ASHRAE Modified Hunter Curve - Flow Charts

1 ASHRAE Modified Hunter Curve - Flow ChartsArmstrongHot Water Group, 221 Armstrong Blvd., Three Rivers, MI 49093 USA Phone: (269) 279-3602 Fax: (269) 1 Determine the total fixture unit load for all the fixtures servicedby your water heater application using the Fixture Units Tableon page 13. See example 2 Using the total fixture units for your application, enter the HunterCurves (Chart 12-1) from the bottom on the total fixture unitsline for your application. Read up to the Curve that best fits theapplication. Then read to the left for the corresponding 3 Select the proper Armstrong Water Heater/Water : College DormitoryRefer to the Modified Hunter Curves in Chart 12-2. Curve Brepresents dormitories. Enter the graph from the bottom at 359fixture units and go up to Curve B. Then move to the lefthorizontally to read approximately 60 gallons per minute of hotwater capacity required. NOTE: Remember to add any constant flow capacities, asdetermined under Important Note below, to this 60 NoteSpecial consideration should be given to applications involvingperiodic use of gang showers, process equipment, laundrymachines, etc.

2 , as may occur in field houses, gymnasiums,factories, hospitals, etc. Because these applications could haveall equipment on at the same time, their total hot water capacityshould be determined and then added to the maximum hotwater demand as read from the Modified Hunter Curves. Usethe following formula to determine total hot water capacityneeded for these applications when final water temperaturesare lower than that of the water :B = Blended water temperature out of the fixtureH = Hot water temperature to the fixtureC = Cold water temperature to the fixtureSeeenlargedchart HWS-24504003503002502002004006008001000 1200 1400 1600 180020002200 2400 2600280030001501005000 Curve A - RestaurantsGallons Per MinuteFixture UnitsCurve B - Hospitals, Nursing Homes,Nurses' Residences, Dormitories,Hotels and MotelsCurve C - Apt. HousesCurve D - Office Bldgs.,Elementary and High SchoolsConversion Factor:L/s = gpm x Per MinuteFixture UnitsCurve A - RestaurantsCurve B - Hospitals, Nursing Homes,Nurses' Residences, Dormitories,Hotels and MotelsCurve C - Apt.

3 Houses1009080604030202550751001251501752 0022525027530032535037540010005070 Conversion Factor:L/s = gpm x D - Office Bldgs.,Elementary and High SchoolsChart 12-1(B - C)(H - C)Total water flow from allgang shower heads in gpm= Hot water needed (gpm)xChart 12-2. Enlarged SectionReprinted from the 1987 ASHRAE Handbook HVAC with permission from the American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. Hunter curves should be used for intermittent, insignificant fixtures only.()150 Private Fixture UnitsNo. Fixtures Type of Fixture Fix. Unit Demand Fix. UnitFlo- 7/30/2009 3:16 PM Page 12 ArmstrongHot Water Group, 221 Armstrong Blvd., Three Rivers, MI 49093 USA Phone: (269) 279-3602 Fax: (269) Modified Hunter Curve - Fixture Units*These items require 180 F hot water. The consumption figures are based on supplying 140 F water with a booster heater used to obtain 180 F water.

4 **Add 20% to all figures when not used in combination with other building services from same heater. The fixture units listed for shower heads are based on a flow rate of 3 gpm. These units should be corrected for other flow rates . Multiply the fixture units by Correction Factor C from the formula: C = G x .33, where C = Correction Factor and G = gpm of shower head being used. Example: Shower head 4 gpm = C = 4 x .33 or From Fixture Units Table,Hotel-Motel (shower) which shows fixture units, multiply x = fixture units per shower head using 4 of FixtureFix. Units Type of FixtureFix. Units Type of FixtureFix. UnitsPrivate Private Private Private Public Public Ward - - Semi-Private - " Half - " Full - Pot (Single) " Half - Flushing - Pot (Double) " Full - - Pot (Triple) - - - General - - - *Type of FixtureFix. UnitsBath - - *Private - - - Private - Public and Pan * Tub and #1 Shower - #2 " Half Flow " Half " Full Flow " Full " Half " Full Sink and of FixtureFix.

5 UnitsType of FixtureFix. Units Type of FixtureFix. UnitsPrivate x 16 Private Private x 18 Public Public x 20 Tub and Tub and - - - - " Half - - " Full Tank Conveyor Clothes " Half " Full of FixtureFix. Units Type of FixtureFix. UnitsPrivate of FixtureFix. UnitsPublic Private Tub and Private - - Tub and - - - " Half - Beauty " Full Clothes " Half " Full of FixtureFix. UnitsType of FixtureFix. UnitsPrivate of FixtureFix. UnitsPrivate Private - Private Tub and Tub and - " Half - " Full BuildingFactory*DishwashersApartmentPriv ate - Public SchoolInstitution - HomeCorrectional or Mental Institution(use booster to heat from 140 to 180 F)Single Tank - Stationary RackMultiple Tank Conveyor TypeHotel - MotelContinuous Flow BathClubGymnasiumAssoc. Bldg. YMCAH ospitalHydrotherapeutic ShowersRestaurant**140 F Temperature From HeaterFlo- 7/30/2009 3:16 PM Page 13 ArmstrongHot Water Group, 221 Armstrong Blvd.

