Humidity problem w/ Trane XL20( South Florida)

[Jeff Bergman]

I recently had an Trane Xl 20 installed replacing a 15 year old Heil unit. Im in south florida and the unit cannot get the humidity below 79%. I believe we have the 8000 thermostat. Should I consider a seperate Dehumidifier. I had a York affinity 8 series installed for a week prior but the fan was very loud and this unit could not reduce the humidity as well. I have a 2 story home with 20 ft vaulted ceilings. The cooling features of the unit work great. The home has 2 units with the other being a 3ton heil 15 yrs old. Any suggestions would be great.

[udarrell]

How well did it dehumidify with the old unit?
Is the new unit oversized & running short cycles?
I doubt that it is performing properly.
---------------
We need as much test data as possible.

I need to have the temperatures below, - that you can easily take for me, us:

“Copy only the data portions & paste in your Word-Processor, make a couple hard-copies, then post the data or send me what you take, & get as much of this data as your Tech will provide for you.” You can delete the (You &/or Tech) before you make hard copies for your Tech.

This is very important: Always tell the tech that you want all the data he takes, clearly recorded with the invoice!

I can run the temperatures data you take with an accurate CFM Airflow & ball-park the Nominal BTUH your new A/C is delivering, at those conditions.

TROUBLE SHOOTING DATA - (You or Your) HVAC Tech can collect.

Not always critical but helpful data:
For our information concerning summer design & your climate, provide your state & nearest large city __________
TONNAGE of Unit or outdoor condenser model number: ___________ You
TXV or orifice metering device? _______You or Tech.

Outdoor condenser’s discharge-air-temperature _____ by You
Out-Door temperature: ____- You
Condenser air Temp split _____ -You

Indoor Total-ESP - External Static Pressure _______ by Tech
All Supply Air velocities in FPM: ___ -Tech
I’ll do the math for the total CFM:

Suction line pressure ___Tech
Suction-Vapor line temperature: ___Tech
Saturated Suction Temp – Gage - Suction Saturated Temperature. ___Tech
Superheat ______Tech

Head pressure _______Tech
SCT – Gage - Saturated Condensing Temp _______Tech
Small Liquid line - temperature: _______You
Subcooling: _______
Return Air temp DB &, WB or %RH: _______You
Supply Air temp DB &, WB or %RH: _______You

Not necessary, but with the information data below and an accurate CFM airflow + approx sea-level height, I can ball-park its BTUH output
Return Air temp DB &, WB or %RH: ____ ____You
Supply Air temp DB &, WB or %RH: ____ ____You
Take a cotton cloth & wet with room temperature water, wrap it around the thermometer & use it for the wet bulb temps above.

Except for the Pressures, Superheat & subcooling you can take most of the other Temp readings for me.

My advice: to every user, get a low cost humidity gage at a local hardware store & see what the percentage-RH is in your home, I can cross-reference that to the wet bulb depression so you could use the humidity gage instead of wet or use both.

If you want to save money you will take the time, when it is hot outside & warm in the house to take all this temperature data!

Getting the Subcooling on a TXV metered system: With a low cost MA-Line Digital pocket thermometer you can take the small liquid line temp where it goes into the indoor plenum.n Then subtract that temp from the condenser's discharge air temp & you have a ballpark subcooling number to evaluate the systems charge

Anyone is welcome to use the Data Collection for use as they see fit! A tremendous number of systems will need a TECH's attention.

The HVAC contractor's phones will ring off the wall because a lot systems will need a good tech's attention to achieve their EER, SEER, & nominal BTUH Ratings..

“Copy only the data portions & paste in your Word-Processor, make a couple hard-copies, then post the data in this forum, e-mail send me what you take, & get as much of this data info as your Tech will provide for you.”

Hand a hard copy to your Tech(s) & witness their response, a good cooperative tech will welcome it, others may roll their eyes & want to leave, ASAP! :):D - Darrell

[motoguy128]

Another thought I'v discovered with my 2 stage system. While a 2 sage unit will run longer on 1st stage, it effectively has a oversized coil, which will reduce latent capacity (humidity removal). I've started to question if a 2 stage system actually outperforms a single stage system set-up to dehumidify on demand by reducing airlfow. It will definitely do a better job of matching sensible loads.

[dash]

Another thought I'v discovered with my 2 stage system. While a 2 sage unit will run longer on 1st stage, it effectively has a oversized coil, which will reduce latent capacity (humidity removal). I've started to question if a 2 stage system actually outperforms a single stage system set-up to dehumidify on demand by reducing airlfow. It will definitely do a better job of matching sensible loads.

Should be in dehum on low stage,reduced cfms .

Properly setup two stage is superior for dehum to a single stage.

[motoguy128]

Should be in dehum on low stage,reduced cfms .

Properly setup two stage is superior for dehum to a single stage.

