Recent standards have defined a lower minimum air velocity in kitchen exhaust air ducts. While the aim remains in place to maintain an acceptable in duct air velocity and expel exhaust air-borne particles or fluids towards filters/exhaust outlet. Steel ducts are usually specified to a standard steel gauge thickness, capable of handling the extreme load conditions of high temperatures, possible corrosive conditions, and negative pressure levels within exhaust duct. This paper simulates a typical kitchen exhaust air duct performing under extreme temperature conditions and the low air duct velocities. Lower exhaust air velocities should correspond to lower in duct negative pressure values and therefore, possibly a reduction in steel duct wall thickness.
A CFD/thermals tress analysis was carried out under the most extreme load conditions specified under recently issued standards. This analysis has demonstrated that a lower steel duct thickness is more than sufficient than what is specified in recent standards, and therefore, a lower steel thickness gauge can be used. Provided a comprehensive simulation is carried out demonstrating that the reduced exhaust duct sheet thickness is well within the steel duct mechanical material properties as explained in this paper.

The primary purpose of this study is to develop engineering methods to assess the impact of increased make-up air velocity in atria. The current restriction defined by NFPA 92 states that make-up air must not exceed 1.02 m/s (200 fpm) during the operation of a mechanical smoke exhaust system. This limitation not only limits creative and aesthetic atria designs but may also represent a significant cost. The present study analyzes the effect of make-up air injected by a variety of vent sizes at elevations at or below the limiting elevation of the flame through numerical simulations. This study focuses on identifying worst-case scenarios for the interaction of make-up air with an axisymmetric plume, by modeling multiple configurations, observing the results, and adapting further simulations to elicit the most extreme cases. A mass flow rate diagnostic is used to assess the increase in entrainment, i.e. smoke production. This mass flow diagnostic is developed to provide a comparative analysis, assessing the increase in the rate of smoke production with a specified make-up air velocity with that produced with no mechanical make-up air. The proportional increase in entrainment is defined as an alpha factor. The most significant smoke production increase and smoke layer stabilization descent is associated with the 1 MW fire, when lesser increases observed for the 2.5 MW and 5 MW fires. As the make-up air is introduced further from the edge of the flame, the apparent effect of the airflow velocity is reduced.

The National Research Council of Canada (NRC) conducted full-scale fire experiments to investigate whether pressure compensating systems are needed to maintain tenable conditions within pressurized stairwells. Ten tests were conducted in the NRC 10-storey test facility with the stairwell in the facility pressurized. The tests were conducted with the stairwell door on the fire floor closed and selected stairwell doors on the other floors open. Two fire scenarios with a shielded sprinklered fire and non-sprinklered fire were tested with varying number and location of open stairwell doors. Tenability analyses were conducted with experimental test results to investigate the performance of pressurized stairwell with and without pressure compensating systems. Without compensating for pressure losses, the pressure difference across the stairwell door on the fire floor decreased considerably with open stairwell doors. However, a non-compensated stairwell remained tenable for 30 minutes as long as the door on the fire floor was closed both for the shielded sprinklered fire and the non-sprinklered fire scenarios. It is concluded that if the base pressurization system meets the requirement of the design pressure difference with a proper arrangement of air injection points, the stairwell remained tenable as long as the door on the fire floor is closed for both sprinklered and non-sprinkled fire scenarios used in the tests.

Exposure to airborne influenza from patient’s cough and exhaled air causes potential flu virus transmission to the persons located nearby. Flu virus can be transmitted through air by patient’s cough creating aerosols containing flu virus. Hospital acquired influenza is a major airborne disease that occurs to health care workers (HCW).

The present study examines the air flow patterns and influenza-infected cough aerosol transport behavior in a ceiling-ventilated mock AIIR and its effectiveness in mitigating HCW’s exposure to airborne infection. The Computational Fluid Dynamic analysis of the air flow patterns and the flu virus dispersal behavior in a Mock AIIR is conducted using the room geometries and layout (room dimensions, bathroom dimensions and details, placement of vents and furniture), ventilation parameters (flow rates at the inlet and outlet vents, diffuser design, thermal sources, etc.), and pressurization corresponding to that of a traditional ceiling mounted ventilation arrangement observed in existing hospitals. The measured data showed that ventilation rates for the AIIR is about 12 ACH (Air changes per hour). However, the numerical results revealed incomplete air mixing, and that not all of the room air was changed 12 times per hour. Two life-sized breathing human models were used to simulate a source patient and a receiving HCW. A patient-cough cycle is introduced into the simulation, and the AI dispersal is tracked in time using a multi-phase flow simulation approach.

