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HVAC Interview Questions On Chilled-Water Systems 1 What are the four types of compressors commonly used in vapor compression water chillers? Answer:- Centrifugal, Helical-rotary, Reciprocating, and Scroll. 2 List one advantage of an air-cooled chiller and one advantage of a water-cooled chiller. Answer:- Air-cooled chiller advantages include lower maintenance costs, a prepackaged system for easier design and installation, and better low-ambient operation. Water-cooled chiller advantages include greater energy efficiency (at least at design conditions) and longer equipment life. 3 True or False: The IPLV equation included in the ARI standards for rating chillers was derived to provide a representation of the average part-load efficiency for a system with multiple chillers. Answer:- False. The IPLV equation was derived to provide a representation of the average part-load efficiency for a single-chiller system only. 4 What are the three most common methods of load-terminal (coil) control? Answer:- Three-way modulating control valve, two-way modulating control valve, and face-and-bypass dampers. 5 In a conventional primary-secondary chilled-water system, each production pump delivers a __________ (constant or variable) flow of water and the distribution pump delivers a __________ (constant or variable) flow of water. Answer:- Constant; Variable 6 What method of load-terminal control should be used in the distribution loop of a primary-secondary chilled-water system? Answer:- Two-way modulating control valves 7 Deficit flow in the bypass pipe of a primary-secondary system is an indication to turn an additional chiller __________ (on or off). Answer:- Turn on 8 Why does a variable-primary-flow (VPF) system require a bypass in the system? Answer:- To ensure that the water flow through the system remains above the minimum flow limit of the operating chiller(s). For More Information Follow YOGESWARAN PANDIAN ‼️ SHARE THIS IF YOU LEARN SOMETHING NEW TODAY‼️ #Chiller #chillers #HVAC #hvaclife #hvacr #hvacservice #MEP #AHU #MEP #mechanicalengineering #mechanical #engineers #BIM #buildinginformationmodeling #buildingautomation #hvac #chiller #mep #hvacinterview #hvacjobs #mepjobs #chillers #interview #design #energy #water #maintenance

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R-value and U-value are two important concepts in HVAC. R-value is a measure of a material's resistance to heat flow, while U-value is a measure of its ability to transfer heat. The higher the R-value, the better the insulation, while the lower the U-value, the better the insulation. The post R-Value and U-Value in HVAC appeared first on HVAC/R & Solar.

4. Absorption Heat Pump: Working: Uses a heat source (usually natural gas, propane, or waste heat) to drive the refrigeration cycle, which then provides heating or cooling. Parts: Absorber, generator, evaporator, condenser, pump, expansion valve. Usages: Used when waste heat or alternative fuel sources are available. Capacity: Depends on system design and heat source. Key Technical Terms: Coefficient of Performance (COP): Ratio of useful heating or cooling provided by a heat pump to the amount of electricity used. A higher COP indicates higher efficiency. Heat Source: The medium from which the heat is extracted (e.g., air, ground, water, waste heat). Heat Sink: The medium to which the heat is released (e.g., air, ground, water). Refrigerant: A fluid that cycles through the heat pump, changing states to absorb and release heat. Evaporator: A heat exchanger where the refrigerant absorbs heat from the source. Condenser: A heat exchanger where the refrigerant releases heat to the sink. Expansion Valve: Regulates the flow of refrigerant and reduces its pressure, causing it to evaporate and absorb heat. Compressor: Increases the pressure and temperature of the refrigerant gas, allowing it to release heat during condensation. Reversing Valve: A component that changes the direction of refrigerant flow, enabling the heat pump to switch between heating and cooling modes. Ground Loop: A system of pipes buried underground that contains a heat-transfer fluid for geothermal heat pumps. Choosing the right type of heat pump system depends on factors such as climate, available heat sources, system efficiency, and building requirements. Heat pumps are known for their energy efficiency and ability to provide both heating and cooling, making them a popular choice for various residential, commercial, and industrial applications.

