Trane Comfort R ?

[jimmydsmith7]

Have a new XL16i 5 ton heat pump with new air handler, both are the communicating models with a trane TCONT900AC43UA comfortlink II tstat.
My question is what would be the difference in having Comfort-R vs not having it on this system. Not sure what the Comfort-R does?
Thanks in advance.

[ACFIXR]

Have a new XL16i 5 ton heat pump with new air handler, both are the communicating models with a trane TCONT900AC43UA comfortlink II tstat.
My question is what would be the difference in having Comfort-R vs not having it on this system. Not sure what the Comfort-R does?
Thanks in advance.
Comfort-R is a fan setting that allows the blower to slowly ramp up while your compressor loads your coil , thereby removing more moisture in cooling mode and increasing initial air temperature in heating mode.

[RyanHughes]

You can leave Comfort-R off and just let the thermostat control humidity when needed, since--when I checked--that thermostat can control blower speed in the air handler to control humidity. This way you get the most airflow when you need it and humidity control when you need it.

[motoguy128]

With the communicating XL900 thermostst, you can have the fan speed reduce to better dehumidify. This is better than Comfort-R because it reduces the fan speed on demand rather than using a fixed amount of time.

Trane claims they have some added control logic to help manage humidity. Not sure if that's just marketing hype or what it does.

A good installer can program the unit to enable the feature. I don't think it's eneabled by default.

[jimmydsmith7]

I have the humidity set for 45%. The system will come on and bring the temp down to the set temp, but does not come on if temp is right but humidity is high. In other words, temp is set at 74degrees and I have tstat set for 45%humidity. The stat is reading 74 degrees, but the humidity is reading 57%, shouldn't the system be running to get the humidity down to the requested 45%? Once the temp is reached, the system stops even though the humidity requested is not reached. Is this correct???

[motoguy128]

I have the humidity set for 45%. The system will come on and bring the temp down to the set temp, but does not come on if temp is right but humidity is high. In other words, temp is set at 74degrees and I have tstat set for 45%humidity. The stat is reading 74 degrees, but the humidity is reading 57%, shouldn't the system be running to get the humidity down to the requested 45%? Once the temp is reached, the system stops even though the humidity requested is not reached. Is this correct???

I thought he same thing. But no, that's how the IAQ works and I'd assume the XL900 works the same way. It will overcool as needed using a reduced airflow (assuming it's programmed for reduced airlfow when there's a call for dehumidification).

However, your thermostst may not be programmed correctly to overcool to dehumidify and may not be using reduced airflows to aid dehumidification. Also, make sure you're using "circ" and not "on" for the fan setting. Leaveign the fan on will reintroduce the moisture that's on the coil before it can drain off completely.


Do an internet search for the XL900 installation manual or guide. Read through it and see if it makes sense. Then ask your installer, nicely, to come back and optimize the settings.

That thermostst has a LOT of capability and control if programmed correctly.


Ultimately if you have a leaky house or a lot of venitlation with a ERV not HRV... on mild days you won't have enough heat load to remove humidity. The only solution durign the "shoulder season" is to runn the A/C a little cooler where it's comfortable and can keep humidity more moderate.

We had a humid 75-80F but mostly coudy day recently. The system struggled to keep humidity under 55% because it wasn't running long enough.

The other option is to use a whole house dehmidifier.

[SmackDabAOK]

With the communicating XL900 thermostst, you can have the fan speed reduce to better dehumidify.
This is better than Comfort-R because it reduces the fan speed on demand rather than using a fixed amount of time....

.

When you say ... "reduces the fan speed on demand" when using Tstat to dehumidify ... is that then based on a "Humidity reading/registering" ability, thus calling for reduced fan etc.?

Actually, I posted this before reading each posting, & I see that jimmydsmith7 pretty much answered this.
It can use Humidity as part of it's function in dehumidifying. I see.

But I believe that no matter what, it doesn't "satisfy" the Humidity setpoint as a cooling on/off rule per se, as many persons initially expect that it would do. Meaning ... cooling will not come on or off ... based on humidity. Only the temperature setpoint will control that.
And as one of jimmydsmith7's questions indicated ... this has been a confusing point for many to realize indeed, including myself.

