5HVAC basics Power versus Energy Kilowatt (kW), or demand, is a measure of power, similar to the speedometer of your car that records the rate at which miles are traveled.A bigger engine is required to travel at a faster rate.Kilowatt-hour (kWh) is a measure of energy consumption, similar to the odometer on your car which measures the miles traveled.Energy cost = energy consumption x unit cost = kWh x $/kWh = kW x hrs x $/kWhA 50-ton chiller with a 0.8 kW/ton efficiency costs about $11,200 annually when operating 2,800 load hours (40 kW x 2,800 hr x $0.10/kWh national average)Source: stock.xchngSource: Commonwealth of Kentucky
6Dry Bulb Temperature (°F) Wet Bulb Temperature (°F) HVAC basicsTemperatureDry bulbNormal thermometerWet bulbBulb wrapped in cloth—called a sock—that is kept wet with water via wicking.Dew pointTemperature to which air must be cooled for the water vapor component to reach saturation and condense into water.Source: Microsoft EncartaDry Bulb Temperature (°F)Relative HumidityWet Bulb Temperature (°F)Dew Point (°F)70100%60%615630%533855484240%4537Not SustainableIce
7HVAC basics Relative Humidity Relative humidity compares water vapor in the air with the concentration of water vapor that the atmosphere could hold (if the atmosphere were at saturation).Usually expressed as a percentage.When the actual concentration of water vapor in air is equal to the water vapor concentration at saturation, the relative humidity is 100%.There is one gallon of water in a 20' x 50' x 8' room at 68ºF and 100% RHThere is only 0.1 teaspoon of water per cubic foot of air at 68ºF and 100% RHOperation at 78°F / 40% RH provides the same level of occupant comfort as 74°F / 50% RH does due to evaporative cooling.4C 40F100% RelativeHumidityH2OIn this example, specific (absolute) humidity does not change until the dew point is reached.
8HVAC basics Degree Days Degree day calculations provide a rough estimate of the heating and cooling load for a particular location.Degree days are based on the difference between a day's average daily temperature and the "balance point" temperature of 65°F (or 18°C).Cooling Degree Day (CDD) = (Average Temperature – 65°F) x days/monthHeating Degree Days (HDD) = (65°F – Average Temperature) x days/monthLocation dependent and data available from National Climate Data Center (NCDC), WeatherUnderground, and other sources.Source: Utility Allowance
9HVAC basicsLoad HoursHVAC load hours may be calculated from degree days using a formula which incorporates Outside Design Temperatures.Cooling Load Hours (CLH) = CDD x 24 / (Cooling Outside Design Temperature – 65°F)Cooling Outside Design Temperature (ODT) is in the range of 70°F to 105°FHeating Load Hours (HLH) = HDD x 24 / (65°F – Heating Outside Design Temperature)Heating Outside Design Temperature (ODT) is typically between -12°F and 40°F.It is necessary to reduce the heating load hours by about 40% to match actual energy consumption.
10HVAC basics HVAC Load Hours Source: Louisiana Department of Natural Resources, Technology Assessment Division
11HVAC basics Efficiency Ratings One ton (12,000 Btu/hr) equals kW at 100% efficiencyCoefficient of Performance (COP)COP = Rated Cooling Output, kBtuh / Rated electrical input, kBtuhFull Load Value (FLV)FLV = kW/tonCOP = (kW/ton) / FLV efficiency rating (kW/ton)Energy Efficiency Ratio (EER)EER = Cooling output (Btu) / Electricity consumed (watt)EER = 12,000 Btu per ton / FLV (watt per ton)EER = COP x 3.413Application Part Load Value (APLV)Other than full loadIntegrated Part Load Value (IPLV)Weighted average of full load and part loadFLV (kW/ton)COPEER0.65.9200.754.7161.03.5121.52.38
12Seasonal Energy Efficiency Ratio (SEER) HVAC basicsSeasonal Energy Efficiency Ratio (SEER)Test conditions for determining SEER values are defined by ANSI/ARI standardIndoor air across the evaporator at 80ºF with 50% RH (wet) and <20% RH (dry)Outdoor air across condenser at 82ºF with 40% RH (wet)Outdoor air at 95ºF and 40% RH (Test A) is used to establish capacity and EERFour categories of air-conditioning systems are tested.ARI does not require manufacturers to report the results of dehumidification performance.SEER = (1 - (0.5 x [1 - (EERC/EERD))/(1 - CLF)]) x EERBEERB = Energy Efficiency Ratio determined from Test B (steady, wet)EERC = Energy Efficiency Ratio determined from Test C (steady, dry)EERD = Energy Efficiency Ratio determined from Test D (cyclic, dry)CLF = Cooling Load Factor