#AskTheExpert If you asked me: “Why do #buildings continue to #waste 30% of their #energy?” Because we’ve been looking in the wrong places 😐 Just about everyone in the #AI #smartbuildings HVAC and mechanical equipment industry (and I used to be there too!) look at the PEAK LOAD exclusively. As well as broken mechanical equipment (FDD?) and non communicating BMS controllers; These narrow views MISS 70% (or more) of the optimization potential? This is true across the board. From a complex Central Plant in a commercial building, Data Center or University campus, all the way down to a fleet of 20,000 20 ton Rooftop HVAC units (RTUs); All of this has been missed. Until now. We must GO, where the data leads us. Not where it’s convenient for an industry built, unfortunately, on (a base of) alarms, call centers, staff and service. Our VP of AI and Machine Learning at facil.ai Paul Campbell speaks extensively to this (human) #bias. Surprisingly, the vast amount of #optimization and #energysaving opportunities come during the so-called “unoccupied” (NO load?) or low to mid load periods. You know, that “dead as a doornail” state that we put our buildings in every night to “save” energy? #BaaB We continue to obsess and focus on the peak load (30%); and miss out on the real (70%) opportunity. Industry #expert Paul Campbell understands this well. So does our customer and friend Kenny Seeton at California State University-Dominguez Hills. Customers like Doug Frame and Mark Facio at California State University, Los Angeles are also “pushing the envelope” of #energyefficiency and #comfort for their campuses. John Barkho and Jason Miller at Rising Realty Partners #proptech We’re all dedicated to changing the status quo when it comes to managing #energy in buildings. But it’s hard work! And it cannot be accomplished without the right #AI #technology designed by a #team of #software and #controls #experts. This work must be performed in a 100% automatic fashion. Meaning, you can’t hire enough humans in a #callcenter to get this work done! For just ONE (1) of our #retail clients with 1,300+ buildings (over 5,000 RTUs) you’d need three shifts of 375 (1,125 total) human analysts and technicians (plus 375 BMS “front ends”, don’t forget) working ‘round the clock 24/7/365 to analyze and manually send the millions of optimization commands, configuration changes and “fine tuning” adjustments required, that our #azurecloud based #AI platform performs! At scale. Customers, do the math yourselves. Ask questions. Ask for #proof of #energysavings. OFF the bills. The bar has been raised. #facilai #shinethelight Art Arnold Art Justice Brian Turner James Dice Scott K. Hoffmann, MBA Stephen Shelton Andy McMahon Rick Des Lauriers John Majeski Portola Valley Partners Tracy Markie Mike McKenna Phillip Kopp Keith Klug Kevin Kurtz Martin Howell Anno Scholten Rachel Wong Patterson, PE David Ochi Los Angeles Cleantech Incubator (LACI)

Heat Tracing of Piping Systems Types of Heat Tracing Systems Heat-tracing systems can be divided into two broad classes, electric and fluid. Fluid heat-tracing systems utilize heating media at elevated temperatures to transfer heat to a pipeline. The fluid is usually contained in a tube or a small pipe attached to the pipe being traced. If steam is the tracing fluid, the condensate is either returned to the boiler or dumped. If an organic heat-transfer fluid is employed, it is returned to a heat exchanger for reheating and recirculation. In general, heating of tracing fluids can be provided by waste heat from a process stream, burning of fossil fuels, steam, or electricity. Electric heat-tracing systems convert electric power to heat and transfer it to the pipe and its contained fluid. The majority of commercial electric heat-tracing systems in use today are of the resistive type and take the form of cables placed on the pipe. When current flows through the resistive elements, heat is produced in proportion to the square of the current and the resistance of the elements to current flow. Other specialized electric tracing systems make use of impedance, induction, and skin conduction effects to generate and transfer heat. Steam Tracing Effective Steam Tracing Steam tracing is the application of steam heat to piping and vessels for the purpose of maintaining desired process temperatures, freeze protection, viscosity control or to obtain a temperature control point within a fluid for its chemical interaction in a process. Steam tracing is usually accomplished by running steam lines in direct contact with the piping or vessels to be heated. The entire assembly is then insulated to direct the heat into the process fluid. Many technical articles have been written concerning steam tracing along with their associated heat loss equations and graphs. The need for steam tracing Steam tracing is very simple in its principle of operation. When a product in a pipeline is at a higher temperature than the air surrounding it, heat will pass through the wall of the pipeline from the product to the surrounding air. This heat loss will cause the temperature of the product to fall. Insulating the pipeline will significantly lower the rate at which heat is lost, but unfortunately, no insulation is 100% efficient. Steam is a very efficient carrier of heat with a fixed relationship between its pressure and temperature. It can transport heat over long distances and gives up its heat at a constant temperature. To make up the heat lost from the product pipeline, small bore steam pipes, or tracers, are attached to the product line. Heat from the steam passes into the product line and replaces the heat lost. The amount of heat transferred, and therefore the product temperature, can easily be controlled by simple self-acting control systems. The same type of control can also be used in winterization applications.