Carrier Inifinity Furnace and Thermostat/Controller Operation

I live in Arlington, Texas and just had a Infinity 80 furnace (Model 58CVA110) installed on December 3, 2010. I kept my old coils and outdoor condenser unit. I do have the Carrier Infinity thermostat.

Since the furnace has been installed, it's within easy earshot in the garage and it seems the only speed the thermostat chooses is high speed. I understand I can dictate the fan speed by choice, but I wondered, in some circumstances, if the variable speed should be chosen by the thermostat. Or is that only for complete systems which have the Infinity coils and condenser (which also makes the outdoor thermometer reading available)?

Also, with this setup, am I getting any value out of the two-stage heat for efficiency?

Finally, does anyone know if the Inifinity Termostat/Controller has any feature which would display how long the unit has run over a period of time which could be reset (say on the day of my meter reading each month). That seems like it would be an extremely easy thing for Carrier to provide in such an intricate Thermostat as the Infinity's. Anyone know by chance?

Tom
tomwilson64@hotmail.com

Tom,

Your furnace should run in both low and high stages. You can verify this with the status screen by pressing the lower right hand button for three seconds. It will display the fan speed and the staging of the furnace. I would expect the furnace to be in the low stage when the thermostat is trying to maintain a temperature set point. If it never goes into low stage, then call your contractor. Something may be wrong with the installation.

There is a run time indicator in the service menu section. You have to hold down the advanced button for 10 seconds to gain access to this menu. Once you are in, select Service, then Run Fault History, then Run Times. You will see display of the number of lifetime hours for the various furnace stages. I don't think you can reset these values. You will have to keep your own history in order to calculate the monthy usage.

The two-stage may be working. I'm also wondering though about the variable speed. The blower sound seems to remain consistently on the high speed. I know how to force it to low or medium speeds, but I don't know if the Infinity, with the furnace only installed, will automatically adjust the fan speed or not. I know this would only save a very small amount on the electricity the blower is consuming, but wasn't sure if anyone happens to know the answer to this additional question.

Thanks!

Check your filter, on any Infinity furnace (or most variable speed furnaces for that matter) the variable speed fan will ramp up its rpm to try to maintain whatever airflow it wants. If your filter is plugged, the fan may reach 100% rpm just to achieve low speed airflow. There are dip switches on the board to control the amount of airflow the furnace will provide on continuous fan and air conditioning but the low and high fire speeds are predetermined by Carrier and can only be adjusted 15% or so. These dip switches are there only for installations with a traditional 24 v thermostat and are ignored by the furnace once the Infinity control is connected, theair flow settings must be adjusted from the infinity thermostat itself.

First, thanks so much for all replies. My new Infinity furnace was installed December 3, 2010 with a 4-inch filter. So I can easily check the filter and will, but having only had the furnace for 25 days with a 4-inch filter it shouldn't normally be the filter I wouldn't think.

Also, something unusual is that the Infinity THermostat displayed a need for me to change the filter a few days ago, exactly three weeks after installation. Should it show that soon?

Typically a 4" filter should last alot longer than 25 days. That being said, if you didn't have your ducting cleaned prior to the install, the higher airflow rate of the new furnace can pull a ton of dust balls into the filter and plug it within minutes. That would be a rather extreme case of dirty duct work though.
Check your filter first, and then call your installing contractor to double check the install. He probably checked his temperature rise and gas pressures at install but with the infinity stat he can also check things like fan rpm at a given cfm and max external static pressure. When the system was first powered up, it would've gone through a series of startup checks one of which is the external static pressure check. As the filter collects dust, the ext static will go up, when it reaches a certain level, the stat will give the filter reminder. This process happens faster if the system has alot of ext static to start with, this could be caused by duct work that is too small (it may have worked ok with the old furnace with a 70-100 degree temp rise, but the new is probably 30-50) or maybe a bunch of the supply air diffusers are closed or restricted.
Anyway, check the filter, check the registers (return airs too!) and if those fail, call your contractor.

Thanks again! I'll call the contractor. I was here during the entire installation, monitoring and learning. They worked on sealing my vents, al 12 of them and then did the startup tests. I think my static pressure number was 45 and they said that was a great number. They said they typically see it much higher in older homes (my home is 42 years old). I live alone in a 2000 sf two-story home. I do have a cat, but I watch the filter for her hair buildup so I'm a little more watchful from that, it hasn't been nearly has bad in this house as it was in 900 sf house I had before this one. I thought the contractor told me the filter change reminder was simply on a timer so after a certain period of days, it gives you the reminder. Do you know if that's true or false? Again I only have the furnace, not the entire system.