This research was sponsored by ASHRAE Technical Committee (TC) 4.3. The purpose of this Research Project is to provide a simple, yet accurate procedure for calculating the minimum distance required between the outlet of an exhaust system and the outdoor air intake to a ventilation system to avoid re-entrainment of exhaust gases. The new procedure addresses the technical deficiencies in the simplified equations and tables that are currently in Standard 62.1-2013 Ventilation for Acceptable Indoor Air Quality and model building codes. This new procedure makes use of the knowledge provided in Chapter 45 of the 2015 ASHRAE Handbook—Applications, and was tested against various physical modeling and full-scale studies. The study demonstrates that the new method is more accurate than the existing Standard 62.1 equation which under-predicts and over-predicts observed dilution more frequently than the new method. In addition, the new method accounts for the following additional important variables: stack height, wind speed and hidden versus visible intakes. The new method also has theoretically justified procedures for addressing heated exhaust, louvered exhaust, capped heated exhaust and horizontal exhaust that is pointed away from the intake.

This paper addresses the challenge of improving the performance of Heat Pumps (HPs) in cold climate condition by applying refrigerant mixtures. The potential benefits of implementing R32/CO2 zeotropic refrigerant mixtures in three different residential air-source HPs for cold climates is studied. The cases studied are: conventional residential HP, HP with variable mixture control system and HP with variable compressor speed. The seasonal performance of a heating system with these air-source HPs, supplemented with an auxiliary electric heater is studied in the cold climate city of Montreal. To this aim, a detailed screening HP model previously developed is modified and used. The obtained results highlight the potential HP performance improvement of applying refrigerant mixtures.

Instances of counterfeit refrigerants causing violent and unexpected explosions, resulting in multiple fatalities, have been reported in mobile refrigeration units around the world. In addition, counterfeit refrigerants have caused system reliability issues in numerous air-conditioning applications. It was initially believed the inclusion of methyl chloride (R40) in the refrigerant composition caused these explosions and reliability issues. ASHRAE research project RP-1665 was commissioned to examine reactivity of R40 with R134a refrigeration system materials. R40 reactivity, in concentration ranges of 0.01 to 10 percent, was studied in the presence of R134a, polyolester lubricant (POE), aluminum 1100 metal, aluminum 380 metal, in the presence of iron metal, copper metal, sodium aluminum silicate zeolite and alumina catalysts. R40 was shown to have varying levels of reactivity, generally mild, but showing the potential for catastrophic reactivity. This paper contains a summary of the work from ASHRAE Research project 1665 and will provide insights into the impact of R40 contamination, by providing the chemistry of the reactions, preventative safeguards, threshold levels, and assessment procedures. RP-1665 was conducted by McCampbell Analytical Inc., located in Pittsburg, California.

The presence of unsaturated fluorocarbon contaminants in the refrigerants used in HVAC&R systems may result in reaction products that could potentially cause problems in system performance or reliability. Since 2007, the 40 ppm limit for unsaturated halogenated contaminants in new and reclaimed refrigerants set by AHRI 700 has proven to be more restrictive to reclaimers, recyclers and HVAC&R system providers than previously thought. In addition, compounds such as hydro-fluoro-olefins (HFO) have been tested as low global warming potential (GWP) alternative refrigerants and shown to have acceptable stability in some applications. So, it may not be appropriate to classify all unsaturated compounds as unstable and blanket them under the same restrictive limit.
This research project aimed at determining the effects of halogenated unsaturated contaminants present in refrigerants on the stability of refrigerant/lubricant systems and recommending a concentration limit specific to the unsaturated contaminant below which the refrigerant/lubricant system is thermally stable. The following refrigerant/lubricant mixtures with their corresponding contaminants were selected for stability study in sealed tube tests: (1) R-134a/POE with with 1,1-dichloroethylene, 1,2-dichloroethylene, R-1131 and HFO-1234yf; (2) R-1234yf/POE with HFO-1225ye(Z), HCFC-1233xf and HFC-1243zf; (3) R-123/Mineral Oil with R-1122, R-1123 and R-1131.
 Based on criteria such as visual changes, Total Acid Numbers (TAN), organic anion and dissolved metal concentrations after aging, it was concluded that the R-134a/POE system was as stable as the control (without contaminant) when the concentration of its contaminants was less than 1000 ppm. The R-1234yf/POE system was stable when its contaminants were less than 5000 ppm, while the R-123/Mineral Oil system was stable when its contaminants were less than three weight-%. These maximum concentration limits were however based on sealed tube stability tests and would need to be balanced against other safety concerns, such as toxicity, flammability, handling and recycling practices.

