Carrier Thermidistat Dehumidify

[kilobravo3]

Let me know if this question is out of line. If so, I will understand. In trying to setup my new Thermidistat with 38YDB heat pump and FV4A fan coil(new construction install). I tried to set the dehumidify function on the thermidistat. The manual says that the acceptible values are from 50% - 90%. For some reason, I can't get it to go below 60%. Did the installer forget something, or am I just doing something wrong?

[kilobravo3]

Let me tack one more question on here. I thought that the thermidistat had an "Ideal Humidity" feature that would automatically adjust the humidity in the house based on the outdoor temp. How would I configure that? I can't seem to find it in the manual.

[baby b]

bravo3,you need the installation instructions that come with the Thermidistat. That will contain the info. on how to configure your particular system(heat pump).If its new construction,call builder to get the hvac people back to check it.

[MechAcc]

Just a guess but have you checked the humidity level setting? It may be set too high and is conflicting with the dehumify setting.

[htinglky]

why didnt you use the infinity and not the themidistat, is leaps and bounds ahead of therm, and very user friendly

[jrbenny]

Originally posted by htinglky
why didnt you use the infinity and not the themidistat, is leaps and bounds ahead of therm, and very user friendly cuz he got an FV vice an FE.

[kilobravo3]

I was able to find the install instructions on Carrier's website, but it says essentially the same thing about the dehumidify that the homeowner's guide says. It just talks about how to set the value and that the valid ranges are from 50-90%. I turned the humidify level of Off, since I don't have a humidifier (in FLA).

As to why I didn't get the Infinity....when I asked my contractor about the Infinity, he told me he wouldn't install them becuase they were too new, and he didn't have any experience with them. Dash told me to ask him to be a guinea pig, but he wouldn't do it. Since the house was built by a builder, he wouldn't let me choose a different contractor. Unfortunately, I found this site a little to late to help me out with that situation.

Thanks gang. I think I might just have the contractor come back out and show me some things

[centralflinstaller]

have him come out and show you it may cost a service call but isn't it worth all the time you spend looking things up, when in reality you may have found the info but have no idea what your looking for or at ???

[htinglky]

when I get home tonight I will go thru my book and post for you.
I definatly would drop this contractor at the end of your warrenty, the infinity is childs play compared to the thermidistat and much more user friendly.

[dash]

Originally posted by kilobravo3
I was able to find the install instructions on Carrier's website, but it says essentially the same thing about the dehumidify that the homeowner's guide says. It just talks about how to set the value and that the valid ranges are from 50-90%. I turned the humidify level of Off, since I don't have a humidifier (in FLA).

As to why I didn't get the Infinity....when I asked my contractor about the Infinity, he told me he wouldn't install them becuase they were too new, and he didn't have any experience with them. Dash told me to ask him to be a guinea pig, but he wouldn't do it. Since the house was built by a builder, he wouldn't let me choose a different contractor. Unfortunately, I found this site a little to late to help me out with that situation.

Thanks gang. I think I might just have the contractor come back out and show me some things


Here a way to get an Infinity.Get your dealer or another one,to put in a request for a damaged FE air handler,in the size you need.When it becomes available,could be months,they can just swap the controls and blower assembly from the FE into the FV,it will save you a bunch of money.

[fat bob]

I believe the humidifier has a setting that automatically adjusts to outside temperature, to prevent foggy windows, but the dehumidifier does not have this function. When you say you can't get it below 60, do you mean you can't set the thermidistat below 60, or you can't get your indoor relative humidity below 60?

[kilobravo3]

I can't set the relative humidity below 60%.

[fat bob]

Originally posted by kilobravo3
I can't set the relative humidity below 60%.

I don't have a heat pump, but I can definitely set thermidistat down to 50 on my AC. I would ask the installer what's going on.

[dash]

we are mostly heat pumps,and it should be able to be set for 50%.No idea why yours won't go to 50%.

[kilobravo3]

I'm wondering if somehow the installer didn't setup the stat to indicate variable speed air handler? I also noticed in the install instructions that there was an option for super dehumidify mode (option 7) in the install manual. If this was not enabled (is it even an option with the FV4 coil?), do you think that could have an effect? Like you all said earlier, I guess it is just time to call the contractor.

