Refrigeration – Processes – Circulating external gas
Reexamination Certificate
1998-06-15
2001-04-24
Wayner, William (Department: 3744)
Refrigeration
Processes
Circulating external gas
C062S176600, C236S04400R, C126S113000
Reexamination Certificate
active
06220039
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to humidity control within an enclosed environment, such as homes and offices. More particularly, this invention relates to a method of controlling humidity within an enclosed environment utilizing dewpoint to control humidity control equipment and thereby change the humidity within the enclosed environment.
BACKGROUND OF THE INVENTION
As shown in
FIG. 1
, a common approach to humidity control in homes and buildings in many parts of the country, such as in the Midwestern United States, is to mount a humidistat
10
on a return air duct
12
at the furnace
14
. This is done, in many instances, in order to simplify the installation of the humidity control equipment. A humidistat is a conventional device that measures humidity and which controls humidification equipment associated with the home or building.
It has been previously thought that a duct mounted sensor provides a good average measure of the relative humidity level in the home or building. However, in many instances the temperature and the relative humidity percentage (%RH) in the duct is different from the temperature and %RH in the living/working space(s) of the home/building. The humidity sensor, which may be a nylon element or electronic sensor, associated with the humidistat, senses the %RH of the air in the duct at the temperature in the duct. This will cause an error in the control point if the temperature and humidity in the living/working space is different from that in the duct.
For example, if the temperature in the living/working space is 72° F. and the furnace is located in an unfinished basement, which is generally cooler that the rest of the building, it would not be uncommon for the temperature in the duct to be substantially lower than the temperature in the living/working space, such as 65° F. or lower. Thus, if the control is set to 40% RH, the actual humidity level in the living/working space would only be 31%.
Further, the periodic cycling of the circulation fan associated with the furnace causes temperature and humidity fluctuations within the duct. During periods when the fan is not running and the air is not moving through the return air duct, it would not be uncommon for the temperature in the duct to be five to ten degrees higher or lower that the temperature in the living space. This temperature difference would change the relative humidity by as much as 16%RH. Thus, a humidity control relying upon the sensing of temperature or humidity within the duct would be inaccurate due to the variation of temperature and humidity within the duct due to fan cycling.
In addition, during periods when the thermostat of the space is set back a large amount, for instance from about 72° F. to about 60° F., the humidity level within the space will not be adequately controlled to achieve a comfortable level for the set temperature.
Although the %RH and temperature may temporarily fluctuate, the dew-point temperature, which is a function of %RH and temperature, remains relatively constant. Thus, the dew-point temperature within the living/working space would be generally equal to the dew-point temperature within the return air duct, regardless of the temperature and humidity differences between the two locations. Therefore, it would be desirable to be able to control humidification equipment based upon dew-point temperature, thereby providing more accurate control of the humidification equipment and reduce unnecessary operation thereof.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method of controlling the humidity level within an enclosed space based upon the actual dew-point temperature and a desired dew-point temperature within the enclosed space.
It is another object of the present invention to provide a method of controlling the humidity level within an enclosed space which eliminates control errors and unnecessary operation of humidity control equipment due to temperature differences and temperature fluctuations, as well as allowing for increased flexibility in designing the humidity control system.
These and other objects are achieved by the present invention which provides a method of controlling humidity within a space, where the space communicates with humidity control equipment. The method comprises determining a dew-point temperature within the space, and comparing the dew-point temperature to a predetermined desired dew-point temperature. The humidity control equipment is then controlled based upon the difference between the dew-point temperature and the predetermined desired dew-point temperature.
The humidity control equipment preferably comprises humidification equipment, which is cycled when the dew-point temperature is less than the predetermined desired dew-point temperature.
Further, the dew-point temperature can be determined by sensing the temperature and humidity within the space, or sensing the temperature and humidity within a duct, such as a return air duct. Further, the dew-point temperature can be determined by sensing the temperature and humidity, either in the space or in the duct, after a predetermined amount of cycle time of a circulation fan has elapsed.
A variety of additional advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed.
REFERENCES:
patent: 3965690 (1976-06-01), Berryhill
patent: 5309725 (1994-05-01), Cayce
patent: 5469707 (1995-11-01), Dadachanji
patent: 5752389 (1998-05-01), Harper
Kensok Timothy J.
Meyer Jeffrey R.
Honeywell International , Inc.
Leonard Robert B.
Wayner William
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