Commercial and industrial refrigeration systems consume a significant portion of US electrical energy. In this paper, advanced expansion valve and control algorithms are evaluated to quantify the potential energy savings due to improved system regulation and efficient start-up of vapor compression refrigeration systems. The performance of the new MEMS actuators with different control strategies is compared with the standard mechanical valves and a commercially available superheat controller. Additionally, this research includes a comprehensive set of experimental tests that identify the most effective elements of advanced valve control strategies, including the impact of refrigerant migration control strategies. The experimental results confirm that 30-50% improvements in cyclic COP are possible using improved expansion valve controls, while the benefits of preventing refrigerant migration do not outweigh the additional cooling achieved if refrigerant continues to flow through the expansion valve during the compressor off period.

Building operations account for approximately 40% of US energy use and carbon emissions, and vapor compression cycles are the primary method by which refrigeration and air-conditioning systems operate. Representing a significant portion of commercial and residential building energy consumption, vapor compression cycles are a target for improvement in efficiency and savings. This paper presents a data-driven approach to find the optimal operating conditions of single and multi-evaporator systems in order to minimize energy consumption while meeting operational requirements such as constant cooling or constant evaporator outlet temperatures. The control problem lies in the development of a control architecture that will minimize the energy consumed without requiring any models of the system or expensive mass flow sensors. The application of the presented approach improves efficiency, and is demonstrated in simulation and on an experimental system.

Centrifugal chillers are a significant investment in a centrally air-conditioned building system. Commercial centrifugal chillers are expensive so their maintenance should be the up-most priority for the buyer. It’s a great responsibility on the part of the buyer to maintain such an expensive machinery to maintain the economy of the company. The procedures presented in this paper apply to standard WSC/WDC/WCC family of chillers and HSC heat recovery chillers.

Optimizing the combustion performance and reduction of emissions of Methane gas by varying excess air has been and continues to be an area of interest for researchers, manufacturers and operators. With the aim of developing more energy efficient systems meeting stricter environmental emission controls. The aim of this paper is to provide a comprehensive graphical presentation for easier optimization of the combustion process in relation to; energy, temperature, and pollutants. Easy to use equations were developed with guidance on how to accurately optimize combustion.

Methodology; numerical software tools were used in analyzing injected; Methane gas and – variable excess air ratios. Emissions such as; Carbon Dioxide, Carbon Monoxide, and Nitrogen Oxides, were also recorded, and analyzed for optimum energy output versus lower emissions. .

Results; were tabulated and graphs generated. Equations were derived using industry established software tools. The accuracy of the developed equations was assessed on statistical basis. Discussions on advantages and disadvantaged on excess air are included.

Enhancement of heat and mass transfer in sorption fluids coulde improve the overall performance of an absorption chiller. Active mechanisums were proposed as a potential effective means to achieve this goal. A testing facility is needed to evaluate the impact on the performance of chiller after adding an active mechanisums. The challenges we face include the fulfillment of mechanism motion to driving extra heat and mass transfer in an absorber, the measurement of related variables and the stablility & repeatability of findings. The issues come from the fact that an absorption chiller is a close-loop system with large heat exchangers, has a low inside pressure and can sustain only small pressure drop along the refrierant loop. Measures are needed to exclude the impact from the vibration to the untargeted components in the system. In this paper, we introduce the details of the lab construction methodology, including the vibator, the auxiliary water loop system, and the measuring instruments. Then, we present several examples to show the operation and testing procedure and stability. At last, the experiment plan matrix and analysis methodology are presented which will be applied in the next phase experiment. This paper provides useful information of active mechanism experiment setup and test methodology for the researchers in the same area who may conduct related work.

