What is a temperature/humidity controlled enclosure?
“Any device which provides a space in which temperature and/or humidity is controlled. Temperature controlled enclosures are designed to maintain a specific temperature and humidity within their working volume, and must not expose their contents to conditions beyond their tolerance limits. It is essential to verify that the enclosure is capable of meeting these tolerances. This is achieved by performing a temperature and humidity mapping of the working volume.” – NSAI Guide to Mapping Enclosures 2012.
What is ‘Mapping’?
Mapping refers to creating a temperature and humidity plan of an enclosure. Through placement of multiple temporary recording devices (dataloggers), a user is able to see the temperature and humidity for each chosen location of a room. This information can then be combined to allow comparisons of the consistency throughout an enclosure. Should the results of a mapping show inconsistencies between different locations, the maintenance team should be consulted. Options available include adjusting ducting or recalculating required number of air changes per hour. The enclosure should be remapped after any changes to the layout of the room or the equipment.
- Homogeneity: Most controlled enclosures will have two monitoring probes, continually feeding results back to a Central Monitoring System, from two set locations within the enclosure. A mapping provides this same information across a multiple of locations within the enclosure, and thus, ensures the Central Monitoring System reflects the conditions within the enclosure. If there are any ‘cold’ or ‘hot spots’ present, they will be immediately visible as the results from all dataloggers are compared.
- Environmental effects: Through the placement of an external datalogger, adjacent to the enclosure, variations in environmental temperature and humidity can be recorded. This information can be cross referenced with the internal results to check if the operating conditions are having an effect on the performance of a room.
- Assessment: Assess the layout and size of the room to calculate the number of dataloggers required. A 3 dimensional plan of the room,
detailing any shelving/racking can be a useful way of ensuring all working areas are being captured. Clearly mark each location on the map, recording the assigned datalogger to each location (seen right).
- Dataloggers: Once the number of dataloggers required is known, the correct datalogger must be chosen. If the room has temperature and humidity control, the datalogger must have the capability to record both. Calibration certificates for each datalogger must be provided, to confirm no certificate has passed its expiry date.
- Protocol: A protocol should be created detailing the enclosure to be mapped, duration of mapping, number of dataloggers and locations. The acceptance criteria should be clearly detailed, providing instructions on the steps to be followed, if the mapping is deemed to have failed.
- Final Report: When the mapping has been completed, a detailed report should be presented, either as a separate document or as an attachment to the protocol. Report should detail minimum, maximum and mean results for each datalogger, across the duration of the mapping. If possible all loggers should then be combined into one graph to clearly highlight any ‘outlier’ results.
- Recovery Rate: If required, door openings can be included into the mapping process. The protocol should allow for clear recording of the time and duration of door openings. The acceptance criteria will need to be adjusted to allow for this.
- Time to reach set conditions: For new or empty enclosures, mapping can be used to establish the time take from ‘power on’ to reach required set point.
A mapping should be completed on any temperature or humidity controlled equipment before it is introduced and used on site. It is advisable to continue to map all temperature and humidity controlled enclosures annually to ensure consistency of performance.