How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask BillyHvac Your Own Question
BillyHvac
BillyHvac, Journeyman HVAC Tech
Category: HVAC
Satisfied Customers: 22311
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
12672042
Type Your HVAC Question Here...
BillyHvac is online now
A new question is answered every 9 seconds

Billy I've got a byrant comfort plus 80. Getting code 31.

Customer Question

Hey Billy
I've got a byrant comfort plus 80. Getting code 31. Inducer fan starts, ignition sequence initiates and it will run for anywhere from 3-10 min before system shuts down. As long as call for heat is coming from t stat it will repeat this cycle every 5 minutes or so.
I know code 31 high pressure switch is often a signal of other problems not necessarily the switch itself. I checked entire exhaust vent to roof termination. I cleaned a bit of ash deposits from a couple spots in duct run, but nothing major was blocking. Combustion and return air grills and ducts have all been inspected and found to be clear. Any advice?
Submitted: 1 year ago.
Category: HVAC
Expert:  BillyHvac replied 1 year ago.

Hello,

the small rubber tube from the pressure switch attaches to a barbed fitting on furnace...have you poked this fitting out all the way through?

Customer: replied 1 year ago.
Sorry that reminds me I left out that info. I poked through that fitting at furnace with small piece of wire and was able to get wire about 2" in felt like was hitting metal at that depth did not try and force wire any further. Also checked tube between low and high switches, both were clear
Expert:  BillyHvac replied 1 year ago.

remove 2 wires fro pressure switch...start furnace..wait until AFTER the exhaust fan starts...then hold the 2 wires together metal to metal...tell me if it still faults

Customer: replied 1 year ago.
Will do, on the last sequence it started and hit temperature and did not fault out. Led is showing steady on right now. I've gotta leave for a couple hours so I'm going to check in on it when I get back and if it has thrown a fault I will try bypassing it as you suggest.
Expert:  BillyHvac replied 1 year ago.

Thank you.

Do the bypass just for testing. Do not leave bypassed as it will fault on next start up.

Billy

Customer: replied 1 year ago.
Ok I'll test it now.
Expert:  BillyHvac replied 1 year ago.

standing by

Expert:  BillyHvac replied 1 year ago.

are you sure this is not code 13?

short blinks first followed by long?

Customer: replied 1 year ago.
3 quick blinks followed by 1 long
Expert:  BillyHvac replied 1 year ago.

ok just making sure...

Customer: replied 1 year ago.
far it's run 5 min with bypass of high fire switch, no fault
Expert:  BillyHvac replied 1 year ago.

ok this means board is ok and the issue is with the air flow....have you looked inside the exhaust blower yet?

Customer: replied 1 year ago.
No I've not, how do you suggest I go about that. Unfortunately I have to run for a while. Anniversary dinner. I did place wire back on
Expert:  BillyHvac replied 1 year ago.

either remove vent pipe or remove the inducer motor from the furnace wall...we nee to see if feathers, missing blower fins etc..

Customer: replied 1 year ago.
Removed inducer looks to be completely clear. Ran all day with no fault finally threw fault code on last start up
Expert:  BillyHvac replied 1 year ago.

any chance of downdrafts or severe wind?

Customer: replied 1 year ago.
No strong winds, it's been in 30 degree range. Suppose down draft could be possible. Exhaust duct runs laterally from furnace about 6 feet gaining about 2.5 ft in height from furnace with a couple 22.5 degree bends. Then goes straight up 15' to roof termination. I have visually inspected entire run and determined it was clear
Expert:  BillyHvac replied 1 year ago.

ok, we have fan working and fittings clear, tube ok, vent clear...either the bypass we did was not at a fault time. (pressure switch) we could simply have a weak pressure switch.

Customer: replied 1 year ago.
you reccomend replacing both the low and high since they are the same age?
Customer: replied 1 year ago.
Sorry meant to say do you?
Expert:  BillyHvac replied 1 year ago.

yes...that would be the next step.

Related HVAC Questions