Trane XV95 & XL15i configured in factory default...

[Sunfox]

A few days ago I had my HVAC replaced with a new Trane variable speed system (TUH2B080A9V3VAC gas furnace + XL15i 2.5 ton air conditioner). Although the system is cooling just fine - in fact much better than the old system, which would run all the time and never reach its target - I'm generally an informed consumer and knew in advance about having to configure the furnace blower to the size of the air conditioner, and when I asked during installation was infomed that everything was set up fine.

Well, today I decided to check and... everything's pretty much still at default. Considering I had to prompt them to hook up W2 to my two-stage thermostat, I should have known. (Note that I don't blame them, because I'm sure they aren't installing a ton of these VS furnaces - at least I hope not!)

* CFM set up for 3.5 ton outdoor unit (I have 2.5 ton + 3.0 ton coil)
* Set up for normal airflow
* Set up for 100%/1.5 minute delay (not Comfort-R)
* No Y-O jumper for Comfort-R
* Set up for medium-low heat (odd that they would change this from "normal")

Now, after living with the system for a few days, it's cooling the house plenty, but it may be doing too good of a job - even on a hot day yesterday, it didn't run between 2AM and 11AM, and by then it was getting a little humid upstairs and someone actually turned down the thermostat.

Due to my large, spread-out bungalow with only one HVAC system, I've always had the fan on at 100%, and am finding that the 50% normal operation of the Trane may not be keeping the air from stratifying. My concern is, because the 50% airflow is already so low, by the time I "right size" the CFM to the tonnage, it's going to be even lower.

So, some questions:

1) Would you configure this for 3.0 ton or 2.5 ton?
2) I'm planning on wiring for 80% continuous fan (I have the instructions). Since this involves adding a jumper to O, would I want to enable the Comfort-R dip switch or not? I realize there won't be fan ramping, but should it still be done?
3) Should I leave heat on "medium-low" or go back to "normal"?

Thanks for your assistance!

[mark beiser]

The airflow should be set to match the 2.5 ton outdoor unit.

(Note that I don't blame them, because I'm sure they aren't installing a ton of these VS furnaces - at least I hope not!)

Sadly it it seems to be the norm, rather than the exception.
In my area, virtually every VS furnace or air handler I run across, that was installed by someone else, is set up incorrectly.

[catmanacman]

I find a lot of units set to factory airflow settings . I would not touch the unit i would call the owner and have them send a tech over to fix it and also recheck the refrigerant level .do to the lower airflow and then ask what the subcool is set at and what is the superheat if he dont know he did not check it .you want the efficiency you paid for

[dunkman]

1) Would you configure this for 3.0 ton or 2.5 ton?
Since you're in Canada, you probably don't need a lot of dehumidification, so running at 3 tons of airflow shouldn't hurt anything if it makes you more comfortable and isn't too noisy. Although, you should start out with it matched to the outdoor unit.


2) I'm planning on wiring for 80% continuous fan (I have the instructions). Since this involves adding a jumper to O, would I want to enable the Comfort-R dip switch or not? I realize there won't be fan ramping, but should it still be done?
Doesn't matter if you hook it up to run 80% continuously. Leave it off.


3) Should I leave heat on "medium-low" or go back to "normal"?
Strangely, I see a lot of these come from the factory at Med-Low, rather than Normal like the nameplate states. They probably didn't touch it. This should be set based on temprise, after verifying correct gas pressure and btu input at the burners.


Thanks for your assistance!

Personally, I have an TUH2B060 with a 2 ton a/c. I run it at 50% continuous, 2.5 ton airflow, comfort-R on. I do it that way to get a little more sensible cooling, since I have to run a stand alone dehumidifier in the basement anyway.

[Sunfox]

It can get quite humid here in Toronto. Wikipedia describes it thusly:

"Summer in Toronto is characterized by long stretches of humid weather. Usually in the range from 23 °C (73 °F) to 31 °C (88 °F), daytime temperatures occasionally surpass 35 °C (95 °F) accompanied by high humidity making it feel oppressive during these brief periods of hot weather."

The house is 42 years old, 2100 square feet on the main level in a big T-shape, with an open stairwell to a fully finished/utilized basement. The main issue I've had is keeping the main level's extremeties cool on hot days, particularly the kitchen which has a lot of south-facing windows and heats up before the rest.

