Humidy control on Trane 15i HP

[pepster2]

We had a 3 ton Trane HP installed with a variable speed air handler. The house in 1600 SF. We had a 2.5 ton but upgraded to a 3 ton when we insulated and added a 240 sf Florida room. It is included in the SF of the house 1600. The system cools great. The problem is the humidity. We have the 803 thermostat. I know would prefer the Honeywell Stat with better humidity control but this is what we got. he house would be 77 as we set it but had humidity set at 45 and it would go to 49%. Moved it to 50% and it would go to 53 or 54%. they came and set the air handler speed down. Was set at high. This weekend doing same thing. Humidity 3 or 4 % above what is set . Does it work like this? If set at 50% will it try and keep it somewhere within 3 or 4 % higher? The moving the air handledown from high to what ever they set it at did nothing, still doing it just as it did before.. Figure for $ we want it to work right. Does the new Trane 900 series control the humidity better. Asked the tech who came out the difference from 803 and the 900. He had no idea.

[Swampfox]

The 803 will simply overcool by up to 3 degrees to try and meet the dehumidification demands

the 900 will slow the fan down to 80% speed

with either method, you may have a hard time achieving 45%, dehumidification is a byproduct of cooling, the system cannot dehumidify only, it cools the house to setpoint and you get what you get with dehumidifiication, slowing the fan helps but is not a cure all.

was a load calculation performed to determine the proper size? or did they just upsize what you had because of the added square footage? typically an oversized system will not dehumidify as well as one properly sized

[Gunnery Sergeant Hartman]

Can you tell the difference in 3-4% more humidity?

[beenthere]

Not sure on the 803 anymore. But the IAQ won't cool to dehumidify until the humidity is 5% above set point.
The 803 is probably the same.
Is comfort r enabled on your blower.

[murphyHVAC]

We had a 3 ton Trane HP installed with a variable speed air handler. The house in 1600 SF. We had a 2.5 ton but upgraded to a 3 ton when we insulated and added a 240 sf Florida room. It is included in the SF of the house 1600. The system cools great. The problem is the humidity. We have the 803 thermostat. I know would prefer the Honeywell Stat with better humidity control but this is what we got. he house would be 77 as we set it but had humidity set at 45 and it would go to 49%. Moved it to 50% and it would go to 53 or 54%. they came and set the air handler speed down. Was set at high. This weekend doing same thing. Humidity 3 or 4 % above what is set . Does it work like this? If set at 50% will it try and keep it somewhere within 3 or 4 % higher? The moving the air handledown from high to what ever they set it at did nothing, still doing it just as it did before.. Figure for $6000 we want it to work right. Does the new Trane 900 series control the humidity better. Asked the tech who came out the difference from 803 and the 900. He had no idea.

The 900 thermostat will not work with your system unless you have an XL19i communicating outdoor unit with a communicating indoor unit. Your best bet is to get a Honeywell VisionPRO IAQ thermostat and a dealer who knows how to remove the BK jumper and properly install this thermostat for dehumidification.

[teddy bear]

Being able to maintain <55%RH is not all bad. Wait for rainy cool weather, the humidity control be poorer. With low/no cooling load, no dehumidification. Slow the fan more for more moisture removal. 40^F-45^F cooling coil temperature is as low as recommended. Think about a good dehumidifier for ideal humidity control without any a/c operation. Regards TB

[mark beiser]

The dehumidification function of the thermostat won't kick in until the humidity level is 5% higher than the set point.

From what you say, your indoor humidity is well under control as things are right now. You don't have a humidity problem.

[pepster2]

do you all feel the Tec did right by turning the fan speed down from high? The installers said they did it to make sue the back room cooled down good. He said he knew what they were looking at but by doing so countered humidity control. When on high it blew really, really hard and cooled dawn fast. In room closest to handler at night you would think it was storming outside it blew so hard

[beenthere]

He did the right thing slowing it down then.

[Airmechanical]

When on high it blew really, really hard and cooled dawn fast. In room closest to handler at night you would think it was storming outside it blew so hard


that is a typical symptom of insufficient ductwork!



.

[nina]

Climatouch makes a tstat that responds to a 2% change in RH.

