How to Ensure Accurate Temperature Control in an Enclosure
Although electrical control equipment generally operates over a relatively wide temperature range, sometimes it’s best if the operating temperature is tightly controlled. The reason for this is that the wide temperature cycling that can occur in an enclosure may be detrimental to the equipment, and the output of carefully calibrated control devices could vary if the temperature variations are excessive.
If required, it is possible to achieve very accurate temperature control in an enclosure. This can be achieved as follows.
Prerequisites for Accurate Temperature Control
There are five prerequisites that need to be considered in order to achieve accurate temperature control in an electrical enclosure. These are:
- Active temperature control: It is essential that an active cooling solution is employed that can remove heat from the enclosure, especially when the external temperature is high. The most effective and efficient way is to use an enclosure air conditioner
- Closed loop cooling: A closed loop cooling solution allows for a completely closed enclosure where there is no contact with the outside air. The enclosure is sealed and the air circulates through the air conditioner evaporator coil.
- Correctly sized air conditioner: The air conditioner should have sufficient capacity to cope with the heat load under all conditions but not be too large because this will cause frequent and detrimental cycling. An online enclosure temperature management calculator helps users select the correctly sized unit.
- Proper enclosure sealing: The enclosure should be properly sealed. The doors should close and seal effectively, there should be no other openings, and conduit and cable entry points should be sealed to prevent air leakage. A NEMA Type 12, 4 or 4X enclosure meets these requirements.
- Digital temperature controller: A high quality digital temperature controller should be installed with precise control capability.
Ensuring Accurate Temperature Control
Assuming the above prerequisites are met, accurate temperature control of an electrical enclosure is possible. For the greatest accuracy, look for an air conditioner with a programmable digital temperature controller. Frequently, the controller is surface mounted on the air conditioner housing, where the enclosure internal temperature and any alarms can be readily observed. Alternatively, it can be remotely installed inside the electrical enclosure where it is safe from unauthorized access and tampering. The standard temperature controller will control the enclosure temperature to within plus or minus 2.5 °F around the set point, and its temperature sensor is mounted at the air conditioner air return.
Special Control Features
Depending upon specific requirements, a number of special features and options are available, and these include:
- Cooling set point adjustment: The standard set point is 90 °F, but by accessing programming parameters on the digital controller it can be adjusted between 70 °F and 95 °F to suit special needs.
- Adjustable cooling hysteresis: The standard setting is 5 °F, giving a plus or minus 2.5 °F temperature variation. This can be adjusted down to 1 °F if required, although it should be noted that this will cause the air conditioner to cycle more frequently.
- Heating: If it’s important to minimize temperature variations, the optional integrated heater package will maintain the enclosure temperature during cool weather. It is controlled by the digital controller and is set to come on at 52 °F and switch off at 55 °F. The set temperature is adjustable as is the temperature hysteresis range.
- Adjustable temperature probe: If more accurate temperature control at a specific location inside the enclosure is required, an optional adjustable temperature probe can be located inside the electrical enclosure to monitor the temperature.
- Temperature alarm: The controller can be specified with a gold plated dry contact that will operate at 105 °F to indicate that the temperature has exceeded the high temperature alarm setting. This setting is adjustable.
- Remote monitoring and control: Either a PLC-connected or PC-connected remote monitoring and control facility can be ordered that will monitor the status of enclosure air conditioner, identify any alarms and allow remote control.
Thermal Edge enclosure air conditioners are designed to cope with the most arduous conditions, and provided they are correctly sized, will accurately maintain the temperature of an electrical enclosure. For further information, please speak to one of our Support Team members who can advise on the best temperature control solution for your application.