Carrier 355MAV with Evolution Control Help

[zw17]

Ran a call today for a customer that has a Carrier 355MAV furnace with a Evolution control stat.

Furnace: 355MAV042080
Thermostat: SYSTXBBUID01



Here's the situation:

Evolution control is showing a variety of errors (listed in the pics below)
I am the third tech to take a look into this
A week ago an April Aire #700 was installed and a clean/inspection was performed, cleaned burners, flame rod, condensate trap.
Ever since this furnace has been throwing codes daily

Here are the codes I saw this afternoon:





The code 33 and 34 is what I am having trouble with, not sure if they are A/C related or heat related? Can anyone tell me what those faults are?

I also checked the humidifier wiring and they have the solenoid connected to the HUM and COM terminals on the furnace control board, this appears right.

Any help is much appreciated.

[pcp]

Bypass humidifiers are wired that way on the furnace, the Evolution will energize hum during a call for humidification and can be set for heat only or with fan. With a bypass humidifier installed go into advanced settings and turn low heat rise on it increases air flow, which you want to do now that your return air is warmer. You can also go into furnace set up and change air flow from comfort to efficiency increasing air flow even more this should take care of the limit fault(33).
34 is ignition proving fault usually dirty flame sensor but could be rough ignition or low inlet gas pressure, 32 can also be low gas pressure if its lp with a lgps switch which is in series with your pressure switches.

[zw17]

Thank you PCP, I will be back at the job tomorrow to do as you advised.

[gravity]

These furnaces always have trouble. You need to increase airflow. Also should setup low, med, and hi fire with a combustion analyzer. Years ago I always had errors with ignition, limits, etc... Until I started tuning with a CA. With a 90% furnace, you need 150cfm per 10,000 input btus

[zw17]

These furnaces always have trouble. You need to increase airflow. Also should setup low, med, and hi fire with a combustion analyzer. Years ago I always had errors with ignition, limits, etc... Until I started tuning with a CA. With a 90% furnace, you need 150cfm per 10,000 input btus

Thanks Gravity. I returned to the job today and increased the airflow per PCP's instructions. Advised the customer to keep and eye on things and let me know.

[gravity]

You also need to watch out for the venting.

If your flue is too small or too long of a run, it may work but it will burn horrible.

No way to tell this unless using a combustion analyzer.

Just make sure the venting is by the book and you use the restrictor plates in the intake properly

[hkempf]

That's funny my last call today was one of these, code 45 on a heat pump, had to replace the board on the heat pimp

[hkempf]

The fn is for the furnace

[0351]

Airflow is a good thing to check, if you get a call back confirm heat rise, gas pressure and if you have an N-coil for the evap that doesn't match the furnace casing size wise make sure its positioned correctly-N coil overhanging the wrong side alone can cause limit trips

[zw17]

To follow up:

I went back Monday and changed the settings per PCP's advice in post #2. It's now Wednesday and there hasn't been a single trip. Turns out the LPS and ignition issues were caused by the tech checking the safeties during the inspection. The date and time were not set properly on the stat.

So far so good. Thanks guys.

[gravity]

Thanks for the update.