Patent Publication Number: US-9416997-B1

Title: Method for providing positive pressure to an interior of a positive pressure facility

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application is a Continuation in Part which claims priority to co-pending U.S. patent application Ser. No. 13/236,375 filed on Sep. 19, 2011, entitled “MODULAR HVAC SYSTEM FOR PROVIDING POSITIVE PRESSURE TO AN INTERIOR OF A POSITIVE PRESSURE FACILITY.” This reference is hereby incorporated in its entirety. 
    
    
     FIELD 
     The present embodiments generally relate to a method for providing positive pressure to an interior of a positive pressure facility using a modular heating, ventilation, and air conditioning (HVAC) system. 
     BACKGROUND 
     A need exists for a method for providing positive pressure to an interior of a positive pressure facility using a prefabricated HVAC system that can provide a pressure differential between an interior of a building and an exterior of a building, such as a portable building. 
     A need exists for an HVAC method with a high reliability that provides warnings through a human machine interface. 
     A further need exists for a method using an easy to use and install HVAC system. 
     The present embodiments meet these needs. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The detailed description will be better understood in conjunction with the accompanying drawings as follows: 
         FIG. 1  depicts an installed HVAC system on a positive pressure facility usable with the method. 
         FIG. 2  depicts a detail of a condenser compartment of the HVAC system. 
         FIG. 3  depicts a detail of an evaporator motor compartment and compressor compartment. 
         FIG. 4  depicts a detail of an evaporator compartment, a return air compartment, and a heater compartment. 
         FIG. 5  depicts a view of an enclosure extension with a human machine interface. 
         FIG. 6  depicts a diagram of an electrical compartment. 
         FIG. 7  depicts a diagram of refrigerant flow. 
         FIG. 8  depicts a home display screen of the human machine interface. 
         FIG. 9  depicts a health display screen of the human machine interface. 
         FIG. 10  depicts a control display screen of the human machine interface. 
         FIG. 11  depicts a set points display screen of the human machine interface. 
         FIG. 12  depicts an embodiment of a real-time values screen of the human machine interface. 
         FIG. 13  depicts an embodiment of a process control unit. 
         FIGS. 14A and 14B  depict an embodiment of the method for providing positive pressure. 
     
    
    
     The present embodiments are detailed below with reference to the listed Figures. 
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Before explaining the present method in detail, it is to be understood that the method is not limited to the particular embodiments and that it can be practiced or carried out in various ways. 
     The present embodiments generally relate to a method for providing positive pressure to an interior of a positive pressure facility using a modular HVAC system. 
     The positive pressure provided can range from about 0.05 water column inches to about 0.25 water column inches, and can be less than or greater than an air pressure surrounding the building of the positive pressure facility. 
     The method can include securing an enclosure of an HVAC system to the positive pressure facility. The enclosure can be made of metal. The enclosure can be secured to an exterior of the positive pressure facility. 
     The method can include lifting and moving the enclosure with a forklift. The enclosure can have a base, which can have two openings. The two openings of the base can allow prongs of the forklift to engage with the base to move the enclosure. 
     The method can include lifting and moving the enclosure with a crane. The enclosure can have lifting eyes for lifting the enclosure as a one piece unit with the crane. 
     The method can include receiving surrounding air in a condenser compartment disposed within the enclosure. The condenser compartment can be mounted to the base. The condenser compartment can be a metal frame, such as an aluminum frame. 
     The condenser compartment can contain an air inlet for receiving the surrounding air. An air inlet grill can be disposed over the air inlet. The air inlet grill can be a frame with metal slats to allow the surrounding air to flow into the air inlet. 
     A condenser coil can be disposed in the condenser compartment. For example, the condenser coil can be one manufactured by Heat Craft of Grenada, Miss. 
     The method can include using an air venturi mounted to the condenser coil to pull the surrounding air through the air inlet grill, which can cover a side of the condenser compartment. 
     The air venturi can function to pull the air across the entire condenser coil, rather than just along the direction of flow from fans within the condenser compartment. 
     By pulling the surrounding air into the condenser compartment using the venturi effect and fans, rather than pushing the surrounding air, energy can be saved and more cooling can be provided due to a lower coefficient of friction. 
