1、4749 A Survey Technique for Evaluating Heating, Vent i I at i n g , a n d Ai r-Co n d it i on i n g Sy s t e rn s H.W. Holder Member ASHRAE M.D. Larranaga, PhD Member ASHRAE W.S. Willis D.C. Straus, PhD S.C. Wilson, PhD ABSTRACT This paper presents a survey technique for rating HVAC systems. System
2、components are grouped into categories. The components inside the categories are numerically rated from 1.0 to 5.0 in terms of mechanical system maintenance, service performance, and operation ejiciency of the mechanical equipment. The component scores are averaged for each cate- gory. These scores
3、are then averaged to give a single score for the wholesystem. To evaluate the consistency ofsuweyratings, a trial was conducted whereby on the same day, ten indepen- dent assessors with different years ofjob experience examined a range of equipmentfrom two major HVACsystems (N = 200). A Cronbach S A
4、lpha Internal Consistency Analysis of the aver- aged ratings gave a result of 0. 76, indicatinggood agreement between assessors. These data show that apart from being able to reduce large datasets into a concise summary, the survey technique is robust and internally consistent. INTRODUCTION High ind
5、oor relative humidity is recognized as contribut- ing to known health effects due to the growth and spread of biological agents including dust mites, fungi, bacteria, and viruses (Baughman and Arens 1996). Inadequate humidity control can lead to increased illness and IAQ complaints in all buildings
6、and can foster the growth of mold on building surfaces (Arundel et al. 1986; Downing and Bayer 1993). This can lead to a number of indoor air quality (IAQ) issues, result- ing in poor occupant health and comfort and property damage. High humidity can arise fi-om a number of sources, such as the buil
7、ding envelope being compromised either through design issues or poor work practices, and other moisture events such as plumbing leaks. A major underlying factor for the occurrence of adverse health symptoms in the modern sealed building can be a poorly functioning or incorrectly designed heating, ve
8、ntilating, and air-conditioning (HVAC) system (Cooley et al. 1998). There- fore, the correct diagnosis of malfunctioning HVAC systems is important, particularly with regard to protecting occupant health and property and to avoid costly litigation associated with poor IAQ and humidity control (Fische
9、r 1996). One of the problems in describing malfunctioning systems is that there can be different systems in operation in a building, thereby making it difficult in terms of comparing their effectiveness. Further, large amounts of data are created, which can be diffi- cult to manage and interpret con
10、cisely for the client. This paper presents a new survey that was developed to create a systematic approach for the examination of HVAC systems and to reduce a large amount of HVAC system-related data into a manageable and straightforward summary. While the survey provides a methodical approach for e
11、valuating HVAC systems, it is important to know what degree of varia- tion might be expected between different assessors. Therefore, a trial was conducted whereby on the same day different asses- sors, who came from a variety of occupations and had different levels of experience, used the survey to
12、assess a large range of HVAC equipment. MATERIALS AND METHODS Survey Design The HVAC system is first broken down into categories. These are plant-level categories, such as chiller plant systems, hot water systems, and pump systems, and then delivery-level categories, such as air-handling units (AHU)
13、, rooftop units H.W. Holder, W.S. Willis, and M.D. Larranaga are with Assured Indoor Air Quality LP, Dallas, Texas. S.C. Wilson and D.C. Straus are at the Center for Indoor Air Research, Department of Microbiology and Immunology, Texas Tech University Health Sciences Center, Lubbock, Texas. 02005 AS
14、HRAE. 83 5 45 4 35 o z3 25 L 2 15 1 c Air-Handling Unit Condition of equipment Fans, motors, service O 2 4 6 8 10 12 14 16 18 20 service years Rating 3.0 3.5 Figure I Rating scores from an HVACsurvey compared to the estimated service life ofHVACsystem components. The average rating of 3.0 represents
15、 the expected score for well-maintained equipment. Condensate systems, drains, pans, etc. Outside air systems: dampers, operation, etc. Table 1. Typical Survey Table Showing Categories and Components with Ratings within the Categories 4.0 3.9 Heating systems: hot water, electric, gas Heating systems
16、: preheat, reheat, mixing, etc. AVERAGE I Coils, filters, belts. gauges, alarms, service I 3.3 2.5 2.9 3.3 Return Air Unit, Direct Expansion Compressors, charges, operation Condition of equipment 3.0 3.5 Coils, filters, belts, gauges, alarms, Condensate systems, drains, pans, etc. I Fans, motors, se
17、rvice I 3.8 3.1 4.4 Heating systems: hot water, electric system AVERAGE 1 Outside air systems: damuers. oueration. etc. 1 4.0 3.3 3.6 (RTU), and direct expansion (DX) and fan coil units (FCU) (Katipamula et al. 2001). These categories then have compo- nents that are to be examined listed inside them
