HVAC engineers

  Fresh Air Requirement in HVAC (Ventilation Basics) Fresh air is essential to maintain indoor air quality (IAQ), comfort, and safety in buildings. Why Fresh Air is Required Removes CO₂ and pollutants Controls odor and humidity Improves occupant health Fresh Air Standards (ASHRAE 62.1 / NBC) Person-Based Office 8-10 L/s/person (17-21 CFM/person) Conference Room 10-15 L/s/person (21-32 CFM/person) Area-Based Office Area 0.3-0.6 CFM/ft² 1.5-3 L/s-m² Conference Room 0.5-1.0 CFM/ft² 2.5-5 L/s-m² Example (Combined Calculation) For an office of 100 m² with 10 persons: Person-based = 100 L/s (≈ 212 CFM) Area-based = 200 L/s (≈ 424 CFM) Final Fresh Air = 200 L/s (≈ 424 CFM) (higher value considered) Methods of Fresh Air Intake Fresh Air Fan (FAF) AHU with mixing box DONATE ERV / HRV Key Point Use both person + area method Select higher value for design Proper ventilation = Healthy + Energy Efficient HVAC System

  Fundamentals about Centrifugal pumps The centrifugal pump mechanics, physics and piping integration  The pump is an energy converter  Classification of pumping machinery The stationary shell : Casings and diffusers The rotating assembly : Generating kinetic energy  Component anatomy of a centrifugal pump  The fluid journey : Suction to eye The physics of velocity 

   

  PRESSURE REDUCING VALVE (PRV) A Pressure Reducing Valve (PRV) is a critical component in fluid systems that ensures the downstream pressure remains at a set level, no matter the fluctuation of the incoming pressure. PRVs are used in various industries. A. Function of Pressure Reducing Valves:  The primary function of a PRV is to reduce high inlet pressure to a lower, manageable pressure to protect sensitive equipment and maintain efficiency. This ensures that downstream systems, pipes, pumps, and other components do not experience damage from excessive pressure. It is especially crucial in systems where pressure must be kept within a certain range to ensure safety, system performance, and energy efficiency. B. Working of Pressure Reducing Valves:   The PRV operates based on the principle of controlling fluid flow. The inlet pressure pushes against the valve’s diaphragm or piston, which in turn adjusts the valve opening. This adjustment allows the fluid to flow through t...

  Vapor- compression refrigeration loop what each part does Flow path (colors match the sketch) High side: Compressor → condenser → receiver →     filter-drier sight glass (liquid & moisture indicator) → solenoid valve →  expansion valve. Low side: Evaporator→ suction accumulator → suction filter ball valve→ low-pressure switch →compressor. Motors drive the condenser fan and the evaporator blower. Component roles (in order of flow) 1 Compressor: Pulls low-pressure vapor from the evaporator and compresses it to high-pressure, high-temperature vapor. Sets the cycle. 2 Oil separator: Strips oil from discharge gas and returns it to the crankcase. Cuts oil carry-over. 3 Condenser + fan motor: Rejects heat to ambient. Vapor condenses to liquid and subcools. 4 Receiver: Stores and stabilizes the liquid charge. Ensures solid liquid feed to the line. 5 Filter-drier: Removes moisture, acids, and debris.  Protects the TXV and compressor. 6 Sight glass / moisture in...

Scroll compressors Scroll compressors (also called spiral compressors) are positive-displacement machines widely used in HVAC, refrigeration and heat-pump systems. They contain two interleaved spiral scrolls one fixed and one orbiting that trap and squeeze refrigerant vapor. As the motor-driven orbiting scroll moves eccentrically (off-center) around the fixed scroll, it continuously traps and pushes refrigerant toward the center at rising pressure. This smooth, pulseless compression (with no metal-on-metal contact) makes scroll units compact, quiet and highly reliable. In the cutaway image you can clearly see the key parts. The orbiting scroll (bolted to the shaft) nests inside the fixed scroll. Surrounding the shaft is the stator (stationary motor coils) and rotor - together they drive the orbiting scroll. Refrigerant enters at the low-pressure suction port, gets caught in the spiral pockets between the scrolls, and is compressed as those pockets shrink toward the center. The high-pre...

METERS AND GAGES PART 1-GENERAL 1.1 RELATED DOCUMENTS A. Drawings and general provisions of the Contract, including Conditions of Contract and Division 1 Specification Sections, apply to this Section. 1.2 SUMMARY A. This Section includes meters and gages for mechanical systems and water meters installed outside the building. B. Related Sections include the following: 1. Division 2 Section "Water Distribution" for water meters outside the building. 2. Division 13 Sections for fire-pump flow-measuring systems. 3. Division 15 Section "Fuel Gas Piping" for gas meters. 4. Mechanical equipment Sections that specify meters and gages as part of factory-fabricated equipment. C. Utility-Furnished Products: Water meters shall be furnished by the contractor to site, ready for installation. Where install exposed to weather conditions, meters and gauges shall be corrosion resistant. 1.3 SUBMITTALS A. Product Data: Include scale range, ratings, and calibrated performance curves fo...