Feel free to correct me if I'm wrong.
.

[beachtech]

Trane Comfort-R™:

This exclusive mode operates quietly and efficiently, gently warming and cooling your home. It also helps control humidity while cooling.


Remove humidity


Also, since a variable-speed fan can run at lower speeds, it better circulates the air and removes humidity. Higher humidity is often what makes you feel muggy and uncomfortable. Simply match a high-efficiency air conditioner or heat pump with a variable-speed indoor unit featuring our patented Trane Comfort-R™ technology. Another benefit: Because dust mites need high humidity to live, they won't survive, so your family can breathe easier.

from Trane's website. seems clear as mud to me :D:D:D

comfort R is an operation of the indoor fan motor. not so much in the heating mode, but more so in the cooling mode. the indoor fan motor at the begining of the cycle runs at 50% for about the first seven minutes. after that it speeds up to about 80%, and then if the run time is long enough the blower will reach to the 100% range :)

[beachtech]

I have the humidity set for 45%. The system will come on and bring the temp down to the set temp, but does not come on if temp is right but humidity is high. In other words, temp is set at 74degrees and I have tstat set for 45%humidity. The stat is reading 74 degrees, but the humidity is reading 57%, shouldn't the system be running to get the humidity down to the requested 45%? Once the temp is reached, the system stops even though the humidity requested is not reached. Is this correct???

am pretty sure that's the actual humidity readung, and not a setting :) if i remember corrrectly :)

if your home is reaching 57%, you have some issues that need to be addressed ;)

[motoguy128]

When you say ... "reduces the fan speed on demand" when using Tstat to dehumidify ... is that then based on a "Humidity reading/registering" ability, thus calling for reduced fan etc.?

Actually, I posted this before reading each posting, & I see that jimmydsmith7 pretty much answered this.
It can use Humidity as part of it's function in dehumidifying. I see.

But I believe that no matter what, it doesn't "satisfy" the Humidity setpoint as a cooling on/off rule per se, as many persons initially expect that it would do. Meaning ... cooling will not come on or off ... based on humidity. Only the temperature setpoint will control that.
And as one of jimmydsmith7's questions indicated ... this has been a confusing point for many to realize indeed, including myself.

Feel free to correct me if I'm wrong.
.

My observatins with my Visonpro IAQ so far in mild outdoor temps match yours. It will not initiate a call for cooling, to decrease the humidity levels. It will only operate the A/C longer to remove more humidity. It hints towards this in the IAQ installer's guide if you read carefully.

The problem I see is that by running the A/C longer to lower indoor humidity, the next calling for cooling will occur later than before and so all you've managed to do is create wider swings in temperature.

So it seems that the only real solution is to get have a higher percentage of latent capacity by using lower airflow and having a matched coil size (instead of oversized which sometimes add efficiency and more sensible capacity). The other solution for very humid climates is a whole house dehumidifier.

Again, you should find that once it warms-up outside, you'll have better control over humidity levels.

[motoguy128]

if your home is reaching 57%, you have some issues that need to be addressed ;)

Don't forget RH is RH. So 57% at 70F (where I think the OP is running his system at) is much less moisture than 57% at 80F... which would defnitely be a problem. Both represent issues, but refrigerant based dehumidification has a limit ot the the level of absolute humidity it can remove... because the surface temp of the coils is limited to 32F. So a dew point of around 35F is the best it can achieve. Realistically, it's only going to drop the coil temp about 30F below the return air temp... maybe less with that amount of moisture in the air. Lets say the coil is about 40F with 70F return. That's an RH of 35%. If the outdoor dewpoint is 55F, that's a RH of 60% at 70F.

Next factor in infiltration rate and system CFM and run time with the outdoor conditions you can determine the minimum absolute humidty level it can achieve. So say a ACH or 0.5, and the A/C running at 25% duty cycle. A 3 Ton system cooling 1500sqft of indoor space has 1 air change every 10 minutes so at 30% duty cycle, that's 1.8 ACH for the A/C, but figure only 1/2 of the moisture actually makes it down the drain so t's really only going to reach 45% RH. So 1.8 ACH at 45% and 60% RH at 0.5 ACH... that averages to 48% RH, but add maybe 5% for cooking, showers and other sources and you'er back to 53% RH.