     Also, pulling the surrounding air from the outside to the inside allows the build-up of dirt and other foreign objects from the surrounding air to be visible on the outside of the HVAC system. As such, the method can include visually inspecting the HVAC system without having to dismantle portions of the HVAC system to inspect the interior portions. 
     A condenser motor can be disposed in the condenser compartment. The condenser motor can be connected with a wall, such as a front wall, of the condenser compartment. The condenser motor can be a 0.5 to 3 HP motor, such as one made by WEG Electric Corporation of Duluth, Ga. 
     A condenser motor bracket can support the condenser motor in the enclosure. 
     The method can include using one or more fan blades which can be mounted to the condenser motor to pull in the surrounding air. The fan blades can operate in conjunction with the air venturi to pull the surrounding air into the condenser compartment. 
     An evaporator motor compartment can be connected adjacent the condenser compartment. 
     The evaporator motor compartment can contain at least one evaporator motor. In one or more embodiments, two or more evaporator motors can be mounted in the evaporator motor compartment. Each evaporator motor can be connected with a power supply, which can be disposed outside of the evaporator motor compartment. 
     Each evaporator motor can be a 0.5 to 3 HP motor, such as one made by WEG Electric Corporation. Each evaporator motor can run on A/C current. 
     An evaporator compartment can be mounted to the evaporator motor compartment. 
     The evaporator compartment can have at least one evaporator fan for each evaporator motor. For example, if the HVAC system includes two evaporator motors, the HVAC system can include two evaporator fans. 
     Examples of evaporator fans usable in the method can include a tri-blade aluminum fan made by Lau of Dayton, Ohio. 
     The method can include using an evaporator coil mounted in the evaporator compartment to receive a refrigerant and cool fresh air from the fresh air inlet section, thereby forming conditioned air. 
     The method can include evaporator coils, such as those available from Luvata of Wayzata, Minn. 
     The evaporator coils, evaporator fans, and evaporator motors can all be connected with a process control unit and a human machine interface, which can be mounted to a side of the HVAC enclosure. 
     The condenser coil, fan blades, and condenser motor can all be connected with the process control unit and human machine interface. 
     A refrigerant liquid line can connect to each evaporator coil. Refrigerant within the refrigerant liquid line can be R-134A. The method can include maintaining the refrigerant at a pressure of about 280 pounds per square inch gauge (psig) within the refrigerant liquid line. 
     A refrigerant suction line can be connected with the evaporator coil. The temperatures of the refrigerant liquid line and the refrigerant suction line can range from about 40 degrees Fahrenheit to about 120 degrees Fahrenheit. 
     A thermostatic expansion valve can be in the evaporator compartment, such as one made by Parker of Cleveland, Ohio The thermostatic expansion valve can be connected with the refrigerant liquid line. 
     The evaporator compartment can have evaporator compartment insulation attached to inner walls of the evaporator compartment. 
     The method can include draining a condensate produced on the refrigerant liquid line in the evaporator compartment through a drain to allow that condensate to exit the evaporator compartment. The condensate can be water. 
     The evaporator compartment and the evaporator motor compartment can be framed shells, which can be made of sheet metal. 
     A compressor compartment can be disposed adjacent the evaporator motor compartment. 
     The compressor compartment can have a compressor, such as a model ZR40K3E-TFD-230 made by Copeland. 
     The compressor can be mounted on a stand or mounted directly to walls of the compressor compartment and connected between the refrigerant suction line and a refrigerant discharge line. 
     A compressor mount can be used in the compressor compartment to support the compressor. 
     The compressor compartment can also have a compressor heater electrically connected with the compressor. 
     The method can include using a high pressure transducer to sense temperature, which can be connected with the refrigerant discharge line and to the process control unit and human machine interface. 
     The compressor and the compressor heater can be connected with the process control unit and human machine interface as well for centralized control of all the components of the HVAC system. 
     In addition to the high pressure transducer, a low pressure transducer can be connected with the refrigerant suction line. 
