{"product_id":"tempstar-40va-transformer-for-t8mpt100j20b1-115v-to-24v-ships-today","title":"Tempstar 40VA Transformer for T8MPT100J20B1 - 115V to 24V | Ships Today","description":"\u003ch3\u003eOverview\u003c\/h3\u003e\n\u003cp\u003eThis OEM 40VA control transformer (Tempstar part 1172810) steps line voltage down from 115V to the 24V low-voltage power that runs the furnace control board, thermostat, gas valve, and relays in the Tempstar T8MPT100J20B1. Every call for heat depends on clean 24V control power; when a transformer shorts or burns open, the entire control circuit goes dead — no thermostat response, no ignition sequence, and often a blown low-voltage fuse on the board. This 40VA rating provides the headroom needed for the furnace's two-stage control loads.\u003c\/p\u003e\n\n\u003ch3\u003eSpecifications\u003c\/h3\u003e\n\u003ctable\u003e\n\u003cthead\u003e\u003ctr\u003e\n\u003cth\u003eSpec\u003c\/th\u003e\n\u003cth\u003eValue\u003c\/th\u003e\n\u003c\/tr\u003e\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eOEM Part Number\u003c\/td\u003e\n\u003ctd\u003e1172810 (TRANS 115\u0026gt;24 40VA)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eType\u003c\/td\u003e\n\u003ctd\u003eControl Transformer\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBrand\u003c\/td\u003e\n\u003ctd\u003eTempstar\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eVA Rating\u003c\/td\u003e\n\u003ctd\u003e40 VA\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePrimary \/ Secondary\u003c\/td\u003e\n\u003ctd\u003e115V to 24V\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFits Model\u003c\/td\u003e\n\u003ctd\u003eT8MPT100J20B1\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFit Type\u003c\/td\u003e\n\u003ctd\u003eOEM Direct Replacement\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\n\u003ch3\u003eCompatibility\u003c\/h3\u003e\n\u003cp\u003eDirect-fit replacement for the Tempstar T8MPT100J20B1 furnace and equivalent Heil\/ICP models requiring a 40VA 115V-to-24V control transformer. Confirm primary voltage and VA rating before installing.\u003c\/p\u003e\n\n\u003ch3\u003eInstallation Guide\u003c\/h3\u003e\n\u003col\u003e\n\u003cli\u003e\n\u003cstrong\u003eSafety First\u003c\/strong\u003e - Disconnect power at the furnace switch and verify zero voltage with a multimeter.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAccess\u003c\/strong\u003e - Remove the control-compartment service panel.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDocument\u003c\/strong\u003e - Photograph the primary (line) and secondary (24V) lead connections before disconnecting.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eRemove\u003c\/strong\u003e - Disconnect the wiring, then unbolt the transformer from its mounting bracket.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eInstall\u003c\/strong\u003e - Mount the new transformer and reconnect primary and secondary leads exactly per your photo.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTest\u003c\/strong\u003e - Restore power, confirm 24V across the secondary, and run a full heat cycle.\u003c\/li\u003e\n\u003c\/ol\u003e\n\n\u003ch3\u003eSigns You Need a Replacement\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eNo 24V control power; thermostat and board are completely dead.\u003c\/li\u003e\n\u003cli\u003eRepeatedly blown low-voltage control fuse.\u003c\/li\u003e\n\u003cli\u003eBurnt smell or discolored transformer windings.\u003c\/li\u003e\n\u003cli\u003eMeasured secondary voltage reads zero or far below 24V.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eShipping \u0026amp; Returns\u003c\/h3\u003e\n\u003cp\u003eShips same day before 3 PM CST. 30-day returns. Backed by the National HVAC Parts fitment guarantee.\u003c\/p\u003e","brand":"Tempstar","offers":[{"title":"Direct Replacement","offer_id":63021709459827,"sku":"1172810-GEN","price":28.0,"currency_code":"USD","in_stock":true},{"title":"OEM","offer_id":63048405483891,"sku":"1172810","price":36.4,"currency_code":"USD","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0984\/1190\/5395\/files\/nhvac-transformer-control-1172810_e18a706c-86f1-4f04-82f2-fcf50ea97687.jpg?v=1782958331","url":"https:\/\/nationalhvacparts.com\/products\/tempstar-40va-transformer-for-t8mpt100j20b1-115v-to-24v-ships-today","provider":"National HVAC Parts","version":"1.0","type":"link"}