So it's not hard to imagine that the OP would struggle to maintian 57% RH with an outdoor dewpoint of 55F but a daytime high of only 75F or 80F causing a low duty cycle on the A/C.

I'm sure you could desing a system to better remove humidity, but it woudl be cost prohibative. better to use protable dehumidifers for a whole house dehumidifier for added comfort.

I'm pretty low tech myself. We prefer to keep the house closed up due ot seasonal allergies, privacy, noise and overall comfort. So if I'm warm... or more importantly if my wife is warm, I lower the thermostst setting. I don't realy care what the indoor temp or humidty is... as long as it over about 55F outside, I'll run the A/C. I do have the IAQ set to overcool up to 1 degree to dehumidify to a target of 45% RH. I run the blwoer at 350CFM/ton to maximize latent capacity. I care more about comfort than efficiency.

[neophytes serendipity]

from Trane's website. seems clear as mud to me :D:D:D

comfort R is an operation of the indoor fan motor. not so much in the heating mode, but more so in the cooling mode. the indoor fan motor at the begining of the cycle runs at 50% for about the first seven minutes. after that it speeds up to about 80%, and then if the run time is long enough the blower will reach to the 100% range :)

That description sounds no different than any other variable speed cooling motor logic. All brands I am familiar with do that very same thing.

Enabling the DEHUM terminal on the board through the VisionPro IAQ is entirely different.

[beenthere]

His stat may not be set up to cool to dehumidify.

Before it will bring on the A/C to dehumidify. It has to have had a call to cool prior the humidity rising.

EG: If at night time. The stat cals for heat. And in the morning there has been no call for cooling. The humidity can be100%, and it still won't do a cool to dehumidify. Until it has done at least one cooling call.

Also. Stat should not be set for auto change over. It interferes with cool to dehumidify.

[beenthere]

And Comfort r has nothing to do with cool to dehumidify/DOD.

[motoguy128]

Beenthere,

How long do you think before someone sticks a temperature switch or sensor on the indoor coil and links it the the VS fan to maximize latent capacity? You could probably link it to compressor loading by measuring comrpessor amps and compare it to discharge temp, return air temp and outdoor air temp to allow not only low ambient cooling, but also maximum latent capacity.

Probably not until inverter based units hit the market, right?

[beenthere]

Thats already done with devices like the Fan Handler, and ICMs fan controller.
There used on non VS blowers.

Inverter compressors are already out.
And Copeland is still working on getting their Variable speed compressor out(in the comfort cooling market).
I think its suppose to be able to drop to 10% of capacity.

So a 5 ton could drop to .5 ton.

[motoguy128]

Thats already done with devices like the Fan Handler, and ICMs fan controller.
There used on non VS blowers.

Inverter compressors are already out.
And Copeland is still working on getting their Variable speed compressor out(in the comfort cooling market).
I think its suppose to be able to drop to 10% of capacity.

So a 5 ton could drop to .5 ton.


I know they have soem of those switches for low ambient, but I didn't think they were implemnting them to maximum humidity control other than with single steps in airflow reduction or preset ramps.

10%? Nice! Now you cna oversize a systme all you want. Heck, you might as well only offer a 5 Ton and maybe a 2.5 Ton size.

Are they doing anything special with the indoor coil to vary its' effective surface area??? Otherwise I would think you'd have issues with latent capacity if you have a 5 ton coil running at 0.5 ton capacity. I guess you could have motorized plates to blind off the lower parts of the coil.

Do you have any links. I'm curious what type of motor they are using. To get that low speed torque performance with good efficinecy, I'd think you'd need a permenant magnent motor. I know some rotary screw air compressors have gone that route.


Somethign ot look forward to in 15 years when I'm looking ot replace again.

[neophytes serendipity]

So a 5 ton could drop to .5 ton.



How would that effect efficiency?

[beenthere]

You still wouldn't install a 5 ton on a house that only needs 3 tons.
The additional cost for the increased duct aize, and nuber of grilles would be prohibitive alone.

