[jonah111]

Hi everyone,

I have a 9 year old Bryant Plus 90, model #CD5AXW024017AAAA that keeps giving a code 33. After doing some investigating, I found that an old filter was still against the blower motor along with the current filter. The old filter was completely clogged- I think it worked its way out of view of the filter slot and I installed another one without realizing I hadn't removed the old one. I assumed this had solved the problem but it still seems as if the igniter area is producing too much heat and triggering the limit or rollout switch. The unit will cycle through the normal startup process and start producing heat, but after a few minutes the metal casing above the pilot is almost too hot to touch, the 33 code starts flashing, and the pilot goes out while the blower continues to run.

Is the shutoff being caused by the unit getting too hot and what are some potential causes?

Thanks for the help and have a great holiday!

John

[jonah111]

I forgot to mention that the furnace runs on propane

[jonah111]

A few more details: looking at the flame, it is pretty jagged and has portions of yellow in it. The box also make a bit of a rattling noise too- don't know if that is normal or not.

Thanks

[hvac1000]

Your problem will not be a simple one. If the blower for the home is running the unit should not overheat unless the A/c coil is blocked with dirt since you removed the clogged filter. Do you have central A/C?

[jonah111]

Yes I do have central AC. Could you give me an idea on how to access the coil? Would compressed air work well for that?

Thanks for the help

[hvac1000]

The coil is mounted on the top of the unit.

You probably have more problems than just that issue. The flames should not look as you described and the box should not rattle.

[mygirlsdad77]

What does the book say code 33 means?

[hvac1000]

33 LIMIT CIRCUIT FAULT - Indicates a limit, draft safeguard, flame rollout, or blocked vent
switch (if used) is open. Blower will run for 4 minutes or until 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 #33 continues to flash until blower shuts off.
Flame rollout switch and BVSS require manual reset. Check for: - Restricted vent
- Proper vent sizing - Loose blower wheel. - Excessive wind
- Dirty filter or restricted duct system.
- Defective blower motor or capacitor. - Defective switch or connections.

- Inadequate combustion air supply (Flame Roll-out Switch open

In his first post there air filter was super dirty and that also means that the furnace has been neglected for 9 years or so. The unit is overheating and it probably needs a complete professional service.

[mygirlsdad77]

Okay, sounds like you need to have evap coil cleaned, and also(on 90+ units) may have to have furnace coil(located directly above squirell cage) cleaned. Agree with hvac, time to call for a pro.

[jonah111]

Is it possible these symptoms are related to a cracked heat exchanger? That's my biggest fear right now.

Yeah, I had the feeling that it wasn't going to be a single issue or simple fix. I'll see if I can get someone to look at it soon- not sure how the holiday weekend will affect that. Thankfully I've got the fireplace to keep things tolerable.


Thanks

[jonah111]

I just spent the last few months finishing half of the basement too. I'm sure the sawdust & drywall dust haven't helped the issue.

[T-Top]

You have two 2inch pvc pipes that exits the furnace, one is the exhaust and one is the intake. The intake should have a cap on the opposite side of the burners. Remove the 2 inch cap and see if it will burn. You may have a slight restriction in the intake or exhausts. A weak or sticking vent pressure switch or a cloged condensate drain will give the same symptom and fault code.

[jonah111]

I checked the vents for blockage and even ran the unit without the intake & exhaust attached for a few minutes without any change. Also cleaned of the AC coil.

I had someone look at it and they felt there was a good chance the problem was being caused by a blocked or bad inducer motor. Any thoughts on whether this diagnosis is consistent with my symptoms?

[mygirlsdad77]

Not likely the inducer motor. If your inducer or vent/ intake were the problem, your pressure switch would fail to close, causing the gas to never actually come on.

You say you cleaned the ac coil? Did you clean it from the top or the bottom. It needs to be cleaned from the bottom if you have an upflow furnace.

It wouldn't hurt to check for carbon monoxide(cracked heat exchanger) Probably not the problem, but better to check and be safe.

In your original post, you say flame rollout or high limit. Really need to know if it is flame rollout OR high limit.

[T-Top]

Your system may have a gas inlet pressure switch(used with L.P gas conversion kits) It wires inline with the vent pressure switch. Lack of gas pressure will cause the switch to open. The gas pressure switch is found on the gas inlet side of the gas valve small round device with 2 wires going to it. (I think yellow and orange but not sure)

[jonah111]

The ac coil was cleaned from the bottom- it was dirty, but not as bad as I had expected.

The flame rollout switch (on the side of the burner box) is the one causing the heat to shut down. I can reset it when things cool off.

Is it possible that the inducer motor functions enough to close the pressure switch but not enough to keep it from overheating?

Thanks

[jimmyleejon]

Is this a high efficient furnace.also have the orifice size been adjusted i.e. has the unit been properly converted to lp.also gas pressures may be to high or a faulty gas valve .possibly more return air in the case of a high efficient it could be improper venting causing condensate to pool in the vent lines. Decreasing the flow of air that would probably be a pressur switch problem though