Example:
RH setpoint 50%, the 24vac DH relay opens at 52% and remains open until RH is 48%, total deadband range 4%.

No other control does that.

[murphyHVAC]

The dehumidification function of the thermostat won't kick in until the humidity level is 5% higher than the set point.

That's not quite accurate.... You can only set the humidty in 5% increments but it controls it to the exact setpoint. I keep mine set at 45% and it maintains 45%.

[beenthere]

Haven't had one of them do a cool to dehumidify call if the humidty wasn't 5&#37; above set point.
They all slowed the blower down when it was 1% above though.

What are your installer set up settings.

[murphyHVAC]

They all slowed the blower down when it was 1% above though.


I'm confused as to what you are saying. Lowering the airflow is how it dehumidifies. Are you saying that it won't call to dehumidify if it's already at the temperature setpoint and less than 5% from the relative humidity setpoint? I set my overcooling limit to 1 degree and set dehumidification with air conditioning on.

[beenthere]

It has both teh abilty to run the A/C to dehumidify, and to slow the blower during normal cooling calls.

Are you sure yours is running in cool to dehumidify, or just able to maintain humidity by slowing the blower down.

I haven't had any cool to dehumidify when the humidity was only 3&#37; above set point.

[murphyHVAC]

It has both teh abilty to run the A/C to dehumidify, and to slow the blower during normal cooling calls.

Are you sure yours is running in cool to dehumidify, or just able to maintain humidity by slowing the blower down.

I haven't had any cool to dehumidify when the humidity was only 3% above set point.

Slowing the blower down during normal cooling cycles is how it dehumidifies. What else do you think it does different to dehumidify than slow the blower down? It will cool to dehumidify as long as the cooling setpoint isn't below the overcooling limit set in the installer setup. Like I said I keep mine at 1 degree of overcooling. If I set my RH to 40% it maintains 40% if I set it to 50% it maintains 50%. The only exception to this is if it is 72 degrees outside or something where the air conditioner isn't coming on at all.

[mark beiser]

That's not quite accurate.... You can only set the humidty in 5&#37; increments but it controls it to the exact setpoint. I keep mine set at 45% and it maintains 45%.

The thermostat the OP has only dehumidifies by over cooling, it won't turn the system on to dehumidify until the humidity is 5% above the set point. This is to prevent excessive cycling of the equipment.

Just going off other posts you have made, you have a Vision Pro IAQ, which is a different thermostat than the poster here has. Your thermostat will lower the blower speed to dehumidify any time the humidity is above the set point.
It will also over cool for humidity control, but I don't think it will do so unless the humidity is 5% higher than the set point, or the system was already running on a call for cooling.

[mayguy]

The 900 thermostat will not work with your system unless you have an XL19i communicating outdoor unit with a communicating indoor unit. Your best bet is to get a Honeywell VisionPRO IAQ thermostat and a dealer who knows how to remove the BK jumper and properly install this thermostat for dehumidification.

Murphy,

The Trane XL900 is the same stat as the IAQ. and it will work with the OP system.




Just going off other posts you have made, you have a Vision Pro IAQ, which is a different thermostat than the poster here has. Your thermostat will lower the blower speed to dehumidify any time the humidity is above the set point.
It will also over cool for humidity control, but I don't think it won't do so unless the humidity is 5&#37; higher than the set point, or the system was already running on a call for cooling.

Mark is right, the IAQ won't start over cooling till 5% over set point.

[mark beiser]

Murphy,

The Trane XL900 is the same stat as the IAQ. and it will work with the OP system.

The XL900 doesn't have an equipment interface module, it only works with the communicating air handlers and furnaces.
The outdoor unit doesn't have to be a communicating model though.

[beenthere]

As others said. The 8320 and 8321 don't work like the IAQ.

[murphyHVAC]

The thermostat the OP has only dehumidifies by over cooling, it won't turn the system on to dehumidify until the humidity is 5&#37; above the set point. This is to prevent excessive cycling of the equipment.

