Carrier Infinity Furnace Troubleshooting

[brewchief]

If you're not getting 24v to the pressure switch at all on the communicating stat but you are with it jumpered out then the problem has to be either the UI or some part of the logic circuit that works with the UI on the furnace board.
I wonder if some update went out that bricked some stats, manufacturer will never ad it but it can happen, some years back we had a bunch of calls on a monday all for the same problem with lennox communicating stats.

With a 2 stage furnace you could run a non communicating stat and get full functionality, depending on what is currently being done with the stat the choices can be a little limited, morso if the wire isn't accessible to be replaced with one with more conductors. If you have a communicating A/C you may be stuck with the communicating stat in some cases.

I have a love/hate relationship with communicating equipment, it's great when it works but when it doesn't it can get complicated and expensive quick.

 

[64coupedeluxe]

Interesting. I am not familiar at all with Carrier Infinity stuff.

Apparently, the thermostat/controller is processing something during normal operation.



Does your tech have access to another system that your thermostat could be tested on?

If the system runs with the thermostat jumpered out, then that should eliminate the whole furnace. If something was wrong, then the safeties would take over and prevent operation.

That leaves the thermostat/controller, the part of the main board that talks to the thermostat, and its interconnecting wiring.

Thermostats are generally durable. Two thermostats with the same issue at the equipment seems awfully suspicious to me.

I would look very, very closely at the Molex connector pins and see if any of them have been pushed out or are otherwise misaligned. That includes pulling on the wires at the connector to see if something is loose.

I have had 2 Carrier junkers with bad pins from the factory. It took a lot of diagnostics with tech support to narrow down the problem. The quoted part above is a clue to me.

Your tech may have to spend time on the line with tech support.

I would also read the instructions and see if twisted and/or shielded wire is specified for the thermostat, and the specified gauge.

I get that it has been working,,, but you never know.

Otherwise, whatever is interfacing the thermostat to the furnace control board could be bad.

At this point, without access to some very in depth information, one is stuck swapping "known good parts".

The Tech said he has a similar carrier system at home. When he gets back on Monday I'm going to ask if I can drop it back to him and when he gets the chance if he can test it on his system. That should pinpoint the culprit.

To refresh on my original thermostat It had been fine and system running fine until I noticed it had connected to Carriers server. I noticed it was connected to wifi when I went to turn it on and thats when the furnace wouldn't start and the furnace was flashing code 32 LPS.

During the troubleshooting I removed the thermostat from the wall(with power off) to test the wires. When I put it back on the wall that is when it could no longer find the furnace.

The newly installed thermostat can find the furnace, I could complete the system setup, and I could call for heat. It shows "gas heating" on it as the inducer spins but I don't get the 27V at the LPS switch.

I have wired the thermostat with new 18 AWG solid strand wires which are around 24" long and it's sitting next to the furnace. So wiring is not the issue. 18 AWG solid is required for runs over 50ft. From my reading the later models had some problems with electrical interference from high power lines running close. There is no high power lines near my existing in wall wiring and using the 24" wiring rules this out. I have ordered new 18/8 wire to run as the wire that's there looks like it was from my old oil burner and they run a new 3 wire as there must have been only a couple of conductors good in the old wiring.

With the molex plug connected to the board I get consistent voltage values across the different pins. I was concerned the connector could be a problem so I wiggled it as I've taken my readings, on several occasions. The readings are rock solid. So from my research that (voltage) states the board is fine, but I'm not so sure.

 

[danski0224]

Interesting.

What features does the Carrier stat provide over a "dumb" stat?

I know with Heil equipment (ICP, like Carrier) you lose the automatic airflow programming unless you use the Observer thermostat. But, the system can still be set manually.

I haven't installed any modulating gas valve systems.

And if there's a 5 stage inverter condenser, you only get 2 stages with a non communicating thermostat.

Unless there's something else, I'd install something like a Honeywell Prestige 2.0.