     The low pressure transducer and the high pressure transducer can be ones available from Johnson Supply of Austin, Tex. The low pressure transducer and the high pressure transducer can be connected with the process control unit and human machine interface. 
     The compressor compartment can include a shut off valve, which can be connected with the refrigerant suction line. Additionally, a hot gas bypass valve can be connected with the shut off valve. The shut off valve and hot gas bypass valves can be those made by Parker, for example. 
     A refrigerant site glass can be connected with the refrigerant liquid line. The refrigerant site glass can be made by Parker, such as model SA-14S. 
     A refrigerant liquid line dryer can be fluidly connected with the refrigerant site glass. The refrigerant liquid line dryer can be one available from Parker, such as model C-164-S. 
     A refrigerant shut off valve can be connected with the refrigerant liquid line dryer. 
     The method can include flowing fresh air into a fresh air intake section disposed in the enclosure. The fresh air can be flowed from outside of the enclosure into the evaporator compartment. 
     The method can include filtering the fresh air using a filter holder supporting an air filter over the fresh air intake section. 
     In one or more embodiments, the enclosure can include a heater compartment adjacent the compressor compartment. 
     The heater compartment can have at least two fin heaters connected with the power supply. The fin heaters can be 1-2 kilowatt heaters, such as those available from Tamman of Taiwan, and can operate on A/C current. 
     A conditioned air grill can be positioned to separate the heater compartment from the interior of the positive pressure facility. 
     A conditioned air temperature sensor can be mounted in the heater compartment for monitoring the temperature of conditioned air. The conditioned air temperature sensor can be one available from Watlow of St. Louis, Mo. The conditioned air temperature sensor can be in communication with the process control unit and the human machine interface. 
     The heater compartment can include a plurality of resistive temperature detectors. Each resistive temperature detector can be connected with and used to monitor a temperature of one of the fin heaters, and can be in communication with the process control unit and the human machine interface. 
     The heater compartment can include heater compartment insulation. The heater compartment insulation can be mounted within the heater compartment to prevent sweating. The heater compartment insulation can be a closed cell neoprene. 
     The method can include attaching an enclosure extension to the interior of the positive pressure facility and to the enclosure. The enclosure extension can protrude through the exterior to the interior of the positive pressure facility. 
     The enclosure extension can include a return air compartment. The return air compartment can have a return air grill, which can be made of plastic or metal, such as anodized aluminum. 
     The return air compartment can have a return air filter. The return air filter can be made of a pleated washable paper filter, cellulose, or another material. 
     The return air compartment can have a plurality of opposed blade dampers, such as from one blade damper pair to about fifty blade damper pairs. 
     The return air compartment can have a humidistat. The humidistat can detect humidity in percentages ranging from about 0 percent to about 100 percent humidity. 
     The return air compartment can include a return air resistive temperature detector, which can be connected with the process control unit and the human machine interface. 
     The enclosure extension can include an electrical compartment connected with the return air compartment. 
     The electrical compartment can have electrical compartment insulation, which can be closed cell neoprene mounted within the electrical compartment. 
     The electrical compartment can have an electrical control box, such as a model ACSEW 091504 available from Appleton of Rosemont, Ill., for receiving power from the power supply. 
     The electrical control box can include a relay, such as one from ABB of Houston, Tex., for each of the evaporator motor, condenser motor, and compressor. 
     The electrical control box can include a connector, such as one from ABB, for each evaporator motor, and condenser motor. 
     The method can include protecting from overload using an overload protection circuit in the electrical control box, such as one from ABB, for each of the evaporator motor, condenser motor, and compressor. 
     The electrical compartment can have an electrical control box with a back panel to which each relay, connector, and overload protection circuit can be mounted. 
     The method can include preventing explosions using a plurality of explosion resistant seals disposed around conduits that pass from an outside surface of the electrical control box to inside the electrical control box. 
     The method can include controlling power flow through the electrical control box in the electrical compartment using control wiring, a control power transformer connected with the control wiring, a D/C power supply connected with the control power transformer, and control power fuses connected with control power transformer. 
     The method can include conveying power through a junction box from the power supply to the evaporator motor using an evaporator flexible electrical conduit. 
