1. Best Direction System Ltd.
Humidity Control Concept
Hot Gas Reheat,
Hot Gas Bypass,
VSD &
DDC Controls System
For DX & CHW Coil
By :
Best Direction System Ltd.
Humidity Control Concept

2. Absolute humidity (g/kg of dry air) Dry air 1.225 kg/m3
What is humidity ?
Absolute humidity
(g/kg of dry air)
Dry air kg/m3
Relative humidity
(%RH)
Humidity Control Concept

3. What is humidity ? Humidity Control Concept Kg/kg of dry air oC 40 150
125 30
Humidity Control Concept
100
Humidity Ratio
Latent Heat Factor 20
Temperature WB 50 10 25 10 20 30 40 oC
Temperature DB
Sensible Heat Factor

4. Relative Humidity Humidity Control Concept 40 30 Humidity Ratio
100%RH
Humidity Ratio
Latent Heat Factor
75%RH 20
50%RH
Temperature WB 10 10 20 30 40 oC
Temperature DB
Sensible Heat Factor

5. Psychrometric Chart 100%RH 50%RH 25%RH 25oC 60%RH DP 16.7oC DP 13.9oC
Vap Pressure kPa
25oC 60%RH
DP 16.7oC
50%RH
DP 13.9oC
25oC 50%RH
25%RH

6. Humidity Effect For Human Being

7. Appropriated Humidity For Various Application
Humidity Control Concept

8. Process of the Air Humidity Control Concept Humidification Cooling
Heating
Dehumidification

9. COOLING MODE HEATING MODE DEHUMIDIFYING MODE HUMIDIFYING MODE
Temperature & Humidity Controls Function
CONTROLS FUNCTION
COOLING MODE
HEATING MODE
DEHUMIDIFYING MODE
HUMIDIFYING MODE
Humidity Control Concept

10. No. Of occupancy & Activity Electrical power appliances
Heat Load Factor
Solar Heat Gain
Wall transmission
Temp. Diff.
No. Of occupancy & Activity
Activity
Internal heat source
Electrical power appliances
Infiltration
ETC.
Humidity Control Concept

11. Heat Load Factor
Solar Heat Gain
Humidity Control Concept

12. Heat Load Factor
Wall Transmission
Humidity Control Concept

13. Heat Load Factor
Occupacy Heat Load
Humidity Control Concept
1,000 BTU

14. Heat Load Profile Selected A/C @maximum range Heat Load (Tons)
Humidity Control Concept
Heat Load (Tons)
Hour of Day

15. Heat Load Profile (Winter)
Cooling
Humidity Control Concept
Heat Load (Tons)
Heating
Hour of Day

16. Sensible Heat (Hs) Latent Heat (HL)
System Cooling Load
Sensible Heat (Hs)
Latent Heat (HL)
Humidity Control Concept

17. Hot Gas Reheat Coil Hot Gas Reheat Coil Energy Saving>30%
Humidity Control Concept
Hot Gas Reheat Coil
Energy Saving>30%
SYSTEM DESIGN

18. Compressor Discharge Gas Temp.
Humidity Control Concept

19. Compressor Discharge Gas Temp.
Humidity Control Concept

20. Hot Gas Reheat Coil
Humidity Control Concept
Energy
Saving
>30-40%

21. Hot Gas Reheat Coil Saving Criteria
Heater
HGR
Annual Energy Cost
Humidity Control Concept

22. Hot Gas Bypass System Hot Gas Bypass System (HGBP)
Humidity Control Concept
Hot Gas Bypass System (HGBP)
Prevents often of compressor cycling on/off and maintains
a very constant of humidity control level.

23. Completted Refrigerant Circuit
Humidity Control Concept
Refrigerant Diagram

24. Controls System
Humidity Control Concept

25. Controls System
Humidity Control Concept

26. Advanced Controls System
Advanced cooling capacity management
with compressor & fan variable speed control drive
lets us manage widely range of system partial
heat load 40%-100% without recycling of
compressor.
Humidity Control Concept

27. Reheat Application For Chilled Water System
Hospital Laboratory Concept
Saving by Nothing to Invest.

28. VFD Retrofit Consideration
Refrigerant Side
Humidity Control Concept

29. Refrigerant Side VFD Retrofit Consideration
Hermetic/Semi-hermetic reciprocating compressors
Refrigerant Side
Humidity Control Concept
Recommended Frequency Range Hz

30. Refrigerant piping sizing to improve capacity
VFD Retrofit Consideration
Refrigerant Side
Refrigerant piping sizing to improve capacity
at minimum and maximum speed.
High suction superheat gas <25oC.
Compressor oil reclaim system.
Refrigerant flood back to compressor.
Maximum and minimum capability of each
compressor type
Humidity Control Concept

31. Controls “POINT”
Humidity Control Concept

32. Controls System
Humidity Control Concept

33. Controls System Controls Network Diagram (Option)
Humidity Control Concept
Controls Network Diagram (Option)

34. Conventional Air Conditioner
Room Temp. & Humidity Controls
Conventional Air Conditioner
Biosafety Laboratory Concept
Humidity Control Concept

35. Air Conditioner with Humidity Control System
Room Temp. & Humidity Controls
Air Conditioner with Humidity Control System
Biosafety Laboratory Concept
Humidity Control Concept