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Heat exchangers using a toxic transfer fluid or having conditioning chemicals in the system shall be separated from the potable water by double wall construction. There shall be an air gap open to the atmosphere between the two walls. No heat exchanger will be permitted on any boiler system operating in excess of 65 psi (448.2 kPa), or high temperature hot water system operating in excess of 250°F (121°C), or any steam boiler operating with a pressure in excess of 50 psi (344.75 kPa), unless:
1. The heat exchanger is double-walled;
2. The heat exchanger has an air gap open to the atmosphere between the two walls; and
3. The heat exchanger has a pressure gradient monitor system with a “fail-safe to off” switch installed to isolate the heat exchanger from the potable cold or hot water system. If pressure on the potable water side reaches less than 20 psi (137.9 kPa) above the pressure of the transfer fluid or steam, and a pressure reducing valve is installed on the inlet to the heat exchanger with a setting of 20 psi (137.9 kPa) lower than the potable water pressure at the heat exchanger, an audible alarm shall be activated and the heat exchanger shall be automatically shut off until the alarm and the heat exchanger can be reset manually. Any boiler using toxic chemicals shall have a label with a minimum size of 5 inches by 5 inches (125 mm by 125 mm) attached to the boiler in a conspicuous place. The label shall read as follows:
WARNING Chemicals and additives used to treat the boiler feed water in this boiler are not approved for potable water. The steam or hot water produced by this boiler is not potable. If the steam or hot water produced by this boiler is used to heat water, the water will not be considered potable if the steam and potable water are mixed. |