Air Conditioning - Relative humidity question
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ibroussard
07-02-09, 08:57 AM
So it's been two days since I had my complete HVAC system (except the ductwork) replaced with a high-efficiency Lennox system (two stage, variable speed, etc.). The thermostat is the Lennox ComfortSense 7000. The thermostat is set to "Basic" for dehumidification mode, which I read to mean that the A/C will continue to try to dehumidify the air until it matches the RH setpoint (50%).
I have an Oregon Scientific WMR100 "weather station" that I use to track indoor temp/RH. I have a wireless temp/RH sensor that is within five feet of the thermostat (at the same height from the floor). With my old system, we kept the temp at 76*. Humidity during the summer was almost always between 45% and 50%. I live in SE Texas 15 miles from the Gulf, so humidity is always high.
With the new system, the ComfortSense has been showing the RH as 54% for the last 24 hours. We have the temp set at 79*, and it seems colder than before. When we set the new system at 76*, both my wife and I thought it was a lot colder than before. The thermostat temperature display and the OS weather station temps are within a degree of each other. However, the really odd thing is that the thermostat shows the RH to be 54% (why not 50%?) while the OS weather station shows it to be 40%. I bought a Radio Shack temp/RH display, and it matches the OS readings within a point.
So...what am I missing here? Why does the thermostat display 54% RH while the other three show 40%? I don't believe the thermostat RH reading because even at 79* in the home, it still seems a little colder than the old system at 76*. I'm thinking that may be the result of the RH really being 5% to 10% less than it was with the old system. Why does the system stop trying to dehumidify at 54% in basic mode instead of 50%? The system seems to be cycling normally. Hard to tell because it is really quite.
I will call my dealer/installer on Monday to discuss, but I wanted to see if I could get some comments/opinions before then.
Thanks,
Ira
I have an Oregon Scientific WMR100 "weather station" that I use to track indoor temp/RH. I have a wireless temp/RH sensor that is within five feet of the thermostat (at the same height from the floor). With my old system, we kept the temp at 76*. Humidity during the summer was almost always between 45% and 50%. I live in SE Texas 15 miles from the Gulf, so humidity is always high.
With the new system, the ComfortSense has been showing the RH as 54% for the last 24 hours. We have the temp set at 79*, and it seems colder than before. When we set the new system at 76*, both my wife and I thought it was a lot colder than before. The thermostat temperature display and the OS weather station temps are within a degree of each other. However, the really odd thing is that the thermostat shows the RH to be 54% (why not 50%?) while the OS weather station shows it to be 40%. I bought a Radio Shack temp/RH display, and it matches the OS readings within a point.
So...what am I missing here? Why does the thermostat display 54% RH while the other three show 40%? I don't believe the thermostat RH reading because even at 79* in the home, it still seems a little colder than the old system at 76*. I'm thinking that may be the result of the RH really being 5% to 10% less than it was with the old system. Why does the system stop trying to dehumidify at 54% in basic mode instead of 50%? The system seems to be cycling normally. Hard to tell because it is really quite.
I will call my dealer/installer on Monday to discuss, but I wanted to see if I could get some comments/opinions before then.
Thanks,
Ira
HVAC RETIRED
07-02-09, 09:36 AM
Well, that comfort level is actually great news, & the humidity is probably lower.
The T-stat humidity gage is only for the indoor humidity, so see how it syncs with the Radio Shack gage indoors.
Perhaps the t-stat can be adjusted to sync with the other humidity stat.
The outdoor humidity varies due to many factors, so weather casts not a reliable test of accuracy.
The T-stat humidity gage is only for the indoor humidity, so see how it syncs with the Radio Shack gage indoors.
Perhaps the t-stat can be adjusted to sync with the other humidity stat.
The outdoor humidity varies due to many factors, so weather casts not a reliable test of accuracy.
ibroussard
07-02-09, 09:57 AM
Well, that comfort level is actually great news, & the humidity is probably lower.
The T-stat humidity gage is only for the indoor humidity, so see how it syncs with the Radio Shack gage indoors.
Perhaps the t-stat can be adjusted to sync with the other humidity stat.
The outdoor humidity varies due to many factors, so weather casts not a reliable test of accuracy.
The OS temp/RH sensors and the Radio Shack device are all inside the house. The OS wireless sensor and Radio Shack device are within five feet of the thermostat. I actually had the OS wireless sensor sitting on the thermostat for a while to see if that made the readings a little closer, but it didn't. All the temperature readings are reasonably close.
The outdoor RH is currently 68% and on its way up.
The T-stat humidity gage is only for the indoor humidity, so see how it syncs with the Radio Shack gage indoors.
Perhaps the t-stat can be adjusted to sync with the other humidity stat.
The outdoor humidity varies due to many factors, so weather casts not a reliable test of accuracy.
The OS temp/RH sensors and the Radio Shack device are all inside the house. The OS wireless sensor and Radio Shack device are within five feet of the thermostat. I actually had the OS wireless sensor sitting on the thermostat for a while to see if that made the readings a little closer, but it didn't. All the temperature readings are reasonably close.
The outdoor RH is currently 68% and on its way up.