Appendix A - Composter Heat Recovery Options Assessment Report (Associated Engineering, Dec 2017)

Transcription

1 RFP E Composting Facility Heat Recovery System Upgrades Appendix A - Composter Heat Recovery Options Assessment Report (Associated Engineering, Dec 2017) The Resort Municipality of Whistler A1

2 REPORT Resort Municipality of Whistler Composter Heat Recovery Composter Facility Heat Recovery Assessment December 2017

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4 REPORT Table of Contents SECTION PAGE NO. Table of Contents i List of Tables ii 1 Background Facility Overview Methodology Data Analysis and Heat Potential 2 2 Heat Recovery Concepts Basic heat recovery for building heating Expanded heat recovery and utilization Top concepts for further analysis 6 3 Basic Heat Recovery System General description Fan coil for building heat Hydronic heat recovery coils Hydronic circulation loop Economic analysis 10 4 Expanded Heat Recovery - Biomass Drying General description Air REQUIREMENTS and Power Consumption Energy and costs recommendations 13 Certification Page Appendix A - Technical Data 4.5 TEST Measurements Raw Data 3 i

5 Resort Municipality of Whistler Composter Heat Recovery List of Tables PAGE NO. Table 1-1 Pressures in Composter Tunnel Zones vs Fan Operation 1 Table 1-2 Potential Renewable Heat Recovery 3 Table 2-1 Preliminary Heat Recovery Concepts 4 Table 3-1 Class D Cost Estimates: Basic Heat Recovery for Building eating 10 Table 4-1 Energy for Forced Drying of 30,000 m 3 /year Wood Chips 11 Table 4-2 Energy Costs (CDN$) for Wood Chip Drying 12 Table 4-3 Cost Estimates: Expanded Heat Recovery for Wood Chip Drying 13 ii \\s-bur-fs-01\projects\ \00_heat_potent_asmnt\engineering\04.00_preliminary_design\rpt_rmow_compost_heat_assess_ _ak.docx

6 REPORT 1 Background The Resort Municipality of Whistler (RMOW) engaged Associated Engineering (AE) to evaluate alternatives for heat recovery systems for the Whistler Composting Facility (WCF). A previous heat recovery system (HRS) had failed due to corrosion issues, depriving the facility of renewable source of building heat energy worth about $ per year. At a minimum, this demand should be covered by the new heat recovery system, but without the corrosion problems of the original system. The cost-benefits of expanded heat recovery to serve additional uses were also investigated and are presented in this report. After review of the report RMOW will be in an improved position to decide on the option that provides the best value to them and a proposal for detailed design will be submitted. 1.1 FACILITY OVERVIEW The facility is a continuous biosolids composter taking biosolids from Squamish, Whistler and Pemberton. The composter has two parallel tunnels with trays of feedstock pushed through the system by large hydraulic rams. The facility operates on a diurnal cycle, with loading and pushing of compost only during the day. Each composter tunnel has two zones; Zone 1 (Aerobic Heating Zone at the front of the tunnels) and Zone 2 (Drying Zone back of the tunnels). Zone 1 is negatively aerated primarily by the Primary Exhaust fan. Zone 1 is allowed to heat up to temperatures above 70 C to provide pathogen reduction and also to generate heat which is transferred by the heat pipe to the Zone 2 supply air. Zone 2 is positively aerated by tempered air drawn from inside the process building which is then heated using the heat pipe. Zone 2 is negatively aerated by both the Primary and Secondary exhaust fans depending on whether the secondary exhaust fan is operating or not. The WCF has two basic modes of operation: (a) Biofuel (biodryer) mode (b) Compost mode. The secondary exhaust fan is temperature controlled in Compost mode and is permanently on in Biofuel mode on at maximum speed to make product drier. Both modes accomplish pathogen reduction, but vector attraction reduction is not accomplished during Biofuel mode as the operating temperatures in Zone 2 are too low. See the Table 1-1 for an overview of operating modes. Table 1-1 Pressures in Composter Tunnel Zones vs Fan Operation Compost Mode Biofuel Mode Exhaust fans: Primary Secondary Primary Secondary Zone1 (-) n/a (-) n/a Zone 2 (+) (-) when fan on (+) (-) fan always on -1

