Hot Water System Design Manual Plumbing schematics for single and multiple Rinnai water heaters in use with domestic systems, recirculation, and storage tanks.
Table of Contents MSB Kits for Connecting Multiple Water Heaters ........ 3 Drawing Water Quality and Scale .................................................. 4 WH1-D 1 Freeze Protection .......................... 35 Pump Sizing for Circulation ........................................... 5 WH2-D 2 Freeze Protection .......................... 36 Additional Guidelines ...................................................... 6 WH3-D 3 Freeze Protection ..........................
MSB Kits for Connecting Multiple Water Heaters Each bank is controlled by an MSB-M control board. These boards are connected to each other with MSB-C2 cables. One MSB-M is the controlling or master MSB-M for the entire system.
Water Quality and Scale The rate of scaling increases with temperature and usage because calcium carbonate and other scaling compounds lose solubility (fall out of solution) at higher temperatures. For example, for every 20°F over 140°F, the rate of scale increases by a factor of 2 (See figure below). Reference target water quality levels below and treat the water if these levels are exceeded.
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, Btu/h-ft 1/2 in. Glass Fiber Insulated 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.
Additional Guidelines Rinnai water heaters not recovering a storage tank: In applications involving a commercial dishwasher, a hot water circulation loop feeding the dishwasher is required. Rinnai water heater recovering a storage tank: In applications involving a commercial dishwasher, a hot water circulation loop feeding the dishwasher may be required depending on the distance between the dishwasher and the storage tank. Refer to local codes when determining the need for circulation loops to dishwashers.
Pump Sizing for Storage Tank Application The following applies when using Rinnai tankless water heaters to recover a storage tank. Drawing WH1-BC is an example. Rinnai Tankless water heaters have a pressure loss which must be considered in the system design. Reference the pressure loss curve for the Rinnai model being used to determine the pump size for the desired recovery rate. For recommended pump sizes use the table below.
Pressure Drop Curves-Non Condensing Models V94i/e,V94Xi RL94i/e, RLX94i Pressure Loss (psi) Pressure Loss (ft head) V75i/e V65i/e RL75i/e Water Flow (gpm) 8 R-TRWH-E-02 Rev E
Pressure Drop Curves-Condensing Models Pressure Loss (psi) Pressure Loss (ft head) RUC80i, RUC90i, RUC98i, RU80e RU90e RU98e, C199i/e 9 R-TRWH-E-02 Rev E
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Rinnai America Corporation • 103 International Drive, Peachtree City, GA 30269 Toll-Free: 1-800-621-9419 • Phone: 678-829-1700 • www.rinnai.us ©2015 Rinnai America Corporation. Rinnai is continually updating and improving products; therefore, specifications are subject to change without prior notice. Local, state, provincial and federal and national fuel gas codes must be adhered to prior to and upon installation.