 

[64coupedeluxe]

If you're not getting 24v to the pressure switch at all on the communicating stat but you are with it jumpered out then the problem has to be either the UI or some part of the logic circuit that works with the UI on the furnace board.
I wonder if some update went out that bricked some stats, manufacturer will never ad it but it can happen, some years back we had a bunch of calls on a monday all for the same problem with lennox communicating stats.

With a 2 stage furnace you could run a non communicating stat and get full functionality, depending on what is currently being done with the stat the choices can be a little limited, morso if the wire isn't accessible to be replaced with one with more conductors. If you have a communicating A/C you may be stuck with the communicating stat in some cases.

I have a love/hate relationship with communicating equipment, it's great when it works but when it doesn't it can get complicated and expensive quick.

There has been times when Carrier sent out updates that bricked the "B" series thermostats. In the cases I read about they did not have the errors I am experiencing. And then an update was sent which fixed the issues.

My original thermostat is the "A" series. I searched online to see if anyone else had this problem and have found nothing similar, which is surprising.

My furnace is a 2 stage variable speed. From my understanding with a 2 stage thermostat I would miss out on the variable speed function. Is this correct?

My AC condenser is only 1 stage at the moment. She is coming up to her 18th birthday and running strong. Even though the salesman said I should swap it out 10yrs ago as it's getting close to the end of it's life I do plan to install a 2 stage AC when it eventually dies to take advantage of better dehumidification. Which I think I also need to stick with the carrier stat to be able to use this fully.

 

[64coupedeluxe]

Interesting.

What features does the Carrier stat provide over a "dumb" stat?

I know with Heil equipment (ICP, like Carrier) you lose the automatic airflow programming unless you use the Observer thermostat. But, the system can still be set manually.

I haven't installed any modulating gas valve systems.

And if there's a 5 stage inverter condenser, you only get 2 stages with a non communicating thermostat.

Unless there's something else, I'd install something like a Honeywell Prestige 2.0.

I think you lose out the variable speed function and due to that some of the efficiency. I don't have any zoning but I think you also lose those functions.

 

[danski0224]

you lose out the variable speed

Shouldn't.

Variable speed is part of the blower motor programming. Could see losing any fancy tricks, like speed reduction due to zoning calls.

Would need to review installation manual to be sure.

 

[64coupedeluxe]

Shouldn't.

Variable speed is part of the blower motor programming. Could see losing any fancy tricks, like speed reduction due to zoning calls.

Would need to review installation manual to be sure.

You are correct on that. I have just re-read it and when using a dumb thermostat the cpu has an "adaptive mode", which controls the high and low heat which transitions the blower speed. I think I might need to adjust some dip switches if I went to a non comm stat.

By variable speed in my system I think that just means a high and low speed, as opposed to a modulating system which would have any speed through the range, from low to high. Is that correct?

I have seen so many people complain about the carrier and other brand communicating thermostats online and wanting to go to a non communicating 2 stage thermostat and every response from a hvac tech has stated they are crazy and they will lose out on so many benefits and lose efficiency. But I also know that a lot of hvac companies push upgrades constantly on an unsuspecting public.

We don't use any of the comfort profiles and like I mentioned the wifi connectivity has been an on and off problem for the last 10 yrs. My wife and I now both work from home so wifi connectivity isn't the attraction it once was. We also use our wood burning insert if we are home for the day and if it's a sunny day the rear of our house is south facing with lots of windows so sometimes we even open up some windows to cool the place down. The ceiling has been air sealed and has plenty of insulation.

So we don't use the furnace 24/7 through winter. It's a 96% furnace. If someone could categorically tell me I would only lose a couple or few % points it would sway me to just get a 2 stage thermostat. Though I don't like knowing something is not working 100% correctly and have invested a lot of time in this and really want to make it right.

 

[64coupedeluxe]

Interesting.

What features does the Carrier stat provide over a "dumb" stat?

I know with Heil equipment (ICP, like Carrier) you lose the automatic airflow programming unless you use the Observer thermostat. But, the system can still be set manually.