7 Resort Municipality of Whistler Composter Heat Recovery Original Heat Recovery System The original HRS circulated refrigerant from a heat pump system, with separate heat recovery units for each composter. The evaporator (heat pickup) coils were in the exhaust stream of the front section, upstream of the heat pipe. The heat pumps, which still exist, are located at the condensers that are suspended in the process building. The evaporator coils have corroded and were removed rendering the system inoperative. The condensers in the building were showing signs of corrosion as well but when coated the corrosion stopped. 1.2 METHODOLOGY Site measurements of flow, pressure, temperature and relative humidity entering and leaving each section of both composters, and across the heat pipe. Measurements by Stasis, an air testing and balancing contractor under direction from Associated Engineering. After the site visit the team evaluated the data and produced data sheets and metrics as shown in a table in Appendix A, for each of four operational modes. Data in each column of that table is for a single exhaust fan only. There are two such fans in each of the exhaust systems. Measured airspeeds and pressures did not correspond to the primary fan s performance curve. Airflows were derived from fan curves using the measured static pressures are considered more realistic. This can be achieved during periods with normal air resistance in the biofilter and/or by adjusting fan speed. Measured building airflow did not balance with exhaust airflows, due to flows from outside air. The following anomalous test results are commented: Test 2 Night biofuel mode shows the building air increasing in temperature from 10.5 C to 41.8 C and at the same time the R.H. increasing from 10 to 42.5%. A similar anomaly is shown on the Test1 Night compost mode results. Leakage has been ruled out as a possible explanation, after discussions with plant personnel. The most likely explanation is that the recorded values are reversed. These data are not critical to the calculations and conclusions presented in the report. 1.3 DATA ANALYSIS AND HEAT POTENTIAL Heat Energy Potential The total potential heating power was calculated for each of the operating modes, as shown in Table 1-2, based on a 10 C air temperature drop and latent heat recovery in the coils. Night biofuel mode has the highest potential, and compost modes the lowest. The exhaust air stream with greatest potential is highlighted in the table. 2 \\s-bur-fs-01\projects\ \00_heat_potent_asmnt\engineering\04.00_preliminary_design\rpt_rmow_compost_heat_assess_ _ak.docx

8 Table 1-2 Potential Renewable Heat Recovery Potential Renewable Heat Recovery Night Compost Night Biofuel Day Compost Day Biofuel Primary air temperature ( C) Secondary air temperature ( C) n/a 38 n/a 49 Primary heating power (kw) Secondary heating power (kw) Total heating power (kw) Annual potential energy (kwh) 470,000 1,451, ,000 1,295,000 At any given time, there is an exhaust stream, primary or secondary, with air temperatures entering the heat recovery of at least 37 C. Heat may be recovered from the primary exhaust in all modes except daytime Biofuel mode, when the temperature (22 C) is too low for practical recovery without the aid of a heat pump. The tunnels always maintain a negative air balance. During the daytime, most of the relief air enters through the loading end whereas at night it seems to enter from the opposite end as indicated by the measured exhaust temperatures in the different operating modes. Air monitoring by another firm was made in response to corrosion issues within the facility. Results 1 showed high levels of ammonia (approx. 40 ppm) in the exhaust ductwork. 2 Heat Recovery Concepts 2.1 BASIC HEAT RECOVERY FOR BUILDING HEATING AE s original assignment was to assess replacement options for the evaporators and to help get the original system operating again. The original system recovered about 70 kw from the composting facility. However, replacement options are limited by the high operating pressures of the refrigerant and the corrosive air mixture. The replacement evaporator coil in that case would be very expensive due to the quality and amount of materials required. Another disadvantage with re-instating the original refrigerant-based system is its fixed capacity to provide heat only to the process building and inflexibility of recovering from only one airstream. This represents only 1 Air Monitoring for Acetic Acid, Ammonia, and Hydrogen Sulfide from Whistler Compost Facility, by Levelton Consultants, for Municipality of Whistler,

