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Len McCauley
05-09-2012, 12:44 PM
The Dectron that I monitor shows a humidity percentage in the mid thirties. The incoming air from outside is mid seventees. The combination of the pool air and outside air should bring the percentage much higher than thirty in the return air. Is it possible that there is a breach in the return ducts that is pulling in air from the space between ceiling and floor above. I have had the sensor verified with a meter sitting next to it in the plenum.
teddy bear
05-09-2012, 02:00 PM
The Dectron that I monitor shows a humidity percentage in the mid thirties. The incoming air from outside is mid seventees. The combination of the pool air and outside air should bring the percentage much higher than thirty in the return air. Is it possible that there is a breach in the return ducts that is pulling in air from the space between ceiling and floor above. I have had the sensor verified with a meter sitting next to it in the plenum.
You must use outdoor dew points, not outdoor %RH to judge the effect of outdoor air on the resulting mixed air %RH. If equal portions of outdoor air at 32^F, 80%RH, 27^F dew point are mixed with 80^F, 50%RH, 60^F dew point indoor air, resulting in 65^F, 50%RH, 47^F Dew point in the return after mixing. I hope you are not pressurizing the building with make-up air in a cold climate. You should be depressurizing the space to avoid moisture loaded from condensating in the walls of the building.
Regards TB
Len McCauley
05-09-2012, 03:16 PM
Thank you for the advice on the dewpoints. I will need a psychometric chart to fully understand dewpoints and the ratio of the mixtures. The room temp is 35C and the pool is 34C. The outside air of late has been10 to 15 C. There is an exhaust fan pulling air out of the room resulting in a negative pressure.
jpsmith1cm
05-09-2012, 04:43 PM
Dectron James

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