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Tankless Water Heater
System Design Manual
Plumbing schematics for single
and multiple tankless water
heaters in use with domestic
systems, recirculation, and
storage tanks.
PRINTED 0708 186965-000
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Table of Contents Certifications..................................................................................3 Water Quality and Scale ................................................................4 Pump Sizing for Circulation..........................................................5 Tank Water Heaters in a Circulation Loop ...................................6 Additional Guidelines....................................................................6 Pump Sizing for Storage
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Approvals ATI-305-N GTS-305-NI GT-305-NI ATI-305-P GTS-305-PI GT-305-PI ATO-305-N GTS-305-NE GT-305-NE ATO-305-P GTS-305-PE GT-305-PE ATI-505-N GTS-505-NI GT-505-NI ATI-505-P GTS-505-PI GT-505-PI ATO-505-N GTS-505-NE GT-505-NE ATO-505-P GTS-505-PE GT-505-PE ATI-705-N GTS-705-NI GT-705-NI ATI-705-P GTS-705-PI GT-705-PI ATO-705-N GTS-705-NE GT-705-NE ATO-705-P GTS-705-PE GT-705-PE ATI-705A-N GTS-705-NIA AGT-705-NI ATI-705A-P GTS-705-PIA AGT-705-PI ATO-705A
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3900 3300 2700 2100 1500 900 300 0 Water Quality and Scale A complete water analysis and an understanding of system requirements are needed to protect the tankless water heaters and water heating systems from scale. Water analysis shows whether water is hard or soft. Hard water, unless treated, will cause scaling or liming of the heat exchanger. The rate of scaling increases with temperature and usage because calcium carbonate and other scaling compounds lose solubility (fall out of solut
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Pump Sizing for Circulation 1. Use the chart below or one appropriate for your conditions to determine the heat loss in the length of the hot water supply and return piping. For example, 100 ft of 1-1/2 in bare copper tubing results in a heat loss of 5300 Btu/h. Approximate Heat Loss from Piping at 140 ºF Inlet, 70 ºF Ambient * Nominal Size, in. Bare Copper Tubing, 1/2 in. Glass Fiber Insulated Btu/h-ft Copper Tubing, Btu/h-ft 3/4 30 17.7 1 38 20.3 1-1/4 45 23.4 1-1/2 53 25.4 2 66 29
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Tank Water Heaters in a Circulation Loop The following applies when using a tank water heater (gas or electric) to provide heat for a circulation loop. Drawing WH-1-RGE is an example. The heat output of the tank must be equal to or greater than the calculated circulation loop heat loss. (Reference page 6, Step 1 on calculating heat loss). Electric Tank Water Heater Since the input and output are the same for an electric tank water heater, this can be expressed as: Electric Tank Input (
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Pump Sizing for Storage Tank Application The following applies when using tankless water heaters to recover a storage tank. Drawing WH-1-B is an example. Tankless water heaters have a pressure loss which must be considered in the system design. Reference the pressure loss curve for the heater model being used to determine the pump size for the desired recovery rate. For recommended pump sizes use the table below. Additional pressure losses in plumbing between the
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Pressure Loss Curves Pressure Loss (ft head) 705 505 305i 305e Pressure Loss (psi) 8 45.0 40.0 60.0 35.0 50.0 30.0 40.0 25.0 20.0 30.0 15.0 20.0 10.0 10.0 5.0 0.0 0.0 01 234 5 6 789 10 11 Water Flow (gpm)
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9 G as S upply 3/4 " C old W ater S upply Line Tankless Equipment List QTY Tankless 1 Water Heaters Tankless Water Heater 3/4" Hot Water Supply Line Domestic Hot Water - Standard Installation Drawing Number: 1 Tankless Water Heater WH-1 Preferred Piping Installation Drawing Date: This is not an engineering drawing; it is intended only as a guide and not Key as a replacement for professional engineering project drawings. This June 11, 2007 drawing is not intended to describe a complete system.