But would reduced CFM's on first stage still outperform a single stage unit also reducing it's CFM's. I think the specific latent capacity of the single stage unit would still be greater, and would overcome the slightly shorter run time. The 2 stage unit is still handicapped by having an oversized coil.

I'm unlucky enough to have a 2 stage unit where you can't reduce the airflow on 2nd stage because of the limitations of the furnace control board. If it was a communicating unit, I could. It also could it it was a 2 comp. recip, instead of a unloading scroll. It's a Trane thing.

[beenthere]

Should be in dehum on low stage,reduced cfms .

Properly setup two stage is superior for dehum to a single stage.

Dash.

I think motorguy has a house that is a 2 ton load.
But had a 3 ton 2 stage installed.
The 16i isn't noted for its ability to remove much moisture in first stage(specially when teh larger coils are used for higher efficiency rating).
And Trane as I recall, says to use it in second stage to remove moisture.

[motoguy128]

Dash.

I think motorguy has a house that is a 2 ton load.
But had a 3 ton 2 stage installed.
The 16i isn't noted for its ability to remove much moisture in first stage(specially when teh larger coils are used for higher efficiency rating).
And Trane as I recall, says to use it in second stage to remove moisture.

Well... I suppose one could use the DHM terminal and a relay and make the unit only use 2nd stage AND 80% airflow when there's a call to dehumidify... and return the unit ot 400CFM/ton airflow.

And to clarify... the dealer suggested the 3 ton and I went along with it... I just didn't realize the consequences at the time and clearly, neither did the dealer.

[beenthere]

Well... I suppose one could use the DHM terminal and a relay and make the unit only use 2nd stage AND 80% airflow when there's a call to dehumidify... and return the unit ot 400CFM/ton airflow.

And to clarify... the dealer suggested the 3 ton and I went along with it... I just didn't realize the consequences at the time and clearly, neither did the dealer.

Or you could have the installer set it up right.

But, I do like the idea of going with a 20i

[motoguy128]

Or you could have the installer set it up right.

But, I do like the idea of going with a 20i

Do you mean with the right sized unit... right sized coil, a communicating furnace, some, or both...or just changing the wiring and adding a relay?


I'll let you negotiate with my wife in regards to spending more money on getting a XL20i to solve the problem. :D

[beenthere]

Right size coil would help.

if you have the IAQ, no relay needed.
If you have the TH8321, you have the wrong stat anyway.

[dash]

But would reduced CFM's on first stage still outperform a single stage unit also reducing it's CFM's. I think the specific latent capacity of the single stage unit would still be greater, and would overcome the slightly shorter run time. The 2 stage unit is still handicapped by having an oversized coil.

I'm unlucky enough to have a 2 stage unit where you can't reduce the airflow on 2nd stage because of the limitations of the furnace control board. If it was a communicating unit, I could. It also could it it was a 2 comp. recip, instead of a unloading scroll. It's a Trane thing.

Can't answer for what you have,but what we sell,a two stage would do a better job of dehum everytime.

Lower stage,less capacity,close to the same SHR,wins every time.

[scac1971]

If your reading the humidity level on the stat. Make sure they plugged the hole in the wall behind the t-stat. Lots of hot moist air in the attic and it will find its way down the wall.

[ppinkston]

Thanks for the troubleshooting sheet. It helps when on a call to have a place to keep a record of conditions at arrival...

[eloy]

is that a comunicating system? if not, are the dip switches set up right for enhance mode? What about cfm setting and ramping options? If the systems is a comunicating one it should set it self up (plug and play). What about the ductwork? is it in good shape? Is the air return duct in one piece? Is the ductwork sized for the cfm for your new system? did the contractor upsized your system? Did they do a heat gain a loss calc? If the ductwork is in poor shape, not sealed properly, missing insulation or too small, your new system will not perform as disigned.

[OldBob]

Most problems are created by the dealerduring set-up. Call TRANE, tell them you need help. Perhaps a factory rep can visit yoyr home with the dealer to check performance and to answer your question about humidity.

[smittyii]

you have the wrong t stat. you need the tcont900ac43ua. if its a communicating system, if not use the tcont803as32da.

[Airmechanical]

what smitty said!



.

[teddy bear]

I recently had an Trane Xl 20 installed replacing a 15 year old Heil unit. Im in south florida and the unit cannot get the humidity below 79%. I believe we have the 8000 thermostat. Should I consider a seperate Dehumidifier. I had a York affinity 8 series installed for a week prior but the fan was very loud and this unit could not reduce the humidity as well. I have a 2 story home with 20 ft vaulted ceilings. The cooling features of the unit work great. The home has 2 units with the other being a 3ton heil 15 yrs old. Any suggestions would be great.

