P-K DURATION® Indirect Domestic Hot Water System

Models: D3-30, D3-50, D3-80

Available in Instantaneous, Pumped, or Base Versions

P-K DURATION® domestic water heating systems are specifically designed to help prevent scale build-up.

Scale is a domestic hot water heating system’s worst enemy. The build-up of scale can reduce the efficiency of a heating system. If allowed to accumulate over time, the scale build-up could ultimately result in premature system failure. For these reasons, preventing scale is critical to maintaining optimal system efficiency and ensuring energy savings.

The DURATION® III is a fully packaged, water-to-water indirect domestic hot water system. Engineered to complement any condensing source, the DURATION® III offers a low cost of ownership through simplicity, high efficiency, durability, and ease of installation.

Indirect water heaters combined with a high-efficiency boiler provide an efficient, economical method of heating water.

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P-K Long Term Durability

To ensure longevity, the DURATION® III has a durable 316L stainless steel double-wall brazed-plate heat exchanger with a true air gap. All wetted parts (potable water side) are lead-free and made of robust stainless steel, copper, or copper alloy materials.


The DURATION® III domestic hot water heater’s small footprint is less than 5.5 ft2 (15″W x 50″L).  This allows it to fit through a standard doorway or onto an elevator and requires no special rigging. It ships fully assembled and needs only four water connections and one power connection. Save space with simplified multiple unit installations and configure your space to meet your needs.

Easy to Integrate

It easily integrates with building automation system (BAS) software via the integrated Modbus RS-485 protocol (instantaneous version only-ref. model #’s). Also supports LONWORKS/BACnet and METASYS N2 are available by adding an optional protocol converter for even greater flexibility. Pumped Versions (D344P/D3-44PE and D3-88P/D3-88PE) are designed to operate seamlessly with the NURO® Control System.


  • Recovery Rates (40°F – 140°F) — 0 – 85 GPM Domestic Water Demand
  • High-quality stainless steel brazed plate heat exchanger
  • Specifically engineered to complement any condensing source
  • Compact footprint is less than 5.5 ft2


  • Easy integration with BAS software via integrated Modbus RS-485 protocol
  • Requires four water connections
    • Two connections for DHW inlet/outlet
    • Two connections for boiler water inlet/outlet
  • Requires one power connection
    • A single 110V electrical power supply connection
  • Pumped Versions (D3-44P/D3-44PE and D3-88P/D3- 88PE) designed to operate seamlessly with NURO touch screen control
  • Models can be placed side-by-side in a multi-unit installation

Contact us to learn more about the Patterson-Kelley difference.

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