For these public safety-critical (fail-safe) interlocks to assure that no chemicals are fed without water recirculation, we must have an electrical expert or engineer on the working group for their opinion. A quick review of controller operation and install manuals states that a flow sensor alone is insufficient to assure success, that intermittant eletrical grid fluctualtions or nearby surges from lightning or other sources (even intentiaonal acts by operators) can overwhelm a controller and allow the chemical feeders to activate. This is because controller manufacturers do NOT have 100% confidence in their flow sensors to cease flow from feeders. Interlocks are generally found in the controllers' relays in their power board. And then there is is my state's pool construction code that requires an electrical interlock for chemical feeders or generators in six different scenarios. BV
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