Carrier Infinity 59MN7 riddled with system malfunctions
Carrier Infinity system
Air Purfier: GAPAAXCC1625-A01 (filter last replaced in October)
By-Pass Humidifier: HCWBB-17A (Lennox)
We own a duplex with 2 separate but identical systems.
2nd Floor system runs great.
1st Floor system is riddled with system malfunctions.
33 - Limit Faults
13 - Limit Lockout
The installers have been out several times.
1st time they adjusted the gas pipe and said it was too close to the limit switch.
2nd time they fiddled with blower speed.
3rd time they fiddled some more.
4th time they replaced the furnace controller board.
5th time they blamed our 1929 duct work and fiddled some more with blower speed.
6th time they cut a new vent in the main air duct just above the A/C coil. I was told that we'd have to keep that open during the heating season and close it during the cooling season.
As the temperatures slowly dropped this fall, I'd open the vent just a little bit more and that seemed to fend off system malfuctions. And that only worked if we kept the thermostat at a constant temperature setting. If we decided to raise the temperature 2 degrees, you are almost guarnteed system malfuctions before the house heats up.
Now the temperature has hit 12 degrees this AM and with the new vent wide open, closed, and several settings inbetween, the thermostat reports system malfunctions.
The installers say that the 2nd floor works because the air ducts narrow as they go up through the wall cavity from the basement to the second floor and that the return ducts are longer. So that furnace doesn't overheat.
Is any of this true? Is this furnace a lemon? Is the furance undersized and working too hard?
Odds are that the system wasn't properly set up. There's a troubleshooting guide available for that furnace on Carrier's site. Have your technician obtain a copy and have him go through the troubleshooting sequence for error code 33 exactly as specified without skipping any steps or skimming over any of the text. The instructions are quite detailed, but should efficiently locate the source of the problem. There are a number of settings/adjustments that can contribute to overheating, and none of them should be ignored by your technician just because he "thinks" that this or that is "probably" ok. Gas input rate too high, excessive static pressure (ESP), excessive air bypass (humidifier), are some of the major causes.
+1. Manuals are a wodnerful thing with electrionics. You cna catch small items that can be big problems.
I I was a betting man, I'd take a wager that the airflow was not increased for the bypass humidifier. That's in the manual too. I'd want to verify that first.
That 1929 ductwork is probably better quality than 90% of the modern installs. Its' only issue might be that it's undersized for a modern furnace with a lower temp rise. I think there is a way to restrict the maximum capacity of the furnace if it's an issue. If nothing else, in the short term so you're not cold, it's possible to lock the unit in at the intermediate firing rate, which probably enough to maintain temp without setbacks. Old homes have high mass with their plaster walls and real hardwood floors, so recovering from a setback can take a lot more energy than just maintaining temp.
If anything the furnace is oversized, but it's the smallest available. 12F within 10% of design temp in most parts of the country. At that temp, if it was the right size, it should be running continously close to mid fire.
Thank you both for taking the time to reply.
IMO, whoever designed the bypass humidifier should be shot. It makes no sense because it causes a very short airflow loop that will overheat the furnance in the winter and freeze the coil in the summer. I have to run it with the damper closed in the winter to reduce system malfunctions and completely tape off the duct opening in the summer because the damper leaks so much air that it effects A/C cooling. If I had known what it was before hand, I never would of bought it. The pictures in the brochure show the unit but not the bypass pipe.
Thinking back, the two-person team that installed the first floor system used wiring charts and I'm almost positive that they changed wiring claiming it was wrong from the factory. Maybe they didn't understand or made a mistake or this unit is just a lemon.
I will call the installer AGAIN and see if they are willing to follow the troubleshooting guide step by step or have other ideas.
Do you think installing the extra duct in the main duct, coming out of the top of the furnance, right above the A/C coil to vent some of the heat into the basement was a correct step to take?
Do you think I would be out of line for insisting on a brand new furnace?
Call the company owner, and insist they send out a tech, not an installer. They can and should make the proper adjustments, even if your duct is undersized. There are a lotof adjustments on the controller itself. We have installed a lot of these furnaces with the infinity control, and all work great if you take the time to set them up properly.
Lots of bypass humidifiers installed with no problems out there. There are other issues that need to be addressed with your system if the bypass is causing that much trouble.
As for the vent right above the furnace, more of a band-aid than anything else to prevent the furnace from tripping on high limit. Have the installers verified the size of your existing ductwork? I'd be curious to know what external static pressure the Infinity controller is reading.
Best of luck rectifying the issue. You have a nice system once they get it working properly. Motoguy made some good comments above.
Just changed the AirPurifier filter and cranked the themostat up two degrees.
Infinity themostat (adv setting | service | furnace status) is showing:
heat stage 100%
lockout timer none
bypass humidifier damper is closed.
new air duct lever is open a little above 50%
update: thermostat reached temperature, fan speed switch on high, furnace was at 95%, and ka-boom...33-limit fault
Originally Posted by joeWI
Static is very low, almost ideal. Temp rise should be around 51F if that CFM is correct. Even if you bypassed 100CFM for the humidifier, you still shouldn't be tripping off on high limit. I think 1070 is "comfort" airflow setting within added airflow for the humidifier.
Seems like there's something else going on. Time to get out gauges and check gas pressure, verfiy airflow manually, check temp rise manually.
wonder if they set the gas pressures properly
Post up the numbers for your identical upstairs furnace when it's running on high.
im thinking they forgot to properly commission the system
second floor system (the one that works well)
lockout timer none
bypass humidifier damper is open
In setup | furnace setup | furnace airflow, 2nd floor is set at comfort. I changed the 1st floor setting to effeciency some time ago because it was my understanding that it would cause the blower to run faster and the air would project out into the rooms better.
update: I called the installer and politely talked with the owner of the company. He's sending a team out tomorrow morning and it sounded like he may be there too. I'll keep my fingers crossed.
repair guy just left after spending 2.5 hours working on it. the owner of the company was here for about 45 minutes.
he replaced the motor module on the blower. he noticed some grease on the end of the shaft and is concerned that there might be slippage occuring which would mean that we're not getting the volume of air that the thermostat is reporting (apparently it uses a formula based on the rpm.)
he checked and adjusted gas pressure slightly.
he is ordering a new limit switch.
he has locked the furnace into low and medium staging as a temporary measure to keep it running while they order the parts and schedule a return visit.
at least the owner saw that as soon as they opened the humidifier bypass damper, it tripped a limit in a short amount of time.