This paper provides recommendations for data-driven interfaces for advanced building operations and maintenance developed through ASHRAE Research Project 1633 (RP1633). Informing operations and maintenance with data-driven information is critical to achieve high performance buildings. Substantial guidance, such as ASHRAE Guideline 13 and Performance Measurement Protocols for Commercial Buildings, has already been created illustrating how to measure and convey building performance information. RP1633 focused attention on operations and maintenance stakeholders, including control technicians, heating ventilation and air conditioning (HVAC) technicians, service providers, commissioning agents, and facility managers by conducting literature reviews, commercial interface reviews, and stakeholder interviews in order to create guidance about data-driven metrics and visualizations that clearly quantify and communicate building operational performance to these stakeholders. The results of this research are presented here, with recommendations to provide metrics and visualizations at multiple scales, including portfolio-wide, whole building, and for specific building areas, systems, and equipment. Metrics span categories related to operating costs, utility consumption, carbon emissions, system performance, controllability, faults, and energy savings. Metrics may be visualized: on maps, system graphics, and in floorplans; as time-series line c harts, in calendar plots, bar charts, and pie charts; and relative to expected performance, past performance or a relevant benchmark. Feedback is presented from operations and maintenance personnel and our research about the types of metrics, at each scale, in which visualization format are most useful for advanced operations and maintenance.

According to some estimates, pumps account for between 10% and 20% of world electricity consumption (EERE 2001; Grundfos 2011). Unfortunately, about two thirds of all pumps use up to 60% too much energy (Grundfos 2011), primarily because of inefficient flow control. Varying pump speed using a variable frequency drive on the pump motor is one of the most efficient methods of flow control. As a consequence, about one-fifth of all U.S. utilities incentivize variable frequency drives (VFDs) (NCSU 2014), and many of these drives control pumping systems.
However, field studies and research show that few variable-flow systems are optimally controlled and the fraction of actual-to-ideal savings is frequently as low as 40% (Kissock 2014; Ma 2015; Song, L., Assistant Professor, Department of Mechanical Engineering, University of Oklahoma, pers. comm., July, 2013.). Utility incentive programs that rely on ideal energy saving calculations could overestimate savings by 30% (Maxwell 2005).
Previous work has shown the importance of changing motor efficiency, VFD and pump efficiency on savings (Bernier and Bourret 1999; Maxwell 2005). This work considers the difference between actual and ideal savings caused by excess bypass flow, position and setpoint of control sensors, and control algorithms. This paper examines the influence of these factors on energy savings using simulations, experimental data, and field measurements. In general, energy savings are increased when bypass is minimized or eliminated, pressure sensors for control are located near the most remote end use, and the pressure control setpoint is minimized.

Variable frequency drives (VFDs) are widely applied on induction motors that drive fans, pumps and compressors. Under partial loads, VFDs not only adjust frequency to reduce motor speed and mechanical output power (load) but also adjust voltage to reduce motor electrical input power. Traditionally, VFD manufacturers recommend controlling the voltage to be proportional to the square of the frequency for variable torque motor loads on fans and pumps, and controlling the voltage to be proportional to the frequency for constant torque motor loads on compressors. The purpose of this paper is to investigate energy efficient voltage-frequency ratios of VFDs using the motor equivalent circuit method. First, the motor load and speed correlation is derived for different applications; then VFD voltage is optimized for a given VFD frequency to maximize motor efficiency; and finally the motor efficiency is simulated and compared under the optimal voltage and different preset voltages. The simulation results show that the motor efficiency with the ratio of voltage to frequency to the power of 1.5 is mostly close to the optimal efficiency for variable torque motor loads and the motor efficiency with the ratio of voltage to frequency to the power of 0.5 is mostly close to the optimal efficiency for constant torque motor loads with efficiency improvement by up to 3% over the traditionally ratios.

This paper summarizes a case study of an innovative ground source heat pump (GSHP) system that uses flooded mines as a heat source and heat sink. This GSHP system provides space conditioning to a 56,000 sq ft (5,203 m2) newly constructed research facility, in conjunction with an on-campus existing steam heating system and an air-cooled chiller as supplementary systems. Heat transfer performance and overall efficiency of the GSHP system were analysed using the available measured data from January through July 2014. The performance analysis identified some issues with using mine water for cooling and the integration of the GSHP system with the existing steam heating system. Recommendations were made for the control and operation of the GSHP system for its improved performance. These recommended strategies, in conjunction with the available measured data, were used to predict the annual energy performance of the system. Finally, the energy and cost savings and CO2 emission reduction potential of the GSHP system were estimated by comparing with a baseline scenario. This case study provides insights into the performance of and potential issues with the mine-water source heat pump system, which is relatively less explored compared to other GSHP system design and configurations.