[htinglky]

as my esteemed collouge stated software switc 7 must be on and so does 5 which signifies variable speed blower.

now try to adjust it lower

[thorton]

Originally posted by kilobravo3
Let me know if this question is out of line. If so, I will understand. In trying to setup my new Thermidistat with 38YDB heat pump and FV4A fan coil(new construction install). I tried to set the dehumidify function on the thermidistat. The manual says that the acceptible values are from 50% - 90%. For some reason, I can't get it to go below 60%. Did the installer forget something, or am I just doing something wrong?

I have the same Thermidistat,and the same FV4A Fan coil. My thermidistat has the range of 50 to 90. But I find that if I use the cool to dehumidify function the heat pump short cycles at night when the cooling load is low. Any body any ideas?

[Edited by thorton on 04-24-2005 at 11:47 PM]

[thorton]

Originally posted by kilobravo3
Let me know if this question is out of line. If so, I will understand. In trying to setup my new Thermidistat with 38YDB heat pump and FV4A fan coil(new construction install). I tried to set the dehumidify function on the thermidistat. The manual says that the acceptible values are from 50% - 90%. For some reason, I can't get it to go below 60%. Did the installer forget something, or am I just doing something wrong?

The guy's below are absolutly right, go into the configuration mode of your Thermidistat and select option # 5(variable speed blower) on, and option #7 variable speed superdehumidify. I'm sure then you will have the correct range of dehumidify (50 to 90)

Thorton

[dash]

Originally posted by thorton

Originally posted by kilobravo3
Let me know if this question is out of line. If so, I will understand. In trying to setup my new Thermidistat with 38YDB heat pump and FV4A fan coil(new construction install). I tried to set the dehumidify function on the thermidistat. The manual says that the acceptible values are from 50% - 90%. For some reason, I can't get it to go below 60%. Did the installer forget something, or am I just doing something wrong?

I have the same Thermidistat,and the same FV4A Fan coil. My thermidistat has the range of 50 to 90. But I find that if I use the cool to dehumidify function the heat pump short cycles at night when the cooling load is low. Any body any ideas?

[Edited by thorton on 04-24-2005 at 11:47 PM]


Cool to Dehum.,should be 10minutes on ,10 off.Is that what you see happening?

[kilobravo3]

I know it has been a couple of weeks on this one, but I just wanted to get some more info. We had a brief power outage and after that, the stat allowed me to set the humidity to 50(can't figure that one out!!). I also got the installer's guide and check the settings for #5 and #7...both look good. Now, here is the question regarding the cool to dehumidify function that was asked by someone else in this thread. My book says that it will overcool by up to 3 degrees in order to reduce the humidity. I have the stat set to 78 and the indoor temp is 78 with RH of 60. To me, it seems that the unit would come on trying to reduce the humidity until it hit the desired humidity, or 75 degrees, whichever came first. This is not happening though. When there is a dehumidify demand, the unit runs for 6 minutes. It turns off for some time (haven't timed this yet), but then runs again for 6 minutes. Either something is not right, or I have a complete misunderstanding of how this thing is supposed to work. Which is the case here?

[docholiday]

I'd buy a bigger hammer if I set my thermostat to 78 it would run as low as 75.

[jrbenny]

Originally posted by kilobravo3
This is not happening though. When there is a dehumidify demand, the unit runs for 6 minutes. It turns off for some time (haven't timed this yet), but then runs again for 6 minutes. Either something is not right, or I have a complete misunderstanding of how this thing is supposed to work. Which is the case here? Unit should run approximately 10 minutes and be off for same amount of time when there is a cool-to-dehumidify call. It is not a constant run down to 75°F.

From page 9 of your installation manual:


During cool-to-dehumidify demand, the compressor runs a maximum of 10 minutes on, followed by 10 minutes off.

Read page 9 slowly. The answers are all right there.

[kilobravo3]

OK. Thanks guys. I guess I just misunderstood how this was supposed to work. I saw the earlier post that said 10 minutes on/10 minutes off, I guess I just missed the "up to" part. 6 minutes just seems kind of random, but it is running that amount of time every time.

[teddy bear]

Originally posted by kilobravo3
OK. Thanks guys. I guess I just misunderstood how this was supposed to work. I saw the earlier post that said 10 minutes on/10 minutes off, I guess I just missed the "up to" part. 6 minutes just seems kind of random, but it is running that amount of time every time.
It takes 6-8 minutes for the cooling coil to get cold enough to remove moisture. Recycling this quickly reduces the moisture removed vs. the sensible cooling. Keep us posted on the indoor %RH during cool wet weather with no cooling load. Contolling %RH with a dehumidifier is more comfortable and prevents moisture condensation on cold surfaces.

