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Douglas
Douglas, HVAC Technician
Category: HVAC
Satisfied Customers: 3089
Experience:  Manufacture Rep for Major Brand, Technical Trainer, NATE
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HAVE 2008 TRANE A/C UNIT (4TXCC037BC3HCAA) ON FORCED AIR SYSTEM

Customer Question

HAVE 2008 TRANE A/C UNIT (4TXCC037BC3HCAA) ON FORCED AIR SYSTEM WITH CONTROL THERM OSTAT(TC803AS32DAA) FROM THE TIME IT WAS INSTALLED WE'RE NOT ABLE TO GET HUMIDITY DOWN BELOW 50% THE CONTROL SETUP IS SET TO 40% BUT WE HAVE NEVER. ORIGINAL DEALER TECHS WERE BAFFLED(SO THEY SAID) MADE CALLS TO PLANT SO WE WERE LEFT WITH SETTING TEMP SO LOW THAT A/C RAN AND RAN ALTHOUGH TEMP WOULD DROP TO 65 DEGREES THE "COLD" AIR WAS DAMP! yuck! THE TECHS FROM THAT OUTFIT WERE OLDER AND BY THERE OWN ADMISSIONTRAINED BUT NOT COMFORTABLE WITH NEWER TECH AND COULD NOT GET TWO STAGE OPERATION TO FUNCTION. THAT BIT OF INFORMATION i.e LOWER SPEED REMOVES MORE MOISTURE CAME TO US BY WAT OF A NON TRANE HEATING COOLING SERVICE GUY WHO TRIED HIS BEST WITH REPEATED CALL TO MFG SUPPORT. MY AREA IS RURAL AND FINDING CERTIFIED FACTORY TRAINED FIELD TECHS IS DIFFICULT. I COULD USE SOME INSIGHTS/TEST/SOLUTIONS THAT WOULD BE PASSED ONTO YOUNGER/ELECTONICALLY INCLINED GUY THATTOLD US ABOUT 2 STAGE BUT WAS UNBLE TO GET DETAILS. AHVE AT IT!
Submitted: 1 year ago.
Category: HVAC
Expert:  gotoman for ac replied 1 year ago.
Russ here. Welcome. I am here to help. Please do not rate until you are satisfied with answer. Always available for follow up questions. Do you have a two stage cooling system. What size is the home? Russ
Customer: replied 1 year ago.
Its 0845 pm just got here home can we resume 2morrow about 0900?
Customer: replied 1 year ago.
Was told by 2nd tech that it was and that by using both stages 3 ton or 1 1/2 would cool then dehumidify maybe not in that order---- might be the other way house is about 2700 sf
Expert:  gotoman for ac replied 1 year ago.
Depending on location that is a small unit for 2700 square feet. Being a two stage unit it should run mostly on low speed. Your humidity should not be a problem.. It may run a long time but that is the way it is designed. Make sure it is running on 1st stage. The way the thermostat works is that it will back temp up 3 degrees to make compressor run longer. Have you had the Factory Service Rep check system. Russ
Customer: replied 1 year ago.
(Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from yo. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Expert:  gotoman for ac replied 1 year ago.
I will opt out for other Experts. Russ
Expert:  Douglas replied 1 year ago.
Hi, I'm Douglas and I am here to help you resolve problems with your heating and cooling equipment.
Let me address a couple points and we'll go from there.
Humidity is not controlled directly, that is to say it is a byproduct of the cooling, and cannot be a cycle of its own. In other words cooling must be on to dehumidify.
The thermostat's humidity setting, depending on the model can address humidity in a couple ways, some will simply "over cool" that is to say if there is a call for dehumidification and a call for cooling, it can force the cooling to stay on below the set point by a couple degrees. This is passive at best. Another way, again depending on the control, it can slow the blower speed by as much as 15%. This will in turn slow the air through the coil, dropping the coil temperature and extracting a little more moisture. Both require decent run times of the cooling.
Next, I will try to explain Relative humidity. This is the amount of moisture relative to the air temperature. Cold air has less capacity to hold moisture than does warmer air. The relative humidity is going to be higher with cold air than warm considering the same grains of moisture in the air.
so lets look at a couple expamples....
Lets say its 73 degrees in your home at 50% RH. In this example there are 60.64 grains of moisture per pound of air...
So lets cool that air without removing grains of moisture to say 68 degrees. 68 degrees with 60.64 grains of moisture is an RH of 59.27%. That's almost a 10% increase in RH. What happens when you attempt to drive the temperature down to lower the humidity, is often times the RH doesn't go down and you net a cold clammy environment.
Again, the thermostat is limited because its just a switch. A true dehumidifier cools the air with a cold coil and pulls moisture from the air, it then reheats the air so as not to change the temperature. HVAC systems do not do this. In hotter weather when the system is on for longer times, it will remove moisture better than short bursts found in mild weather.
Some two stage systems result in longer run times, but that's not always a given to remove humidity because the coil may not be as effective at removing moisture when on 1st stage
Customer: replied 1 year ago.
(Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from yo. Let me know if you need more information, or send me the service offer(s) so we can proceed.