     The method can include conveying power through the junction box from the power supply to the condenser using a condenser flexible electrical conduit. 
     The method can include conveying power through the junction box from the power supply to the compressor and compressor heater using a compressor flexible electrical conduit. 
     The process control unit can be connected with the electrical control box to control electrical flow through the electrical compartment. The process control unit can be an IDEC programmable logic controller (PLC) for example, a model FC5A. 
     In one or more embodiments, the method can include using the human machine interface (HMI) disposed in the enclosure extension to present real-time information and controls to users for monitoring and controlling the HVAC system. 
     The method can include using a pressure transducer to determine differential pressure between a pressure outside the positive pressure facility to the pressure interior of the positive pressure facility. 
     The pressure transducer can be connected with the process control unit. The pressure transducer can be one available from Dwyer of Michigan City, Ind., such as model 668-1. 
     The human machine interface can be used to provide real-time temperature values. The real-time temperature values can include a temperature for the return air, fin heaters, conditioned air, refrigerant discharge line, refrigerant liquid line, and refrigerant suction line, as well as other portions of the HVAC system. 
     The human machine interface can be used to determine and present real-time humidity values, such as a humidity level of the return air. 
     The human machine interface can be used to determine and present real-time building pressure of the positive pressure facility. 
     The human machine interface can be used to present a home control button, which can be initiated by a user to present a home display screen on the display of the human machine interface. 
     The human machine interface can be used to present a control button, which can be initiated by a user to present a control screen on the display of the human machine interface. 
     The human machine interface can be used to present a health control button, which can be initiated by a user to present a health screen on the display of the human machine interface. 
     The human machine interface can be used to present a set points control button, which can be initiated by a user to present a set points screen on the display of the human machine interface. 
     The human machine interface can be used to present a values control button, which can be initiated by a user to present a real-time values screen on the display of the human machine interface. 
     The human machine interface can be used to present a heating, cooling, and dehumidifying indicator, which can indicate that the HVAC system is heating, cooling, dehumidifying, or combinations thereof. For example, the heating, cooling, and dehumidifying indicator can be the color blue to represent cooling. 
     The human machine interface can be used to present an operating indicator. The operating indicator can be of various colors, such as an operating indicator which can be the color green. 
     The operating indicator can be an online indication that the process control unit is operating. A different color can be used to indicate that the unit is off. 
     The human machine interface can be used to present a building pressure “OK” indicator, which can be the color green. The building pressure OK indicator can indicate that the building pressure is within the defined set points. Red could be used if the positive pressure building is outside the set points. 
     The human machine interface can be used to present a system OK alarm, which can indicate that the system is operating properly and can be colored green. The color red can be used to indicate that the system is not operating properly. 
     The human machine interface can be used to present a time, which can include a day of week indication, a month, a day of month, a year indicator, and a time of day. 
     A health screen can be formed using computer instructions in the process control unit linked to the health control button. For example, when a user initiates the health control button the health screen can be presented on a display of the human machine interface. 
     The health screen can present real-time health information. The real-time health information can be updated in various intervals, such as in one to five second intervals. 
     The real-time health information can include a rotation OK, indicating a status of the input power phasing to the system. 
     The real-time health information can include a fire smoke OK, indicating an alarm of the fire or smoke system. 
     The real-time health information can include a gas detection OK, indicating an alarm of the gas detection system in the positive pressure facility. 
     The real-time health information can include a 100 percent recirculate off, indicating the HVAC system is pulling at least a portion of fresh air into the system. 
     The real-time health information can include a condensate level OK, indicating condensate is not in the condensate drain pan. 
     The real-time health information can include a low building temperature OK, indicating whether or not the temperature of the building is above a low temperature set point. 
     The real-time health information can include an indication of high building temperature within first building set point, indicating the building temperature is below a building temperature high set point. 
     The real-time health information can include a high building temperature within second building set point, indicating the building temperature below a second building temperature high set point. 
     The real-time health information can indicate a building pressure OK is above a building pressure set point. 
     The real-time health information can include a humidity OK, indicating that the humidity level of the return air is below a set point. 