9 Resort Municipality of Whistler Composter Heat Recovery a fraction of the renewable heat energy in the exhaust air streams, which could be extracted for other purposes as well. Therefore, if the system is to be significantly modified or replaced, consideration should be given on how to include future extra capacity and/or more end-uses for the energy that can be extracted. New, more robust hydronic coils and an intermediate water-glycol loop operating at lower pressure is recommended as the basis for heat recovery for all concepts reviewed in this report, as shown in Table EXPANDED HEAT RECOVERY AND UTILIZATION The alternatives initially discussed with RMOW for expanded use of waste heat energy were: (a) to supplement the composter s dryer section (b) accelerated drying of wood chips in nearby area (c) drying to decreasing the moisture content of the final composter biofuel product. If moisture content of compost could be decreased, then it could be a marketable commodity such as fuel for the Lafarge or Lehigh cement plants in Richmond. To be able to sell the compost as a fuel, it would require a moisture content of around 20%, down from the current 45% levels. Roughly 18 GJ/tonne heating value is the threshold at which efficiency gains make this fuel attractive for such clients. Table 2-1 Preliminary Heat Recovery Concepts Concept Advantages Disadvantages 1. Using existing building heat pump & condensers with new water-glycol recovery coils 2. New water-to-water building heat pump with new water-glycol recovery coils Re-use of existing heat pump equipment in the building. All new equipment, no conversion risk. More corrosionresistant options on the type of coil material used. Risk with converting to an intermediate heat exchanger. Existing condensers have already experienced corrosion prior to being coated. Higher cost due to new heat pump and coils. 3. Run-around loop without heat pump, using recovery coils in both primary and secondary exhaust, for building heating. Low equipment cost. No heat pump = low service and maintenance costs. Can be retrofitted with heat pumps in the future to increase capacity Increased airflow pressure drop and fan energy consumption. 4 \\s-bur-fs-01\projects\ \00_heat_potent_asmnt\engineering\04.00_preliminary_design\rpt_rmow_compost_heat_assess_ _ak.docx

10 Concept Advantages Disadvantages 4. Same as #3, but using heat pipe No hydronics, no heat pump = instead of coils and pumped circuit. low service and maintenance costs. Air-to-air transfer would be used to transfer heat to the building Concepts for expanded heat utilization: Limited capacity: provides ventilation and building heat only. Installation cost due ducting building air out to heat pipe. Increased fan energy Cannot easily be expanded in the future without complete replacement. Risk of breakthrough of contaminated air if air to air transfer is used 5. Same concept as #3 but with a heat pump to supplement the composter s drying section with new heat exchangers downstream of the heat pipes. Higher quality biofuel product with less moisture; lower transport costs. Use of existing facility; no need for separate air-bed dryer Increases the drying section airflow, which will require more heat to the building as it acts as the supply plenum and more outside air would be drawn in. More energy required for dryer supply air to maintain the same supply temperature. 6. Same concept as #3 but with a heat pump supplying a new airdrying bed with blowers for accelerated drying of wood chips in a separate area. 7. Same concept as #3 but with a heat pump supplying a new biomass dryer process unit to make compost suitable for sale as fuel More effective drying of woodchips using dry air instead of already saturated exhaust air. Improved process performance with regard to moisture removal Reduced ROI compared with option #6 More effective and extended drying season compared to option #6 Improved process performance with regard to moisture removal Higher airflow would be needed due to the limited drying capacity of already saturated air. This may require re-ducting of secondary section. Greatly increased energy consumption for blowers vs natural drying. Large capital cost for new equipment Greatly increased energy vs natural drying. Not as effective as concept#5. Complex system with high maintenance costs Very large initial capital cost 5

11 Resort Municipality of Whistler Composter Heat Recovery 2.3 TOP CONCEPTS FOR FURTHER ANALYSIS Based on discussions and a preliminary analysis of all the initial concepts, it was concluded that #3 is the best concept for heat recovery to resupply the building with waste heat, but which also has flexibility for a future expansion. Of the most promising concepts for expanded heat utilization for drying, we looked at #6 in detail, but consider #7 also worthy of investigation. Both concepts build on the heat recovery loop described in Concept #3. 3 Basic Heat Recovery System 3.1 GENERAL DESCRIPTION Four new, more robust hydronic coils connected to a water-glycol runaround loop is recommended as the basis for heat recovery from the composter exhaust airstreams. For basic heat recovery, this energy is transferred to a fan coil for building heat. The coils will be sized for building heat, but can recover more if aided by a heat pump in the future. The loop piping will have provision to connect a future water-to-water heat pump, as shown in Figure \\s-bur-fs-01\projects\ \00_heat_potent_asmnt\engineering\04.00_preliminary_design\rpt_rmow_compost_heat_assess_ _ak.docx