This article attempts to address the issue of making the right choice between a Direct Expansion Ground-Source Heat Pump (DX-GSHP), an Air-Source Heat Pump (ASHP) and a hybrid of the two in a given heating need context. Detailed screening models previously developed for ASHPs and DX-GHSPs are first used to compare the seasonal performance of these two options for a residential building in the cold climate city of Montreal. Then, the performance of a so-called “Hybrid Ground Source Heat Pump (HGSHP)”, integrated air source and ground source system is also investigated. Furthermore, different parameters including borehole total length and heat pump capacity are varied in order to determine the appropriate design in terms of borehole size and heat pump capacity. The results show that by adequate sizing, energy consumption of the DX-GSHP system can be reduced by 50% but performance improvement using HGSHP system is marginal. Such results highlight the importance of further investigations in the area of DX-GSHPs, in order to reduce the borehole installation cost and increase its performance.

Most commercial ground source heat pump systems (GSHP) in the United States are in a distributed configuration. These systems circulate pure water or an anti-freeze solution through multiple heat pump units via a central pumping system, which usually uses variable speed pump(s). Variable speed pumps have potential to significantly reduce pumping energy use, however, the energy savings in reality could be far away from its potential due to improper pumping system design and controls. In this paper, a simplified hydronic pumping system was simulated with the dynamic Modelica models to evaluate three different pumping control strategies. This includes two conventional control strategies, which are to maintain a constant differential pressure across either the supply and return mains, or at the most hydraulically remote heat pump; and an innovative control strategy, which adjusts system flow rate based on the demand of each heat pump. The simulation results indicate that a significant overflow occurs at part load conditions when the variable speed pump is controlled to main a constant differential pressure across the supply and return mains of the piping system. On the other hand, an underflow occurs at part load conditions when the variable speed pump is controlled to maintain a constant differential pressure across the furthest heat pump. The flow-demand-based control can provide needed flow rate to each heat pump at any given time, and with less pumping energy use than the two conventional controls. Finally, a typical distributed GSHP system is studied to evaluate the energy saving potential of applying the flow-demand-based pumping control strategy. This case study shows that the annual pumping energy consumption can be reduced by 66% using the flow-demand-based control compared with that using the conventional pressure-based control.

This paper presents the results of research project RP-1561, “Procedures to Adjust Observed Climatic Data for Regional or Mesoscale Variations”. This project included a WRF modeling campaign designed to cover ten significant climate regions across North America. Model results were compared against mesoscale monitoring data in order to assess the model’s performance for a single year’s hourly weather. Subsequently, a long-term climate model evaluation was performed by running WRF over 4 regions in North America for 8 years. Overall, the model performed well against observed temperature and humidity, reasonably well against observed wind, and relatively poorly against observed solar and precipitation. Guided by this evaluation, a complete mesoscale numerical modeling procedure was developed for coastal, mountain valleys, mountain plateaus, and major city centers, to provide site-specific climate data, i.e., a freely-available software solution for developing localized climate data.

As air-conditioning demand increased significantly during the last decade, efficient energy use has become more important due to large electric power demands and limited reserves of fossil fuel. Electrical energy use fluctuates significantly during a 24-hour day due to variable demand from industrial, commercial and residential activities. In hot and cold climates, the dominant part of the load fluctuation is due to cooling and heating demands, respectively. If electric loads could be shifted from peak hours to off-peak hours, not only would building operation costs decrease, the need to run peaker plants, which typically use more fossil fuels than non-peaker plants, would also decrease. Thus, shifting electricity consumption from peak to off-peak hours promotes economic and environmental savings. This paper utilizes simulation and experimental work to examine a total of twelve precooling strategies in three residential buildings in the Phoenix, Arizona climate. The selected buildings are considered to represent majority of residential buildings in the area. Results of this project show that precooling can save up to 46% of peak energy demand in a home constructed with concrete or cementitious block and up to 35% in wood frame homes. Homeowners can save up to US $244/year in block construction and up to US $119/year in wood frame homes.