I haven't installed any modulating gas valve systems.

And if there's a 5 stage inverter condenser, you only get 2 stages with a non communicating thermostat.

Unless there's something else, I'd install something like a Honeywell Prestige 2.0.

Man that honeywell is the same price as I can get the newest carrier stat for, from ebay.

 

[64coupedeluxe]

1 thing I would lose is the carrier stat does have a dehumidification setting that works even with my 1 stage AC unit.

 

[danski0224]

1 thing I would lose is the carrier stat does have a dehumidification setting that works even with my 1 stage AC unit.

Nope.

Honeywell Prestige 2.0 does that.

 

[danski0224]

Man that honeywell is the same price as I can get the newest carrier stat for, from ebay.

Not cheap, but it works.

Have had only 1 EIM module failure.

 

[danski0224]

By variable speed in my system I think that just means a high and low speed, as opposed to a modulating system which would have any speed through the range, from low to high. Is that correct?

Probably.

It would have to be modulating in order to turn down the fan speed based on zoning calls, but I am not familiar with that.

Variable speed really refers to the ramp up and down (on and off) and the ability to count RPM and maintain the set airflow.

 

[64coupedeluxe]

1 thing I would lose is the carrier stat does have a dehumidification setting that works even with my 1 stage AC unit.

Also my humidifier is run by my stat. Though it was previously run by the controller that is installed in the duct work. They cut the wires flush at the old controller...

 

[64coupedeluxe]

Probably.

It would have to be modulating in order to turn down the fan speed based on zoning calls, but I am not familiar with that.

Variable speed really refers to the ramp up and down (on and off) and the ability to count RPM and maintain the set airflow.

Gotcha.

 

[64coupedeluxe]

Not cheap, but it works.

Have had only 1 EIM module failure.

A quick google shows people having problems. It looks like a good option if I needed different sensors etc and perhaps automation, but I need none of that.

I will wait to see if it really is the stat that's the problem before I look at a replacement.

 

[danski0224]

I've put plenty of them in without issues.

 

[Wiz02]

@danski0224 , I am not trying to hijack this thread, but I believe that my Honeywell T6 Pro short cycles the heat pump because it's using an algorithm to keep the interior temperature at the setpoint instead of the actual interior temperature (I have a thread about this as well).

I am very concerned about equipment life when the heat pump runs for only a minute, then runs again for a short time only a few minutes later.

If changing the cycle per hour setting on the tstat doesn't improve the situation, I am going to ditch the Honeywell. But since it's too cold outside for the HP, the gas furnace is running. Therefore, until it warms up outside, I can't tell if the tstat setting change worked.

Have you seen this issue in other Honeywell thermostat installations? If so, don't see how you can recommend a tstat that behaves in such a manner.

 

[danski0224]

I have been told to set cycles per hour for a heat pump to 1.

 

[PT Doc]

I have a similar Carrier system. 2 stage furnace and 2 stage AC. Modulating gas valve in my system allows the gas valve to close down to 30 % to allow optimal heating based on some algorithm. Either stage 1 or stage 2 for cooling or heat is related to the blower speed.

 

[64coupedeluxe]

Just an update for the fans at home...

The hvac tech who lent me the stat was going to let me know when I could drop it back to be tested and never heard from him again. Going to reach out 1 more time.

I purchased the cheapest old school stat from lowes and she has been running fine without any codes.

 

[64coupedeluxe]

So I managed to meet up with the tech and give him back his thermostat. That was a month ago and never heard back from him.

3 weeks ago the furnace sheets the bed and throwing code (forget the exact #) but basically a few different problems or a failed board. Was starting the process to fire and the ignitor glowed but no click and gas valve opening. The board was not sending 24v to tell the valve to open.

Purchased a new board and installed it and she was off to the races again.

 

[hobie18]

Why can't they be made simpler and fool-proof. Sigh.

Thanks for updating the thread.