Trane Variable Speed, Humidity, Comfort-R

[markk]

I have a single Trane 5Ton XL14i Compressor (410a) matched with a Variable Speed Air Handler (4TEE3F), Trane EAC, and WR 1F80-261 Thermostat on 1 zone (servicing 2 floors - 2700sq ft in New York). When we were shopping systems, all bids came back with either 5 Ton split systems or 5 Ton single. We run the air handler in continuous mode since my wife and daughter have bad allergies.
We asked for Comfort-R to be turned on when the system was installed. The system is ramping up / down as
described and is quiet, but I find the humidity level a bit high for my tastes (approx 60+%). It can go as high as 68% overnight when the indoor temp stabilizes and the outside temp is mild (the compressor may not not kick in at all).
The Thermostat normally is set to 71-72 degrees.
I find that the level drops to (50% or below) when the system runs longer when it changing temps (i.e. 76 - 72).
A normal maintain cycle rarely exceeds the 1 + 7.5 minute run time. The serviceman will be in next week for my annual visit.

Several Questions
1) I believe the fan is set at the standard 400CFM per ton, I was going to have it reduced to 350CFM.
Would this help?


2) I have seen some correspondence with regards to Jumpers on the control board. That a jumper should be installed between Y and O for Comfort-R to work properly. The DIP switches must be set properly as my system is ramping up / down. What does this jumper do? If the jumper is not installed and the Comfort-R DIP switch settings are turned on, what would the result be?

In the installers guide that I have, one of the diagrams show a Single Stage Cooling / 2 Stage Heat system
(I only have Single Stage Cooling) - with the following note
'Connections to "R", "BK", "O" and "Y" must be made as shown for proper operation of Blower
with Humidistat in cooling' - I do not have a humidistat.
There is no diagram for Single Stage Cooling alone.


3) Would installing an external humidistat help as well?

Thanks in advance.

[daverubin]

This is one area my installers messed up. Not only did they set the CFM wrong, they didn't enable Comfort-R.

Thanks to the Trane documentation and verification from this forum I was able to get everything set properly. I'm pretty sure you must jumper Y and O at the furnace or Comfort-R is not enabled.

As for the CFM, I made sure mine was set to match the tonnage of my system. I think messing with it is a bad idea; without enough air flow the coils could freeze.

The system needs to run for longer intervals to get the humidity out. If your system doesn't run long enough then it just might be oversized.

[Swampfox]

350 CFM per ton will help keep humidity lower, but may not be the best seeting for heating if you have a heat pump

Dont run the fan continously, the moisture that collects on the coil and in the drain pan during the cooling cycle will evaporate and come right back into your house, this may be contributing to your humidty being higher.

The jumper to O simply tells the speed control that the thermostat is set for cooling, without it the speed control would default to the heat airflow....no Comfort R

A humidistat will help as well



[Edited by swampfox on 06-06-2005 at 02:41 PM]

[old yeller]

I have noticed that my humidity would jump way up if I left my fan on continuously during the summer.

I do have the comfort-R on and during the summer I leave the fan on auto. The helps humidity dramatically. I have allergies also, also but this does not seem to affect them.

Someone else can better explain why, but you get the same effect in your car if you put it on recirc and then turn the AC off with the fan runnning. It immediately feels warm and humid even though most of it is coming from inside the car.

Just a thought-

[mayguy]

I turned our A/C on today for the first time, it was around 65% in the house, This evenign when I got home, it's 42%.

I have ti set at 76, and it comfy here..

Going off subject, seems like lot of people has the A/C set at 70.. why?? I am comfy at 76

[jerrod6]

I had my units(Trane gas furnace/ XL14Ii) installed in the winter so the AC operation was not configured until the summer. Before the configuration the DIP switches were in the correct position but the jumper was not installed.

If I remember correctly without the jumper installed the unit would start and the blower would run on low speed for a minute, then ramp up, ONCE to the set speed of 400CFM. When the jumper was installed the unit then would ramp up to middle slow speed and stay there for 7 minutes and then would move up to the set speed. So without that jumper I was missing the middle 7.5 minute speed that would have removed more humidity.

