COOLING EQUIPMENT SELECTION

COOLING EQUIPMENT SELECTION

 Tables 7-4 and 7-5 show equipment charts for two sample air conditioning units. Each system provides a wide range of outputs, depending on the blower speed and the temperature conditions. The SHF (Sensible Heating Fraction) is the fraction of the total output that cools down the air temperature. The remainder    of the output dehumidifies the air and is the latent cooling. Note that both systems provide about 36,000 Btu/hour of cooling.

Consider System A (Table 7-4) with 80°F return air :

¾      At low fan speed, System A provides 35,800 Btu/hour, 0.71 SHF, and thus 29% latent cooling (dehumidification).

¾      At high fan speed, System A provides 38,800 Btu/hour, but a 0.81 SHF, and only 19% latent cooling. This is not enough dehumidification in many Kentucky homes.

Table 7-4 Sample Cooling System A Data,
Total Air Volume (cfm)	Total Cooling Capacity (Btu/h)	Sensible Heating Fraction (SHF)
		Dry Bulb (°F)
		75°F	80°F	85°F
950	35,800	0.58	0.71	0.84
1,200	37,500	0.61	0.76	0.91
1,450	38,800	0.64	0.81	0.96

Consider System B (Table 7-5) with 80°F return air:

¾      At low fan speed, System B provides 32,000 Btu/ hour, 0.67 SHF and 33% dehumidification.

¾      At high fan speed, System B provides 35,600 Btu/hour, 0.76 SHF and 24% dehumidification.

Table 7-5 Sample Cooling System B Data
Total Air Volume (cfm)	Total Cooling Capacity (Btu/h)	Sensible Heating Fraction (SHF)
		Dry Bulb (°F)
		75°F	80°F	85°F
950	32,000	0.56	0.67	0.78
1,200	34,100	0.58	0.71	0.84
1,450	35,600	0.61	0.76	0.90

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