No one addressed the the question about a dehumidifier. During high cooling loads, a properly setup a/c with air tight ducts should be able to maintain <50%RH without a dehumidifier. As the cooling load declines during cool weather, the moisture removed by the a/c delines because a decrease in run time. The moisture load of normal occupants and infiltration/fresh air ventilation is 50-100 lbs. of moisture per day. A 65-100 pint per day dehumidifier is needed to control indoor humidity during wet cool weather in a 2,500 sqft home.
Regards TB

[mark beiser]

I believe we have the 8000 thermostat

Exactly what thermostat do you have?

If you don't have a XL900 communicating thermostat, none of the advanced dehumidification and airflow features of the Comfortlink communicating system are available to you.

I'm not sure why any contractor would install anything but the XL900 communicating thermostat with an XL20i, but apparently it happens.

[dash]

Yep,regrdless of brand some chose the wrong stat,plus fail to find other issues,and along comes teddy selling a bandaid to solve the humidity issues.

[Michael Mills]

Like Jeff, I'm having the same problem.
My TRANE cooling system, XL20i, 5 Ton, has not operated properly and the service from my Dealer and from TRANE is going nowhere fast. This SEER20 system was installed at the first of April 2009. When the cooling season began, the system did not remove the humidity. The dealer acknowledged the wrong thermostat and installed the correct one with humidistat. The system has been tweaked and lots of measurements have been taken over the course of the 2009 summer.
Now it is 2010 and I am still cold and damp. Among other indicators, my wife notices that some foods go stale quicker, the doors swell, and the wall paper is unsticking at the edges.
Michael Mills
Tulsa, Ok.

[teddy bear]

Yep,regrdless of brand some chose the wrong stat,plus fail to find other issues,and along comes teddy selling a bandaid to solve the humidity issues.

YEP YOU are right. Little or no cooling load, my C Inf over cools 3^F and shutts off. The humidity slowly rises and the house is over cooled 3^F. Whats wrong with my C Inf? You sound like the salesman that sold me the system. My question, Will your system maintain 50%RH during wet cool weather. His answer was, yep pretty much. I call the a/c co.when the %RH is +60%, they send out a tech, His comment, ya that salesman really does not know how these things work. The coil is 40^F in a couple minutes. After the system over cools 3^F, nothing is going to happen until the home warms up. My bandaid keeps my home 50%RH removing 26 gals of moisture per week now. The a/c operates ocasionally, removing a couple gals. a week.
Tell me what is wrong with all these a/c that we are shipping thousands of bandaids out to. I should condede that I am getting 60 cfm of fresh air into my home when occupied. This is also part of the FL code-fresh air ventilation
Or are like the salesman who sold me "yep, pretty much".
I understand how impossible it would be for any a/c co. to admit that their equipment will not provide 50%RH during wet cool weather with adequate fresh air ventilation and occupants in the home. We have homeowners who figure it out real quick. There are a few a/c contractors who have also figured this out.
Regards TB

[Michael Mills]

This is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise here. Please apply to the AOPC today, thank you.

You can find the rules for posting and qualifications here (http://hvac-talk.com/vbb/showthread.php?t=957002).

Further infractions may result in loss of posting privileges.

[beenthere]

Michael Mills, this is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise, commentary or ask questions of the OP here. Please apply to the AOPC today, thank you.

You can find the rules for posting and qualifications here (http://hvac-talk.com/vbb/showthread.php?t=957002).

Your post has been deleted.
Further infractions may result in loss of posting privileges.

[teddy bear]

During these three summers, my son had a new house built, 200 miles south. He had humidity problems. His unit was a Lennox. The neighbors also had problems and had Lennox units. Guess what. Their problems were also solved by correcting the wiring.

End of story and we all lived happily ever after (though our teeth are now ground a little shorter).

Well yes, you fixed you a/c problem. For me, there is one puzzle left. Are you getting a fresh air change in 4-5 hours when the homes are occupied? For ideal indoor air quality, a fresh air change is needed to purge indoor pollutants and renew oxygen. You can tell by checking you indoor dew point compared to your outdoor dew point. Occupants add moisture from breathing and respiration. So you expect the indoor dew point to be slightly above the outdoor dew points. The rise in indoor dew point will be dependent on how much air is flowing through the home and the number of occupants. An air change on a 2,500 sqft. home in 5 hours is 75 cfm. Two occupants would raise the indoor dew point 10^F above the outdoor dew point.
The point of all of this is that the home will have a high moisture when the outdoor dew point is +60^F when occupied and low/no cooling load.
In general, homes that are dry in the summer and wet in the winter are usually under ventilated. So what? Certian pollutants and sensitive people may not do well. Best to have an air change in 4-5 hours and keep the indoor %RH <50%RH. In green grass climate, this requires supplemental dehumidification. When outdoor dew points are <25^F and minimal occpancy, humidification is also desireable.
Merry Christmass, I here Sleigh bells.
Regards TB

[beenthere]

Ooops, forgot to close this old thread.

Closed to prevent more people from posting in it that are not Pro * members.