Just going off other posts you have made, you have a Vision Pro IAQ, which is a different thermostat than the poster here has. Your thermostat will lower the blower speed to dehumidify any time the humidity is above the set point.
It will also over cool for humidity control, but I don't think it will do so unless the humidity is 5% higher than the set point, or the system was already running on a call for cooling.

If you read back through the thread you'll see that the VisionPRO IAQ is what I said he needed to install and is the thermostat I've been talking about. I know the one he has doesn't have any real dehumidification control. As I stated earlier the 803 doesn't have true dehumidification and the 900 only works with fully communicating systems or systems with a communicating furnace or air handler and a non communicating outdoor unit with an adapter wiring harness.

[murphyHVAC]

As others said. The 8320 and 8321 don't work like the IAQ.

Yah I said that too. Lets try to read more than the first and the last posts before we respond.

[murphyHVAC]

Murphy,

The Trane XL900 is the same stat as the IAQ. and it will work with the OP system.



The VisionPRO IAQ is completely different than the XL900. For one thing the IAQ has a seperate equipment module. If you were somehow able to get the XL900 to work with a noncommunicating system I would love to see your wiring diagram. As far as when it will overcool... I don't know. I live in south texas and mine has never had to overcool to reach the humidity setpoint. The point is that the VisionPRO IAQ is the only stat made by Honeywell or Trane that will begin to dehumidify before overcooling (with the exception of the TCONT402 or the XL900 on a communicating system).

[mayguy]

The VisionPRO IAQ is completely different than the XL900. For one thing the IAQ has a seperate equipment module. If you were somehow able to get the XL900 to work with a noncommunicating system I would love to see your wiring diagram. As far as when it will overcool... I don't know. I live in south texas and mine has never had to overcool to reach the humidity setpoint. The point is that the VisionPRO IAQ is the only stat made by Honeywell or Trane that will begin to dehumidify before overcooling (with the exception of the TCONT402 or the XL900 on a communicating system).

ok, My bad. I will admit I was wrong.. I swore I read somthing somewhere that this was like the IAQ with the EIM, and there one for the XL19, and XC95.

[beenthere]

Yah I said that too. Lets try to read more than the first and the last posts before we respond.
WHAT? And take all the fun out of it. :)

But if your getting your to cool to dehumidify before the humidity rises to 5&#37; above set point. Myself and others want to know waht installer settings you have yours at.

[murphyHVAC]

ok, My bad. I will admit I was wrong.. I swore I read somthing somewhere that this was like the IAQ with the EIM, and there one for the XL19, and XC95.

I think they changed it at the last minute or something to make it proprietary. I remember seeing on the Trane web page in their marketing images library pictures that they labeled XL900 and they showed an equipment interface module. I wish they had a version that was identical to the VisionPRO IAQ but at the least they should have made the XL900 so that it could also use an optional equipment interface module for non-communicating systems. It screws me up when I'm trying to do extended warranties on Trane equipment and I have to use the Honeywell thermostat. Also we use mostly 80% furnaces down here and I don't think they have the 80% communicating furnace out yet. So if I want to do true dehumidification control say on a XL19i, i've got to use the VisionPRO IAQ and the harness on the outdoor unit. One good thing about the VisionPRO IAQ and (I assume) the XL900 is no more clicking noises. I won't miss installing the quietest system as customer has ever had then hearing them complain about their thermostat making a clicking noise.

[murphyHVAC]

WHAT? And take all the fun out of it. :)

But if your getting your to cool to dehumidify before the humidity rises to 5&#37; above set point. Myself and others want to know waht installer settings you have yours at.

I'll look them up when I get home this evening and post it on here. Not sure if it makes a huge difference but mine is installed on a Lennox XP19 heat pump and variable speed air handler. On the Lennox variable speed air handlers the dehumidification terminal forces the outdoor unit to 2nd stage cooling at 1st stage (80%) airflow. This is something that I posted about in another thread (http://www.hvac-talk.com/vbb/showthread.php?t=170469&highlight=XL16i+dehumidification) when I was trying to accomplish the same thing with the Trane XL16i. It also looks like this has come up recently in this post (http://www.hvac-talk.com/vbb/showthread.php?t=171136&highlight=XL16i+dehumidification). I'm getting way off subject though.