carrier fault code 33 on 58mvc

[workhc]

have fault code 33 on carrier mvc, works fine in high fire, ran fine for 10 minutes each in low and medium fire through the check out in infinity controller. brand new infinity air purifier filter installed in november and is clean, all gas pressures are in range when tested and temperature rises in all 3 stages are good. anyone with a possible solution or something i missed would be appreciated. i am in the business and have installed many of these furnaces without trouble.

[ChrisRisi]

Make sure the metal around the main limit isn't too close to the heat exchanger. If its too close it'll pick up the heat and give you a false limit trip.

[beenthere]

Moved to Tech to Tech forum.

[stay gold jonny]

How long is it on high fire? I've seen the limit trip many times on the MVC and all I can say is that it's a crap shoot as to why in some cases.
I personally hate that furnace, do a google search for the troubleshooting guide, that might help you out.

[workhc]

How long is it on high fire? I've seen the limit trip many times on the MVC and all I can say is that it's a crap shoot as to why in some cases.
I personally hate that furnace, do a google search for the troubleshooting guide, that might help you out.

ran in high fire 10 minutes, been installed since 2008 and trouble free

[54regcab]

How close are you on temp rise?

[stay gold jonny]

How many limit faults did the Infinity Control have listed? It's possible that this has been going on for a while. 10 minuets might not have been a long enough run time for the heat to build up and trip the limit.
What is the set back on the control? I've found that if it has to raise the room temp by 5* or more that high fire will be on for a long time, factor in colder outdoor temps and it will run even longer on high fire
I did notice that on an 80k btu MVC the limit size is 180* and on a 120k btu it's 170*, not saying its wrong just didn't seem right.

[lloydct]

We had this issue in our unit. 33 and 34, unit would only run in high heat. There was a service bulletin out for this problem, the tech had to remove some metal shrouding inside the unit and the codes went away.

[rchristie420]

Try bumpin up the blower speed I think it's normally med low I would try med high and see if it stops

[philjafo]

Secondary hx partially plugged with the liner peeling off. What kind of numbers are you getting with the combustion analyzer?