SELECTION6PROCEDURE EXAMPLE
1.Determine cooling and heating requirements at design conditions. Example:
Total cooling capacity | 43,600 BTUH |
Sensible cooling capacity | 34,000 BTUH |
Heating capacity | 96,000 BTUH |
Condenser entering air | 95°F |
Evaporator entering air | 63°F wbt/76°F dbt |
Indoor air flow | 1600 CFM |
External static pressure | 0.6 in wg |
Required efficiency | 13 SEER |
2.Select unit to meet cooling requirements.
Since total cooling is within the range of 4 ton unit and
requires 13 SEER efficiency level, enter cooling performance from the TGC048C at 95°F outdoor temperature, 63°F wbt
entering indoor air, and 1550 CFM:
Total capacity | ....................................47,300 BTUH |
Power input | 3.5 kW |
And also, at 76°F db indoor entering air, and using the formula
at the bottom of the table: |
|
Sensible capacity | 41,708 BTUH |
3.Select heating capacity of the unit.
In the general data tables, note that the heating capacity of the 4 ton model with the 135,000 input heater can deliver 106,500
BTUH, which is suitable for this application.
4.Determine blower speed and power to meet the system
requirements.
At the given external static pressure of 0.6 in wg, the belt model must be selected. Enter the belt drive blower performance data at 1580 CFM and 0.6 in wg ESP:
Watts........635
5.Calculate indoor blower BTUH heat effect.
BTUH = Watts x 3.413 = 2168
6. Calculate net cooling capacities.
Net total cooling = 47,300 – 2168 = 45,132 BTUH
Net sensible cooling = 41,708 – 2168 = 39,540 BTUH
Heat Controller, Inc.