Assuming they set the rest of the system up correctly (they seemed like a good crew, we had 3 guys almost for the full day), I'll probably set it for 2.5 tons and 80% and leave everything else as-is. If I don't like the 960 CFM airflow, I'm guessing I could always bump it up to the next level (ie. 1080 CFM at 2.5 tons "high", or 1170 CFM at 3.0 tons "normal").

[duckman06]

It can get quite humid here in Toronto. Wikipedia describes it thusly:

"Summer in Toronto is characterized by long stretches of humid weather. Usually in the range from 23 °C (73 °F) to 31 °C (88 °F), daytime temperatures occasionally surpass 35 °C (95 °F) accompanied by high humidity making it feel oppressive during these brief periods of hot weather."

The house is 42 years old, 2100 square feet on the main level in a big T-shape, with an open stairwell to a fully finished/utilized basement. The main issue I've had is keeping the main level's extremeties cool on hot days, particularly the kitchen which has a lot of south-facing windows and heats up before the rest.

Assuming they set the rest of the system up correctly (they seemed like a good crew, we had 3 guys almost for the full day), I'll probably set it for 2.5 tons and 80% and leave everything else as-is. If I don't like the 960 CFM airflow, I'm guessing I could always bump it up to the next level (ie. 1080 CFM at 2.5 tons "high", or 1170 CFM at 3.0 tons "normal").

If were me with what you are stateing about Humdity in your home. I would have the installers set dip switchs for (2.5) ton, comfort r mode with 350 cfm per ton. Then let the comfort R mode do its job. I have installed a lot of variable speed Trane systems in this is the best set up for Humdity control. Let the blower do it's job 50% for (1) min, then 80% for (7.5) mins, then 100% if needed. These will give you the ability to control Humdity in your home, save $ on electrical use and be comfortable.

I would not try to match or set cfm for (3) ton coil you have. The installing company must likely Chosse that selection to get a little more eff. Out of the system. While I don't have a variable speed furnace, i do have variable speed Trane air handler with mind set this way and maintain 72 degress with Humdity levels in 42-45% area while only paying less then $100 for electric bill.

It is not uncommon to see a installing crew not set up a variable speed correctly in our area. That is why all our installers have a quality check form to review after the unit is installed and running to ensure per my notes that they set it up properly as every home is different and so is every customer for that matter. The good news is this is a simple fix for your installing company!

[motoguy128]

It can get quite humid here in Toronto. Wikipedia describes it thusly:

"Summer in Toronto is characterized by long stretches of humid weather. Usually in the range from 23 °C (73 °F) to 31 °C (88 °F), daytime temperatures occasionally surpass 35 °C (95 °F) accompanied by high humidity making it feel oppressive during these brief periods of hot weather."

The house is 42 years old, 2100 square feet on the main level in a big T-shape, with an open stairwell to a fully finished/utilized basement. The main issue I've had is keeping the main level's extremeties cool on hot days, particularly the kitchen which has a lot of south-facing windows and heats up before the rest.

Humidity, pun intended, is relative. You design conditions however, are very, very moderate. Your 99% & 1% design termpatures are 1F winter, 84F summer with only a 70F dewpoint. Very easy to oversize in your climate. But it does persent a problem, you won't have much load, except around mid June and early July when you have direct sun, to get enough runtime to dehumidify well. So using the reduced airflow should help. 960, isn't all that reduced for 2.5 Tons. THat's retty much normal airflow. 875-900 CFM (around 350CFM/ton) might work even better. With lower airflow, you might get a little longer run tiems too sicne overall capacity will be slightly reduced. That should help even temperatures between rooms. Then as mentioned use the Comfot-R mode to help even more.


Also as mentioned, proper sizing, long run times and managing humidty to be comfortable at a higher setpoint will really save on your utility bill. Even with a string of 90-100F days this month, I estimate my 1700sqft upstairs with a 2 ton system will use <$100 this month for cooling. It has run 55% of the time, about 2/3rds in low stage, 1/3 in high stage.

[edbrown]

Have the installers set up the blower correctly - as said before.

We see this ALL the time!! Even occasionally from our installers - that is wh our Home Comfort Consultants (Salesman) always go back to the job to check it over.

Once set up correctly - Set the Thermostat FAN switch to ON - this will allow the fan to run slowly between AC cycles and should help balance/mix the air in the home. Due to the variable speed this is less than 100 watts of draw!