Trane xl20i/ Honeywell Prestige - High Humidity
I recently had three new trane sytems installed in my house with Honeywell Prestige thermostats:
(1) xl20i - 5 ton
(1) xl20i - 4 ton
(1) xl16i - 2 ton
I understand that because these are two stage systems, I could expect to need to set the temp a little higher due to dehumidification process of the system. Instead, I am seeing the exact opposite. My daughter has been complaining that the carpet feels damp and my wife never seems to get comfortable (imagine that!). Yesterday, the outside humidity showed 39% and the inside humidity showed 72%. The contractor came out and charged one of the systems because he said it was a little low. This helped a little but the humidity inside is still in the 60%'s. The more the system runs, the more the humidity climbs.
I don't mean to sound like Captain Obvious but the system doesn't seem to be working properly.
Are there compatibility issues with the Trane xl20i and the Prestige thermostat?
Are there special settings required to make the systems work properly? (for example, I see a "dehumidification equipment" setting in my owners manual but my thermo is set to "none". I am not sure if the thermostat must instruct the system to dehumidify or if the two stage systems do it naturally regardless of the thermo settings.)
Any insight would be appreciated. I didn't get very far with Trane or Honeywell customer service as they directed me to the dealers for technical help. That is where I am getting the "head scratching". I am convinced this is an installation issue since it is happening on more than one unit.
The 16i isn't known for great humidity control. The 20i's are suppose to be good at it though. Sounds like it may not be set up properly. blower settings may be incorrect.
Yes, the stat has to be told that you want to dehumidify by using the A/C.
Something is not setup properly, has this contractor ever installed an XL20i? I would say no because the Prestige HD is NOT a match for that heat pump. The XL20i should have either a TCONT900 or a TZONE950 thermostat(both can be viewed in my youtube link to my installs) The XL20i is a communicating AC or heat pump meaning it will slow the blower speed to match the compressor that is being called for cooling. They also have overcooling for advanced dehumidificaiton settings. While I do like the Prestige HD and use it alot, this is not the right application for it.
Where are you located?
Thanks for the quick responses. This will give me something to direct the contractor to. It is good to know that the thermostat actually directs the humidification process and may explain part of the problem. I can see the dehumidification settings options which are 1) None 2) AC - Low Speed Fan 3) AC - High Speed Fan and 4) separate humidifier. Since all my themos are set to 1) None, it makes sense that the system may not be attempting to remove the humidity.
I assume the contractor has installed xl20i's because they said so but I guess I really don't know for sure.
As far as the Prestige choice for thermos, that was the recommendation of the contractor since I wanted to access and control via internet. As I understand, the Trane 950? product allows for that but for a monthly fee. I will push to confirm that it will work with the Trane or I guess I'll have to have them switch out the thermos. Thanks.
Not to be rude... but if you have 3 XL20i systems you can probably afford the $99 a year cost of the XL950 to connect to the internet. Its not $99 per thermostat its just $99 per account(which I think allows up to 64 thermostats)
Originally Posted by HV-RWD
The XL950 is a MUCH more powerful thermostat, really the best on the market and it will open up the communicating capability of the XL20i unless your contractor did not install a communicating furnace/air handler. Do you know what furnace or air handler they installed?
You have 11 tons, wow. What size is your house? Was a manual J heat gain/loss done?
That would be the problem.
Originally Posted by HVAC/Stud
I live in the DFW area. My house is around 6000sqft but is three levels. The furnace/air handler is XC80 for the xl20i and XV80 for the xl16i. I have no idea what a manual j heat gain/loss is so I am assuming not.
You make a great, and true, point SkyHeating. My wife could not stop laughing at your post and I may not live that one down for a while.
Oh, and I think I learned more about HVAC systems in the last two hours on this site than I have in my entire life. Thanks.
Any basic system should be able maintain <50%RH during high cooling loads. Provided that the a/c is setup properly and that you do not have excessive air infiltration.
Originally Posted by HV-RWD
Get familar with dew points verses %RH for this to make any sense. Outside air at 55^F, 100%RH has a 55^F dew point. When this 100%RH air infiltrates the home, a 75^F home without occupants will equalize to 50%RH (also a 55^F dew point). On a 100^F, 50%RH day infiltrating air raises a 75^F home to 75%RH without any dehumidification from the a/c. Plus the moisture from the occupants raises the %RH even higher.
The cooling coil needs to be cold enough to remove the moisture in the air flowing through it. You do not need a special t-stat for this. It's in the basic setup of initial air flow. As the air flow is slowed, the cooling coil gets colder removing more moisture and less sensible heat. For 75^F, 50%RH, which is a 55^F dew point. The a/c coil needs tobe below 45-50^F to provide <55^F dew point air to the home. On startup, the air flowing through the a/c coil will have a 10^F dew point drop.
After this setup, a couple hours of operation should get you down to <50%RH in the space. The first 15-30 minutes of cooling, moisture accumulates on the cooling coil/condensate pan. This is 1-2 LBS. of moistue per ton of capacity. At the end of the cooling cycle coil moisture is re-evaporated back the home. A a/c short cycling does not remove much moisture. Longer cooling runs reduce re-evaporation back into the home. During wet cool weather and cooler evenings, your multi speed a/cs have fewer off cycles, thus slightly better humidity control.
For real <50%RH during low/no cooling loads and outside dew points +55^F, supplemental dehumidification is required like from a whole house dehumidifier.
First get your a/c working properly, this will provide <50% during high cooling loads. If your a/c is setup right and your home is damp, find the excess infiltrating air leaks and fix them. Duct leaks and room supply imbalances are the leading causes of excess infiltration. Monitoring the CO2 levels in a home will indicate the amount of infiltration in the home. More on that if needed.
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"
Ok. Just to close the loop on this. I had the contractor come back out. He adjusted the blower settings and enabled the "dehumidification on demand" settings on the Prestige 2.0 stats so that I can set the desired humidity.
One thing he noted was air leakage through the hole behind the thermostat which caused the humidity reading at the stat to be 5-7% higher than in the rest of the room. We sealed and seems to be registering consistent with the rest of the house.
Overall, the systems perfom much better. I am finding myself adjusting the temp set points as high as 77 or 78 degrees since the humidity levels are staying around 50-51%. It is just too cold with my normal settings of 73 or 74.
Seems like adjustments helped to solve the problem. Thanks.