re: running dehumidifier with central a/c, yes or no?
19 jul 2004
>> stormy weather wrote:
>> >if your intention is to control the humidity, then yes run your
>> >de-humidifiers. the trade off is more money. the heat added by the
>> >de-humidifiers will cause the a/c to run longer...
the heat is bad news, in summertime.
>>...just let the ac filter get dirty.
to reduce the airflow over the cold side...
>well, it is wrong, but filters isn't the answer. (although they may
>help with the constant volume problem.)
i disagree. (what's the "constant volume problem"?)
>i don't think his intention is to control humidity, i think it is to
we might use night air for cooling, with ac mainly for dehumidification.
>...normal household ac does not control humidity. it controls temperature,
>and reduces humidity by happy thermodynamic accident.
it's no accident. if c cfm of 70 f air at 50% rh with pa = 0.374" hg enters
a box with a 20 ft^2 40 f coil and mixes well before leaving, we might have
something like this (viewed in a fixed font):
70 ---www-------www--- 40
t = exit air temp = 40+30c/(c+40).
cfm t rh@70f = 100e^(17.863-9621/(t+460))/(2x0.374)
100 61.4 50%
50 56.7 50%
20 50.0 49% |
10 46.0 42% | dirty filter
5 43.3 38% |
>one way to get better control is to use a humidistat and add reheat.
reheat is bad news, in summertime.
>a dehumidifier could sort of function that way. i think you would want
>to change your basic ac parameters if you wanted to do that though.
we might add a freezestat...