13Estimation of annual operating cost HVAC basicsEstimation of annual operating cost300 ton chiller; FLV = 0.75 kW/ton (EER=16, COP=4.7); $0.10/kWh; national averageEnergy cost = Size (ton) x FLV (kW/ton) x CLH (hrs) x Electric rate ($/kWh)Energy cost = 300 ton x 0.75 kW/ton x 600 hrs x $0.10/kWh = $13,5005 ton heat pump; 13 SEEREnergy cost = [Size (MBtuh) x CLH (hrs)]/ SEER (Btu/watt) x Electric rate ($/kWh)Energy cost = [5 ton x 12 Mbtuh/ton x 600 hrs]/ 13 Btu/w x $0.10/kWh = $275
15HVAC basics Refrigerants Issues are depletion of the ozone layer and contribution to global warmingManufacturers still are allowed to produce R-22 to service existing equipmentAfter 2020, cannot produce R-22, but can service existing systemsRefrigerantODP1GWP2ApplicationCFC-111.04,680Centrifugal chillersCFC-1210,720Chillers, refrigeratorsHCFC-220.041,780AC, chillersHCFC-1230.0276R-11 replacementHFC-134a<1,320R-12 or R-22 replacementHFC-407c1,700R-22 replacementHFC-410a1,890AC1Ozone Depletion Potential 2Global Warming Potential
16HVAC basicsDeliveryWater is much denser and stores much more heat [cooling].A 1" (25 mm) diameter pipe containing hot/cold water can deliver more energy than a 18" x 12" (0.45 m x 0.3 m) duct, even though the air is moving much faster in the duct than the water in the pipe.
17HVAC basics Indoor Air Quality ASHRAE Ventilation for Acceptable Indoor Air Quality“Air in which there are no known contaminants at harmful concentrations as determined by cognizant authorities and with which a substantial majority (80% or more) of the people exposed do not express dissatisfaction.”Ventilation Rate ProcedurePeople Outdoor Air Rate (Rp)Area Outdoor Air Rate (Ra)For instance, office areas—5 cfm/person and 0.06 cfm/ft²Indoor Air Quality (IAQ) ProcedureBased on an analysis of contaminant sources, contaminant concentration targets, and perceived acceptability targets.CO2 sensors are one methodCredit is given for controls that remove contaminants, such as filters and UV light, that can achieve concentrations equal to or lower than those achieved by the Ventilation Rate Procedure.
18CoolingSource: EEREChillersSource: ORNLCentrifugal ChillerChiller Minimum Efficiency Requirements (ASHRAE )Compressor Type/CapacityFull-Load Rating, COP (kBtu)Full-Load Rating, FLV (kW/ton)Part-Load Ratings, IPLV (kBtu)Reciprocating ( tons)4.200.845.05Screw/Scroll (<150 tons)4.450.805.20Screw ( tons)4.900.725.60Screw ( tons)5.500.646.15Centrifugal (<150 tons)5.000.705.25Best available Full-Load FLV is kW/ton for large (>150 ton) water-cooled chillers
19CoolingWater-cooled centrifugal chiller versus air-cooled screw chiller (20-year life) in office buildingEnergy simulation using DOE-2.2 Calculation Core EngineNet Present Value (NPV) of total costs of ownershipCost Category100-ton500-tonAirWaterNew York CityInitial50%68%22%42%Energy40%20%63%45%Maintenance10%12%15%13%Minneapolis72%78%60%16%35%Source: Total Cost of Ownership For Air-Cooled andWater-Cooled Chiller Systems, Ramez Naguib
20Chiller Maintenance Tips CoolingChiller Maintenance TipsVisual check of compressor oil (darker is worse).Change oil on large systems once a year and clean particles from case.Take superheat and subcooling temperature readings to obtain chiller's maximum efficiency.Install water gauges so you can see pressure drops, particularly through the evaporator.If tubes need cleaning and the interiors of the tubes are smooth bore, technicians can remove the sludge with bristle brushes attached to long metal rods.Put a bypass valve on the end of the pipe run going to the chillers to get the proper water flow (overflow can cause vibration, damaging the copper tubes).Clean water tower condensers and unclog spray nozzles, especially in the spring.Check for high vibration on a capillary line (causes leaks) and secure all vibrating lines.Source: John C. Schaub Inc., Mt. Laurel, NJ
21Full-load EER (Btu/watt) Cooling / heatingPackaged RooftopImage courtesy of McQuay InternationalUnitary Air Conditioner Minimum Efficiency Requirements ASHRAEFull-load EER (Btu/watt)Size RangePre-2010As of 2010*kBtu/hr (5-11 ton)10.311.2kBtu/hr (11-20 ton)9.711.0kBtu/hr (20-63 ton)9.510.0>760 kBtu/hr (>63 ton)9.2*Phase-out date for R-22 refrigerant
