Infinity furnace trouble

[wyounger]

My 58CVA-070 with Infinity control had a temper tantrum last night. It's 13 months old (a bit young for a tantrum!). It had never set any trouble codes before last night.

First, I noticed that the system was running at the usual cooling airflow rate, but the air was lukewarm. It's wasn't calling for cooling. LAT was 74 degrees, so it's definitely not blowing out residual cold at the end of a cooling cycle. Fan is on auto... and I have no accessories that demand the fan to run aside from heating and cooling cycles. I check in the diagnostics, and the Infinity control even knows that the blower is running. 700 cfm, 0.39"wc., heat pump status off, furnace status off. There's just no reason for the blower to be running, that's all. Switched the Infinity control off, blower still keeps going.

I cycle the furnace circuit breaker. When the unit comes back up, it decides to start a cooling cycle (after the appropriate delay). The outdoor unit runs for about ten seconds, everything shuts down abruptly. The display has gone to the "Critical Failure- Call Technician" screen. I check the codes, and I have #41- Blower Fault, and #25- Model/Setup error. I power cycle again, and try calling for constant fan as soon as it comes up again; this time it goes to the Critical Failure screen almost immediately. I just went to bed without A/C.

This morning, it was still in Critical Failure. I tried flipping the breaker one more time, and it started up and ran in cooling for a half an hour without complaint. Then I had to leave for work.

Any bets? It doesn't seem like it will be a fluke given how stubborn it was last night... yet it's also strange that it ran happily this morning after all that. My Carrier guy is calling the distributor for advice, as he's never seen this before.

My guess at this point has to be the ECM board or the furnace board, though.

[seadragon]

wyounger,

I'm surprised there have been no replies to this post. Although I cannot offer any ideas as to what may be wrong, I am curious as to how things are now? I have enjoyed reading your posts in the past and you have been very helpful. Hope everything turns out good with this problem.

Ken

[dash]

We have had blower faults,that turned out to be loose connections,but nothing like what you describe.

[wyounger]

It has run without complaint since... not a hint that anything happened in the first place.

I went up into the attic to see if anything looked out of place. Everything looks perfectly normal. Weeeeeird.

[seadragon]

This is a long shot, but since the Infinity Control is basically a computer, could a power brown out cause something like this to happen? I am in the IT field and have seen very strange things happen to machines when the voltage drops below acceptable levels. Just a thought...

[Edited by seadragon on 09-22-2005 at 12:43 PM]

[bananaboy]

Fault code #41 (and #21 if I am not mistaken) indicate "Not enough Air Flow". Damn Carrier does not have a Fault code for Blower motor not working. Code #41 is the closest.

It's either the V.S. motor or the board.

Run a "Self check" (depending on the model, Dip switch #4 should be turned "ON") that will eliminate the guess work.

Last one I had - it was the same #41 and it was the V.S. motor.

But than again a week later same symptoms - it was the board.

Do run the "Self check"

[jetstream]

This won't help you wyounger, except insofar as misery loves company, but I've had a couple of weird probs with my own MVP80 with Infinity control.
In one case in the heating season, controller was showing heat on, no fault codes, but the furnace was not working, just low speed fan, as usual. House temp was several degrees below setpoint. No time to diagnose right then, I just turned power off, then back on, unit fired up, and that problem never repeated.
Another time, I switched from cooling to heating at the controller, testing something, I don't recall what. Then set it back to cool, with no call for cooling. Unit should have been running on constant low speed fan. I didn't notice right away, so this may've gone on for 1/4 hour or so, I walked past the furnace and noticed blower was ramping up, then dropping off, over and over, continuously. Again, I powered off, then back on, unit came up to proper speed and has worked fine since.
I do think seadragon is correct, it's a computer and sensitive. Just like the one I'm typing on now, sometimes it gets mixed up and has to be restarted to get it's little brain all sorted out.

[2hot2coolme]

The problem is ....you made the most common mistake consumers usually make....you bought a Carrier!! :D



Sounds like a faulty IFC to me.

[wyounger]

The problem recurred last night. I cut the power to it for a few minutes and it was ok when I restored power.

I don't have excessive static. The only time I exceed 0.45"wc (per the Infinity control) is on high heat, which hasn't happened in at least ten months. OK, high fan will do it too, but I don't use that setting (for the sake of the blower and because it makes the ductwork whistle).

I read through the service manual for the furnace, and as I understand it, code 25 is the "the control board doesn't know what size furnace it's installed in anymore" failure. I can see where code 41 could indicate a static problem, but since in this case that code only occurs in conjunction with 25, I am more suspicious of the main board than the ECM system.

My contractor will have a tech out this afternoon, and the service manager has already given permission to go ahead with a board replacement today (if they can locate one in time to do so).

The power quality question is a decent one. I live in the big city and have underground utilities, but my power goes out frequently anyway. I'll check the logs from my computer's UPS to see if I find anything that correlates.

[hvac r us 2]

It is in the board, we have seen this already. The software gets confused.

Of course be sure your total ESP is in line.

Most of the time just changing the 022 board will correct the issue; I have had three cases where a specially "flashed" board had to be installed.

Have your heating contact the local distributor if this continues...the answers are out there.

[dash]

Are there simailar issues with air handlers as well?

[hvac r us 2]

Originally posted by dash
Are there simailar issues with air handlers as well?

I have not seen this issue with the FE DASH, only on the MVP and CVA with the HK42FZ022 board.

There is no SMB issued, my understanding was this was just an issue when combined with the 022 board?

Just got back from a "zone meeting" and there was no mention of Fan coils having this problem?

Are you seeing this in the FE's DASH?

[dash]

No we haven't ,but we do have a few CVA's,so thanks for the heads up.

[ewbennett]

Wyounger,
The problem sounds like the electronics are misbehaving. The symptoms suggest that a computer/controller circuit is going into a "trapped state" and requires a reset to restore proper operation. As an electronic engineer, I know this is customarily a design issue. Also, it could be a electromagntic problem too.
Lightning strikes nearby may have induced transients into the power and/or control lines and caused the problem. Was there an electrical storm prior to the failure?
YOu can do some checking yourself. Check each electrical connection in the furnace and in outdoors unit to verify that it is tight, especially, all ground connection. The outside unit should be connected to a ground rod near the condenser unit that meets National Electric Code, NEC. Likewise, the ground connections inside the house should meet NEC.
Another source may be an electrostatic discharge that occurs typically in dry weather. The finger touching the buttons on the Thermostat may be the culprit if a charge has been built up on an individual. This can be design issue too unless the t-stat was hooked-up incorrectly.

[wyounger]

The contractor replaced the furnace board on Friday. No reappearance of gremlins (yet).

No chance of static electricity building up on my fingers. We're talking about Georgia in the summer. Humidity is guaranteed :) And strange though it is, today is the first day we've even had rain this month, much less a thunderstorm... so no voltage transients.