ANSI/AHRI standard 420-2008 for fan and coil evaporators - benefits and costs
Fan and coil evaporators as used in the industrial refrigeration industry can be certified for performance per ANSI/AHRI Standard 420-2008, Performance Rating of Forced-Circulation Free-Delivery Unit Coolers for Refrigeration. This paper will explain how the standard works and illustrate the costs related to evaporators that may not meet the performance criteria of the standard.
ANSI/AHRI standards benefit the HVAC and Refrigeration industry by ensuring the performance and efficiency of manufactured equipment is accurate and reliable. These standards are produced by the Air-Conditioning, Heating and Refrigeration Institute and its member companies under ANSI guidelines. There are numerous standards for many different types of HVAC equipment. For instance Standard 410 is for fin and tube air heating or cooling coils only without an attached fan and standard 510 is for positive displacement ammonia compressors. AHRI Standard 490 and Cooling Technology Institute (CTI) Standard 106 both cover aspects of evaporative refrigerant condensers which also can be thermally certified under CTI Standard 201, Thermal Performance Certification of Evaporative Heat Rejection Equipment. The standards typically define testing criteria and the associated instrumentation tolerances for various operating conditions and set the minimum and maximum acceptable capacity and power deviations. When a manufacturer states that a product line is per a certain ANSI/AHRI or CTI standard, then that manufacturer is subject to having a random production unit tested by an independent laboratory to confirm the product performs per its factory rating.
Standard 420-2008 applies to refrigerant fed evaporators, of either the direct expansion or liquid overfeed type.
There are five standard rating conditions as listed below:
Condition #1 Wet Coil 50 °F 75% RH air on with a 35 °F refrigerant evaporating temperature
Condition #2 Dry Coil 50 °F less than 45% RH air on with a 35 °F refrigerant evaporating temperature
Condition #3 Dry Coil 35 °F less than 50% RH air on with a 25 °F refrigerant evaporating temperature
Condition #4 Dry Coil 10 °F less than 46% RH air on with a 0 °F refrigerant evaporating temperature
Condition #5 Dry Coil -10 °F less than 43% RH air on with a -20 °F refrigerant evaporating temperature
When an evaporator is marketed, it will have two published ratings, one of the 5 standard rating conditions above and the application rating, reflecting the actual operating condition, if different than the closest standard rating condition.
To pass the performance test, an evaporator must meet the applicable standard condition rating per section 5.3, which states:
“Tolerances. To comply with this standard, any representative production unit selected at random, when tested at the Standard Rating Conditions, shall have a Gross Total Cooling Effect not less than 95% of its published Standard Rating and not exceed 105% of its Rated Power”.