[kilobravo3]

It's been relatively cool here in FL the last couple of weeks. We've had a couple of days of rain and 75 degrees. The humidity tends to stay around 60%...sometimes creeps up to 63-64, and sometimes down to 57-58. I usually have to turn the stat down though to add a cooling demand in order to get the humidity in the 50's. Things are starting to warm up here, and I imagine as I have more of a cooling demand, the humidity will get under control. I guess I am too optimistic that I can get the humidity down in the low 50's in FL. I'd really like to have the temp around 78-80 with the low humidity, but usually have to turn the stat down to around 76 to get the humidity into the 50's.

[dash]

If it's working as designed,it will control the humidity just fine,assuming no other problems ,like high infiltation,duct leaks,etc..

I know because mine does,we have had very cool ,wet weather the past two months ,and it works.

Keep the stat at 78 ,so the overcool,doesn't go below 75 and you'll be very comfortable.

[kilobravo3]

Dash,

I think I read on here that you are in the Tampa area..I'm just up the road in Gainesville. What are the RH readings that you typically see in your house?

[dash]

Never more than 55% and that's in rainy ,mild weather,it does run to dehumidify often in that type weather.I have two system one with Infinity ,one with Thermidistat,in this type weather the Infinity is always 1 or 2% lower RH.

In warmer/hot weather it's at the set point or often even lower.

I'm actually in Crystal River,our daughter is at UF ,we bought a condo there in Pick Wick Village two years ago.

BTW it has a Thermidistat as well,but not a two speed.She says it goes to 59% occasionally.She has the lowest power bill of anyone she knows there,13 SEER heat pump system,the rest are <10SEER and electric strip heat.

[teddy bear]

Last week in Orlando, Florida Air-Conditioning Contractor Ass. (FACCA) had a good presentation for continuing education credits on the limitations of a/c controlling indoor relative humidity. The main point was that without significant cooling load, an a/c is unable to maintain low humidity during high outside dew points. How many lbs. of moisture is removed per hour with a 6 min on/off at what cost? Supplemental dehumidification allows <50%RH without any a/c operation at a fraction of the operating cost. The cost of the equipment about as much as the up-charge of the deluxe a/c.

[kilobravo3]

Dash...congrats on buying real estate in Gainesville. You might be able to retire soon on that! The HVAC contractor said he would come out and have a look at the system to make sure everything is configured properly since it is a new house. If he tells me everything is OK, I will just wait until there is a larger cooling demand. I think one thing that is helping/hurting us is the fact that we have a large unfinished bonus room above the main part of the house. I'm guessing that there isn't a lot of heat laying near the top of the main floor. I'm curious to see what our power bill is going to be as we've only had a partial month bill so far. I really appreciate all you guy's help on this forum.

[kilobravo3]

Just one last follow up on this. I spoke with the HVAC contractor and he said he would come out and have a look at the system. I did find the section that said that in cool to dehumidify that the unit would run a maximum of 10 minutes. Since mine is running for 6 minutes it is definitely in that range. My question is, should it run for 10 minutes all the time, or does the thermostat decide how long it should run? I ask because I don't want this guy to come out to the house and waste his time if it is doing what it is supposed to be doing. If it should be running for 10 minutes, and it isn't, then I would like to have it adjusted because I assume the extra 4 minute run would remove more humidity. With a little more cooling demand this week, the humidity has been around 54...which is much better than the 60+ that it was last week.

[thorton]

Originally posted by kilobravo3
Just one last follow up on this. I spoke with the HVAC contractor and he said he would come out and have a look at the system. I did find the section that said that in cool to dehumidify that the unit would run a maximum of 10 minutes. Since mine is running for 6 minutes it is definitely in that range. My question is, should it run for 10 minutes all the time, or does the thermostat decide how long it should run? I ask because I don't want this guy to come out to the house and waste his time if it is doing what it is supposed to be doing. If it should be running for 10 minutes, and it isn't, then I would like to have it adjusted because I assume the extra 4 minute run would remove more humidity. With a little more cooling demand this week, the humidity has been around 54...which is much better than the 60+ that it was last week.


I have the same Carrier Thermidistat, and a Carrier heat pump. In the cool to dehumidify setting my heat pump runs only 5 or 6 minutes, usually at night this happens. I think two things might be happening-the duhumidify set point is satisfied after 5 or 6 minutes(remember cool to dehumidify has it's own set point, independent from the cooling set point)or, if you have one, the evaportator freeze stat is shutting the system down as the evaportor starts to freeze. My thoughts, anyways

Thorton