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10 Tankless Equipment List QTY Tankless 2 Tankless Water Heaters Tankless Water Heater Water Heater Electronic Connection * * Refer to Tankless Accessories and Model Applicability for Primary Sub 1 electronic connection details. Gas Supply Cold Water Supply Line Hot Water Supply Line Domestic Hot Water - Standard Installation Drawing Number: 2 Tankless Water Heaters WH-2 Preferred Piping Installation Drawing Date: This is not an engineering drawing; it is intended
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11 Tankless Equipment List QTY Tankless Tankless Tankless Tankless 3 Water Heater Water Heater Water Heater Water Heaters Electronic Connection * Primary Sub 1 Sub 2 * Refer to Tankless Accessories and Model Applicability for electronic connection details. Gas Supply Cold Water Supply Line Hot Water Supply Line Domestic Hot Water - Standard Installation Drawing Number: 3 Tankless Water Heaters WH-3 Preferred Piping Installation Drawing Date: This is not an engineer
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12 Tankless Equipment List QTY Tankless 4 Water Heaters Tankless Tankless Tankless Tankless Water Heater Water Heater Water Heater Water Heater Electronic Connection * * Refer to Tankless Accessories and Model Applicability for Primary Sub 1 Sub 2 Sub 3 electronic connection details. Gas Supply Cold Water Supply Line Hot Water Supply Line Domestic Hot Water - Standard Installation Drawing Number: 4 Tankless Water Heaters WH-4 Preferred Piping Installation Drawing D
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13 Tankless Equipment List QTY Tankless 5 Tankless Tankless Water Heaters Tankless Tankless Tankless Water Heater Water Heater Water Heater Water Heater Water Heater Electronic Connection * * Refer to Tankless Accessories Primary Sub 1 Sub 2 Sub 4 Sub 3 and Model Applicability for electronic connection details. Gas Supply Cold Water Supply Line Hot Water Supply Line Domestic Hot Water - Standard Installation Drawing Number: 5 Tankless Water Heaters WH-5 Preferred P
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14 Tankless Equipment List QTY Tankless Tankless Tankless Tankless Tankless Tankless Water Water Water Water Water Water Tankless 6 Heater Heater Heater Heater Heater Heater Water Heaters Sub 1 Primary Sub 2 Primary Sub 1 Sub 2 Electronic Connection * * Refer to Tankless Accessories and Model Applicability for electronic connection details. Gas Supply Pressure Regulator Set to 5 PSI Below Street Pressure Hot Water Supply Line Cold Water Supply Line Domestic Hot
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S 15 Minimum 3/4 " C old W ater S upply Line IMPORTANT! Tankless Vacuum Equipment List QTY Breaker With electrical power supplied to a Tankless water heater, it will not freeze in Outdoor Tankless 1 Water Heater enviornments as cold as -30ºF, when protected from direct wind exposure. Outdoor In the event of a power failure at temperatures below freezing, the water Tankless heater should be drained of all water to prevent freezing damage. Water Heater The unit may be drained manually
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S S 16 IMPORTANT! Vacuum Tankless Breaker Equipment List QTY With electrical power supplied to a Tankless water heater, it will not freeze in Outdoor Outdoor enviornments as cold as -30ºF, when protected from direct wind exposure. Tankless Outdood 2 Tankless Tankless Water Heaters Water Heater Water Heater In the event of a power failure at temperatures below freezing, the water heater should be drained of all water to prevent freezing damage. Electronic Connection * Primary Sub 1 Th
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S 17 Tankless IMPORTANT! Equipment List QTY Vacuum With electrical power supplied to a Breaker Outdoor Outdoor Outdoor Tankles water heater, it will not Tankless Outdoor 3 Tankless Tankless Tankless Water Heaters freeze in enviornments as cold as Water Heater Water Heater Water Heater -30ºF, when protected from direct wind exposure. Electronic Connection * Sub 2 Primary Sub 1 In the event of a power failure at * Refer to Tankless Accessories NOTE: and Model Applicability for tem
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S 18 IMPORTANT! Tankless Equipment List QTY With electrical power supplied to a Outdoor Outdoor Outdoor Outdoor Outdoor Outdoor Tankless water heater, it will not Vacuum Tankless Outdoor 6 Tankless Tankless Tankless Tankless Tankless Tankless freeze in enviornments as cold as Breaker Water Heaters Water Heater Water Heater Water Heater Water Heater Water Heater Water Heater -30ºF, when protected from direct Pri mary Sub 1 Sub 2 Sub 2 Pri mary Sub 1 wind exposure. Electronic Connec
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19 Tankless For this application: Equipment List QTY Tankless Pump should be controlled by an Aquastat, Tankless 1 Water Heater Timer or Combination Aquastat and Timer. Water Heater Pump to be sized to maintain circulation loop temperature. The pump should be sized to overcome the pressure loss through the tank water heater, and supply and return plumbing in the circulation loop. Reference the section Pump Sizing for Circulation. Pump to be of bronze or stainless
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20 G as S upply Tankless For this application: Equipment List QTY Tankless Tankless 1 Pump should be controlled by an Aquastat, Water Heater Water Heater Timer or Combination Aquastat and Timer. Pump to be sized to maintain circulation loop temperature. A minimum of 3 GPM flow is recommended for the circulation system. The pump should be sized to overcome the pressure loss through the Tankless water heater, optional storage tank, and supply and return plumbing in t
