Bryant Evolution +95s Plus – Error 33, Hi Limit Trip (2024)

01-25-2016,10:02 PM #1


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Bryant Evolution +95s Plus – Error 33, Hi Limit Trip (1)New Guest

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Jan 2016
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I own a Bryant Model 355CAV060100 natural gas furnace that was installed in my house in 2010 and worked well for 2-3 years and then occasionally/rarely indicated a failure on the Evolution thermostat. The LED on the circuit board would indicate Error 33. The filter was changed regularly and the registers were all open and unobstructed. The system would reset automatically and run fine. Over then next couple winters the problem would occur more often especially when it would get bitter cold outside. I was primarily using a wood stove along with the gas furnace as an auxiliary unit, therefore the repair was not urgent to maintain comfort.

The inducer would spin, the igniter would glow, the solenoid would switch on the gas and the burner would ignite, once the heat exchanger warmed up the blower would start, after a few minutes the unit would trip off for a few minutes and then the cycle would repeat.

I attempted troubleshooting the unit including: replace air filter, verify registers open/unobstructed, verified combustion air intake/exhaust piping is free of obstruction, cleaned condensate trap and drain lines, verified blower spins freely with firmly attached blower squirrel cage blades and nothing seemed abnormal. I purchased a manometer and checked the three-stage gas valve pressure and monitored the voltage to the solenoids with a digital volt meter. The input gas pressure and each Low/Med/High gas pressure settings were within specification. The solenoid 24V control signals controlled the valves and the gas pressure followed as expected (ie. not a stuck solenoid issue).

I found the limit switch was opening due to high heat condition in the heat exchanger. The flame roll-out switch was not open, and the manual reset was in a normal position (not requiring manual reset). I replaced both of these sensors with OEM parts because they were inexpensive and possibly the source of the fault. The problem was not resolved. I tried one cycle with the filter removed and the filter door open to provide plenty of air intake, with no change to the problem.

I modified the original hi limit switch to accommodate a thermometer and allow me to jumper/bypass the limit circuit. I first measured the temperature at which the limit switch opened, then with the limit circuit bypassed I measured the temperature and it continued to rise. I shut the furnace off manually once it reached maximum operating temperature to avoid a fire safety issue. This confirmed for me that the unit is not just running a little hot or the limit switch is a little out of spec, the system is not balancing the heat generated with the airflow around the heat exchanger.

I measured temperature rise to be 62 deg F when the unit shuts down on medium heat, this value is in spec however I don’t know if it reached a steady state temperature before shut down.

I opened the evaporator and inspected the coil for restricted airflow. The coil looked fairly clean and a flashlight easily shined thru. I used CRC coil cleaner to clean the evaporator while I had it open for inspection. This did not fix the issue. I measured the static pressure with a pressure probe and found it less than the maximum 0.5 inches H2O (med=0.1 and high fan speed=0.2 inches H2O).

I determined the unit uses an electronic control module to run the DC motor and not start/run capacitors that could affect the RPM of the blower motor. So a simple capacitor replacement is not an option for my unit.

I concluded that the issue is with either the thermostat, main circuit board, motor control module or the blower motor. These parts are too expensive to randomly replace. I then called the company who installed the system, they checked many of the same items that I verified/replaced. On the third service call the circuit board was swapped and the furnace now runs properly. I don’t know the exact circuit board failure mode, but assume the blower speed directed by the board was an incorrect slower speed than required.

I don’t have a question, I just wanted to share this overall experience as it may help others with similar issues.

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Bryant Evolution +95s Plus – Error 33, Hi Limit Trip (2024)


What is error code 33 on Bryant Plus 95s evolution? ›

I have a Bryant furnace showing error code 33. This indicates that the filter needs to be changed - and it did (badly). Further on it says that the Furnace Rollout Switch and the BVSS require manual reset.

What is code 33 on furnace limit circuit fault? ›

Code 33 is a Limit Circuit Fault code. This means that the flame rollout switch is open. If the high limit or flame rollout switch is open, you will experience error code 13.

What causes a limit circuit lockout? ›

If the temperature is too high or the pressure too low, the limit switch will close, instructing the furnace to shut down and enter lockout mode. A dirty filter may also cause the limit switch to trip by reducing the air flow.

How do I fix code 33? ›

Error 33 is likely the furnace is overheating. Please set your fan switch to on and see if the house fan comes on. If the house fan does not come on then you should look at the relay for the house fan. This can be found by tracing the fan circuit.

What is system error 33? ›

Code 33 “Windows cannot determinewhich resources are required for this device. (Code 33)”

How do you reset the limit switch? ›

Begin by turning off the power to the furnace. Locate the limit switch, which is usually near the heat exchanger. Carefully remove the cover and gently press the reset button. If this doesn't solve the issue, you may need to replace the limit switch altogether.

How do you fix an ignition lockout fault? ›

Solution For Furnace Ignition Lockout
  1. You should replace the air filter to prevent limit switch tripping.
  2. Not only do filters need to be cleaned, but you should also clean the vent pipes. ...
  3. Dirty flame sensors also cause this problem. ...
  4. You should also schedule furnace service twice annually to prevent any such situation.

How do I reset my furnace limit circuit lockout? ›

Find the 'limit switch'

Once you've opened the control panel, search for a red or yellow elevated switch or button near the ignition control box. Now all that is left is to push and release the limit switch to reset your furnace manually.

How to tell if a limit switch is bad? ›

If you observe the following signs, your furnace limit switch may be faulty, and you may need to schedule a gas furnace repair in Everett, WA, to fix the furnace: Your furnace blower won't turn off. The furnace distributes cool air. The furnace keeps switching on and off in short intervals.

What causes furnace limit switch to trip? ›

Dirty Air Filters: One of the simplest reasons is a dirty air filter. Over time, filters can accumulate dust and debris, causing a restriction in airflow. When air can't circulate properly, heat builds up inside the furnace, causing the high limit switch to trip as a protective measure.

How to clean a limit switch? ›

Remove the furnace access panel to locate the high limit switch on the outside of the plenum. Unscrew the switch from the plenum. Use steel wool or sandpaper to gently clean away soot and other materials stuck on the rod. Replace the switch and access panel.

What is error 33 on air conditioner? ›

The 33 error is an open limit error code. (electrically), automatic reset, temperature-activated sensor. conditioned air passing over the heat exchanger. blower and monitors heat exchanger compartment temperatures.

What is the E3 code on a Bryant thermostat? ›

The E3 is telling us the outdoor temperature sensor is not being read. First make sure it is connected and if so, replace the sensor.

What is error code 33 on inverter? ›

Event number 33 and the corresponding 4-digit event numbers indicate that the power supply at the DC input is not sufficient for stable operation of the inverter and the inverter therefore cannot connect to the utility grid yet.


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