If you take proper measures before commencing a mapping study of a cold room, you can avoid chances of failure.
A temperature mapping study of a cold room is complicated since it has a lot of different tests and the satisfactory completion depends on a lot of factors.
Few of the reasons for the failure of a cold room are listed below:
1. There is a controller connected with sensors for the cooling units. The display unit of this controller may not be very accurate and display resolution is mostly 0.5 °C. What this means is that it will show 4 °C, 4.5 °C, 5 °C etc. and will not show the digits in between them. Also, the calibration of the same has to be done along with the corresponding sensor which does not happen properly. During the calibration of this device, the calibration company has to inject a current corresponding to a certain temperature and check whether the display shows the right temperature. Most of the time, this procedure is not done correctly. Hence what you see on the display may not be the right temperature. The result is that if the display shows the temperature at 4.5°C, it is very well possible that the temperature near the sensor will be 5.5°C or 3.5°C.
2. The racks and the loading pattern may not be properly designed to allow proper air flow. If there are any blocks in the path of the circular air flow within the room, the temperature distribution will not be proper.
3. Humidity is higher than the specified limit of 65% RH. This happens very often because humidity is not considered during the design stage. For all cold rooms, the temperature is likely to go to a very high level of humidity. It may reach levels of 90-95%. In order to reduce the humidity, you will have to consider dehumidifiers. Also, air curtains at the doors will help slightly in reducing the humidity. The humidity inside a cold room increases as soon as the door is opened. Once humidity increases, it doesn’t go out of the cold room and require dehumidifiers. There is a design calculation involved for selecting the right dehumidifier based on the size of the room, normal temperature, maximum humidity, desired humidity etc.
4. The positioning of the cooling units in relation to the position of the doors is important for proper retention of temperature. Most often, the HVAC contractors do not differentiate between the construction of a cold room for medicines and a cold room for fruits and vegetables. The design and installation of a cold room for medicines and vaccines require much more efforts since the auditing requirements are stringent.
5. If the defrost cycle of the cooling units are not programmed properly, the temperature retention can be affected. This is especially important if you have multiple cooling units in the same cold room. Air curtains may be required at the doors.
6. Installation of PVC strip curtains at the doors also will help in preventing the loss of temperature while opening the doors. This might be slightly inconvenient for a cold room with frequent door openings. However, this helps in preventing outside from entering into the cold room.
