{"product_id":"heater-control-firemans-switch-kit","title":"Intermatic Heater Control (Fireman's) Switch Kit","description":"\u003cp\u003eThe Intermatic 156T4042A is a heater control kit, the part most people call a fireman's switch. It coordinates a gas fired pool or spa heater with the filter pump so the heater is always shut down first.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eHow it works\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eThe switch turns the heater off roughly 20 minutes before the filter pump stops. During those minutes the pump keeps water moving through the heat exchanger and carries the leftover heat away.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eWhat that prevents\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eWhen a heater shuts off at the same moment as the pump, the water trapped in the exchanger keeps absorbing heat with nowhere to go. That is what causes the pounding and knocking owners hear at the pad, and it drives scale and lime deposits onto the exchanger surfaces. Running the pump on for a while afterwards avoids both and adds years to the heater.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eFitting\u003c\/strong\u003e\u003c\/p\u003e\u003cp\u003eIt is supplied as a kit for installation with an Intermatic time clock controlling the filter pump.\u003c\/p\u003e","brand":"Intermatic","offers":[{"title":"Default Title","offer_id":48634472071380,"sku":"INT-30-684","price":47.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0801\/9568\/2516\/files\/default_a63b2794-646e-496e-ac9b-53c4527fd36e.jpg?v=1788831757","url":"https:\/\/www.activepoolsupply.com\/products\/heater-control-firemans-switch-kit","provider":"Active Pool Supply","version":"1.0","type":"link"}