[DamienM]

So everything was fine on the unit until we had a bad wind storm that knocked out power. Since then I have been getting Error 13. I can reset the flame rollout switch and power the unit back on and the unit will run just fine when CFH is requested. Once the temperature reaches the temp and it should technically turn off, that seems to be when the error is throw and the blower continues to run eventually blowing cold air unless I turn it off.

I have replaced the limit switch and flame rollout switch myself. I can't fathom that it's a bad heat exchange if it was fine until a power outage happened. I called a local shop initially and they quoted $150 to just come out and $250 for a limit switch ($12 part which is an insane markup). I'm trying to gather other opinions before biting the bullet and having a tech out. Was hoping to fix it myself. Exhaust looks fine, 4" filter was recently replaced. Obviously the airflow is fine and I believe the heat exchange/coil are fine because the unit runs just fine for hours until the CFH is no longer there and the unit is supposed to turn off.

Model: 58MXA120-F-17120
Serial: 2504A10464

 

[Chris616]

Taking a guess that you’re located in the USA, I’ve looked at the US Carrier website, but the model number that you’ve shown doesn’t appear. Can you point us to a manual for the furnace, please.

Chris

 

[DamienM]

I uploaded a picture of the sticker showing the model #.

 

[DamienM]

https://imgur.com/nA10nhd

 

[DamienM]

Found this by searching...
https://dms.hvacpartners.com/docs/1009/public/09/58mxa-10si.pdf

 

[Chris616]

There isn't anything in the manual about the error codes, but from what I can see on the web there is probably a label on the inside of the unit that describes them and is likely what you've been using so far to diagnose the issue. Can you give us a picture of that, please.

Chris

 

[DamienM]

There is, I already checked it which is why I replaced the limit & rollout switches since they were really cheap.

Error code 13 - Limit Circuit Lockout
Lockout occurs if the limit or flame rollout switch is open longer than 3 minutes. Control will auto reset after 3 hours - refer to #33

Error code 33 - Limit Circuit Fault
Indicates a limit, or flame rollout 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.
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 rollout switch open)

https://imgur.com/e7ePaKW

 

[Chris616]

I'm afraid that I have no useful suggestions except to say that some searching indicates that this is a not uncommon problem. I'm sure that the answer is out there on the web, if you search enough. Here's one example from this forum (with a slightly different process but ending up with the same codes):

https://www.diychatroom.com/f17/carrier-weathermaker-9200-error-code-33-turns-into-13-help-597193/

Chris

 

[DamienM]

I can try running it with no filter but it's the same kind of filter I've used for years now so I have a hard time believing it's the filter since that has stayed the same and it ran fine before that. Stupid wind storm/power outage.

 

[user_12345a]

Restrictive filters don't cause rollouts to trip.

You most likely have a bad secondary heat exchanger, it's likely producing a lot of carbon monoxide and isn't safe to run.

You need to call a pro out to check carbon monoxide in the exhaust or do a complete combustion analysis.

If it's bad enough the metal will be rusted through and that can be checked by pulling the blower assembly.

There is a 20 year warranty on the part and a small amount of labour coverage from carrier. Many contractors may not bother with getting the labour coverage - small amount, wouldn't cover the full cost.

If it's reaching end of life anyway (16+ years old) and the entire cost isn't covered it's better to get a new furnace.

They do give some credit towards a new unit if you choose not to repair but only if you stay with carrier -> why give them more business, they had to be sued to acknowledge the problem.

Edit:
You have a 120k btu furnace and before opting to repair, you really need to make sure it's not oversized. There's no point if it is.

It looks like a 2004 so repair is probably not a good option.

Unless you have a very large house I can guaranty you it's too big.

 

[DamienM]

I have CM detectors all throughout my house and they are not going off at all. 2 in the basement, 3 on the 1st floor and 2 on the 2nd floor. The house is over 3700 sqft not counting the basement and over 6k sqft when counting the basement. The home was built in late 2004 so the unit is just over 15 years old. There is also a 2nd furnace upstairs to cover the upstairs which is functioning just fine.