18、. These include, but are not limited to, fans, motors, coils, filters, belts, gauges, alarms, condensate system drains and pans, outside air dampers, electrical wiring, compressors, etc. Table 1 shows a typical category table with accompanying scores. Numerical scores on a scale from 1 .O to 5.0 are
19、 applied to the components. The scores are not limited to whole numbers (e.g., a score of 2.4 or 3.6 can be given). The assessor evaluates the equipment using these numbers in terms of mechanical system maintenance, service performance, and operation effi- ciency of the mechanical equipment with reg
20、ard to energy managementhuilding automation systems. Benchmark scores for ratings are as follows: 1. 1 .O: New equipment or systems, in warranty, and/or correct intended operating condition. 2.0: Exceptionally maintained for equipment of its age and is operating as intended and designed. 3.0: Mainta
21、ined, good condition, and fully functional for equipment age, operating as intended. Preventive mainte- nance is required to maintain present status. 4.0: Neglected and/or not maintained. Repairs and substan- tial work are required by skilled technicians for the restora- tion of equipment to serve t
22、he intended purpose. Life-cycle costs should be considered to determine if repair or replace- ment is appropriate before committing substantial funds for restoration. 5.0: Nonfunctional and needs replacement. These scores were derived from the ASHRAE Hand- book-HVAC Applications (ASHRAE 2003). Figur
23、e 1 shows the relationship ofthe scores to the service life of a component. Reliability of components as compared to equipment age influences the curve during the early and late years of the expected service life. An overall rating called the HVAC Component Mean Evaluation (HVAC CME) is then generat
24、ed from the compiled ratings. In this procedure the scores on each component are averaged to give a score for the HVAC system category. Cate- gory scores are then in turn averaged to give an overall mean score for that particular HVAC system. Different categories can be weighted to reflect their imp
25、ortance in the HVAC system. For example, a rating for a chiller system can be given more weight than a rating for a fan coil unit. This rating can be based on value, importance to operation of the HVAC system, and cost of replacement. 2. 3. 4. 5. 84 ASHRAE Transactions: Research Table 2. Mean Rating
26、s from an Investigation of the HVAC System of One School By Up to Ten Assessors Using a New Survey Rating System* RTUDX-AHU# 135 FCU UNIT # 4 4.1 4.3 3.1 3.7 4.0 4.5 3.6 3.9 0.09 5 3.7 3.0a 3.0a 4.3 3.2 a 3.4 0.19 5 Survey Eva1 uat ion A trial was set up whereby ten assessors evaluated 200 component
27、s from two major HVAC systems that were situated in two different geographical locations on the same day. Professionals from three independent companies were the assessors. To determine if there was a range of operating conditions in the HVAC equipment, the authors had previously evaluated the compo
28、nents. Components were found to range between scores of 1 .O and 5.0. The assessors were technicians with varying degrees of expertise in either HVAC mechanical or HVAC control systems or indoor air quality technicians. Experience of the assessors ranged from 4 to 40 years. A two- hour informational
29、 session was provided to the assessors, which was intentionally designed to introduce the survey form without implying what ratings should be assigned during the inspections. During the two-hour session, assessors were instructed as to which equipment was to be surveyed, told not to collaborate with
30、 each other, and told to stay within the confines of their expertise and principles of the survey system. Statistical Analysis Component scores for each category were averaged to give an average category score per assessor. Category means across assessors were then analyzed using a one-way analysis
31、of variance (ANOVA) after the data had been checked for normality and equality of variance. A Tukey post-hoc analysis was performed on all significant results (Sigma Stat 2.03 SPSS, ILL). A Cronbachs Alpha Internal Consistency anal- ysis was conducted on the ratings given by the assessors. This proc
32、edure provides a measure of rating reliability (SAS 8.2, North Carolina). RESULTS The results for the trial are shown in Tables 2 and 3. Table 2 presents expanded data, whereas Table 3 presents a more concise summary. Results from Table 2 demonstrate that there were signif- icant differences between
33、 assessors (P 0.05) for 9 of the 1 1 categories examined. In these nine categories, a trend was evident whereby assessors 6 and 7 who had the most experi- ence (around 40 years) assigned higher ratings to the equip- ment than assessor 5 with four years of experience.The results of assessors 6 and 7