Probaly one reason they aren't out yet. Is now the air flow velocity is too low. You could get condensation in the duct work.

[beenthere]

How would that effect efficiency?
I don't know.

Since they aren't out yet, that may be one of the things that is holding them up.

[beachtech]

Don't forget RH is RH. So 57% at 70F (where I think the OP is running his system at) is much less moisture than 57% at 80F... which would defnitely be a problem. Both represent issues, but refrigerant based dehumidification has a limit ot the the level of absolute humidity it can remove... because the surface temp of the coils is limited to 32F. So a dew point of around 35F is the best it can achieve. Realistically, it's only going to drop the coil temp about 30F below the return air temp... maybe less with that amount of moisture in the air. Lets say the coil is about 40F with 70F return. That's an RH of 35%. If the outdoor dewpoint is 55F, that's a RH of 60% at 70F.

Next factor in infiltration rate and system CFM and run time with the outdoor conditions you can determine the minimum absolute humidty level it can achieve. So say a ACH or 0.5, and the A/C running at 25% duty cycle. A 3 Ton system cooling 1500sqft of indoor space has 1 air change every 10 minutes so at 30% duty cycle, that's 1.8 ACH for the A/C, but figure only 1/2 of the moisture actually makes it down the drain so t's really only going to reach 45% RH. So 1.8 ACH at 45% and 60% RH at 0.5 ACH... that averages to 48% RH, but add maybe 5% for cooking, showers and other sources and you'er back to 53% RH.

So it's not hard to imagine that the OP would struggle to maintian 57% RH with an outdoor dewpoint of 55F but a daytime high of only 75F or 80F causing a low duty cycle on the A/C.

I'm sure you could desing a system to better remove humidity, but it woudl be cost prohibative. better to use protable dehumidifers for a whole house dehumidifier for added comfort.

I'm pretty low tech myself. We prefer to keep the house closed up due ot seasonal allergies, privacy, noise and overall comfort. So if I'm warm... or more importantly if my wife is warm, I lower the thermostst setting. I don't realy care what the indoor temp or humidty is... as long as it over about 55F outside, I'll run the A/C. I do have the IAQ set to overcool up to 1 degree to dehumidify to a target of 45% RH. I run the blwoer at 350CFM/ton to maximize latent capacity. I care more about comfort than efficiency.

hhmmmmnnnnn

[beachtech]

Beenthere,

How long do you think before someone sticks a temperature switch or sensor on the indoor coil and links it the the VS fan to maximize latent capacity? You could probably link it to compressor loading by measuring comrpessor amps and compare it to discharge temp, return air temp and outdoor air temp to allow not only low ambient cooling, but also maximum latent capacity.

Probably not until inverter based units hit the market, right?

invertor is on the market :) ;)

[beachtech]

That description sounds no different than any other variable speed cooling motor logic. All brands I am familiar with do that very same thing.

Enabling the DEHUM terminal on the board through the VisionPro IAQ is entirely different.

who said it was any different than anything else???

they just put a label on it :D

actually it started way way back when they where using the TDR on indoor fan ;)

[beachtech]

Again, you should find that once it warms-up outside, you'll have better control over humidity levels.

and why so??? :D

[SmackDabAOK]

Also. Stat should not be set for auto change over. It interferes with cool to dehumidify.



Thanks for that point, I've not heard that before.

.

[motoguy128]

and why so??? :D

Since the A/C removes moisture without reintroducing heat back into the system like a dehumidifer or a commercial or industrial HVAC sytem with reheat coils, the amount of water that can be removed from the air is limited to the run time of the equipment and it's precentage of latent capacity. So if your heat gain in a home is only 25% of the sensible capacity the equipment, you can take the latent capacity, divide it by 970 and that will tell you how many pints you can remove per hour.

So If I have a 2 Ton system, with 45% latent capacity at the indoor conditions, and the heat gain on the home is 5000 BTU's.... then the duty cycle is 37% of sensible capacity. I'm going to remove about 4.1 pints per hour. It's actually a little less since latent capacity drops and sensible goes up as humidity levels go down... but you need calculus to determine the exact amount.