22Packaged Terminal Air Conditioners (PTACs) Cooling / heatingPackaged Terminal Air Conditioners (PTACs)EER of 10 to 12 available todaySuppliers include Amana, Bard, Carrier, ClimateMaster, Friedrich, GE, and SkymarkPTAC/PTHP Minimum Efficiency Requirements ASHRAEReplacementNew ConstructionCoolingFull-load EER (Btu/watt)PTAC (7,000 Btuh)9.411.0PTAC (15,000 Btuh)7.79.3PTHP (7,000 Btuh)10.8PTHP (15,000 Btuh)7.69.1HeatingFull-load COP (Kbtuh)2.73.02.52.8Source:
23Geothermal or Water-Source Heat Pump Cooling / heatingGeothermal or Water-Source Heat PumpTakes advantage of underground temperatures that range from 45°F (7°C) to 75°F (21°C).Roughly 30% savings compared to AC/Boiler or AC/Furnace combinationGeothermal requires higher capital investment and requires a significant amount of spaceHybrid geothermal saves on first cost but operating costs are higherImage courtesy of ECS GeothermalLoopDepthLength/tonVertical''/tonHorizontal5-6'800'/tonPond>8'400'/ton
24Cooling / heating Coil Cleaning Most commercial HVAC units have multiple coils stacked or sandwiched together.Outdoor condenser coils lose less performance with blockage than indoor evaporator coils.If the evaporator airflow of a 3-ton rooftop unit is restricted by 36%, the capacity drop is 19.4%.This changes the 3-ton unit to a 2.5-ton unit.On the other hand, when the condenser coils are 56% restricted, the capacity drops only 10.9%.Blocked condenser coils can increase condensing temperature by 8°F to 10°F resulting in a 6% to 8% increase in power consumption.You can check coil performance by measuring the air temperature drop across the coils.Larger temperature drops of 30ºF or higher indicate that a coil cleaning is in order.You can also measure supply-fan amperage or filter/coil pressure drop (with fresh filters) and compare this data against last year's readings.Image courtesy of Coil-Tech
25Heating Electric Boilers Electrode Steam Boilers Available from 10 kW for the smaller units up to over 3,000 kWOften used in tandem with a gas-fired boiler in a fuel-switching strategyReplacement of an electric element bundle (13-18 year life) can range in price from $2,000 to $2,500 for a 75 kW to 100 kW electric boilerElectrode Steam BoilersOperate at high voltages (12 kV or 24 kV)Submersible electrode boilersRely on immersed electrodes to conduct electricity through the boiler waterHigh-velocity jet electrode boilersIn this design, the water jet (striking an electrode plate) is the resistance elementPros include lower installed capital cost, higher reliability, higher efficiency (99.5% at 100% output) and rapid responseSource: Precision Boilers
26HeatingSpace HeatersAll portable electric heaters using a heating element are equally efficient in that they essentially convert all the electricity they use into heatOnly more cost-effective than whole-house furnaces if temperature is reduced in other roomsQuartz "Infrared" space heaters such as SunHeat and EdenPureInfrared radiation does not warm you directlyTraditional infrared (picture) has the coils and lamps exposed for direct line of site radiationCeramic and oil-filled heaters arguably provide greater heating comfort because they retain some heat after the current is offSource: Fostoria Industries
27Economizers bring in cool outside air AccessoriesEconomizers bring in cool outside airTypical 2 to 5 year payback for economizersRequired by ASHRAE 90 for >5 tons in cool/dry climates (West) and >11 tons in cool/moist climates (Midwest), but not in warm/moist climates (Southeast)Four Economizer ModesModeTemp. (ºF)MechanicalDamperHeating<30OnClosedModulated Economizer30-55OffVariesIntegrated Economizer55-75OpenCooling>75
28Heat Recovery Ventilators AccessoriesHeat Recovery VentilatorsCan recover about 60% to 70% of heat in exiting airLow grade heat for space heating and equipment expense results in long paybacksA solution to ASHRAE 62 IAQ requirementsSource: George Retseck Illustrations
29Energy/Enthalpy/Desiccant Wheels AccessoriesEnergy/Enthalpy/Desiccant WheelsCan recover about 70% to 80% of the energy in the exiting air and deliver that energy to the incoming air.Desiccant wheels are most cost effective in climates with extreme winters or summers, and where fuel costs are high.In mild climates, the cost of the additional electricity consumed by the system fans and drum motor may exceed the energy savings from not having to condition the supply air.Source: Fläkt WoodsSource: EERE
