Criterion 6.1.3.6 Heat Exchanger

Criterion text:
When toxic fluids are used as the heat transfer medium, a double wall heat exchanger shall be used. The heat exchanger design shall be such that any failure of a barrier material shall allow the discharge of exchanger fluid and/or potable water to the atmosphere. The discharge location shall be visible to the operator or owner of the system and be located so that no hazards are created by such discharge.

A single wall heat exchanger may be used when in compliance with both of the following:

1. Heat transfer medium is taken from a potable water source or is distilled water suitable for domestic use. Any additives shall be listed in the Code of Federal Regulations, Title 21, Food and Drugs, Chapter 1, Food and Drug Administration, Part 182, “Substances Generally Recognized as Safe,” Part 184, “Direct Food Substances Affirmed as Generally Recognized as Safe.”

2. Operating pressure within the heat exchanger shall be less than the normal minimum operating pressure of the potable water system.

Comments:
A review of the heat exchanger and fluids used in the system is conducted during the formal SRCC system certification review process.

This is a very critical criterion that impacts client safety. The installer must use the specific heat exchanger and fluid that has been provided by the manufacturer with the SRCC certified system.

Installers should review and become familiar with the manufacturer's installation manual since it provides critical information related to system installation, components, and materials.

The installation manual is also invaluable after the system has been installed since service personnel may not be familiar with the particular system. The manual describes the type of heat exchanger as well as the type of heat transfer fluid used.

Figure 1 illustrates the difference between a single wall and double wall heat exchanger. Installers should be aware of the differences and how these differences impact the approved type of heat transfer fluid. Each type has specific requirements.

Figure 1

For general information, Figure 2 provides examples of various heat exchanger models. Note that heat exchangers can be internal to a storage tank or external.

Figure 2

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