Hi, first post and very new to HVAC systems. I have a 6 year old Lennox system model number SLP98UH090XV60C with zoning (2 zones) and an iComfort thermostat. If I run the air conditioner on Zone 1, it pushes 1000 CFM with no errors. If I run the air conditioner on Zone 2, it pushes 1200 CFM with no errors. If I run both zones simultaneously, it pushes 2000 CFM, and I get an error E312 flashing on the furnace integrated control board. No errors whatsoever show on the thermostat, and the system operates fine regardless of the error. The filter was changed last week.
The manual describes the error as follows: "Restricted air flow in cooling or continuous fan mode is lower than cfm setting." It then elaborates, saying....
Two techs came to take a look at the unit. Both inspected the ducting, and saw no issues. All dampers are fully opened. Air flows normally into the house from all vents while the code flashes. We tried removing the filter entirely, as well as running the unit with the front panel removed exposing the blower motor -- still getting the same error when running both zones.
The first tech suggested decreasing the blower motor speed, but he wasn't sure how to do so, which is why the second tech came out. At first, I didn't love the idea of decreasing the blower motor speed, since I think it's set to factory default, and the techs told me the ducting should be fine with the current settings. However, I am interested in seeing if a slower blower speed will allow the unit to run error-free, so I've changed my mind and am open to trying it.
After about an hour of testing, going by the manual, we (the tech and I) were unable to adjust the blower speed. We were trying to do so by turning the DIP switches on/off on the integrated control board based on settings specified in the manual. We followed everything to the letter, and there was no effect whatsoever on the blower motor speed. We tried multiple settings, nothing worked. The tech then mentioned that when there's an iComfort thermostat connnected to the unit, the blower speed is controlled from the thermostat and the DIP switches likely have no effect. I double-check the manual, and there is something in there that more or less confirms this. It says: "NOTE: When the SLP98UHV is used with an icomfort Touch communicating thermostat, all indoor blower speed selections and DIP switch settings are made by the communicating thermostat."
So if that is indeed the case, and I can only adjust the speed using the thermostat, how do I actually go about doing that? There is no information in the manual, and there is no such setting on the touch screen thermostat. Does anyone know?
My second question is, is this error code serious? Am I damaging the motor? The second tech told me not to worry about it. He said it's likely been flashing that error for a long time, and if it were serious the error would appear on the thermostat screen. He checked everything and said the system appeared to be running exactly as it should. I want to believe him -- it is a variable speed motor so maybe the motor adjusts its speed accordingly? Either way, I wouldn't mind trying to decrease the blower motor just to see if running it at, say, 10% less would clear the error. I'd be ok even with 20% less. The system works well, and cools the house just fine, so running it at a slightly lower speed, shouldn't be an issue and would give me peace of mind.
Any help/advice would be greatly appreciated. Thanks!
Oh, one last thing.... the second tech mentioned that my touch-screen thermostat is the older white one, and it will not allow me to control the blower speed. The newer black one does. But he recommended that I not upgrade to the newer one because it'll give me more headaches. For one thing, it will shut off the system entirely if with any error. He basically suggested that the system is working fine, it's hitting the target temperature on the thermostat, and not to worry about this. He might be right, but I'd still like to learn how to control the blower motor speed, if possible.
The manual describes the error as follows: "Restricted air flow in cooling or continuous fan mode is lower than cfm setting." It then elaborates, saying....
Restricted airflow - Indoor blower is running at a reduced cubic feet per minute (Cutback Mode) - The variable speed motor has pre-set speed and torque limiters to protect the motor from damage caused by operating out of its designed parameters (0 to 0.8 inches water column total external static pressure). Check filter and ductwork. To clear replace filter if needed or repair/add ductwork.
Two techs came to take a look at the unit. Both inspected the ducting, and saw no issues. All dampers are fully opened. Air flows normally into the house from all vents while the code flashes. We tried removing the filter entirely, as well as running the unit with the front panel removed exposing the blower motor -- still getting the same error when running both zones.
The first tech suggested decreasing the blower motor speed, but he wasn't sure how to do so, which is why the second tech came out. At first, I didn't love the idea of decreasing the blower motor speed, since I think it's set to factory default, and the techs told me the ducting should be fine with the current settings. However, I am interested in seeing if a slower blower speed will allow the unit to run error-free, so I've changed my mind and am open to trying it.
After about an hour of testing, going by the manual, we (the tech and I) were unable to adjust the blower speed. We were trying to do so by turning the DIP switches on/off on the integrated control board based on settings specified in the manual. We followed everything to the letter, and there was no effect whatsoever on the blower motor speed. We tried multiple settings, nothing worked. The tech then mentioned that when there's an iComfort thermostat connnected to the unit, the blower speed is controlled from the thermostat and the DIP switches likely have no effect. I double-check the manual, and there is something in there that more or less confirms this. It says: "NOTE: When the SLP98UHV is used with an icomfort Touch communicating thermostat, all indoor blower speed selections and DIP switch settings are made by the communicating thermostat."
So if that is indeed the case, and I can only adjust the speed using the thermostat, how do I actually go about doing that? There is no information in the manual, and there is no such setting on the touch screen thermostat. Does anyone know?
My second question is, is this error code serious? Am I damaging the motor? The second tech told me not to worry about it. He said it's likely been flashing that error for a long time, and if it were serious the error would appear on the thermostat screen. He checked everything and said the system appeared to be running exactly as it should. I want to believe him -- it is a variable speed motor so maybe the motor adjusts its speed accordingly? Either way, I wouldn't mind trying to decrease the blower motor just to see if running it at, say, 10% less would clear the error. I'd be ok even with 20% less. The system works well, and cools the house just fine, so running it at a slightly lower speed, shouldn't be an issue and would give me peace of mind.
Any help/advice would be greatly appreciated. Thanks!
Oh, one last thing.... the second tech mentioned that my touch-screen thermostat is the older white one, and it will not allow me to control the blower speed. The newer black one does. But he recommended that I not upgrade to the newer one because it'll give me more headaches. For one thing, it will shut off the system entirely if with any error. He basically suggested that the system is working fine, it's hitting the target temperature on the thermostat, and not to worry about this. He might be right, but I'd still like to learn how to control the blower motor speed, if possible.
source https://hvac-talk.com/vbb/threads/2242937-Changing-Blower-Speed-amp-Error-Code-E312-on-Lennox-SLP98UHV-System?goto=newpost
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