Any HVAC Experts Here?

Our new place has a two year old Bryant series 915-S heating & air conditioning system. If you work in the HVAC field, you probably know what's coming next.

Now that the cooler weather has arrived, we're using the heat function for the first time, and it cuts out before reaching the desired set point on the thermostat, flashing the error code 33. Within a minute or so the system restarts. Lather rinse repeat.

I changed the filter, which was absolutely necessary since the previous owners had a dog and the existing filter was entirely covered in dog hair. That improved things only slightly. The literature from Bryant indicates a washable filter is recommended, but that's not what was in there. The replacement I used was a 3M Filtrete. Yesterday I bought a washable filter and replaced the 3M with it. Again, there's further slight improvement, but this morning it was 60 in the house so I set the thermostat to 68, and the system cut out at 64, then restarted and cut out a few more times before reaching the set temperature.

I went on line and googled error 33 and it appears to be an air flow issue (apparently the 3M Filtrete is the worst possible filter to use in this rig). Everything is blowing out fine through the registers in the house. One video on line has a guy cutting the sheet metal to provide an additional air intake into the side of the blower housing, stating that these Bryant furnaces all have a design flaw that allows it to get hot enough to trip a limit switch. Our model has a single speed blower, so there's no option to move the air any faster. I'm not going to cut into the blower housing, although doing so did resolve the guy's issue.

Is there any other way to fix this once and for all? I know it's a heat issue because we ran the A/C during the summer and it never cut out before meeting the set temperature.

Has there been any class action suit filed about this? It seems to have been a problem for several years. How does Bryant get away with selling something like this? How many perfectly good limit switches have been replaced on unnecessary service calls that ended up not resolving the issue?

Additionally, the heat function creates an odd odor. It doesn't smell like burning dust, which would have all burned off by now anyway. Instead and coincidentally, it smells similar to the smoke we're dealing with from the fire up north, but it was making this same smell before the fire started, and for the past week or so it hasn't stunk outside -- just really lousy visibility.

Thanks for any advice on this.


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Post# 1015027 11/19/2018 at 13:15 (1,984 days old) by RP2813 (Sannazay)
Checkrate/Likes Our new place has a two year old Bryant series 915-S heating & air conditioning system. If you work in the HVAC field, you probably know what's coming next. Now that the cooler weather has arrived, we're using the heat function for the first time, and it cuts out before reaching the desired set point on the thermostat, flashing the error code 33. Within a minute or so the system restarts. Lather rinse repeat. I changed the filter, which was absolutely necessary since the previous owners had a dog and the existing filter was entirely covered in dog hair. That improved things only slightly. The literature from Bryant indicates a washable filter is recommended, but that's not what was in there. The replacement I used was a 3M Filtrete. Yesterday I bought a washable filter and replaced the 3M with it. Again, there's further slight improvement, but this morning it was 60 in the house so I set the thermostat to 68, and the system cut out at 64, then restarted and cut out a few more times before reaching the set temperature. I went on line and googled error 33 and it appears to be an air flow issue (apparently the 3M Filtrete is the worst possible filter to use in this rig). Everything is blowing out fine through the registers in the house. One video on line has a guy cutting the sheet metal to provide an additional air intake into the side of the blower housing, stating that these Bryant furnaces all have a design flaw that allows it to get hot enough to trip a limit switch. Our model has a single speed blower, so there's no option to move the air any faster. I'm not going to cut into the blower housing, although doing so did resolve the guy's issue. Is there any other way to fix this once and for all? I know it's a heat issue because we ran the A/C during the summer and it never cut out before meeting the set temperature. Has there been any class action suit filed about this? It seems to have been a problem for several years. How does Bryant get away with selling something like this? How many perfectly good limit switches have been replaced on unnecessary service calls that ended up not resolving the issue? Additionally, the heat function creates an odd odor. It doesn't smell like burning dust, which would have all burned off by now anyway. Instead and coincidentally, it smells similar to the smoke we're dealing with from the fire up north, but it was making this same smell before the fire started, and for the past week or so it hasn't stunk outside -- just really lousy visibility. Thanks for any advice on this.

Post# 1015033 , Reply# 1 11/19/2018 at 14:02 (1,984 days old) by Yogitunes (New Jersey)
Checkrate/Likes I never had this error code.... the lower panel that allows access to the blower/motor---what would happen if you took that off and ran the heater?...still the same issue.....worst case you would have to buy a filter to go over the opening and duct tape that in place.... I used to do this trick to allow return air from the basement, since there were no return air vents down there, just registers only....it actually gave a better equalization of temps throughout the house.... I used 3M filters only during the winter, as for the Summer A/C use, it was too restrictive, and would freeze up the unit....

