carrier furnace lock-out

Steve724

we are currently working on a carrier furnace m#58mxao8-12.propane.approx. 12 to 15yrs. old.furnace runs between 2 and 4 days before a lock-out.31 code. checked intake and exhaust piping,cleaned condensate trap and lines,checked tubing from pressure switch,checked pressure@ switch with magnehlic (2.1" with burners and blower running/ no real flucuation at all). removed and inspected blower wheel on inducer/looks okay.inducer amps ok.finally replaced pressure switch.still the same problem.runs a couple days then locks out on 31 code.any ideas would be appreciated.

VictoriaEnergy

intermitent carrier

The MXA was, I think, a 2 stage, condensing furnace, sealed combustion.



If code 31 is somthing along the line of 'pressure switch fails to make', then fire it up and after 5 min sample with your CO tester exhaust.  If it's over 200 PPM, (usually waaaay over) then suspect cloged/failing seccondary heat exchanger.



Carrier had some issues with the laminating material they were using for thier seccondary heat exchangers during that era.  Carrier has a warranty that covers this failure with customer option for repair or credit towards new replacment furnace.



If it passes the breathilizer test, don't bother tearing it apart just to look at the 2nd hx, it will be fine.



Let us know.

Empire_2

Another check

Good call Victoria Energy.  Also, take a look for any bows in the exhause that may have a build up of water from condensate.  I have seen this only once or twice, but take a look and make sure pitch is back to the furnace.



My .02

Mike T.

Steve724

carrier lock-out

Furnace still locking out w/31 code.Checked the co level as you suggested.approx. 175 to 180 ppm.I still think there is a problem with the secondary hx even though the readings were slightly below what you had suggested.contacted carrier tech support,and they seemed to think it was also a problem with secondary hx.The labor credit or furnace credit for these heat ex no one really knows.I heard that it ended in 2008? As of right now looking to change furnace vs replacing hx.

VictoriaEnergy

Condesate trap?

Did you take the condensate trap out & clean it out?  These can get full of crud that settles and clogs the lower port to the secondary hx, and then the hx runs 1/2 full of water with similar results.  There's a little 3/8" hose that's only 1 1/2" long (when it's set up for up-flow config) be ready to see a quart of water gushing out when you disconnect it.



The 200 ppm was from an old Carrier/Bryant service bulletin for diagnosing for failed hx issue.  When I've run run into failed 2nd hx in the past they pushed over the 2500 ppm max of my Bacharach.  So I'm still a little doubtful it's the 2nd hx.



If it does indeed turn out to be a failed hx, it'd be worth repairing.  They were otherwise very good furnaces.

Steve724

carrier furnace lock-out

yes. On 1st visit we removed condensate trap and tubing.cleaned and flushed out.checked all connection points for debris.see original post.any other suggestions?

Steve724

carrier furnace lock-out

yes. On 1st visit we removed condensate trap and tubing.cleaned and flushed out.checked all connection points for debris.see original post.any other suggestions?

VictoriaEnergy

more info

Post an e-mail address, and I'll send you the lengthy heat exchanger failure evaluation bulletin from Carrier.