ASHRAE-Standard-55 - Page 025
Extracted Content
Table 7-1 Instrumentation Measurement Range and Accuracy
| Quantity | Measurement Range | Accuracy |
|---|---|---|
| Air temperature | 10°C to 40°C (50°F to 104°F) | ±0.2°C (0.4°F) |
| Mean radiant temperature | 10°C to 40°C (50°F to 104°F) | ±1°C (2°F) |
| Plane radiant temperature | 0°C to 50°C (32°F to 122°F) | ±0.5°C (1°F) |
| Surface temperature | 0°C to 50°C (32°F to 122°F) | ±1°C (2°F) |
| Humidity, relative | 25% to 95% rh | ±5% rh |
| Air speed | 0.05 to 2 m/s (10 to 400 fpm) | ±0.05 m/s (±10 fpm) |
| Directional radiation | –35 W/m2 to +35 W/m2 (–11 Btu/h·ft2 to +11 Btu/h·ft2) | ±5 W/m2 (±1.6 Btu/h·ft2) |
b. Height above floor: Air temperature and average air speed Va shall be measured at the 0.1, 0.6, and 1.1 m
(4, 24, and 43 in.) levels for seated occupants at the plan locations specified in Section 7.3.2(a)(1) and Section 7.3.2(a)(2). Measurements for standing occupants shall be made at the 0.1, 1.1, and 1.7 m (4, 43, and 67 in.) levels, and measurements for horizontal occupants shall be made at the mean height of the body. Operative temperature to or PMV shall be measured or calculated at the 0.6 m (24 in.) level for seated occupants, the 1.1 m (43 in.) level for standing occupants, and the mean height of the body for horizontal occupants. Floor temperature that may cause local discomfort shall be measured at the surface by contact thermometer or infrared thermometer (Section 5.3.5.5).
Radiant temperature asymmetry that may cause local thermal discomfort (Section 5.3.5.2) shall be measured in the affected occupants’ locations, with the sensor oriented to capture the greatest surface temperature difference. 7.3.3 Timing of Physical Measurements. Measurement periods shall span two hours or more and, in addition, shall represent a sample of the total occupied hours in the period selected for evaluation (year, season, or typical day) or shall take place during periods directly determined to be the critical hours of anticipated occupancy.
Measurement intervals for air temperature, mean radiant temperature tr, and humidity shall be five minutes or less, and for air speed shall be three minutes or less.
Assessment of control measures for occupant control of environmental factors shall be evaluated for compliance with the requirements of Section 6.1.1, including accessibility, time response, and magnitude of PMV influence.
7.3.4 Physical Measurement Device Criteria. The measuring instrumentation used shall meet the requirements for measurement range and accuracy given in Table 7-1. Air temperature sensors shall be shielded from radiation exchange with the surroundings.
7.3.5 Measurements from Building Automation System (BAS) 7.3.5.1 Location. BAS space sensor locations shall be evaluated against the location criteria in Section 7.3.2. 7.3.5.2 Precision. BAS space temperature sensor accuracy shall be 0.5°C (1°F) or less, and space humidity sensor accuracy shall be ±5% rh.
7.3.5.3 Trending Capabilities. The BAS shall have the ability to trend space temperature data at intervals not exceeding 15 minutes over 30 days or longer.
7.3.5.4 Additional Concurrent Data. Data such as equipment status, supply and return air, and water temperatures shall be observed for time periods concurrent with the space temperature data. 7.4 Evaluation Methods 7.4.1 Evaluation Based on Survey Results
a. The percentage of occupants satisfied shall be calculated from seven-point satisfaction survey scores by
dividing the number of votes falling between +1 and +3, inclusive, by the total number of votes. Responses to diagnostic dissatisfaction questions shall be tallied by category. b. For point-in-time surveys, comfort shall be evaluated using votes on the satisfaction and/or thermal sen sation scales. On the satisfaction scale, votes between +1 (slightly satisfied) and +3 (very satisfied), inclusive, shall be divided by total votes to obtain the percentage of thermal satisfaction observed during the survey period. On the seven-point thermal sensation scale, votes between –1 and +1, inclusive, shall be divided by total votes to obtain the percentage of thermal satisfaction observed during the survey period.
ANSI/ASHRAE Standard 55-2023 23