However, it’s important to make sure that if the limit switch tripped repeatedly, it was really due to the switch being bad and not due to actual overheating. That’s why it’s so important to have your system installed and maintained by highly-trained and skilled technicians. These devices are used in process control applications where independent limit switching for over or under temperature is required. Rather, it is wired in series with the 24-volt control circuit of your furnace. That fan/limit control has a timer to turn the fan on, hence the two low voltage wires directly below the dial. Home / Articles that Educate / Get to Know Your HVAC: The High Limit Switch, Tagged: furnace, heating and cooling, high limit switch. The LIMIT STOP control is an extra safety device to make it difficult for an amateur to set the LIMIT OFF to an unsafe or too-high temperature. Note that the limit switch has nothing to do with the thermostat. When looking for a replacement, it’s important to note that there are numerous limit switches used in many different applications. HVAC systems consist of complex equipment with a lot of delicate parts. How to Remedy a Sprayed HVAC Unit, Daikin: Upholding a Promise of Comfort and Quality. The High Limit switch "breaks" or opens to turn the burner off if the plenum temperature reaches the high limit setting. When the burner first comes on, it takes a while to heat up the heat exchanger. A local specialist will contact you shortly. Ready to get a quote from an HVAC contractor? When the temperature reduces to normal, the burner will come back on. Temperature limit control with auto reset. A pair of wires is connected to the switch. Note that the limit switch has nothing to do with the thermostat. It reads the temperature of the plenum and waits until it gets appropriately warm. The design of some of these furnaces didn't allow the fan switch to sense the heat properly, this is why they use the timed on fan switch. One of the most common issues that happens when a high limit switch goes bad is that it fails to signal the blower fan to turn off. B13701-55 - Goodman OEM Furnace Replacement Limit Switch. This can lead to your furnace going into lockout mode even though it wasn’t really overheating. Limits are available in a broad range of packaging options, allowing selection of the best version for an application. However, if the temperature of the supply air gets too high, indicating that the inside of the furnace is overheating, then the high limit switch performs its second job—shutting off the gas valve to stop the heating. Users will find electromechanical and solid-state switches, as well as three possible choices for contact: momentary, maintained or positive-opening. This switch plays a role in the normal operation of your furnace. 025-29041-007 - York OEM Furnace 3" Replacement Limit Switch L170 Then for that heat to transfer into the supply air waiting inside the furnace takes longer. Turning the fan motor on and off is the high limit switch’s main job. Turn the power back on and run the furnace through one complete heating cycle to verify that it’s running appropriately. Furnace limit switches are electromechanical devices with momentary contact. Service@ConditionedAirSolutions.com, Get to Know Your HVAC: The High Limit Switch, Upgrading Your Gas Furnace with New Technology, Protecting Your Home From an Air Conditioner Fire, SPECIAL HEALTH SAFETY ANNOUNCEMENT – COVID-19. It also can shut down the furnace burners if things are getting too hot inside the furnace. During normal operation, the high limit switch’s main job is to control when the blower fan turns on and off. Depending on your furnace model, the switch will be surrounded by a silver or white cover. When the furnace begins running, the switch’s role is to turn on the blower fan when the supply air gets hot enough. The temperature limit controller Series LV is available with an operator interface and can be ordered in 1⁄8 DIN-square panel mount or DIN-rail mount design configurations. High Pressure Limit Switch, Manual Reset 36" Capillary, 440Op 47-21604-03 High Pressure Limit Switch, Manual Reset 36" Capillary, 440Op. This snap disc thermostat features SPST flanged airstream mounting. That’s because it’s blowing all the heated air that’s already in your supply ducts on into your home. The high limit should not have been changed. Remove the cover by lifting it upwards or pulling it off to reveal the body of the switch and two metal arms. Sometimes the temperature of the supply air inside the furnace drops below a certain temperature. Limit Switch Functions. There is a difference between a limit switch and a rollout switch. One of the most common causes of furnace overheating is a clogged furnace filter. Fan/Limit Controller 125°F On/100°F Off 200°F high limit, 11-1/2" Insert L4064B2210 Fan/Limit Controller 125°F On/100°F Off 200°F high limit, 11-1/2" Insert SKU : L4064B2210 Brand : Honeywell This is done by measuring the outlet and return air temperatures. If the temperature inside of the plenum gets too hot, it shuts off the gas supply to your burners to prevent … Modine part # 5H73593 (Works with most Modine gas unit heaters) Modine PA Overheat Limit & Fan Switch : Some older PA models use this 3 wire limit switch which also runs the fan instead of a timer. Top-to-Bottom School Rankings were replaced by the Parent Dashboard for School Transparency on www.MISchoolData.org and the Michigan School Index System upon implementation of Michigan's approved plan for the Every Student Succeeds Act (ESSA).. Support for school accountability reports can be reached at 877-560-8378 or MDE-Accountability@michigan.gov. A limit switch also acts as a safety device for your furnace. Future Design Controls FM Approved High Limit Series 7Lallows for DIN Rail or Surface Mounting providing hi-limit protection for process applications. Home / Replacement Parts / High Limit Switch. If the blower came on at the same time as the burner, it would pump cold air through the house at first. Do UV Light Air Purifiers Help Protect Against Coronavirus? A high-limit switch is a protective part of a furnace designed to keep the mechanism from overheating itself. Coleman 02535381000 Furnace Temperature Limit Switch Genuine Original Equipment Manufacturer (OEM) Part. A clogged filter or squirrel cage can limit the airflow and, without a high limit switch, the furnace would continually cycle until it burned itself out.