Minimize EATR to reduce re-circulation of exhaust air. System design,
35、including separate exhaust air duct systems for class 3 exhaust, multiple exhaust points including class 1 and 2 air, purge, etc., will influence dilution performance. Class 4 Air Biohazard Facility, etc. Re-circulation prohibited. AAERVE may not be an acceptable technology. Only specific designs wi
36、th zero EATR and not susceptible to failure should be used in this application. 8.1.8.1 Fouling. Spaces that generate dust, powder, grease, wax, etc. could require special treatment of the exhaust air or may not be candidates for AAERVE. Verify with the AAERVE manufacturer. 8.1.8.2 Humidity Control.
37、 AAERVE in combination with the air-conditioning system may provide adequate humidity control to meet ASHRAE Standard 62.1 requirements. In applications where humidity must be closely controlled (within 5%) additional dehumidification equipment may be required. 8.1.8.3 Smoking Areas. If smoking is a
38、llowed inside the space, additional amounts of outdoor air may be required. Consult local codes for the minimum amount required. Consult the AAERVE manufacturer for appropriate product application. 8.1.9 Building Structure Installation Considerations. Listed below are examples of limitations created
39、 due to the structure of a building. This is just a partial list. 8.1.9.1 The amount of room required for ductwork 8.1.9.2 The size of the mechanical room as it relates to the size of the equipment 8.1.9.3 The location of exhaust and flue gas and plumbing vents on a roof 8.1.9.4 Maintenance access t
40、o the AAERVE 8.1.9.5 Electrical requirements 8.2 Selection of Cooling Design Conditions. Outside air can be a significant source of humidity. ASHRAE Handbook -Fundamentals provides three different sets of cooling design conditions. The dry-bulb/mean wet-bulb data prioritizes sensible Copyright Air-C
41、onditioning and Refrigeration Institute Provided by IHS under license with ARINot for ResaleNo reproduction or networking permitted without license from IHS-,-,-ARI Guideline W-2005 8 load; the wet-bulb/mean dry-bulb data prioritizes latent load; the dewpoint/mean dry-bulb data prioritizes humidity
42、ratio. The choice of design conditions may impact the efficiency of the system and its ability to control indoor humidity. 8.3 Tonnage Reduction Method. The air-conditioning equipment size can be determined by reducing the Total Building Load by the tonnage saved due to the AAERVE. 8.3.1 Total Air-C
43、onditioning Requirement. Determine the total air-conditioning required for the Total Building Load including the amount required for the ventilation. 8.3.2 AAERVE Tonnage Savings. Determine the amount of air-conditioning tonnage that the AAERVE is saving from the manufacturers data. Reduce the total
44、 air-conditioning requirement by the savings amount to determine the net air- conditioning requirement. 8.4 Entering Outdoor Air Method Determine the total air conditioning load by replacing the entering outdoor air conditions in load programs with the entering tempered outside air conditions. Secti
45、on 9. AAERVE Sizing 9.1 General. The following information is required to determine the AAERVE needs. a. Outside air required per zone b. Exhaust air required per zone. c. Summer design conditions d. Winter design conditions e. Desired sensible Effectiveness f. Desired latent Effectiveness g. Extern
46、al static pressure requirements (supply and exhaust) as applicable Section 10. Specification Practices for AAERVE 10.1 AAERVE Requirements. 10.1.1 Energy Recovery Performance and Effectiveness. Specify either sensible or enthalpy type recovery device with the desired Effectiveness. Enthalpy devices
47、should be used where it is advantageous to conserve or reject humidity. Sensible devices provide an advantage when it is desirable to allow dehumidification with outside air (winter ventilation of pools or other spaces with excessive humidity, for example). 10.1.2 Other Performance Requirements. Spe
48、cify additional performance ratings that may be applicable to the design such as pressure drop, EATR, and OACF. 10.1.3 Recovery Type. Specify either Heat Pipe Heat Exchanger, Plate Heat Exchanger, or Rotary Heat Exchanger that corresponds to the recovery performance and Effectiveness selected. 10.1.
49、4 Installation Type. Specify installation and application for AAERVE that is applicable for the recovery type selected. Example: Rooftop, indoor, coupled, unitized, etc. 10.2 AAERVE Design Information. 10.2.1 Balancing Method. Specify the method to be used for balancing the airflow of exhaust and supply (intake) air. Specify the airflows and locations for airflow measurement, including the impact of OACF and EATR on those flows. 10.2.1.1 Integrated systems should
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