trane xl16i 2 stage, high humidity
Hello all, after researching various options for my Austin, TX home I decided on a two stage system to swap out a 25 yr old trane.
(Disclaimer - I am not HVAC expert so apologies for not using proper terms, if something isn't clear I'm happy to clarify, I also don't know whether info here is 100% relevant, so could be over detailed.)
House - 2000 sq ft, 2 story, high ceilings, low pitch roof, it bakes
Old system - trane (4 ton?) kept humidity at 30 - 45% Never more than outside humidity, rarely above 45%.
New system - xl16i, humidity 54 - 56% VERY uncomfortable. We have 38% avg. humidity outside.
The main reason I decided on two stage was recommendations from owners and various manufacturers claims that it lowers humidity and will run at low speed most of time.
It does run a low speed cycle most of time even in 100F Texas - that's good.
However it has turned house into steam bath. That's bad. It does seem to hold temp where we want it, but air isn't as cold as I think it should be. That's just my perception. Air also doesn't smell "fresh".
When I go into closet where unit is installed (upflow) I notice that when unit runs. a strong blast of air comes streaming out of PVC condensation drain (it exits unit and goes into a tee, top side is open, bottom side goes routes down into wall, is it allowed to run into waste vent(?)).
If it does indeed go into waste drain/vent with that strong blast of air, that doesn't make sense to me, I don't think old unit did that. The air coming out of drain didn't seem particularly moist.
Any ideas on what might be wrong? Unit is installed all of 36 Hours. I heard good things about 2 stage for keeping humidity low, so I am stunned. It's never been this high in the house and we will be dealing with serious mold issue soon and can't just turn it off.
I have call into contractor, but I thought I'd throw this one out to see if anyone has encountered this before or has some experience with this puzzler.
Did you get a new furnace with a Variable speed blower when you got your new A/C?
The 16i isn't known for good moisture removal.
With a 16i you should have a variable speed air handnler or furnace. Do you? If so, the blower speed may be set inappropriately for your system. If not, then you may be moving too much air on 1st stage to do any effective dehumidifying. Was a load analysis done on your home before the equipment size was specified?
Originally Posted by bobl
The unit is probably not set up correctly probably set up for 5 tons of air also I find the 16i works better at 350 cfm airflow
Hello all - thanks very much for replies. Here are some answers-
- The size of new unit is 4 ton.
- I don't know about the load analysis, I don't have any docs that say "load analysis".
- Air handler on furnace is variable speed.
- The unit is actually adding humidity as I can watch our humidity gauge go up when the unit comes on and air actually feels "sticky" when it runs.
- Air is roaring out on high, but perfect very gentle speed on low.
One other piece of into - tstat is a honeywell touch screen, pretty good (although I wish light would stay on, difficult to read). It has the multistage option.
Does it seem normal to have high volume of air streaming out of drain?
You should have air streaming out of only your supply outlets. Air should be streaming in only through your return grilles.
I didn't see any model numbers so I've got make some assumptions but the variable speed blower can be set for several different configurations. You need to have someone knowledgeable from the installing company pay a visit and set up and/or confirm that the blower is set as follows:
1. Airflow set for a 4-ton system.
2. Airflow set for 350 CFM/ton
3. Comfort 'R' mode selected 'On'.
It's very likely that no matter which stage the outdoor unit is using, the airflow for the system is set too high. The variables are 3.5-5.0 tons, (yours is 4.0-tons) and from 350 to 450 CFM (Cubic Feet Per Minute). The faster the airflow, the less dehumidification you'll get. Comfort 'R' is a Trane patented method of enhancing 'short cycles' by restricting blower operation to 50% of full speed for 1-minute (slow airflow to allow the indoor coil to cool faster) followed by 7-1/2 minutes of 80% of airflow. That's all to assist in greater moisture removal than would otherwise happen.
More info - this morning humidity gauge said 58% - this must be at or near all time high in 5 yrs of owning gauge, so it seems moisture is accumulating in the house.
bobl, did you see this post?
Originally Posted by skippedover
skip- thanks so much for the info, I will give another call into company today.
Here are model number details from invoice:
Bob, this sounds like it might also be a ductwork issue. In the trane manuals it says that if humidity starts getting high turn the constant/continous fan to auto. Because you have two stage equipment and your system is running twice as much as before, your system could actually be PULLING IN humidity through the negative pressure of the return air duct. Is your ductwork that is in the crawl space and attic sealed or is it the original ductwork. Along with adjusting to 350CFM per ton. It looks like you have a Trane XV80 furnace which does have the comfort-R mode, some of the older units came set from the factory without comfort-R turned on, it is a simple dipswitch setting to change this.
Seal ductwork if not done yet
Change to 350CFM
Have tech ensure comfort R is setup.
Reduce fan runtime if set to constant.
Measure the supply temp/%RH on high and low speeds. Possible to catch the consdensate going to the drain for a day? Blower should be on auto.
Using the %RH comparison from outside to inside is confusing you. Better to use the outdoor dew point compared to the inside dew point. Research the difference on the web. Outside currently 70-75^F for most of south central US. You want about 55^F dew point in side with 75^F,50%RH.
Typically with 2-3 occupants and 100 cfm of infiltrating air, 6 lbs. per hour of moisture must be removed from the home to get to 55^F DP. 6 X 24 = 125 lbs. per day. If you are removing this much moisture per day and the home is still damp, you have excess infiltration of outside air or unusal moisture source in the home.
Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
Use +Merv 10 air filter. -Don't forget the "Golden Rule"
Also Follow This Thread
You might also want to follow this thread.
Since your system is only 36 hours old, hopefully its just an installation problem.
Old system 4ton, New is 4ton (tends to rule out sizing).
Old system kept humidity (tends to rule out duct work).
This to ask you contractor to check.
(0) Keep FAN in auto mode, not continuous on
(1) Switch settings in furnace, match size (4 ton) of you Outdoor Unit
(2) Switch settings in furnace for Comfort-R is on.
(2) Airflow settings (400cfm default) with 350 cfm Comfort (better humdity removal?)
(3) Correct low voltage wiring as xL16i is "unique"
(4) Is thermostat programmed for 2-stage system.
What theromstat did they install??
Above is recap of what others have mentioned. Start a laundry list and work with your installer to verify. I can't speak to all xL16i in all geographic and how well, but in my case it does remove humidity and keeps house at 43-45%with outdoor of 96 and 44% which sounds similar to your conditions.
P.S. Sounds like you need a "trap" on your condensate drain line. My install has a p-trap connected at the coil drain and then out to sump pump. I beleive this would stop the air you're feeling.
That is how a drain line should be installed. This is an XL20i and XC95modulating install my company had just finalized a week or two ago.