geothermal systems using water source heat pumps northrich company / roberts mechanical
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Geothermal Systems Using Water Source Heat Pumps
Northrich Company / Roberts Mechanical
Presentation FocusTypes of SystemsBuilding types and advantagesWater LoopDifferent types of loopsSystem IdeasHeat PumpsHeat RecoverySystem SchematicsFully Package Geothermal SkidCost Benefit ExamplesUp front cost vs. life cycle cost
What Type of Buildings use Geo Systems?Virtually Any Building can use a Geothermal Heating and Cooling System
Schools (Terminal units, AHU, VAV, multi-zone, unit vents)Office Buildings (Terminal units, AHU, VAV, fan coils)Hotels (AHU, fan coils)Government Buildings (AHU, VAV, fan coils)Residential homes
Advantages of Geothermal Environmentally friendly Design flexibility Terminal unitsCentral PlantLow energy costs eliminate or reduce natural gas usageLong term Solution extended life cycleMajority of equipment is indoorsGround loops last a long timeLower maintenance No cooling tower or boilerNo chiller
Earth - Heat Sink and Heat SourceHeat Sink - SummerGeothermal systems use the ground as a heat sink in the summer excess energy is rejected into the ground via a water loop
Heat Source - WinterGeothermal systems use the ground as a heat source in the winter energy is added to the building via a water loop
Ground is Heat Sink
Ground is Heat Source
Water Loop Variables
**Cooling & Heating load (ventilation)**Equipment Performance (EER & COP)Load diversityLoops can be oversized if building diversity is not accounted forSite characteristicsLand available?Pond or Lake?Soil Conditions?
The Water Loop - 4 Main TypesClosed Loop Boiler/TowerCooling Tower to reject heat in summerBoiler to add heat in winter System temperatures typically range from 60 to 95Tower and boiler maintenanceGeothermal Loop Closed loop HorizontalVerticalClosed PondSystem temperatures range from 35 to 90
The Water Loop - 4 Main TypesOpen LoopPump and Dump Directly into the heat pump with suitable waterIntermediate heat exchanger if the water is a problemSystem temperatures typically range from 40 to 90Hybrid Loop Any combination of the two typically a boiler and/or cooling tower attached to a closed loopLower first cost due to smaller loopPopular with Geo retrofits
Most common for large commercial projects
Smaller Land Requirement150 to 250 feet per ton depth depends on thermal250 square feel per ton (15 foot centers)Soil borings Thermal conductivity of soil will dictate the amount of pipeVertical boresWell drilling machineryPolyethylene pipePipe is joined by heat fusion that make the joints stronger than the pipe itself
Vertical bores4.5 to 6.5 inch bore holesGrout is pumped down the bore holesReverse return Freeze ProtectionAverage water temps 33 to 90 Methanol, Ethanol, or PropyleneDesignSystems should be designed & installed by a certified Ground Loop Engineer
Can be placed under a parking lot
Ground WaterPond or LakeMan made or natural10 to 12 feet minimum10 to 50 tons per acreAverage Water Temperature 35 to 87Evaporative effect of water in summerThermal conductivity of the earth in the winter
Traditional Plastic Pipe on Pond Floor300 to 350 feet of plastic pipe per tonPipe coils separated by spacersReverse Return pipingFloat out the pipes and then fill them with water to sink to the floor of the pondLabor intensive
Geo Lake Plate from Slim JimAWEBB Supply - Baton Rouge, LAStainless steel plates connected to building MountingFeetSkidsFloating
Geo Lake Plate from Slim JimLong lasting SimpleCustom configurationsLower labor costs200 Tons8 Tons on skid
Pump and DumpColder water in coolingFilter out debris in the waterIntermediate heat exchanger
What is a Heat Pump?
A heat pump is a traditional compressor driven air conditioner with a refrigerant reversing valve. When engaged the reversing valve reverses the flow of the refrigerant through the liquid line changing the evaporator into the condenser and vice versa.