30Thermal Energy Storage (TES) AccessoriesThermal Energy Storage (TES)Thermal energy storage makes ice or chilled water during the night—shifts peak.Full Storage system shifts the entire load to off-peak hours and is driven by electric rates and rebates.In a Partial Storage system, a much smaller chiller runs during both peak and off-peak hours with help from stored cooling during peak hours.Attractive when more cooling capacity is needed or when a chiller needs to be replaced.Ice Energy (Windsor, CO) offers factory assembled modular ice making systems (Ice Bear) for small to medium-sized commercial applications.Image courtesy of CALMAC Manufacturing Corporation
31Thermal Energy Storage (TES) AccessoriesThermal Energy Storage (TES)Ice can absorb eight times the thermal energy of chilled water.Three up-front decisions during system design:How the ice is made and stored (ice on coil—internal melt, ice on coil—external melt, or encapsulated ice).How the ice bank is discharged.How cold is transported to the load (slurry systems versus brine or glycol transfer).Image courtesy of FAFCO, Incorporated
32Accessories Thermal Energy Storage (TES) Example: Shifting from peak to non-peak times with a resultant 600 kW drop in peak demand (1,500 kW to 900 kW)For example– at a demand charge of $8.00/kW, that saves $4,800 per month.Additional savings are possible if time-of-use rates result in a lower $/kWh energy charge during off-peak hours.Example: A normally 400-ton chiller outputting 3,000 ton-hours per day might be replaced by a 160-ton chiller.Produces 1,600 ton-hours during a 10-hour peak time period.Produces 1,400 ton-hours during a 14-hour off-peak period.
33Energy-savings tips Temperature Setback/Setforward Save 3% per °F per 24 hr72°F 68°F ( 4°F) for 12 hr saves 6%Obtain Proper Humidity ControlIn the summer, decrease relative humidity (RH) to feel cool.Operation at 78°F / 40% RH provides the same level of occupant comfort as 74°F / 50% RH does.74°F 78°F setforward for 24 hr saves 10% to 12%Remove moisture with desiccant or enthalpy/heat wheelRelative humidity >70% with temperature > 70°F can encourage mold growth!In the winter, opposite applies—raise RH to feel warm.Add moisture with evaporative humidifierUltrasonic humidifiers require filtered water
34Energy-savings tips Narrow your chiller water temperature set points Typical conditions are chilled water temperature of 42°F and condensing water temperature of 80°F to 85°F.2% savings per °F that chilled water temperature is raised5°F to 10°F increase is possible; more may cause damage and reduce cooling capacity (ton rating)Efficiency benefits from lowering condensing water temperature are offset by increased fan and pump operation, along with reduced cooling capacity.Variable Frequency Drives (VFDs) and oversizing the cooling tower can helpThe larger the system, the greater the net energy savings
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39Rocky Mountain Power FinAnswer Express FinAnswer Express is for commercial and industrial customers– either retrofit or new constructionPre-calculated incentives for HVAC equipment and high-efficiency lightingCustom incentives may be available for other types of equipmentIncentive process (pre-purchase agreement or post purchase application) varies by technology and project typePlease understand the process before you purchase!Check our website for on-line forms plus trade allies available to helpAlso check for state and federal tax incentives at dsire.org
40RMP Energy FinAnswerApplies to comprehensive commercial or industrial projects– either new construction or commercial retrofit*Lighting and non-lighting projects can be packagedStarts with an energy analysis to identify options and highest priority measuresCommissioning is required for most measuresIncentives are project-basedPayable by one-time lump sum check, per projectIncentive agreement must be signed before equipment is purchasedCheck our website for participation steps and online forms*Commercial retrofit projects must be at least 20,000 sq. ft. to be eligible
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