Bryant 376cav & 395cav problem

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Old 03-06-12, 09:57 PM
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Bryant 376cav & 395cav problem

I recently replaced my old CESO110057-01 with a ICM281 since the blower ran all the time even when the flame was off.
After the ICM 281 is installed, the blower starts and stops as it is supposed to do. However, the furnace sometimes does not turn on even the thermostat (honeywell chronotherm 3) instructs "heat on". I found that the LED default code is 33 when it happens. I cleaned the filter, but it did not do anything. Can you give me an idea what is the trouble that I have? Thanks in advance.
Sam
 
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Old 03-06-12, 10:41 PM
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Does it just come on randomly or wont come on at all? Could it be a timer?
 
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Old 03-06-12, 11:37 PM
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The Carrier 33 diagnostic code is signaling that the limit switch is open. An open limit switch would have caused the fan to run with either the new or old circuit board.

So I'd use a multimeter to check and see if the limit switch is remaining open in fact. If so, replace it.
 
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Old 03-07-12, 08:31 AM
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Evap coil may be plugged up as well or you are using too restrictive of a filter.
 
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Old 03-07-12, 10:11 AM
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Bryant 376cav & 395cav

Thanks for your prompt responses.

It has ran the heat cycles most of time after I replaced the control board and the blower starts and stops as it is supposed to. However, occasionally it does not start the heat cycle (that means the blower does not start) and the LED flashes faulty code 33. When I reset the limit switch on the left side of the furnace, the blower starts, but the faulty code is there and no flame. After the power turns off and on, it starts heat cycle again.

I don't find any evap coil from my furnace. Please let me know where it is located if any. I also need part# of limit switch if anybody has.

Thanks much
 
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Old 03-07-12, 11:58 AM
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You need to use a multimeter to see if the limit switch is sticking open when you get the 3-3 code.
 
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Old 03-08-12, 12:21 PM
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376cav & 395cav

I tested the pressure switch, the limit switch, the roll out switches with a volt meter. When it stop working, I found 24 v or more from one terminal of the pressure switch connected to the control board, but no voltage from other side terminal of the pressure switch to the roll out switches on the blower. Should I change the pressure switch or the roll out switch on the blower?

Thanks
 
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Old 03-08-12, 12:48 PM
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another observation

When the machine stops, the upper side of furnace (upper cabinet has the blower) is vacuumed and it was hard to remove the cabinet front cover.
Please help me.
 
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Old 03-08-12, 01:04 PM
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Sorry for wrong observation. The negative pressure is only the blower runs. Still wonder if it is normal that the neg pressure of inside of cabinet containing the blower when the blower runs
 
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Old 03-08-12, 02:21 PM
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Connect one lead from your multimeter to the C terminal on the furnace or the furnace sheets metal.

While the inducer motor is running, check both sides of the pressure switch. If the switch is closed, you would have about 24 VAC on both sides of the pressure switch. If it's failing to close, you would have 24 VAC on one side only.


And no, don't change out the pressure switch. There's only a 2% chance the pressure switch is bad.
 
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Old 03-08-12, 03:38 PM
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376cav & 395cav

Thanks SeattlePioneer for all of your advices.

When it works normally and the heat is off, either side terminals of the pressure switch have no voltage.
When it stops working, LED gives fault code 33 and only one side terminal has 24 VAC.
When the inducer motor (the blower) is running (heat on), both sides has 24 VAC.

Then, does the roll out switch of blower go wrong?

Thanks
 
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Old 03-08-12, 05:30 PM
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Originally Posted by sessko View Post
Thanks SeattlePioneer for all of your advices.

When it works normally and the heat is off, either side terminals of the pressure switch have no voltage.
When it stops working, LED gives fault code 33 and only one side terminal has 24 VAC.
When the inducer motor (the blower) is running (heat on), both sides has 24 VAC.

Then, does the roll out switch of blower go wrong?

Thanks

No doubt you explanations seems clear to you, but to me you are being vague about critical issues so I can't understand what is happening in detail.

Sorry.
 
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Old 03-08-12, 06:19 PM
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Sorry for ambiguity of my explanation.

What I meant by my previous message;

My furnace most of time starts heat cycle as the thermostat instructs, but sometimes, it does not start heat cycle even when the thermostat instructs "heat on".

I am trying to explain you what happened once more,
When the thermostat is turned off (meaning "not heat on"), either side terminals of the pressure switch has no voltage. (I think that it is normal)
When the thermostat instructs "heat on", a heat cycle starts, and the inducer motor (the blower) is running, both sides has 24 VAC.
When it does not start a heat cycle even with the "heat on", LED gives fault code 33 and only one side terminal has 24 VAC.

Thanks
 
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Old 03-08-12, 07:27 PM
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But when only one side has 24v and your furnace is giving you a code 33 is the inducer running or no?
 
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Old 03-08-12, 08:08 PM
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The inducer does not run when only one side has 24v and my furnace is giving me a code 33.
 
