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Ambient Temperature Guide

Accurate ambient temperature readings are crucial to properly selecting an air conditioner for your sensitive electronic equipment. For the purpose of this selection process, “ambient temperature” refers to the temperature of the air in the environment immediately surrounding an enclosure. Both indoor and outdoor environments have a variety of factors that should be considered when determining the ambient temperature.

Measuring Indoors

Indoor, environmentally-controlled temperatures range from 65-77F/18-24C degrees in many cases, but on uncontrolled plant floors ambient temperatures can exceed 100F/38C. Indoor applications can also be exposed to additional heat sources that increase the ambient temperature. If an electronic enclosure is located near a furnace, compressor, engine, or other industrial equipment, the heat generated during operation will have a significant impact on the air temperature. For example, if the ambient temperature is typically 70F/22C but then rises to 90F/32C when industrial equipment is running, then 90F/32C is the maximum ambient temperature. Although it may only reach 90F/32C for one hour during an eight-hour day, it is recommended to use the worst-case scenario. The most accurate way to determine the maximum ambient temperature in an uncontrolled, indoor environment is to research the historic air temperatures in the space the enclosure will be located, during the hottest months of the year. The average high temperatures during this time period will serve as an accurate maximum ambient temperature for this specific environment. Do NOT add a safety factor to the temperature. It will result in oversizing the cooling requirement.

Measuring Outdoors

Outdoor ambient temperatures can vary significantly based on both the location, and time of year. It is recommended to research the temperature history of where the electronic enclosure will be located to obtain the most accurate ambient temperatures. Use historic averages to determine the typical high temperatures for cooling and lows if heating is required. Annual extreme highs and lows are usually infrequent and should only be considered if they are regularly occurring, or above the threshold of catastrophic failure. It is not recommended to use the all-time record high or low temperatures. Record temperatures are typically an anomaly and may only occur once every 20+ years. Another method of determining the ambient temperature is taking actual readings; however, the readings must be taken on the hottest day in the summer and coldest in the winter which may be difficult. When taking outdoor temperature readings use the actual temperature. It should not be based on relative humidity, wind chill, or “feels like” temperatures. Ambient temperature readings should also not include solar heat load, so it is important to measure the air temperature surrounding the enclosure and not the surface temperature of the enclosure. However, radiant heat can increase ambient temperatures. For example, an ambient temperature reading taken on a black rooftop will be higher than the ambient temperature taken on a light-colored surface at the same location. Darker colors absorb more sunlight while lighter colors reflect more of the sun’s radiant energy. Heat is then radiated from the darker surface, resulting in higher ambient temperatures in the immediate vicinity. As with indoor applications, do NOT add a safety factor to temperature readings.

Air Conditioners

  • Solid state thermoelectric air conditioners are ideal for high ambient environments. EIC Solution’s standard thermoelectric air conditioners are designed to operate in ambient temperatures up to 140F/60C. High ambient models are available for extreme environments up to 170F/77C. Thermoelectric air conditioners have numerous benefits including flexible mounting orientations, compact footprints, minimal maintenance, and longer life cycles compared to compressor-based systems. Ranging from 200BTU-5,500 BTU, the robust design of EIC’s thermoelectric air conditioners can withstand the harshest environments. Integrating these units to your sensitive electronic enclosures can avoid downtime and heat related failures due to high ambient temperatures.
  • Compressor-based air conditioners are rated to operate in temperatures up to 131F/55C and are available in 5,000BTU- 27,000BTU. This product line also offers select high ambient models rated to 135F/57C. Most outdoor environments around the world do not exceed 120F/49C, making the standard product a suitable solution for numerous applications. Due to their larger cooling capacity, compressor-based air conditioners are ideal for full-size electronic enclosures to protect your sensitive electronic equipment.

Capturing accurate ambient temperatures without adding a safety factor is essential to avoid oversizing your application. High ambient temperatures can lead to equipment downtime or failure, therefore, environmentally controlling the equipment is crucial. If you have sensitive electronics subject to extreme conditions and require assistance to determine the best solution, contact EIC Solutions’ knowledgeable sales engineers to review your application.