HVAC engineers

  HVAC Design for Clean Rooms - Hospitals & Pharma 1. Clean Room Classifications (ISO & GMP)  Classification Max. Particles ≥0.5µm / m³ Typical Use ISO 5/ Class 100 3,520 OT, IV Room ISO 7/ Class 10,000 352,000 Compounding Area ISO 8/ Class 100,000 3,520,000 Packing Area 2. Air Changes Per Hour (ACH) Room Type Recommended ACH Operation Theater (OT) 20-25 ICU/NICU 15-20 Cleanrooms ISO 7 60-90 Cleanrooms ISO 8 15-20 Example: Room Volume = 5 m x 5 m x 3 m = 75 m³ ACH = 25 Airflow = (25 x 75)/60 = 31.25 CMM ≈ 1100 CFM 3. HEPA Filter Design HEPA Efficiency: ≥99.97% @ 0.3µm 1 HEPA filter (24"x 24") handles ~500 CFM OT needing 1000 CFM Use 2 filters 4. Room Pressure Differential Area Type Pressure Difference OT vs Corridor +10 to +15 Pa ICU vs Corridor +5 to +10 Pa Isolation Room -10 to-15 Pa 5. Laminar Airflow (LAF) Velocity: 90 ± 20 ft/min (0.45 ± 0.05 m/s) Area: ~9 ft x 6 ft above OT table 6. Humidity & Temperature Control Area Temp (°C) RH (%) OT 21-24 50-60 ICU / Pa...

  HVAC MEP Thumb Rules & Formulas (With Examples) 1. Heat Load Calculation  Formula: Q = Area (sq.ft) x Heat Load Factor (BTU/hr per sq.ft) Example: 500 sq.ft office: Q = 500 x 30 = 15,000 BTU/hr TR = 1.25 2. CFM Calculation Formula: CFM = Sensible Heat (BTU/hr) / (1.08 x Delta T) Example: 12,000 BTU/hr, Delta T = 20°F CFM = 556 3. AHU/FCU Sizing Rule: 1 TR = 400 CFM 2 TR Airflow = 800 CFM 4. Duct Sizing Velocity Limits: Main: 1400-1800 FPM 800 CFM @ 1000 FPM 0.8 sq.ft 14"x10" 5. Chilled Water Flow Rate Formula: GPM = BTU/hr / (500 x Delta T) Example: 24,000 BTU/hr GPM = 4.8 6. Pipe Sizing 1" pipe: 8-12 GPM 2" pipe: 30-40 GPM 35 GPM Use 2" 7. Chiller Sizing Formula: TR = BTU/hr / 12,000 Example: 60,000 BTU/hr → 5 TR 8. Cooling Tower Sizing Rule: Heat Rejection = 1.25 x Load 10 TR → Tower = 12.5 TR 9. Pump Head Calculation Formula: Power (kW) = (Q x H x 9.81) / (Efficiency x 1000) Example: Q = 5 L/s, H = 20 m, Efficiency = 0.75 Power 1.31 kW 10. Fresh Air Re...

  VALVES USED IN A CHILLER SYSTEM AND THE TYPICAL VALVE PACKAGE 1.Chilled Water Side Valves ⇒Isolation valve (manual/electric actuated). ⇒ Installed on CHW supply and return lines.  ⇒ Used to isolate chiller for maintenance. 2. Balancing Valve (Manual or Automatic)  ⇒ Ensures correct flow rate to/from chiller.  ⇒ Helps maintain Delta T and proper flow distribution.  ⇒ Located after evaporator outlet (return line). 3. Differential Pressure Bypass Valve (if 2-way valves in system)  ⇒ Prevents excess pressure build-up when terminals shut.  ⇒ Maintains flow through chiller. 4. Flow Switch  ⇒ Senses chilled water flow across evaporator.  ⇒ Safety interlock: trips chiller if flow is lost.  ⇒ Usually paddle type or electronic. 5. Air Vent Valve (Manual or Automatic)  ⇒ Removes air pockets.  ⇒ Placed at high points of piping and chiller headers. 6. Drain Valve  ⇒ For flushing, cleaning, and maintenance.  ⇒ Located at low poin...

