Product Overview
The Rinnai / Grundfos GTK03U is an external recirculation-pump kit for compatible Rinnai tankless water heaters that support Circ-Logic control. It adds a Grundfos circulator with an internal check valve to an approved recirculation layout, allowing the heater's Circ-Logic settings to control scheduled or demand-based circulation according to the connected heater and installation design.
The kit includes the pump, prewired conduit with fuse protection, and connection components identified for the GTK03U installation. The required piping arrangement is model and application specific. Do not assume that this kit eliminates a dedicated return line or that every crossover configuration is approved. Follow the installation-manual section assigned to the exact Rinnai model and design the loop according to the manufacturer requirements.
The confirmed pump data lists a 20 GPM flow-range reference, 17 ft head range, 150°F maximum liquid temperature, 145 PSI maximum system pressure, 115V power, and 3/4 in. flange connections. Total equivalent pipe length must be calculated by the installer; the confirmed data references up to 200 ft of equivalent 3/4 in. piping at 120°F under the stated conditions.
Key Features:
- External Circ-Logic recirculation-pump kit
- For compatible Rinnai tankless water heaters
- Grundfos stainless steel circulator with internal check valve
- Prewired conduit with fuse protection
- 3/4 in. flange connection format
- 115V, 60 Hz operation
- Model-specific installation instructions
Common Uses:
- Adding external recirculation to an approved Rinnai Circ-Logic heater
- Dedicated-return or other manufacturer-approved loop configurations
- Reducing hot-water wait time when the complete system is correctly designed
- Replacement of a matching GTK03U pump kit
Technical Specifications:
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Model: GTK03U
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Pump Housing: Stainless steel with internal check valve
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Flow Reference: 20 GPM
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Head Range: 17 ft (5 m)
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Maximum Liquid Temperature: 150°F
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Maximum System Pressure: 145 PSI
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Voltage: 115V, 60 Hz
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Maximum Amperage: 0.75A
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Connection Size: 3/4 in. flange
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Combined Pump and Flange-Kit Weight: 8.6 lb
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Equivalent Pipe-Length Reference: Up to 200 ft of 3/4 in. piping at 120°F under the stated design conditions
Compatibility:
Follow Section 2 of the installation manual for the listed RU199i/e, RU180i/e, RU160i/e, RU130i/e, CU199i/e, and CU160i/e models. Follow Section 3 for the listed RLX94i, RL75i/e VC, RL94i/e VC, RU98i/RUC98i and RU98e KB, and RU80i/RUC80i and RU80e KB models. Confirm the complete model number and current Rinnai documentation before installation.
Installation Notes:
Calculate total equivalent pipe length, confirm the approved loop design, heater configuration, electrical supply, connection sizes, check-valve placement, insulation, and Circ-Logic settings. Installation should follow the Rinnai/Grundfos manual and be completed by qualified plumbing and electrical professionals where required.
FAQ:
Does the GTK03U work with every Rinnai tankless water heater?
No. Use it only with compatible Circ-Logic models listed in the current installation instructions.
Does this kit always remove the need for a return line?
No. The approved piping arrangement depends on the heater model and manufacturer instructions.
What is the maximum liquid temperature?
The confirmed maximum is 150°F.
How is allowable pipe length determined?
The installer must calculate the total equivalent length, including supply, return, and fittings.
Why Buy From Big Frog Supply?
Big Frog Supply provides clear technical information, helpful support, and convenient online ordering for tankless-water-heater recirculation equipment.