6 , Three Rivers, MI 49093 USA Phone: (269) 279-3602 Fax: (269) Water Storage versus Semi-Instantaneous Hot Water GenerationStand-by heat losses associated with larger storage vesselsand the additional energy required to run the inter-tankcirculating pumps is neither cost effective nor green .With Flo-Eco, large storage vessels are not required and inmost installations facility demands for hot water are moreeffectively met by increased btu input. Generally, only applications with large demands, over a shortperiod of time, justify the use of large capacity storage High Efficiency SolutionIn many cases high efficiency water heaters such as the Flo-Eco can be sized down in comparison with or when being compared with a standard efficiency water heater with the same Btu addition, the ability to stack up to three Flo-Eco on a singlefootprint offers system redundancy below 200,000 Btu/hr perheater historical tendency to rely upon storage vessels to providea feeling of security that the facility has an ample supply ofstored hot water in the event of a significant sudden demandrequires some example a design might call for a water heater to operateunder the following conditions:Based on the shaded information above, a typical selectionmight be 600,000 BTU input and 600 gallons of storage.

7 Thethinking being that 600 gallons of 120 F stored water will coverany and all surges in demand and allow the water heater ampletime to actual fact however the moment there is hot water demandon the water heater the 600 gallons of 120 F water isimmediately diluted with cold water as it enters the tank. Thehigher the flow the greater the turbulence within the tank thefaster the temperature falls the same installation scenario, Armstrong can replace600,000 btu s of input and 600 gallons of storage with 600,000btus of input and 180 gallons of storage and deliver superior hotwater generation :Standard Efficiency Water Heater Input = 600,000 = 498,000 = 83%Storage Capacity = 600 gallons Incoming Water Temperature = 40 Set Point = 120 = 498,000 = 497 GPH @ 80 F 95- 3 (Triple) High Efficiency Water HeaterInput = 600,000 = 570,000 = 95%Storage Capacity = 180 gallons Incoming Water Temperature = 40 Set Point = 120 = 570,000 = 568 GPH @ 80 F rise (+12%).

8 11411220 Comparison Heater03 Flo-Eco Heaters10304050108110116118120122 Time (t) (minutes)Temperature (T), FIncoming Water Temperature = 40 FWater Heater Set Point = 120 FTemperature Rise = 80 FDemand = 15 GPMFlo- 7/30/2009 3:16 PM Page 14 ArmstrongHot Water Group, 221 Armstrong Blvd., Three Rivers, MI 49093 USA Phone: (269) 279-3602 Fax: (269) and General Application SizingBTU/h Input Requirement Apply Modified Hunter Curve to fixture count Convert to GPM Select Incoming Water Temperature = F Select Desired Outlet Temperature = F Calculate Temperature Rise GPM (Temperature Rise) X 500 = BTU Apply Armstrong Diversity factor of .72 Divide BTU/h by 200,000 to determine number of Flo-Eco modules of Stored Hot Water Number of modules required multiplied by 60 = Amount of Stored Hot WaterRecovery RateRecovery Rate in Gallons Per Hour = Btu/weight of 1 gallon of water/Temperature RiseGPH = Btu / / TIntegrating The Brain Digital Recirculating Valve (DRV)Flo-Eco water heaters are designed to generate and store hotwater at elevated water temperature control is incredibly with the high temperature alert and systemconnectivity features we can confidently specify higher hot watergeneration a result, at a typical hot water setpoint of 120 F, an elevatedgeneration and storage temperature enhances the total addition, higher hot water generation and storagetemperatures promote compliance with OSHA, CDC and othernational and global Legionella management - Water Heater only.

9 Storage Capacity = 180 gallonsCold Water Temperature = 40 FWater Heater Set Point = 120 FSystem Set Point =120 FHot Water availability at 120 F = 180 gallonsExample - Water Heater with integral Brain:Storage Capacity = 180 gallonsCold Water Temperature = 40 FWater Heater Set Point = 160 FSystem Set Point = 120 FAdditional Cold Water added to mix to 120 F = 92 gallonsHot Water availability at 120 F = 272 gallons What about the on call hot water in the buildingpipework?Factoring in the building s re-circulating plumbing system furtherenhances the principle that in many cases smaller is that a 2 diameter 12 long piece of copper pipe holds .375 US gallons of water. That means a 1000 linear footre-circulating hot water system contains 375 gallons of water ator at least close to the desired system temperature. Total Hot Water Solution Btu inputs which deliver satisfactory recovery Storage capacity which supports periods of high demand Digital mixing valve integration which offers enhanced capacityby adjusting the generation set point an understanding of the amount of on call domestic hot water the plumbing system has available.

10 Are all important components of a total High Efficiency HotWater and Digital Control simplicity purposes we provide a rudimentary sizing formula below. For more specific application and sizing support pleasecontact Armstrong directly or visit our website at to access sizing SizingFlo- 7/30/2009 3:16 PM Page 15