34、on the first two surveyed AHUs showed that higher scores were applied to the three subcategories of (1) fans, motors, service, (2) coils, filters, belts, gauges, alarms, etc., and (3) condensate systems, drains, pans, etc. These higher scores increased their average score for that cate- gory. The re
35、sult from the Cronbachs Alpha Internal Consis- tency analysis was 0.76, indicating a good agreement between assessors. Table 3 shows that for 10 of 13 categories there were significant differences between assessors. The average range between assessors in these categories was 2.7-3 3. The overall CME
36、 for both school HVAC systems was 3.3. In this exercise, weightings were not applied to the categories or components. DISCUSSION The higher scores given by the more experienced asses- sors may be due to the fact that these assessors paidmore atten- ASH RAE Transactions: Research 85 RTU/DX Unit 3 RTU
37、/DX Unit 10 FCU Unit 8 FCU Unit 3 FCU Unit 10 AHU = air-handling unit, RTUiDX = return air-handling unit, direct expan- sion, FCU = fan coil unit. A P value of greater than 0.05 indicates that there are no significant differences between means at the 0.05 level. SE = standard error. N= number of ass
38、essors rating the equipment. tion to smaller details inside the categories and therefore saw more components that were not functioning optimally. The design of the survey is such that this issue can be overcome to a degree through the addition ofmore subcategories inside the major categories, allowi
39、ng for less experienced assessors to check these smaller details. Other checklists have been developed for HVAC systems; for example, Persily (1 993) presented a method whereby the HVAC system is inspected as part of an overall building system and most standard texts provide detail on HVAC fault ana
40、lysis (e.g., Kreider 2001). This survey technique differs from these other approaches in that it provides a numerical output that helps in providing a concise interpretation as to the status of the HVAC system. Katipamula et al. (2001) list five requirements for meth- ods of HVAC predictive maintena
41、nce, and these requirements have application to this survey. The requirements are that (1) the system must identify abnormal systems accurately, (2) the system must not give false alarms, (3) the system must report the levels of confidence associated with each diagnosis, (4) the system must rank the
42、 conclusions, and (5) the system must be able to cope with insuficient data. The format and nature of the survey addresses requirements 1, 4, and 5. However, requirements 2 and 3 are dependent on the skill and experience of the assessor. To evaluate a building in terms of sick building syndrome (SBS
43、) status, an indoor occupational survey in conjunction with an overall building inspection and this HVAC survey can provide the basis for a comprehensive assessment. Many stud- 3.4 0.10 0.05 10 3.4 0.11 0.05 10 3.1 0.10 0.001 5 3.2 0.10 0.001 6 3.2 0.10 0.001 6 ies have shown the association between
44、 poor HVAC operation and indoor air quality. For example, Seppanen and Fisk (2002) have shown that air conditioning can be consistently associ- ated with a statistically significant increase in the prevalence of SBS symptoms. Hiipakka and Bufington (2000) reported on the critical role that HVAC syst
45、ems play with regard to reducing fungal numbers in indoor environments, and Pejtersen et al. (2001) detailed an intervention study that involved the renovation of an HVAC system, consequently leading to significantly reduced complaints from the occu- pants. This association has been reported for som
46、e time. For example, Rask and Lane (1989) reported that improving HVAC maintenance procedures in conjunction with other housekeeping procedures will lead to improved indoor air quality. CONCLUSION This paper presents a survey technique for evaluating HVAC systems. The technique is methodical and fle
47、xible, has strong internal consistency, and appears able to be success- fully used by a wide range of assessors. ACKNOWLEDGMENTS Dr. Wilson and Dr. Straus were supported by Center of Excellence Research Grant in Indoor Air by Texas Tech University Health Sciences Center. Mr. Holder, Mr. Willis, and
48、Dr. Larraaga, were supported by Assured Indoor Air Quality LP of Dallas, Texas. REFERENCES ASHRAE. 2003.2003 ASHRAE Handbook-HVAC Applica- tions, p. 36.3. Atlanta: American Society of Heating, Refrigerating and Air-conditioning Engineers, Inc. Arundel, A., E.M. Sterling, J.H. Bggin, and T.D. Sterlin
49、g. 1986. Indirect health effects of relative humidity in indoor environments. Environmental Health Perspec- tives 65:351-361. Baughman, A.V., and E.A. Arens. 1996. Indoor humidity and human health, Part 1: Literature review of health effects of humidity-influenced indoor pollutants. ASHRAE Transactions 102( I): 193-2 1 1. Cooley, J.D., W.C. Wong, C.A. Jumper, and D.C. Straus. 1998. Correlation between the prevalence of certain fungi and sick building syndrome. Occup. Environ. Med. 55:579-584. Downing, C.C., and C.W. Bayer. 1993. Classroom indoor air quality vs. ventiIation rate. ASHRAE T
