I've made a simple coil to sense current flowing to the upper and lower elements of two hot water heaters of a hydronic heating system. An led with current limiting resister lets led show when a heater element is on so I can tell if the system is keeping up with the demand or not. But, the collapsing ac when heater turns off is frying my led after a few weeks. I need a bit of guidance to add a diode or choke or what?
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