This article documents measurements of temperature and relative humidity (RH) over 10 days prior to implementing the fan solution to provide a baseline for designing the Fan controlled by humidity sensor.
A RC-4HC datalogger was used to collect temperature and RH measurements over 10 days which included a range of late winter weather, some rain, some fine clear days. The logger was located at 1.5m above floor level in the shed in a relatively clear spot in the middle of the area..
Above is a chart of temperature and RH. The daily RH peaks are typically between 08:00 and 09:30, and pretty much coincide with the minimum observed temperature. There is clearly a lag from outside temperature which would tend to be minimum a few hours earlier, and a lower minimum (there were plenty of frosty days in the sample set).
Above is the RH chart alone with expanded scale.
The total time where RH approaches condensing conditions is relatively small, but occurs on quite a few days.
The original design criteria of setpoint=70%, differential=10%, alarm=90%, and minimum run time of 1h seem ok, but in the light of the measurements I am inclined to revise it to setpoint=75%, differential=5%, alarm=90%.
Above, the revised EEPROM contents for the new criteria.
A trial will be conducted with the RH controlled fan and similar measurements taken along with visual observation of evidence of condensing.
- Duffy, O. 2012. Generic heating / cooling controller. http://owenduffy.net/module/hcctl/index.htm.