12 Figure 3-1 Basic heat recovery system schematic 7

13 Resort Municipality of Whistler Composter Heat Recovery 3.2 FAN COIL FOR BUILDING HEAT The building heating in the plant could be provided by a suspended fan coil unit with overall heating capacity equal to the original system. The original system s capacity of 100 kw is based on a 30 kw heat pump compressor and assuming a COP slightly over 3. This size provided a comfortable environment inside the plant, according to staff. It is difficult to properly size a unit in a building with an open door as in certain conditions it will not be very effective. If a warmer indoor climate was desired, then system sizing could be adjusted. The 100 kw water-glycol heating coil would be installed within the new fan coil unit. This would be a hung unit, suspended in the same or similar location to the original condenser unit; only minimal new ducting is required, as the hot air can be directed into existing nearby ductwork in two places. A high-volume ceiling fan should be considered for improved air destratification in the building, but this cost is not considered here. Specifications used in cost estimation: Electrical components for Class 1, Division 2 building atmosphere MERV 8 filter 10 C air in from building 32 C water in from run-around loop Material mild steel and epoxy construction, with Heresite on the cu/al coils 3.3 HYDRONIC HEAT RECOVERY COILS Sizing of the exhaust air heat recovery coils depends on the required heat load and whether it is aided by a heat pump. To supply only building heat load with the help of a heat pump, then it will be sufficient with coils only in the primary exhaust airstream, as in the original system, but downstream of the heat pipes. A run-around water-glycol loop without a heat pump will require a larger coil surface area and access to higher temperatures. This is most easily achieved by putting additional coils in the secondary airstreams as well. These added coils will allow expanded heat recovery if a heat pump is installed in the future. All coils in the corrosive exhaust air should have a corrosion resistant Heresite coating. Heresite is used on the existing heat-pipes, which show no signs of corrosion after many years in service. Due to the large volume of material for a 10-row configuration, stainless steel was found to be too expensive. The coating must withstand ammonia air and repeated pressure-washing. The heat recovery coils should be sized such that either primary of secondary systems can supply the entire load of 100 kw. 8 \\s-bur-fs-01\projects\ \00_heat_potent_asmnt\engineering\04.00_preliminary_design\rpt_rmow_compost_heat_assess_ _ak.docx

14 Specifications used in cost estimation are: Each secondary exhaust coil sized for C. (for nighttime biofuel mode). Each primary exhaust coil sized for C (for all compost modes). Coil material: Heresite coated cu-alu to resistant corrosive ammonia atmosphere. Capable of being pressure washed. Water out of coil 32 C. Delta T of water-glycol about 10 C. Control of system for coil switching for optimal heat recovery performance. The specified coils will increase static pressure by about 330 Pa (1.3 inches water column) in each duct. Design airflow can be maintained by using existing VFDs to increase fan speed. This will use slightly more energy, but some of this will be recovered as heat anyway Coil Ducting and Condensate Collection Coils will be flanged into existing 450 mm PVC ventilation duct. The coils will be in a housing with access hatch for cleaning and service to maintain optimal performance. If made removable, it may be advantageous to relocate the exhaust fans and place the coils on the suction side to reduce the possibility of leaks, and allow service while in operation, this would only be possible with the secondary exhaust. This relocation is not included in the current cost estimate. Condensate carryover from the recovery coils will be collected in a drain pan with clean-out drain. While the original HR system was operational, there was reportedly a large amount of condensate produced. Since a condensate collection and coil cleaning system must be developed anyway for the new coils, it is recommended to extended it include collection condensate after the heat pipe, but not cost estimated here. Condensate is contaminated water and was previously discharged to ground as there is no sewage main from the composting plant to the wastewater treatment plant. Provision for collection and alternate disposal should be considered through the septic system, but this is not cost estimated here. 3.4 HYDRONIC CIRCULATION LOOP Specifications used in cost estimation: Plastic piping 90 mm diameter Circulation pump 0.5 hp Expansion tank 3-way temperature control valve Isolation valves on all coils 9