One other question out of curiosity. I don't like dry air and it seems to be at 29% or lower on cold days and nights. I am considering the humidifier option even though it would mean running a new water line and install. Does anyone have experience with the value and effectiveness of the humidifier tank and process doing a great job of keeping a good level humidity? Also is there any real reason to be concerend about moisture in the ducts from a cold wate humidification system like the Inifinity has as an option?

No reason to be concerned about a humidifier and your ducts. However, it is better to fix the primary reason for your low humidity rather than patch it with a humidifier. It is coming from the infiltration of cold dry outside air through leaks in your home "envelope". If you tighten your envelope, your humidity will go up, and as a huge benefit, your energy costs will drop.

Commerce48,

I don't think you're describing the problem in my case. I've lived in the Dallas Fort Worth area my entire life and our winters are mild. Also we aren't a dry climate. We're not ultra humid like Houston, but we're not dry. I've run indoor and outdoor hygrometers and it's nearly always more humid outdoors on cold days here. I also am comfortable outside and then become uncomfortable inside because of the dry air. With the house envelope tight and forced hot air blowing from the furnace, the house dries out. Growing up this was always solved using a big free-standing 10-gallon humidifier appliance my dad purchased. When we used it things felt great indoors and out. And I'll add that Dad was the plant engineer for the GM assembly plant and he had the envelope sealed :-) So while I may have some windows which aren't sealed as well as I'd prefer, this house is pretty well sealed, for its age and I think the humidifier option remains one I'd like to pursue. Also, quite reasonable in terms of the cost of replacing windows and doing a complete house seal.

If others have direct experience with the humidifier option on the Infinity, I'd love to hear!

Tom

That's interesting. I'm certainly not an expert on humidity and I'd have to think about it a bit, and read up on the physics and math involved. I was just spouting so-called common wisdom (that I learned here).

At the risk of opening my mouth again and removing all doubt about whether I'm a fool or not, I will say that relative humidity at different temperatures cannot be compared directly without intervening calculations.

I'm not doubting your perception of being inside and outside on how you feel, however we may both guilty of oversimplifying.

The one thing I know is the indoor air at less than 30% humidity is uncomfortable :-) Also, when my furnace went out for a week, before I got this new one, we had a cold spell outside with no rain and I toughed it out and the humidity was measured higher inside than it would have typically been of my heat was running.

As far as scientific explanations and proofs, I don't have them either :-)

I live a long way from Texas so I can't say for sure what the best solution is. Up here, in the winter, the outdoor RH drops because the cold air outside can't hold much moisture. Over ventilation of a space would drop the RH just as commerce48 wrote, because you are drawing low RH air from outside and forcing the (usually) high RH air from your living space out through some other leaky hole in the vapour barrier, this could be caused by a leaky building envelope. Sealing your home could help a dry house in these conditions and has the much larger benefit of lowering your heating and cooling costs. There are some fairly simple things you can do to control infiltration like spray foaming around windows and in penetrations through the exterior walls. Realistically however, installation of a humidifier is the quickest, easiest way to address the issue.
The infinity control has the ability to control humidification and de humidification (either with an HRV or by running the fan at lower speeds while running the condensing unit) The cool thing about the infinty is that it will automatically adjust the RH setpoint based on outdoor ambient temp to prevent high humidity and condensation on windows at low outdoor temps, probably not a real issue in Dallas... The furnace control board has a terminal that supplies 24v (if i remember right...or it might be a dry contact ) to energize a soleniod or run a drum style humidifier and the rest of the controls are already wired from the stat you have.
You mentioned that you don't have the full infinity system, but you basically do, the furnace and the thermostat are the heart of the system, HRV's, humidifiers, u.v. lights e.a.c.'s are all modular and can be added and integrated into the infinty controls system easily, the hardest one is the HRV because you need to purchase a net work inteface so it'll communicate with the infinity.

if your humidity is dropping to 30% and lower you definately want a humidifier, levels that low can cause health issues. as far as choosing a humidifier they are typically sized according to how many gallons of water they can shed to the airstream per day so check with your contractor to recommend the appropriate size. there are also different types of humidifier with different levels of required maintenance. one of the most worry free humidifiers i'm used is a "bypass" type which is installed on the supply duct and warm air from the furnace is forced through the humidifier pad inside and out through a short duct back to the return duct where the humidified air is mixed thoroughly back into the air stream. as for the option on the infinity to humidify with only the fan running and not the heat you should not have an issue with mold or mildew in the duct because the dry air will act like a sponge to absorb the water from the humidifier and there should not be any condensation in the ductwork if the humidifier is properly adjusted.
also somone mentioned the dip switches on the furnace, when using the infinity control those dip switches are deactivated and all setup is done at the infinity controller