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The most common method to defrost appropriately in refrigeration involves both time for initiation and a combination of time and temperature for defrost termination (ending defrost). But why can't we just use temperature or time alone? (You may wonder.) Imagine a common freezer with a designed box temperature of -10°F and a coil temperature of […]

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HVAC School – For Techs, By Techs

Real training for HVAC ( Heating, Ventilation, Air Conditioning and Refrigeration) Technicians. Including recorded tech training, interviews, diagnostics and general conversations about the trade.

In this short podcast episode, Bryan talks about EER (Energy Efficiency Ratio) and SEER (Seasonal Energy Efficiency Ratio) and how to calculate EER in the field.

EER and SEER are ratings that we often see on equipment (as are SEER2 and EER2) based on a ratio of an output to an input. Whereas coefficient of performance (COP) is a direct ratio of watts out to watts in, EER and SEER account for BTUs and watts. EER and SEER indicate the cooling capacity (in BTUs) we get from the watts we put in.

The ratio changes based on field conditions, and EER2 and SEER2 have more realistic test conditions than EER and SEER (the static pressure for systems rated below 65,000 BTUs per hour was 0.1″wc for EER and SEER, and it is now 0.5″wc for EER2 and SEER2, which is much closer to average field conditions).

To determine EER, you have to figure out BTU production and stack it against your wattage. You’ll need to know your delta enthalpy (delta H), multiply it by the CFM, and then multiply the product of those by 4.5 to get your BTU output. A calculator on apps like measureQuick can help you find out your delta H, but you’ll need a proper wet-bulb temperature before you can do that. You can determine CFM with a TrueFlow grid or manufacturer’s blower charts.

Finding watts can be a challenge with ECMs and inverter-driven systems; it’s not as simple as volts x amps, and you will need a meter that can measure power factor and take readings from the condenser fan, compressor, and blower motor. That wattage becomes the number you divide into BTUs to get the EER. SEER is averaged over a season, HSPF is for heating instead of cooling, and you can convert the BTUs to watts (by multiplying by 3.41) and determine the ratio of watts out to watts in.

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