Need Help with My new install - Trane XL20i system
Hello and thank you for all that you do!
I have just had a complete TRANE XL20i system installed in my home.
The system is as follows :
XL20i 4 ton 2 stage
XV 80 Furnace
Trane comfort coil
Trane Pro 8000 Thermostat
New ducts designed and installed
I can provide numbers later if you need them - it is difficult to read the handwriting from my invoice.
I live in North Texas and the average temperature is 95-98 with about a 35% RH.
1200 sq ft. - I keep thermostat at 78 during the day and 79 at night.
Heat Load was done and system sized for 105 degrees as it seems our summers are getting hotter each year.
System runs all day at low stage ( 2 ton ) only except when I call for a lower temp then it kicks up to full stage ( 4 ton )
These are my possible problems....
Delta T seems a bit low
the difference between return air and nearest register is only 10 degrees on low stage , and 14 degrees at high stage cooling.
Furthermore , the humidity is reading 20% higher coming out of the supply duct as opposed to the humidity at the return
Testing Tools -
I have a temperature / humidity gauge with a remote.
both the main unit and remote read exactly the same when right next to each other in the same air space
there is cold air leaking from the coil case where the unused condensate drains are located ... is this normal?
I have contacted installing company and have not heard anything as of yet.
What do you think?
Your contractor may need to address the low Delta T and air leaks at the coil, but the high relative humidity at the supply is normal. The lower the temperature of the air, the higher the relative humidity will tend to be. RH% is not a measurement of water content.
The most important question is, are you comfortable overall?
Originally Posted by k-fridge
Hi, thanks .. I've been lurking on these forums for a while - listening and learning from you Pros.
Yes I am comfortable for the first summer since I bought the house in 2004.
I had a broken central hvac system when I moved in and survived on 2 window units until last summer when we had 60 days of over 100 degree days.
I said enough is enough and dug deep into my pocket.
Overall, I am happy, but I just want the system to run optimally.
Optimally would be using the correct design temperature. You have proven that it is over sized and your airflow is probably high giving you lower than normal DT and the charge is probably low.
Originally Posted by Night_Owl
I do not understand what you are saying ?
The manual J indicated 3 tons
it is 98 degrees currently and holding 79 on first stage
can airflow be adjusted by tech to a lower cfm on both stages? XV 80 furnace!
charge may be low....I do not know
unit was charged when ambient temp was only 80 degrees ....
I have heard it can make difference what ambient temp is when charging??
Assuming the house isn't an uninsulated barn, or has massive amounts of window area, a 4 ton system in a 1200 square foot house in North Texas is most likely grossly over sized, possibly as much as double the required capacity considering what you set your thermostat at.
Hi...its not a barn ...but I do have some chickens in my yard
heat load was performed and it came out to 3 tons
I am happy with the system and do not think it is oversized
the unit runs on 2 tons 95% of the time and when I need to lower the temps then it kicks up to the 4 ton stage and cools to set temp very quickly, at which point the 2 ton first stage resumes running to keep desired temperature as long as I want
just think of the 4 ton stage as reserve capacity not what I am running on
These units only come in full ton sizes so at some point there has to be a compromise
I do plan to add on to the house in the next 5 years or so and this gives me some tonnage to do that.
And yes the house is facing East / West and does have a lot of window area, something in the area of 140 sq feet
I am also converting my garage to living space so this requires additional capacity
my day / night thermostat settings will begin to decrease as the summer gets hotter and I get used to 78/79 degrees .. most likely end up at 76/77 pretty soon
Im going to grow into the system , but right now it feels about right
I just want to know about the Delta T temps I have given.
Those deltas may or may not be ok. Delta would have to be taken at the unit also to know anything.
98 outside and holding set temp in first stage indicates that a 3 ton would have been larger then what you need for your homes current size and thermal values.
What is your indoor humidity?
140sqft on a 1200 sqft home is a pretty small window area, around 12% of the wall surface. Pretty typical of most newer homes. WIndows are expensive to to reduce the cost per sqft of construction, fewer windows are installed. Plus everyone has AC now, so natural ventilation isn't a concern. Some older home have 25-30%. My 3200sqft home has around 850 sqft of window area. Yet, depite that, combined I only need 4 tons of capacity. However north Texas will need about 25% more capacity than where I'm at because of outdoor design conditions.
With a 3 ton instead of a 4 tons, even in mild weather, you can run constantly on low stage and have nice long efficient runs times.
I didn't fully believe the impact of energy use due to haivng longer run times, but the savings were pretty shocking when i downsized my system and follows what I've witness when upsizing in another home i owned previously.
That being said, not much you can change now, and fotunately it's a XL20i that dorp ot 50% capacity. Most all other 2 stage units only drop to 70-80% capacity.
You oversized the system now for future expansion? I saw that alot of times and the jobs never worked correctly until the future renovations were completed (if at all completed).You should have sized it correctly for now and then added another system later on.
As wrong as it is, I believe he feels that he has made the right decision.
Originally Posted by skibme
The money he would have saved, along with the money he would be saving with the correct size, he could have paid for a good chunk of the expansion.
What is the real %RH in the living space? If it is higher than you want, slow the air flow to get a lower coil temp. It should be easy to get the %RH you want by adjusting the air flow. The fun starts during cool wet weather. There will not be enough cooling load to remove the moisture in the home. You endup cold and clamy. If you want to maintain low humidity with low/no cooling load, get a good dehumidifier.
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"
Hi guys ... thank you for bothering to reply to my thread
you are right the delta T needs to be measured inside supply plenum , just above the coil to get a more accurate reading
supply plenum is not insulated on outside - I hope it is on the inside .. will ask installer or drill a hole in to see while I take temperature , unless I can get original installer to step up
currently temps / RH is as follows
Outside 102 / 20%
Inside 78 / 40 %
system on first stage currently , but has ramped up several times to second stage within the afternoon and then resumed 1st stage
Also I got a great deal on this system and will be increasing the attic insulation to R-30 in the future - currently is loose rock wool filling to tops of joists - maybe R-11 / R-13 at most
I am also going to get window shades on west facing windows as there is a lot of heat gain coming through - currently is regular single pane with single pane storm window on outside of that
and in a few years when my roof is redone I will go radiant barrier or completely encapsulate with foam and condition attic as I have reserve capacity.
again thank you for the feedback fellas
now if I could just get the installing company to call me back