CHILLER CONTROL PARAMETERS 1.Chilled Water Supply Temperature (CHW Supply Temp) ⇒ Setpoint usually 6–7°C.  ⇒ Maintained by controlling compressor operation and refrigerant flow.  ⇒ Impacts building cooling efficiency directly. 2.Chilled Water Return Temperature (CHW Return Temp)  ⇒ Normally around 12–14°C from building side.  ⇒ Indicates cooling load — higher return temp = higher demand. 3.Delta T (Temp Difference)  ⇒ CHW Return – CHW Supply. Ideal: 6–8°C.  ⇒ Lower delta T = flow too high or load too low.  ⇒ Important for energy optimization and sizing. 4.Chilled Water Flow Rate  ⇒ Must meet minimum flow for evaporator (to avoid freezing).  ⇒ Controlled by VFD pumps, 2-way valves, or bypass lines.  ⇒ Flow switch protects evaporator from dry run. 5.Evaporator Pressure & Temperature   ⇒ Used to monitor refrigerant evaporation process.  ⇒ Sudden drop = low refrigerant or blocked flow.  ⇒ Used to trip chiller on low pressu...

  CHILLER WORKING PRINCIPLE – SIMPLIFIED A chiller removes heat from water to produce chilled water for air conditioning. It works on the refrigeration cycle — just like your fridge, but bigger and more complex. Step-by-Step Process: 1. Evaporator  → Warm return water from the building enters the evaporator.  → The refrigerant absorbs this heat and evaporates.  → Now you get chilled water (~6–7°C) sent back to AHUs/FCUs.  2. Compressor  → Vaporized refrigerant is compressed, increasing its pressure and temperature.  → This step consumes the most power. 3. Condenser  → The hot, high-pressure refrigerant releases heat to air (in air-cooled) or water (in water-cooled).  → The refrigerant condenses back into liquid. 4. Expansion Valve  → The liquid refrigerant passes through an expansion valve.  → Pressure drops, temperature drops.  → It’s now ready to absorb heat again in the evaporator. This cycle repeats continuously.

Chiller Installation Requirements. 1. Foundation & Mounting ⇒ Concrete Plinth/Base: Should be flat, leveled, and minimum 150 mm above FFL.  Designed to take dead load + dynamic load of the chiller. Ensure plinth length/width matches OEM mounting dimensions. ⇒ Vibration Isolators:  Use spring isolators or neoprene pads below the chiller to reduce vibration and structure-borne noise. For rooftop units, include seismic restraints if required by local codes. 2. Piping Arrangements ⇒ Chilled Water Lines Inlet & Outlet properly labeled.  Use flexible rubber bellows at inlet/outlet to absorb vibration and thermal expansion. Provide isolation valves, y-strainer, and flow switch. Install thermometers & pressure gauges at inlet and outlet for monitoring. Ensure correct pipe supports as per spacing schedule to avoid sagging. ⇒ Condenser Water Lines (for water-cooled only) Similar provisions as above.  Ensure proper sloping and venting. Include chemical dosing point,...

WHAT IS A CHILLER? A Chiller is a machine that removes heat from a liquid (usually water or glycol mix) via vapor-compression or absorption refrigeration. The chilled water is circulated through AHUs or FCUs to absorb heat from the building, making it a central part of HVAC systems. MAIN TYPES OF CHILLERS 1. Based on Heat Rejection: ⭐Air-Cooled Chiller  Heat is rejected to ambient air via condenser fans. No cooling tower needed. Higher power consumption (low efficiency). Used where water availability is limited (like UAE rooftops). ⭐Water-Cooled Chiller  Heat is rejected to condenser water, then to a cooling tower. Higher efficiency and longer lifespan. Requires more maintenance (cooling towers, water treatment). Ideal for large-scale commercial or industrial applications. 2. Based on Refrigeration Cycle:  →Vapor Compression Chiller  Commonly used. Uses mechanical compressor (screw, scroll, centrifugal). →Absorption Chiller  Uses heat source (steam, hot water, g...