Guessing it might be nearing end of life.

 

[DamienM]

The thing i struggle with most is it was working just fine until a wind storm => power outage then it suddenly stops working which makes me think something electrical (control board, fan, etc) that isn't functioning properly. The unit runs just fine, i can touch the outside of the unit when it's running (it's warm and not burning hot), i can touch the box inside but not keep my hand on it because its much hotter. I can crank the heat up to 80 and it'll run till the temp hits 80 then it'll throw the error instead of turning off and the blower stays on when the heat is up. I check on it frequently when it is running and the flame stays the same and it never shuts off/throws an error until the temperature his what I set the thermostat to. To me, if it were a heat exchange, it would fault much sooner due to the temperature getting too high. If it shut off every time after 1 hour or so then I would agree but that's not the case. I tested the theory over the last 2 days with different temperatures.

I have a tech coming out to diagnose the issue today. Went with a local family owned shop. We'll see what happens. I'll add their diagnosis here once they have left for reference

 

[user_12345a]

Your heat exchanger has probably been slowly plugging up for a while and it had to get bad enough for the rollout to trip.

It probably had to run for a long time to warm the house up after the outage and the problem showed itself.

CO alarms provide a very false sense of security, they don't go off until 70ppm in the house and don't have to alarm for up to 4 hours of exposure at that level.

It's not safe to run. Not only can the co in the exhaust be very high (thousands of ppm), the intake and exhaust pipes can also burn up. There can be property damage.


Turn it off - forget the theories, forget changing out parts. It needs to be professionally checked - spend the money on a service call.


---------
If 120k is only covering half the house (basements have minimal heat loss and don't count much), I can bet it's at least double the size it should be.

Hopefully if there's a/c and u want to keep it, it's 3 tons or less so blower capacity isn't a concern when downsizing.

A load calculation should be done before replacement if u go that way - https://www.loadcalc.net/, https://www.hvaccomputer.com/

 

[roughneck]

I have CM detectors all throughout my house and they are not going off at all. 2 in the basement, 3 on the 1st floor and 2 on the 2nd floor. The house is over 3700 sqft not counting the basement and over 6k sqft when counting the basement. The home was built in late 2004 so the unit is just over 15 years old. There is also a 2nd furnace upstairs to cover the upstairs which is functioning just fine.

Guessing it might be nearing end of life.

Are they UL listed? What brand are they?
That unit is on the list of units affected by the class action lawsuit involving secondary heat exchanger failure.
If you can’t keep your hand on the burner box then you likely have a secondary failing.

 

[DamienM]

Well my basement is a full basement with walkout (3 doors to the outside) and like 9 full windows. I believe it's around 2800 sqft so the 120k unit covers about 5k sqft total maybe a little more. Tech should be here anytime in the next 4 hours and I will ask to run the tests mentioned here. Diagnosis should be here shortly.

 

[roughneck]

Ask for a combustion analysis. Hopefully the tech has an analyzer with him.
If it’s the secondary your unit will be putting out high CO, among other out of range readings.
UL listed CO detectors available at hardware stores will only alarm after being exposed to 70 PPM or higher for 1 hour.
By contrast, most fire departments will not enter a building if the CO is over 25 PPM.
The UL listed models are a false sense of security and only for major failures like a plugged chimney.
They don’t do much good otherwise.
Low level CO detectors are much better at preventing CO poisoning.
Equipment isn’t sized via square footage.

 

[roughneck]

Read here-

http://hipspro.com/pubs/Furnace-clasaction-detailed_notice.pdf

 

[user_12345a]

Well my basement is a full basement with walkout (3 doors to the outside) and like 9 full windows. I believe it's around 2800 sqft so the 120k unit covers about 5k sqft total maybe a little more.

Sizing is not done by sq ft, hence needing calculations should the secondary be bad and you choose to replace the furnace.

Don't just get another 120k - could need less. Maybe 60 to 80k.

While the tech is there would be wise to get the other furnace checked - it can still be bad without the rollout opening.