So if you have a higher heat gain, you're system will run longer and therefore remove more moisture.

The system is somewhat self adjusting af course, because your latent capacity will increase or decrese depending on indoor humidity levels. It of course cna be optimized further by reducing airflow to 350CFM/ton or by DOD and using a 80% airlfow rate, which 320CFM/ton.


This all brings up a interesting point. My 2 stage XL16i, accoridng to the data sheets actually has a lower percentage of latent capacity on low stage than high stage. In theory, then, since run time is dependant on heat load, it would remove less moiture total on low stage even with longer run times than high stage.... because it's all porportional. So longer run times will remove more moisture only because there's less opportunity for water to reevaprote off the coil and a smaller coil form a properly sized system will have less surface area to "trap" water on the coil.


Am I missing something?

[motoguy128]

I don't know.

Since they aren't out yet, that may be one of the things that is holding them up.

Perhaps I'm just looking for the easy solution... but couldn't you just measure the return air temp and humidity level and then measure the discharge air temp and adjsut hte airflow to keep the discharge air temp bove a minimum value. Monitoring discharge air temp is already done in zoned systems.

Actually it sounds like zoning is almost a requriements for these vairable capacity systems.

Have any companies considered using a desuperheater inline with the indoor coil to allow for dehumidification without reducing air temp??? I wonder if you could use a control valve to split the vapor between a indoor desuperheater and the outdoor coil. it could require a duble linesets between indoors and out, but I don't see why it couldn't work.

[ACFIXR]

Since the A/C removes moisture without reintroducing heat back into the system like a dehumidifer or a commercial or industrial HVAC sytem with reheat coils, the amount of water that can be removed from the air is limited to the run time of the equipment and it's precentage of latent capacity. So if your heat gain in a home is only 25% of the sensible capacity the equipment, you can take the latent capacity, divide it by 970 and that will tell you how many pints you can remove per hour.

So If I have a 2 Ton system, with 45% latent capacity at the indoor conditions, and the heat gain on the home is 5000 BTU's.... then the duty cycle is 37% of sensible capacity. I'm going to remove about 4.1 pints per hour. It's actually a little less since latent capacity drops and sensible goes up as humidity levels go down... but you need calculus to determine the exact amount.

So if you have a higher heat gain, you're system will run longer and therefore remove more moisture.

The system is somewhat self adjusting af course, because your latent capacity will increase or decrese depending on indoor humidity levels. It of course cna be optimized further by reducing airflow to 350CFM/ton or by DOD and using a 80% airlfow rate, which 320CFM/ton.


This all brings up a interesting point. My 2 stage XL16i, accoridng to the data sheets actually has a lower percentage of latent capacity on low stage than high stage. In theory, then, since run time is dependant on heat load, it would remove less moiture total on low stage even with longer run times than high stage.... because it's all porportional. So longer run times will remove more moisture only because there's less opportunity for water to reevaprote off the coil and a smaller coil form a properly sized system will have less surface area to "trap" water on the coil.


Am I missing something?
motoguy...Is it possible to have an even smaller 1st stage compressor that would run all the time and only cycle off by demand and /or time. Thereby having continuous low airflow and a coil that is constantly below dewpoint.

[motoguy128]

motoguy...Is it possible to have an even smaller 1st stage compressor that would run all the time and only cycle off by demand and /or time. Thereby having continuous low airflow and a coil that is constantly below dewpoint.


Sure, but would the net amount of water removed still be any different??? Not if the percentage of latent capacity is the same. An to improve the percentage, at some point you'll have to sacrifice efficiency. Basically if you get the sensible BTU's down to hte heat gain balance point, you're latent capacity is low enough that you're still on average, not removing anymore water.

I guess what I'm saying is low run times are still good, but I'm not sure you actually remove smore water from the air on low stage with most 2 stage compressors, because with an oversized coil, your latent capacity goes down... and hte amount of actual water making to to the drain goes even lower since there's more wetted surface.


Hmmm... I wonder if you could coat the fins with a micro thin film that would cause water to bead and run off better, but not significantly effect heat transfer.