Carrier Inifinty Heat Pump System: Indoor Fan Cutting Off

[Tevye]

About four months ago we replaced our existing heat pump system with a Carrier Infinity heat pump system (25HNB636 outdoor, FE4ANF005T indoor, SYSTXCCUID01-V Infinity Control) that incorporates an Aprilaire 5000 electronic air cleaner. We run this system with the indoor fan speed set at "Low" to ensure air circulates in the house even when there is no call for heating or cooling (i.e., the temperature in the house is at the temperature set in the Infinity Control.)

After two months of trouble-free operation, we noticed one day, in a period of no call for heating/cooling, that the indoor fan had stopped, even though in the controller it was set to run at low speed. In this situation, the fan would not run at any speed setting (low, medium, or high.) When a subsequent call arose for heating/cooling, the fan would however come on at a speed chosen by the Controller. When the call for heating/cooling was satisfied, the indoor fan shortly thereafter would stop as noted above, even though set to run at low speed.

We requested the installer to return and he determined that the main circuit board in the air handler was defective and replaced it. That action seemed to fix the problem, and the indoor fan then ran, as desired and set, at low speed in between calls for heating/cooling.

But now, after two additonal months of operation, the problem of the indoor fan cutting off has recurred, albeit in a somewhat different form. The problem is intermitant; now in periods of no call for cooling, sometimes the indoor fan will run at low speed as desired; sometimes it's off, and when it's off the fan will not run at any speed that we set in the controller (low, medium, or high.)

What is causing this problem?

Any assistance will be appreciated!

Thanks,

Tevye

[Damien]

Ran in to a similar situation once with the Bryant Evolution, replaced the stat, problem solved.

These problems can be hard to figure out. It was only an educated guess on my part.

[Tevye]

Ran in to a similar situation once with the Bryant Evolution, replaced the stat, problem solved.

These problems can be hard to figure out. It was only an educated guess on my part.

Thanks, Damien. I will mention your experience to the installer when we contact him.

Tevye

[beshvac]

Does the fan shut off for longer than 5 minutes?

This is from the controller manual for continuous fan operation:


Dehum Drain
Turns off the continuous fan at the end of cooling for five minutes
in order to drain the indoor coil of water. The fan will only be
turned off if a dehumidify demand existed at the start of or during
the cooling cycle. Default is enabled.

[Tevye]

Thanks, beshvac. I don't recall just off-hand whether the fan shuts off for longer than five minutes, but I will monitor the system's behavior and watch for this. I'm glad you pointed out this feature; I had no idea that it existed!

Tevye

[comfortdoc]

I think there was an undocumented change to that algorithm. Default out of the box may be 15 mins, and it is user configuarable. Have your dealer check the settings of dehum drain. It seems like a random event due to conditions that have to be present to activate the feature. If you are in a humid climate it is advisable to leave it active.

[Tevye]

Thanks, comfortdoc! I will have the installer check that setting. Before doing so, I am going to more-closely observe the system to see how long the fan actually remains off.

How do you find out about such 'undocumented' changes?

Tevye

[comfortdoc]

.....

How do you find out about such 'undocumented' changes?

Tevye

Call your dealer. The enhancement happened faster than the manual could be updated and printed. It might be updated now I have not checked.