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Conversions and General info:
1 watt = 3.4 BTUH
1 HP = 746 watts = 2,545 BTUH
12,000 BTUH = 1 ton of refrigeration
400 CFM per ton nominal
Volts X Amps = watts (single phase)
Volts X Amps X 1.73 = watts (three phase)
Watts X 3.4 = BTUH
Chilled water coils usually require between 2 and 3 GPM per ton for cooling.
Make-up air = 1.08 x CFM x Delta T
Ventilation / Indoor Air Quality = 1.08 x CFM x Delta T, 20 CFM per person OSA
Determining Cooling Loads:
This information is for sensible (dry) cooling only.
Wet processes or Humidity requirements need special consideration not included in this information!
Calculations:
Number of lights – (96 watts for 3 bulb fixture)
Number of HEPA filters - (1065 BTUH for 115 volt Mac 10 filter)
Envelope load – wall and roof construction and materials, window size and type, unconditioned
adjacent spaces, etc.
Process equipment – List from Customer with voltages and amp draws is best.
Not Nameplate info.This number will be too high and the air conditioning will be oversized.
(Use a multiplier of .5 to .65, if nameplate is only number available.)
PC’s = approx. 350 watts each.
Workstations = approx. 500 watts each.
Exhaust requirements – Quantify amount of exhaust.
Air to make-up for exhaust will usually increase heat load significantly.
Diversity factor – How much of the time is process equipment running?
People – 250 BTUH sensible, 230 BTUH latent. (at rest or light duty)
Approximately 80% of the capacity of packaged air conditioning equipment
is available for sensible cooling. (Not 100%) |
