The electrical symbols not only show where something is to be installed, but also what type of device is being installed. I tested it and it started and stopped. If the plenum gets too hot, the limit switch shuts off the burner. Connect the outgoing load black wire to terminal 4. I have 3 wires, a power wire, fan and a limiter wire, i cant figure out what terminals they go on. The photo at the top of this page shows all of the controls and wiring terminals in a Honeywell combination fan and limit control installed horizontally on a gas furnace.
Note: Parts that have physical evidence of being installed may receive a 50% refund at our discretion. Sensing Furnace Temperatures How to manually turn on a furnace or air conditioning blower fan. I dont think the camstat is turning on the fan by temp. The high limit switch is bad. Details for your model may vary: The primary limit control guards against overheating resulting from insufficient conditioned air passing over the heat exchanger If the primary limit control does not function during this test, the cause must be determined and corrected. Then, from the new 24vac transformer's secondary, run the hot and return to the power contacts of the new thermostat.
The term limit switch is derived from the operation of the device it-self. Load voltage to the fan is wired at the upper left push-in terminal. The four wire dude has 240 between red and black, it has 120 between white and red and 120 between white and black. Amanda is an asset worth holding on to and a credit to your company. All models may be used as limit controllers by wiring only the limit side. Check the test specifications provided by the manufacturer of your particular control.
The National Oilheat Research Alliance,. This tip may help: Aug 23, 2010 Please read all of this post. The fan limit switch contains a bi-metallic spring shown at left which is inserted into the warm air plenum of the heating furnace. This White Rodgers fan limit control sports an 11-inch long insertion probe that projects into the supply air plenum. Causes of furnace blowing cold air at start-up of heating cycle.
You do not need to worry about any 24V in this wiring set up. Watch out: Warning about wiring fan limit switches or other controls in reversed polarity: I don't know what specific fan limit switch you are using reverse wiring effects and I suspect that the risk of damage from wiring in reverse polarity is manufacturer and model-dependent as well as dependent on an additional detail I'll note. The time frame depends on your location and is determined by the Post Office. A set of wiring diagrams may be required by the electrical inspection authority to approve connection of the residence to the public electrical supply system. After an acceptable temperature is reached during the cool down period, the limit control will reset and allow the furnace to resume normal operation. The current in a parallel circuit flows along each parallel branch and re-combines when the branches meet again. The same test between the Cam stat power terminal and the cam stat limit terminal will be closed.
Newer versions of this control have a brass jumper in the same location. Details: In normal warm air furnace operation, by moving building air across the heat exchanger, the blower is warming air that will be delivered into the occupied space, but at the same time this process is keeping the heat exchanger from reaching too-high a temperature. How to Check that the Fan Limit Switch is Working Properly Excerpting from the 2017 document given below: When installation is complete, disconnect the fan motor circuit at the L4064. He wrote that this control was used on a dual-zone heating and air conditioning system. Obstructed air flow can occur because of a dirty air filter, blocked or disconnected air ducts, or if someone has fouled up the system controls.
Usually they are tripping because the plenum is sooted up and excessive heat builds in the combustion chamber. Thanks to reader Larry C. The manufacturer provides details for surface mounting, rigid-bracket mounting, or swivel-mounting of the control. But just want to know why the heater works but not the air conditioner with the limit switch bypassed. Once removed, it is not replaceable. This should work on most systems unless they use line-voltage thermostats or millivolt control not absolutely positive on that, though. The wiring for White-Rodgers universal fan limit switches is at Watch out: for safety and for proper furnace temperature and fan operation it is essential that the fan limit control's temperature sensing device be located where the furnace manufacturer has specified and that the probe be of the proper length.
In our photo of the interior of the fan limit control immediately above you can see that switch again in the lower left of the image white arrow. On systems where we have installed high quality air filtration to address an indoor air quality issue, and where the fan is rated for continuous duty, we may pull this switch out to keep the fan on continuously. Sorry im such a novice when it comes to this section of the furnace, and i appreciate all your patience with me! If a line to line short circuit does not occur, these contacts are said to be connected to the same polarity. They are also not clear on where to connect the wires. Well i cant do that because the old one disintegrated.