During mild weather the unit will run about 6 minutes at the lower speed every once in a while. During warm weather once the house temperature stabilizes and provided it is not very hot outside the unit will usually run for about 13 to 15 minutes so the majority of the run time is at the slower speeds. Today it was 90 and very humid. Right now it is 70 and the humidity is 91%. The inside temperature is 73 and the humidity is 40% so it is comfortable.

I have one unit in a 3 story house and run the fan continuously in the winter to circulate the air through the EAC. In the summer circulating the air when the unit is off will return the removed moisture back into the house so I use the AUTO setting during AC season. 350CFM per ton using the one unit with my blower in the basement does not cool a 3 story house well. Been there tried that. May work fine if I had a unit for each floor. 400CFM works well and I think is a bit more efficient.

[markk]

Thanks to all who responded.

I have tried putting the fan to the Auto position rather than On. This had the effect of reducing the humidity level to 49-50% from 60%

When the serviceman comes next week, I will make sure the jumper is installed

I will also discuss the pros / cons of reducing the airflow from 400cfm to 350cfm based on tonnage. I have 2 floors with the air handler in the attic. Will have to check whether he thinks the system would work okay with that airflow and what is more efficient, plus we don't use the system for heat.

As far as my comfort level, I don't do well with humidity. My wife thinks I am crazy. She is fine the way the system works today. I would probably keep the thermostat a little higher, if the humidity level was lower.
BTW, we keep the thermostat at 67 during the winter.

I will let you know how it goes.

Thanks again.

[daverubin]

When Comfort-R is working on a properly sized system (i.e. it runs almost continuously during the very hot days) the system is really great.

I have my T-Stat set for 78 when it is in the high 80s outside and I am very comfortable. At 76 it almost feels chilly.

[mayguy]

I agree. After a day it been running. 76 is chilly,, I bump it up to 78 now..

[dash]

1.) Yes

2.)Make sure they set it up properly.

3.)yes ,setup properly it will reduce the cfms ,whenthe humidity is above the setpoint.

[markk]

FYI
The serviceman was in this week - he did the following
1) Put the jumper in between Y and 0 - for Comfort-R
2) Slowed the blower to 350cfm per ton (air flow is still okay for cooling)
3) Tweaked damper positions (reduced some airflow - not turned off) for most upstairs registers to force more air downstairs. Thermostat is located upstairs - 1 zone Upstairs was always 2 degrees cooler than downstairs.

Earlier this week was hot (90's) and humid - Thermostat was set at 73, temp variation was 1 degree (of 73) between floors and about 52% Rel Humidity with running the fan continuous. I know the humidity level would be lower if I had the fan set to Auto, but this is a big improvement over last week when the same settings would left me with 60-65% humidity. Run time was also increased.

Thanks Again!

[edbrown]

You can also have a humidistat installed to work with the AC.

It is set to keep the blower in the lower comfort R range to increase DEhumidification.

Set it at 40RH and if the RH in the house is above the blower will run at lower speed

This is per my trane rep and I have not tried this YET!


ed

[newhomeboston]

edbrown,
I have a similar problem with my newly installed trane...the hvac sub my builder used doesn't usually install trane so could you explain to me a little more about how connecting a thermostat with rh% on it would be able to control the trane? thanks.

[edbrown]

You can also have a humidistat installed to work with the AC.

It is set to keep the blower in the lower comfort R range to increase DEhumidification.

Set it at 40RH and if the RH in the house is above the blower will run at lower speed

This is per my trane rep and I have not tried this YET!


ed

[newhomeboston]

I think I found a good thermostat for this model...Trane's don't seem to control humidity. Does anyone know if I can have my tech install the Carrier Thermidistat which will control blower speed and humidity by operating the blower on a 20% lower CFM mode and drop the temp by 3 degrees to dehumidify when it needs it? Will it match up? Thanks.

[dash]

Originally posted by newhomeboston
I think I found a good thermostat for this model...Trane's don't seem to control humidity. Does anyone know if I can have my tech install the Carrier Thermidistat which will control blower speed and humidity by operating the blower on a 20% lower CFM mode and drop the temp by 3 degrees to dehumidify when it needs it? Will it match up? Thanks.

It's been posted here that it can be done.I'd do a search or post a new thread ,asking the question.