On 7/17/2015 8:17 AM, trader_4 wrote:
On Thursday, July 16, 2015 at 9:23:47 PM UTC-4, J Burns wrote:
On 7/16/15 7:32 PM, Rebel1 wrote:



One thing I'm missing is the humidity connection. The thermostat
responds only to temperature, so why does humidity affect run time?

The output temperature can't be below the output dew point. The
evaporator has to soak up a lot more heat to bring the dew point down a
degree (condensing moisture) than to bring dry air down a degree.

I monitor the output with a thermometer probe in the vent nearest the
evaporator. It won't cool the air as many degrees when the air in the
house is humid. It is making me more comfortable by removing humidity,
but it will take longer to cool the thermostat to the shutoff point.

A common problem happens most nights here in central Florida, 20 miles
from the Gulf. During the evening, the outside temperature drops so the
a/c doesn't run as often. At the same time, outside humidity increases
and the house becomes mildly uncomfortable. At 6:30 am, it not unusual
for the outside temp to be 75 and the humidity to be 93%.

Some mornings, the indoor temperature is great, but it's very humid.
That's uncomfortable and can cause caked salt, caked sugar, and mildew.
I may turn down the thermostat to run the AC a little.

I find that just running the system for 20 mins or so will
take enough humidity out so that it feels a lot more comfortable.
During that time, the temp reading may not even move down one
degree.

Very good point. I have a Honeywell that has a humidity setting. It
allows the AC to run, actually overrun in order to try to achieve better
humidity. And because of what you just said, it can do it with only
minor temperature change. That's very important where I live because
the temp is usually cooler but, because of the rich forestation and lots
of streams, the humidity is high. I have a 2 stage compressor and it
usually only runs on stage one. In fact, it just turned on now at 8:30
AM; the set point is 77 it currently reads 74 inside. The humidity is
51%. Outside it is 68 degrees but humidity is 91%. That thermostat is a
great product, at least for my area.