15 Resort Municipality of Whistler Composter Heat Recovery In compost mode there is no secondary airflow: water-glycol to those coils may be may turned off or allowed to flow. In Biofuel mode during the daytime, use the coils in secondary exhaust, due to low primary temperatures. In Biofuel mode during nighttime the coils in primary exhaust can be prioritised. 3.5 ECONOMIC ANALYSIS Table 3-1 shows Class D cost estimates (30% accuracy) for a basic heat recovery system to cover building heat demand, but with provision for expanded heat recovery later. This system has a simple payback of 9.5 years, assuming an annual cost savings of $25,000 on reduced propane heating and increased annual fan energy consumption of $1,500 (from about 22,000 kwh/year) The supplier s estimate for a fan-coil unit with stainless steel coils and cabinet was three times the cost for a typical steel coated unit. Stainless steel is not needed for the fan coil, so the lower typical price is used. Table 3-1 Class D Cost Estimates: Basic Heat Recovery for Building eating Description Price estimate (CDN $) Comment Fan coil unit 50,000 Equipment and installation Heat recovery coils (4) 42,000 Equipment only, 10 row configuration Coil ducting 40,000 Incl. coil install, transitions and access hatches Hydronic Circulation Loop 20,000 Incl. pump, piping, valves Power and Automation 20,000 SUBTOTAL (Capex) 155,000 Engineering & Administration (20%) 31,000 Unforeseen (10%) 16,000 TOTAL 225,000 Rounded 4 Expanded Heat Recovery - Biomass Drying 4.1 GENERAL DESCRIPTION Increasing the hydronic capacity of the HR system will allow use of waste heat from the composter to be used in other nearby applications, in addition for building heating. The most promising application is as a heat source for hot air drying of wood chips. Drier wood chips are lighter, burn more reliably and at much higher efficiency. This drying would take place in an existing covered area, where wood chips are currently seasoned. RMOW initially set a target of m 3 /yr ( yd 3 ) wood chips to be processed. 10 \\s-bur-fs-01\projects\ \00_heat_potent_asmnt\engineering\04.00_preliminary_design\rpt_rmow_compost_heat_assess_ _ak.docx

16 Hot air drying would require a heat pump for greater heating power extraction from the composting facility. An insulated water-glycol hydronic line and pump would transport the heat to the nearby wood drying area. There are many different types of modular, wood biomass dryers which can be connected to a waste heat source. Low-temperature belt and fluid air-bed dryers would allow the heat pump to operate effectively compared to other, high-temperature drying methods. These dryers are available as complete packaged units, but a custom-built, open design is chosen here for increased future flexibility for drying of other biomass, such as compost. The main equipment items are the air bed itself, the water-to-water heat pump, blower fans, and the heating coils. Any need for additional equipment for exhaust air cleaning from the dryer was not investigated, and such equipment is not included in the price estimates here. 4.2 AIR REQUIREMENTS AND POWER CONSUMPTION The energy needed for drying down to about 20% water content depends on throughput; yearly volume of woodchips divided by the length of the length of the drying season, assuming continual operation. The air requirement for air-bed drying is 400 to 500 m 3 /h/m 3 for green wood chips in fan beds with depths 0.8 to 1.5 m (Helin, 2005). Normal static pressure drop through a typical air bed is 7 in. water (1.74 kpa). High velocities are needed to prevent re-condensation in upper layers of biomass. In this simplified analysis based on empirical data 2, the use of waste heat for drying is modelled by assuming a longer drying season. Table 4-1 shows results for drying of 30,000 m 3 /year of wood chips. Table 4-1 Energy for Forced Drying of 30,000 m 3 /year Wood Chips Fan with Ambient Air Only Fan with Waste- Heated Air Drying season months 7 9 Days on air bed days Batches # Batch size m Air requirement cfm 210,000 64,000 Fan power kw Fan energy input kwh/y 1,490, ,912 Heat pump output kw Heat pump input kw Heat pump energy kwh/y 0 660,000 Total energy input kwh/y 1,490,000 1,240,000 Total energy input kwh/m Woodchip Drying, by M. Price, Centre for Forest Resources & Management, UK,

