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Lennox gas furnace code E311

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zepfan
zepfan Member Posts: 397
in Gas Heating
Having an issue with a Lennox gas furnace that is a model# EL296UH090XV36c, installed in 2014. The furnace is two stage gas, and displays a code E311, that says "heating stage reduced, to match system air flow" change air filter, or remove duct restriction. So I interpret as the variable speed motor is sensing high static pressure, such as would be caused by a dirty air filter, or closed damper. The furnace also makes a pulsating sound while this code is displayed, however the noise goes away when the blower door is opened, or the air filter is removed. The air filter is clean, and is brand new. Both the supply, and return duct has patches on them, I assume from having the duct cleaned at some point, that I was able to remove and look down with a flashlight (20' in either direction), and saw no restrictions. When the patches were removed ( 14" x14" in size) both the code, and the noise were still present. I would think if it is a static pressure issue, by removing these patches the static pressure would be reduced. Has anyone else had experience with this furnace or this E311 code? Thanks to all

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  • mattmia2
    mattmia2 Member Posts: 9,637
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    Is the blower clean? is there an ac coil, is the inlet side of it clean if so? do the motor bearings have play? try up/down, front/back, and end play.
    zepfan
  • pedmec
    pedmec Member Posts: 973
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    has anything changed in the system? meaning have you done anything to the ductwork or programming in the control. is it a problem that just showed up out of the blue? if nothing has changed then check the blower wheel. make sure you don't have any paper stuck in the blower wheel or if the returns are lined maybe duct liner stuck in the blower wheel. that would cause the pulsation and cause a higher amp (torque) draw on the motor, thinking it has way to much static pressure in the ductwork so its slowing down to save its self. had this happen in american standard furnaces. wiring diagram is stuck on inside cover of blower compartment door and the glue dries up and it gets sucked into the blower wheel. depending on how much of the diagram gets loose it gets sucked into the blower wheel it will sound awful.
    zepfan
  • pecmsg
    pecmsg Member Posts: 4,845
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    You need a T E S P test. That will tell you how much air the ducts can handle and where improvements can be made, Supply Return or both.
    zepfan
  • zepfan
    zepfan Member Posts: 397
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    Thanks to all that responded. Both the return and supply ducts are not lined. There have not been from what I can tell, any changes to the existing ductwork. I did not install the furnace, and this is the first that I have worked on it,
  • pecmsg
    pecmsg Member Posts: 4,845
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    zepfan said:

    Having an issue with a Lennox gas furnace that is a model# EL296UH090XV36c, installed in 2014. The furnace is two stage gas, and displays a code E311, that says "heating stage reduced, to match system air flow" change air filter, or remove duct restriction. So I interpret as the variable speed motor is sensing high static pressure, such as would be caused by a dirty air filter, or closed damper. The furnace also makes a pulsating sound while this code is displayed, however the noise goes away when the blower door is opened, or the air filter is removed. The air filter is clean, and is brand new. Both the supply, and return duct has patches on them, I assume from having the duct cleaned at some point, that I was able to remove and look down with a flashlight (20' in either direction), and saw no restrictions. When the patches were removed ( 14" x14" in size) both the code, and the noise were still present. I would think if it is a static pressure issue, by removing these patches the static pressure would be reduced. Has anyone else had experience with this furnace or this E311 code? Thanks to all

    Thats the sound of the blower surging. It will lead to an early death of a very expensive motor. I bet your static pressure is out of range.
    zepfan

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