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Old 03-08-12, 08:13 PM
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next step is to check voltage to the inducer while you are getting a code 33.
 
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Old 03-08-12, 08:35 PM
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What color are the wires to the part that you are calling a pressure switch?



The wires will not leave the pressure switch and procede to the limit switch on the blower.

You have a limit switch lockout and probably have a dirty evaporator coil or a plugged air filter.



 
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Old 03-08-12, 08:38 PM
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No voltage (0 VAC) is found on either terminals of the roll out switch on the inducer when I get a fault status code "33".
 
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Old 03-08-12, 08:54 PM
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You listed 2 furnaces. Which one has this problem?





 
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Old 03-08-12, 08:55 PM
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I have a honeywell duct mounted electronic air cleaner with my furnace. I already cleaned the filter and cells. I don't know where the evap coil is. Please let me know where it is located if any in my furnace.

The wire connections as follows;

control board -(yellow)- pressure switch - (orange) -blower - (orange) - roll out switch on safeguard box - (orange) - control board.

Thanks
 
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Old 03-08-12, 08:59 PM
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376cav downflow (the top figure)
 
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Old 03-08-12, 09:02 PM
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Yellow and orange are the colors that I would expect.


An upflow application would have the evaporator coil above the furnace. A downflow would have it below the furnace. A horizontal application would have it next to the furnace.




Does your house have AC as well as heat? The evaporator coil is used for cooling.
 
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Old 03-08-12, 09:05 PM
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No. we don't have an air conditioner.
 
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Old 03-08-12, 09:20 PM
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Do you have a digital "meat" thermometer?

The heat rise is listed inside the burner section panel. (probably 30 to 60 degrees)

Measure the temperature entering and leaving the furnace to get your heat rise.
 
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Old 03-08-12, 09:28 PM
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Is that electronic air cleaner the only filter on this system?

Do the curved blades of the blower wheel look clean?
 
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Old 03-08-12, 09:49 PM
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Yes, it is the only one. I did not check the blower wheel. I will check it tomorrow morning. Thanks.
 
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Old 03-09-12, 04:31 AM
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as Houston is getting you to do, we need to go back to the code 33. It is a high temp limit or roll out switch that is the problem. It is not a roll out switch because they are manual reset. Stop checking the pressure switch. stop checking the draft safeguard (what you have called a roll out switch) on the inducer. Focus on a square or rectangular limit with 2 (commonly red) wires going to it. That is the main temp limit. You need to do as Houston suggested (check the temp rise). You need to ensure all vents are open and your filter is new or clean.
 
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Old 03-09-12, 09:10 AM
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Now, I could explain the situation a little better after I have learned more technical terminologies for furnace parts.
My furnace is now getting worse. Once it starts a heat cycle and works for several min (5-10min), then it stops running.
Before (I mean yesterday), it ran several heat cycles before stopped running. I disconnected the pressure switch with the tubing and vacuumed it briefly and reinstalled it. That might be a bad idea. I am afraid that I ruined the pressure switch.
Anyways, the current situation is as follows.
At heat on, all of switches are closed (24VAC for roll over, rectangular limit, and pressure switches).
The "heat on" sequence : blower on – inducer on – blower off – flame on – (it runs several min and goes wrong from this point) – code 33 and flame off and blower & inducer run another a few min and stop.
Temp rise (listed: 50-80 F, max 180 F) :
Measured: inlet 54 F (entering) and outlet 112 F (leaving was measured immediately after the furnace)
I measured inside of panel of burner section too, it gives ~80 F
When it stops running with code 33 while “heat on”, R and W terminal on control board is 24VAC, one side of the terminals on the pressure switch gives 24 VAC, but other side gave no voltage (the roll out switches on blower and safeguard don’t have voltage).
The rectangular limit switch and other roll out switches have 24VAC at both terminals.
I tried to open more vents and checked filter. The filter if fairly clean.

I wonder if it is normal to have a high negative pressure in blower cabinet when the blower is running. I feel a vacuum inside of the blower cabinet when I try to open the panel while the blower runs.

Thank you everybody for responding all of my issues.
 
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Old 03-09-12, 02:58 PM
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the blower neg pressure is normal, but it also sounds like your filter may be plugged. Try running with out your filter for a cycle. When you get the code 33 is your blower running? If not then your heating speed relay maybe faulty. FORGET the pressure switch. IT HAS NOTHING TO DO WITH A CODE 33.
 
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Old 03-09-12, 04:25 PM
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I tried to run a heat cycle without filter and the furnace failed. When I get the code 33, the blower does not run. Is the heating speed relay on the control board? I replaced the control board from Ceso110057-01 to ICM281 a few days ago.
 
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Old 03-09-12, 08:32 PM
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The ICM is an aftermarket board and may have a blower on delay adjustment....The ICM board is an aftermarket board. I would suggest an OEM.
 
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