17 Resort Municipality of Whistler Composter Heat Recovery Scenario with Reduced Yearly Volumes Reduced yearly volumes will reduce fan airflows proportionately, but fan power will be reduced by much a higher factor. In the above example, reducing the annual volume to 12,000 m 3 /year over the same length of drying season will reduce the needed airflow by 65%. This will reduce the pressure drop by over one-third 3. Fan power is pressure drop x flow, so the necessary fan power, and energy costs, will be more than onefifth of the original values. In the above example, halving the annual volume will reduce fan power to roughly 50 kw instead of 290 kw. Annual fan energy consumption will be about 250,000 kwh/yr, costing roughly $16,000 per year which is $1.3 per m 3. This analysis assumes that the total drying time remains the same as in the high-volume scenario. If drying time is limited to only the shoulder seasons, then energy costs per m 3 will be the same as in the highvolume scenario. 4.3 ENERGY AND COSTS Energy costs are shown in the table below. Maintenance costs are estimated at between $5,000 up to $10,000 for system with heat pump. Power demand charge used was 5$/kW, and energy charge 5 cents per kwh. Taken together, these give an average total energy cost of between 6.0 to 8.2 cents per kwh, depending on the scenario. Fan Motor Costs Table 4-2 Energy Costs (CDN$) for Wood Chip Drying Fan Air Only With Heat Demand costs 17,000 5,000 Energy costs 75,000 29,000 Subtotal 92,000 34,000 Heat Pump Costs Demand costs 0 6,000 Energy costs 0 33,000 Subtotal 0 39,000 Total costs Demand costs 17,000 11,000 Energy costs 75,000 62,000 TOTAL 92,000 73,000 Per m 3 wood chips Pressure resistance to air flow during ventilation of different types of wood fuel chip, Kristensen \\s-bur-fs-01\projects\ \00_heat_potent_asmnt\engineering\04.00_preliminary_design\rpt_rmow_compost_heat_assess_ _ak.docx

18 Estimates of the capital costs are shown in Table 4-3, to 40% accuracy. Table 4-3 Cost Estimates: Expanded Heat Recovery for Wood Chip Drying Description Price Estimate (CDN $) Water-Water Heat Pump 45,000 Hydronic Lines 20,000 Pumps 15,000 Blower Fans 80,000 Drying Bed 100,000 Power and Automation 20,000 Building-related 50,000 SUBTOTAL (Capex) 330,000 Engineering and Admin (20%) 66,000 Unforeseen (20%) 66,000 TOTAL 462, RECOMMENDATIONS The results show only marginal benefit to using heat for forced drying of wood chips, compared to forced airdrying only. Energy costs are significant for annual drying 30,000 m 3, ranging from $2.40 to $3.00 per m 3 of wood chips. This represents 14% to 18% of a typical market price of about 75 $/tonne. Capital depreciation costs will be extra. Reduced volumes, dried over the same period of 32 weeks, will have much lower energy costs, corresponding to about 8% of the market price. The concept for drying using heat and increased airflows in the existing composting tunnels may be a better alternative, but was not investigated in detail this report. Increasing the air flow, balance or temperature of the supply air to the drying section would lower the moisture content, although this could have an adverse effect on the lifetime of the biofilter media. Perhaps the most economical alternative of all for wood chip drying would be to establish a larger covered area optimized for natural drying using ambient air. 13

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22 REPORT Appendix A - Technical Data SITE PLAN Figure A-1: Site Plan and Source of Air Pressure Drops A-1

23 Resort Municipality of Whistler Composter Heat Recovery TEST RESULTS AND CALCULATIONS SUMMARY Results from the test measurements are shown, after minor adjustment for error. Adjusted data is highlighted in yellow in Table A-1 (see table key). Table A-1 Preliminary Test Results and Calculations Summary A-2 \\s-bur-fs-01\projects\ \00_heat_potent_asmnt\engineering\04.00_preliminary_design\rpt_rmow_compost_heat_assess_ _ak.docx

24 Appendix A - Technical Data REFERENCES WCF drawings and documents: 1. Results from airflow measurements by C. Smeenk, AE, Air Monitoring for WC, report# R by Levelton, Fan drawings and specs, drawing # by Daltec Industries Ltd, Tunnel Layout Drawings, by Wright Tech Systems, RFP# for Supply & Installation of a Heat Exchange System at WCF, Wood Chip Storage Building Extension (preliminary), drawing #005-P1, General references: 1. Woodchip Drying, by M. Price, Centre for Forest Resources & Management, UK, A.1 TEST MEASUREMENTS RAW DATA The following datasheets show three sets of recorded measurements. Each set measured properties of primary, building and secondary airstreams during each of the four modes of operation. Measurements were made by Stasis, an air testing and balancing contractor under direction from Associated Engineering. A-3

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