Post# 1015036 , Reply# 2 11/19/2018 at 14:09 (1,984 days old) by RP2813 (Sannazay)
Checkrate/Likes There's large PVC piping that runs out to the side of the house, and one short stub of it with an elbow that I noticed has some slight suction when the unit is running. I wonder if that suction should be stronger, and if that's the extent of any fresh outside air intake on this system.

Post# 1015038 , Reply# 3 11/19/2018 at 14:15 (1,983 days old) by pulltostart (Mobile, AL)
Checkrate/Likes *Ralph,* Do you know how old the system is? Is there any identification on the equipment as to who did the installation? If the system is reasonably new I'd be contacting someone who can speak for Bryant (preferably the installation company). lawrence

Post# 1015052 , Reply# 4 11/19/2018 at 16:23 (1,983 days old) by toploader55 (Massachusetts Sand Bar, Cape Cod)
Checkrate/Likes Email Mr. Turbokinetic. He'll take a ride out and change the system over to a Belt Drive Frigidaire A/C-Heat pump with. piston compressor ; ) He would possibly be able to tell you what is going on.

Post# 1015077 , Reply# 5 11/19/2018 at 18:56 (1,983 days old) by GusHerb (Chicago/NWI)
Checkrate/Likes 1 *Error code 33* "LIMIT CIRCUIT FAULT - This status code indicates the limit, or flame rollout switch is open or the furnace is operating in high-heat only mode due to 2 successive low heat limit trips. Blower will run for 4 minutes or until the open switch remakes whichever is longer. If open longer than 3 minutes, code changes to lockout #13. If open less than 3 minutes status code #33continues to flash until blower shuts off. Flame rollout switch requires manual reset." Well it's not the flame rollout switch or it'd be error code #13 according to this, but the rollout switch is in the same circuit as the high limit, so it's not to be completely ruled out until making sure it hasn't tripped or is faulty. My money's on an airflow issue causing the high limit to trip, just as you said. You've already changed the filter, the next thing I would do is run it without the filter for a short while (never leave it running without the filter for long), and after that try running it with the blower door off (tie a zip tie around the door switch in the mean time, and make sure nothing is around to get sucked into the blower, and leave the door to the room open so it doesn't start pulling flue gases into the room). If it stays running with the blower door removed then you've got an airflow issue on the return side. If it's still tripping then your evaporator may be plugged (very possible if the filter was filthy and never changed), also could be the supply ductwork is undersized. I like to use the MERV 7 True Blue filters, the "Rheem" branded or whatever they call them these days, MERV 7 filters at Home Depot are more restrictive than the True Blue. I don't care for the cheap woven fiber ones that you can poke your finger through but can try that in your case since they're least restrictive. Lastly, your high limit switch could be faulty due to it cycling off high limit due to the plugged filter for so long, I'd stick a digital meat thermometer in the plenum and see what the temperature rise is. Furnaces usually call for a maximum rise of 70�, and the high limit usually trips at 200�.

Post# 1015103 , Reply# 6 11/19/2018 at 23:19 (1,983 days old) by RP2813 (Sannazay)
Checkrate/Likes How would the evaporator itself get plugged up, and with what? Dust? I like that theory and it makes sense, but I'll have to figure out where it's located.

Post# 1015144 , Reply# 7 11/20/2018 at 06:54 (1,983 days old) by arbilab (Ft Worth TX (Ridglea))
Checkrate/Likes Gawd forbid, prev owner w/dog ran it without filter for a time?

Post# 1015145 , Reply# 8 11/20/2018 at 07:14 (1,983 days old) by retro-man (- boston,ma)
Checkrate/Likes 1 I had a similar problem last year with an American Standard unit. The a/c worked fine but when the heat came on it was the same as yours. I kept letting it go and it would work for a while, then sometimes I would have to turn the power off of it to be able to reset itself. Then finally it stopped all together. Come to find out it was the heat exchanger had developed a hole in it. Changed the dynamic pressure inside the unit and it would shut down. Had to have the heat exchanger replace, fortunately it was covered under warranty and I just had to pay for labor. It was out of service for almost 3 weeks during the winter in NH. 4 space heaters and the broiler running made do for us. The unit was only 6 years old at the time. I had also noted some water in the pan under the unit during this time. It was the condensation that was leaking out of the hole. Jon

Post# 1015148 , Reply# 9 11/20/2018 at 07:51 (1,983 days old) by combo52 (50 Year Repair Tech Beltsville,Md)
Checkrate/Likes *Forced Air Gas Furnace Issue* I think Johnathan [ reply #5 ] is on the right track. This problem also sounded to me like an air flow problem. Was the A/C coil replaced two years ago with the furnace ?, it could be clogged. What is the BTU output of the new furnace ?, it could easily be too large for the duct-work. What are the supply and return registers in the house like ?, many times they have been painted so many times that they restrict air-flow too much, or worse yet some one installed decorative wooden or even patterned metal ones that restrict air movement too much. John L.