Environmental concerns and limited energy supply today make energy storage to be very important especially in solar energy utilization. The latent heat storage method has the advantage of storing a large amount of energy in a relatively small volume. Achieving thermal energy storage with latent heat application using Phase Change materials (PCMs) involves the heat of fusion at the solid-liquid phase transition. The problem with today’s PCMs is that their very low thermal conductivity values severely limit their energy storage capability. This also makes the melting and solidification times to be too long for meeting the desired results. Investigations to solve this problem include improved design configurations and addition of nanoparticles to the PCM to enhance the thermal conductivity. This study is on the effects of nanoparticle dispersion in melting of a phase change material (PCM) in a triplex-tube heat exchanger heated under constant surface temperature conditions. The governing equations for the configuration and process were discretized via finite volume method and solved numerically. The model developed, which was validated shows good agreement when compared to a previous related experimental study. The computations were performed for nanoparticle volume fractions ranging from 1% to 3%. The results which are shown in the form of isotherms and contours of the solid – liquid interface over different periods of charging time are presented and discussed. The results show an enhancement in the melting rate with doping nanoparticles of different volumetric concentrations. The results also show melting time saving of 17% as a result of adding nanoparticles to the PCM. This is for nanoparticle volume fraction of 1%. Higher volume fractions were found to not result in significant melting time savings for the process in the triplex-tube heat exchanger.

This paper details experimental measurements and mathematical modeling of air flow through a perforated duct with an open area of 22% and capped at the end. Measurements were conducted on ducts with uniform diameters of 12 in., 10 in., and 8 in. (0.20 m, 0.25 m and 0.30 m). All ducts were 20 ft (6.10 m) long and inlet flow rates ranged from approximately 350 to 700 cfm (165 to 330 L/s). Flow rates were measured along the length of the duct using the pitot traverse method. The static pressure was also measured. The flow through the duct was modeled assuming one-dimensional flow and a differential equation was derived using the mass, momentum and energy equations. The resulting differential equation was solved numerically and the results were compared to the experimental measurements. Good agreement was achieved when comparing the experimental and model flow rates for all test runs with a maximum difference of 14.0% and an average difference of 2.0%. Results for the static pressure showed the same trends between the experiments and the model. The pressure was largest at the capped end of the duct where the experimental measurements exceeded the model results by a maximum of 21.8%.

Low evaporator airflow is one of the common faults for rooftop units, which can be caused by dirty filter, evaporator fouling, or loose belt. Low airflow could result in frozen evaporator coil, reduced cooling capacity and indoor comfort issues. Accordingly, more fan power is consumed as longer operating time is required. With the widespread use of variable frequency drives (VFDs) on rooftop units, low evaporator airflow can be potentially detected by monitoring the fan power variation. In the paper, the principle of fan-power based detection is introduced first. Then, the detection algorithm is proposed including development of baseline and comparison of operational data with baseline. At last, the field test was conducted to verify the proposed method. The test results indicated that fan power based method can effectively detect low evaporator airflow for rooftop units.

A traditional mass and energy balance component approach was used to characterize the performance of fixed airflow series fan powered terminal units for applications in building simulation programs. The approach included developing relevant energy and mass balance equations for the components in a fan powered terminal unit – heating coil, fan/motor combination, and mixer. Fan motors that included permanent split capacitor motors controlled by silicon controlled rectifiers or electronically commutated motors were included in the model development. The paper demonstrates how to incorporate the fan/motor combination performance models for both permanent split capacitor and electronically commutated motors into the mass and energy balance approach. The fan models were developed from performance data that were provided by multiple fan powered terminal unit manufacturers. The fan/motor performance data included a fan airflow range from 250 to 3500 ft³/min (0.118 to 1.65 m³/s) and a motor size range from one-third to one hp (248.6 to 745.7 W).

A mass and energy balance approach was used to characterize the performance of parallel fan powered terminal units for applications in building simulation programs. The approach included developing relevant mass and energy balance equations for each component in a parallel fan powered terminal unit – heating coil, fan/motor combination, and mixer. Only fixed airflow applications were included. Two locations of the heating coil were considered. One location, designated as the traditional configuration, was at the discharge of the unit. The second location, designated as the alternative configuration, was at the secondary air inlet. Fixed airflow parallel FPTUs use fan motors that include either permanent split capacitor motors controlled by silicon controlled rectifiers or electronically commutated motors. The paper demonstrated how to incorporate fan/motor combination performance models for both permanent split capacitor and electronically commutated motors into the mass and energy balance approach. These fan models were developed from performance data provided by multiple fan powered terminal unit manufacturers The fan/motor performance data included FPTU a fan airflow range from 250 to 3500 ft³/min (0.118 to 1.65 m³/s) and a motor size range from one-third to one hp (249 to 746 W). Leakage was included in the models. Sample runs were used to illustrate the effect of leakage in both cooling and heating operations.