Types of Heat Pumps
Air to air some commercial applications mainly a residential product.Water to Air water in one side hot or cold air out the other side (3.0 GPM/Ton)Water to Water water in one side hot or cold water out the other side (3.0 GPM/Ton)
Source TemperatureTemperature of geo loopLoad TemperatureTemperature of building side of the system (typically used with water to water product)Cooling Capacity Amount of cooling at a certain source water tempHeating CapacityAmount of heating at a certain source water temp KWElectricity used at a certain source water tempUsed to calculate EER in cooling modeUsed to calculate COP in heating mode
EERCooling Capacity (BTU) / (KW) Inverse of KW/Ton (( 1 / EER) X 12)COPHeating Capacity (BTU) / (KW input X 3412 BTU/KW) Heat of ExtractionEnergy taken out of the loop in heating modeHeat of RejectionEnergy added to the loop in cooling mode
Old ARI ConditionsARI 320-93 Boiler/Tower (85 Cooling / 70 Heating)ARI 325-93 Ground Water Open Loop (70 Cooling / 50 Heating)ARI 330 93 Geothermal Closed Loop ((77 Cooling / 32 Heating)
ARI/ISO 13256 joint StandardBoiler/Tower (86 Cooling / 68 Heating)Ground Water Open Loop (59 Cooling / 50 Heating)Geothermal Closed Loop (77 Cooling / 32 Heating)
EER and COP data is certified at ARI/ISO conditions
Geothermal Heat Pumps
Extended RangeHeat generated at low source temperatures 30 F or lowerBetter constructionDesigned for longer lifeCoated evaporator coils Painted cabinetsNew equipment on the market due to 410a refrigerantECM motors
Higher EERsEnhanced control capabilities
Geothermal Pump SkidIntegrated boilersIntegrated domestic water (IWH)Integrated controlsSystem FlexibilityMaximize the use of your boilers and equipmentComplete redundancyMinimize Installation, start-up, integration costs
Selecting a proper boilerLook closely at efficiency curvesControl sequencing must be reviewedMODULATION IS CRITICAL TO EFFICIENCY ON MODULATING BOILERSRETURN WATER TEMPERATURES ARE CRITICAL TO EFFICIENCY ON CONDENSING BOILERS.First determine boiler type.CONDENSING (LOW RETURN TEMP)COPPER MODULTING (MID RETURN TEMP)COPPER OR STEEL 85% (HIGHER RETURN TEMP)
Condensing Boiler90% - 99% efficient at return temperatures below 120FA good choice could eliminate redundant controlsFlow to control temperature and delta tee.Primary secondary often not required.AL29-4C!
Copper Modulating Boiler89% to 85% based on modulation.Return temps to 115F acceptable, 100F with proper piping and accessories.Primary / Secondary always required.Modulation controls CRITICAL and should not be left to the BMS.AL29-4C!
Copper Mid Efficiency Boiler85% flat line efficiency curve.Return temps to 115F acceptable, 100F with proper piping and accessories.Primary / Secondary always required.Simple staging. Desirable with multiple boilers.Category I or III venting acceptable.
Steel Boilers80% to 85% but can lose efficiency based on age. (Scale/Soot)Return temps to 140F.Available with built in low temp heat exchanger.Forced draft Category III.
Other boiler considerationsSeasonal efficiencySome condensing fire most the season below 85% when temperatures are above 140F.Load vs. Savings (life cycle payback)Boiler manufacturersScaled down controls (residential type)True Freeze Protection.Small tubing to attain efficiencyCommunication abilitySupport and ServiceLocal service and supportNational backboneProprietary combustion controlsIgnition systems / reliabilityFootprint vs. Service ClearancesHeight!!Depth of piping and venting
Conceptual Layout OptionsHYDROTHERM KN6 CONDENSING BOILERS Geothermal Suggested Piping - NTSFrom Building200 GPMBoilers @ 100 GPM each 10F Delta Tee / 2.7 psi dropTo BuildingHX1CT-1ST1System shall flow through the boilers. The boilers shall sense the temperature and be set to fire below 50F. Boilers will be wired to each other and modulate together on the highest point of the efficiency curve. This drawing is for conceptual purposes and should not be used for installation. The drawing does not include many required accessories such as expansion air elimination, etc.
Critical Spec Items Heat PumpsHeat pump performance capabilities: EER: 30.0; COP: 5.0 (Part load at ARI/ISO 13256-1 (Ground Loop Heat Pump) minimum 23.0 EER cooling and 4.0 COP heating) Temperature range Loop design is based on Heat Pump performance. WSHP not meeting ARI certified operating performance requirements are responsible for added ground loop requirements.Insulated coaxial heat exchanger - extended range of temperatures eliminates condensation410A refrigerant (Ozone depletion)Dual speed compressor for energy & eliminates auxiliary heat requirementMulti-speed ECM Motor for energy, and to monitor & control humidityFoil faced cabinet insulationPainted cabinet longer lifeMicroprocessor control
Critical Spec Items GeoSkidPump performance (VIL for long life)Proper boiler selectionProper control selectionBoiler efficienciesSingle point responsibility:PumpsBoilersControlsIntegration
LEED POINTSMeet all minimum pre-requisites for Energy & AtmosphersEnergy performance above minimum ASHRAE 90.1 standards1-10 point possible for optimum energy performanceASHRAE requires EER-12, WFI operates at EER-23 at ARI standards 30-50% increase