Heating system with humidity control for avoiding water condensation on interior window surfaces

• US 5,651,498 A
• Filed: 07/21/1995
• Issued: 07/29/1997
• Est. Priority Date: 07/21/1995
• Status: Expired due to Term

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Original Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Inventors: Meyer, Jeffrey R., Tinsley, T. Michael
• Primary Examiner(s): Wayner, William E.
• Application Number:
  US08/505,571
• Time in Patent Office: 739 Days
• Field of Search: 236/44 C, 236/44 A, 236/91 C, 165/20, 165/21, 165/223, 374/28
• US Class Current: 236/44.00C
• CPC Class Codes: B01F 23/21311 for spraying the liquid radially by centrifugal force
• CPC Class Codes: F24F 11/30 for purposes related to the operation of the system, e.g. for safety or monitoring
• CPC Class Codes: F24F 11/63 Electronic processing
• CPC Class Codes: F24F 11/70 Control systems characterised by their outputs; Constructional details thereof
• CPC Class Codes: F24F 2013/221 to avoid the formation of condensate, e.g. dew
• CPC Class Codes: F24F 2110/20 Humidity

Abstract

A space heating system with a controllable air humidification capability calculates a theoretical value for the temperature of the interior surface of the space'"'"'s windows. The system controls humidity in the space to a level just below that at which water will condense on the window surfaces.

Claims

1. A controller for apparatus for controlling both temperature and humidity within an enclosed space requiring addition of heat and humidity to maintain comfort, to preselected temperature and humidity set points respectively, said apparatus including a) a plenum;

b) a return air duct connected to provide air from the space to the plenum;

c) a heated air duct connected to allow air flow from the plenum to the space;

d) a fan within the plenum for extracting air from the space through the return air duct and forcing the extracted air through the conditioned air duct into the space;

e) a heating unit operating responsive to a first value of a heating active signal to heat air flowing through the plenum and not operating responsive to a second value of the heating active signal, and having a heat exchanger within the plenum;

f) an air humidification unit operating responsive to a first value of a humidification active signal to humidify air flowing through the plenum and not operating responsive to a second value of the humidification active signal;

g) an indoor temperature sensor within the space supplying an indoor temperature signal encoding a value indicative of the internal temperature of the space;

h) a humidity sensor within the space providing a humidity signal encoding a value indicative of the relative humidity for the air within the space;

i) an outdoor temperature sensor providing an outdoor temperature signal encoding a value indicative of the outdoor temperature; and

j) a humidity set point generator providing a humidity set point signal encoding a humidity set point value, wherein the controller comprises;

I) a window temperature calculator receiving the outdoor temperature signal and the indoor temperature signal, and providing a window temperature signal encoding a window temperature value functionally depending on the temperatures encoded in the outdoor temperature signal and the indoor temperature signal;

II) a dew point temperature calculator receiving the indoor temperature signal and the humidity signal and providing a dew point temperature signal encoding a dew point temperature value for the space functionally depending on the temperature encoded in the indoor temperature signal and on the value encoded in the humidity signal; and

III) a humidification unit controller receiving the window temperature signal from the window temperature calculator and the dew point temperature signal from the dew point temperature calculator, and responsive to the dew point temperature exceeding the window temperature, providing a humidification active signal having the first value to the air humidification unit.

2. The controller of claim 1, further comprising a frost index register in which may be recorded a frost index value indicative of the heat transfer characteristics of a window defining a part of the periphery of the enclosed space, said frost index register issuing a frost index signal encoding the frost index value, and wherein the window temperature calculator comprises means receiving the frost index signal, the outdoor temperature signal, and the indoor temperature signal, and providing a window temperature signal functionally depending on the values encoded in the outdoor temperature signal, the indoor temperature signal, and the frost index signal.

3. The controller of claim 2, wherein the frost index register records a frost index encoded in a frost index input signal, and wherein the controller further comprises manual input means for receiving a frost index value from a human user.

4. The controller of claim 1, further comprising a frost index register in which may be recorded a frost index value indicative of the heat transfer characteristics of a window defining a part of the periphery of the enclosed space, said frost index register issuing a frost index signal encoding the frost index value, and wherein the window temperature calculator comprises means receiving the frost index signal, the outdoor temperature signal, and the indoor temperature signal, and providing a window temperature signal functionally depending on the product of the frost index and the difference between the temperatures encoded in the indoor temperature signal and the outdoor temperature signal.

5. The apparatus of claim 4, wherein the dew point temperature calculator includes means for encoding in the dew point temperature signal, a dew point temperature value functionally depending on the product of the value encoded in the humidity signal and the square of the value encoded in the indoor temperature signal.

6. The apparatus of claim 1, wherein the dew point temperature calculator includes means for encoding in the dew point temperature signal, a dew point temperature value functionally depending on the product of the value encoded in the humidity signal and the square of the value encoded in the indoor temperature signal.

7. A controller for apparatus for controlling both temperature and humidity within an enclosed space requiring addition of heat and humidity to maintain comfort, to preselected temperature and humidity set points respectively, said apparatus including a) a plenum;

b) a return air duct connected to provide air from the space to the plenum;

c) a heated air duct connected to allow air flow from the plenum to the space;

d) a fan within the plenum for extracting air from the space through the return air duct and forcing the extracted air through the conditioned air duct into the space;

e) a heating unit operating responsive to a first value of a heating active signal to heat air flowing through the plenum and not operating responsive to a second value of the heating active signal, and having a heat exchanger within the plenum;

f) an air humidification unit operating responsive to a first value of a humidification active signal to humidify air flowing through the plenum and not operating responsive to a second value of the humidification active signal;

g) an indoor temperature sensor within the space supplying an indoor temperature signal encoding a value indicative of the internal temperature of the space;

h) a humidity sensor within the space providing a humidity signal encoding a value indicative of the relative humidity for the air within the space;

i) an outdoor temperature sensor providing an outdoor temperature signal encoding a value indicative of the outdoor temperature;

j) a humidity set point generator providing a humidity set point signal encoding a humidity set point value;

k) an inside temperature set point source providing an temperature set point signal encoding a set point temperature value; and

l) a heating demand detector receiving the indoor temperature signal and the indoor temperature set point signal and providing a heating active signal having a first value responsive to a preselected relationship between the set point temperature value and the indoor temperature value, and a second value otherwise, wherein the controller comprises;

I) a window temperature calculator receiving the outdoor temperature signal and the indoor temperature signal, and providing a window temperature signal encoding a window temperature value functionally depending on the temperatures encoded in the outdoor temperature signal and the indoor temperature signal;

II) a dew point temperature calculator receiving the indoor temperature signal and the humidity signal and providing a dew point temperature signal encoding a dew point temperature value for the space functionally depending on the temperature encoded in the indoor temperature signal and on the value encoded in the humidity signal;

III) first decision means receiving the heating active signal for responsive to the first value thereof providing a condition signal having a first value responsive the heating active signal changing from its first to its second value;

IV) second decision means receiving the window temperature signal and the dew point temperature signal for responsive to the dew point temperature value exceeding the window temperature value providing a condition signal having a second value and leaving the present value unchanged otherwise; and

V) third decision means receiving the condition signal for providing the humidification active signal with its first value responsive to the first value of the condition flag and the humidification active signal with its second value responsive to the second value of the condition flag.

8. The apparatus of claim 7, wherein the third decision means further comprises fourth decision means receiving the heating active signal, for providing the humidification active signal responsive to the first value of the heating active signal.