{"id":16,"date":"2015-04-11T16:10:00","date_gmt":"2015-04-11T16:10:00","guid":{"rendered":"https:\/\/keithspecialty.com\/blog\/?p=16"},"modified":"2019-12-27T22:11:16","modified_gmt":"2019-12-27T22:11:16","slug":"what-is-a-limit-switch-and-why-does-it-shut-off-my-furnace","status":"publish","type":"post","link":"https:\/\/keithspecialty.com\/blog\/what-is-a-limit-switch-and-why-does-it-shut-off-my-furnace\/","title":{"rendered":"What is a limit switch?"},"content":{"rendered":"\n

And why does it shut off my furnace?<\/h2>\n\n\n\n

Written April 25, 2011, updated March 9, 2015, moved to WordPress Nov 21, 2019<\/p>\n\n\n\n

What is a limit switch and why does it shut off my furnace?<\/p>\n\n\n\n

\"\"<\/a><\/figure>\n\n\n\n

\n Trane SWT 01635 thermal limit switch,\n\n<\/p>\n\n\n\n

\"photo<\/figure><\/div>\n\n\n\n

The limit switch is a small, silver bi-metal disc about the size of a\n dime or quarter which turns off the furnace if the temperature inside \n the furnace gets too hot (see another example<\/a>)\n  It is a safety device and should not be disabled or bypassed.  Limit \n switches do go bad sometimes, especially if the furnace routinely \noverheats.  However, you should try to determine why your furnace is \ngetting too hot before you replace the switch.  An overheated furnace is\n usually the result of inadequate air flow through the furnace or a \nfurnace that is too large for the building.  An overheated furnace is \nnot only inefficient, it will shorten the life of the heat exchanger in \n the furnace.<\/p>\n\n\n\n

The first thing to check is your registers.  Make sure all registers \n are open and not blocked by furniture or other items.  Be sure the \nfilter in the furnace is clean.  If you have recently added \nair-conditioning to your system, it may be possible to increase the \nblower motor speed.  Get a furnace technician to do this if you are \nunsure how to safely change the speed.<\/p>\n\n\n\n

If you have tried all of the above and replaced the limit switch but \n the furnace still overheats, the size of your ductwork or furnace is \nsuspect.  Do you have at least as much cold return air coming back to \nthe furnace as there is warm air going to the home?  If not, add more \ncold air runs or increase the size of existing runs.  You may also need \n more warm air runs to get the heat away from the furnace.  The main \ntrunk or ductwork may be too small to handle the needed air flow.  Call a\n trusted HVAC technician to do a heat loss and\/or heat gain \nassessment for your house to see if the ductwork and furnace are \nproperly sized.<\/p>\n\n\n\n

More information can be obtained at the links below:<\/p>\n\n\n\n

More about high limit switches at furnacecompare.com<\/a><\/p>\n\n\n\n

Interesting forum entry regarding limit switch on DoItYourself.com<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

And why does it shut off my furnace? Written April 25, 2011, updated March 9, 2015, moved to WordPress Nov 21, 2019 What is a limit switch and why does it shut off my furnace? Trane SWT 01635 thermal limit switch, The limit switch is a small, silver bi-metal disc about the size of a dime or quarter…<\/p>\n

Read More<\/a><\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[17,3,10],"tags":[],"yoast_head":"\nWhat is a limit switch? -<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/keithspecialty.com\/blog\/what-is-a-limit-switch-and-why-does-it-shut-off-my-furnace\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"What is a limit switch? -\" \/>\n<meta property=\"og:description\" content=\"And why does it shut off my furnace? Written April 25, 2011, updated March 9, 2015, moved to WordPress Nov 21, 2019 What is a limit switch and why does it shut off my furnace? Trane SWT 01635 thermal limit switch, The limit switch is a small, silver bi-metal disc about the size of a dime or quarter...Read More\" \/>\n<meta property=\"og:url\" content=\"https:\/\/keithspecialty.com\/blog\/what-is-a-limit-switch-and-why-does-it-shut-off-my-furnace\/\" \/>\n<meta property=\"article:publisher\" content=\"https:\/\/www.facebook.com\/KeithSpecialty\/\" \/>\n<meta property=\"article:published_time\" content=\"2015-04-11T16:10:00+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2019-12-27T22:11:16+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/keithspecialty.files.wordpress.com\/2011\/04\/68-825.jpg?w=450\" \/>\n<meta name=\"author\" content=\"Dave Keith\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:creator\" content=\"@keithspecialty\" \/>\n<meta name=\"twitter:site\" content=\"@keithspecialty\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Dave Keith\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"2 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\/\/keithspecialty.com\/blog\/what-is-a-limit-switch-and-why-does-it-shut-off-my-furnace\/#article\",\"isPartOf\":{\"@id\":\"https:\/\/keithspecialty.com\/blog\/what-is-a-limit-switch-and-why-does-it-shut-off-my-furnace\/\"},\"author\":{\"name\":\"Dave Keith\",\"@id\":\"https:\/\/keithspecialty.com\/blog\/#\/schema\/person\/96d65398e56fac09a6360cad9dc82391\"},\"headline\":\"What is a limit switch?\",\"datePublished\":\"2015-04-11T16:10:00+00:00\",\"dateModified\":\"2019-12-27T22:11:16+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\/\/keithspecialty.com\/blog\/what-is-a-limit-switch-and-why-does-it-shut-off-my-furnace\/\"},\"wordCount\":397,\"publisher\":{\"@id\":\"https:\/\/keithspecialty.com\/blog\/#organization\"},\"articleSection\":[\"furnace maintenance\",\"HVAC\",\"Limit Switches\"],\"inLanguage\":\"en-US\"},{\"@type\":\"WebPage\",\"@id\":\"https:\/\/keithspecialty.com\/blog\/what-is-a-limit-switch-and-why-does-it-shut-off-my-furnace\/\",\"url\":\"https:\/\/keithspecialty.com\/blog\/what-is-a-limit-switch-and-why-does-it-shut-off-my-furnace\/\",\"name\":\"What is a limit switch? 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