     The real-time health information can include a communication OK, indicating portions of the HVAC system are communicating to another HVAC system. 
     The real-time health information can include a redundancy OK indication, which indicates that two or more connected HVAC systems do not have any alarms. 
     The real-time health information can include a stage 1 low refrigerant pressure alarm and a stage 1 high refrigerant pressure alarm. 
     The stage 1 low pressure alarm means a low refrigerant level exists. 
     The stage 1 high pressure alarm means a high refrigerant level exists. 
     The real-time health information can include a stage 1 #1 heater high temperature OK, which indicates that heater 1 is within a set point range. 
     The real-time health information can include a stage 1 #2 heater high temperature OK, which indicates that heater 2 is within a set point range. 
     The real-time health information can include a stage 1 #3 heater high temperature OK, which indicates that heater 3 is within a set point range. 
     The real-time health information can include a stage 2 #1 heater high temperature OK, which indicates that heater 1 is within a set point range. 
     The real-time health information can include a stage 2 #2 heater high temperature OK, which indicates that heater 2 is within a set point range. 
     The real-time health information can include a stage 2 #3 heater high temperature OK, which indicates that heater 3 is within a set point range. 
     The real-time health information can include a compressor malfunction alarm, indicating whether or not the compressor has malfunctioned. 
     The real-time health information can include a compressor amps OK, a condenser amps OK, an evaporator #1 amps OK, and an evaporator #2 amps OK, indicating that amperage being used by the compressor and evaporator motors are within set points. 
     The health screen can also present the home control button, control button, health control button, set points control button, values control button, the heating, cooling, and dehumidifying indicator, operating indicator, building pressure OK indicator, and system OK alarm. 
     The method can include using computer instructions in the process control unit, which can be linked to the control button for presenting on the display real-time control information, which can be updated in one to five second intervals. When the control button is initiated, the process control unit and human machine interface can present a control screen on the display. 
     The real-time control information can include: a first step button for changing a status of the HVAC system from off, to auto, to on; a second step button for changing the status of the modular heating, ventilation, and air conditioning system from on, to auto, to off; the real-time temperature values; real-time humidity values; real-time building pressure; home control button; control button; health control button; the points control button; values control button; and heating, cooling, and dehumidifying indicator. 
     The control screen can also present the operating indicator, the building pressure OK indicator, and the system OK alarm. 
     The method can include using computer instructions to provide real-time set points information. 
     The computer instructions, which can be in the process control unit, can be linked to the set points control button for presenting on the display real-time set points information. 
     The real-time set points information can be updated in one to five second intervals. 
     When a user initiates the set points control button, the human machine interface can present the real-time set points information. 
     The real-time set points information can be log-in information, alarm history information, temperature set points for the positive pressure facility, and humidity set points for the positive pressure facility. 
     The real-time set points information can include low building temperature set points, high building temperature set points, high humidity set points, low pressure alarm delay intervals caused when personnel enter or leave the positive pressure facility, and an update all HVAC button that synchronizes all of the HVAC updates with a single stroke for a given set point. 
     The set points screen can present the home control button, control button, health control button, set points control button, and values control button. 
     The method can include using computer instructions in the process control unit to present instructions for a user to enter a password, cancel, clear, and enter new values in the process control unit. 
     The method can include using computer instructions in the process control unit to provide to the display a plurality of preset values and a meter button in real-time. The plurality of preset values and meter button can provide refrigerant pressure status. 
     The method can include using computer instructions in the process control unit to provide a listing of spare parts to the display for viewing by a user. 
     Turning now to the Figures,  FIG. 1  depicts a perspective view of an installed heating, ventilation, and air conditioning (HVAC) system  6  usable with the method having an enclosure  10 . 
     The HVAC system  6 , which can be modular, can be installed at a positive pressure facility  7  for providing positive pressure to an interior of the positive pressure facility  7 . 
     In one or more embodiments, the HVAC system  6  can be configured to maintain positive pressure in the interior of the positive pressure facility  7  ranging from about 0.05 water column in inches to about 0.25 water column in inches. 
     The enclosure  10  can be secured to an exterior  8  of the positive pressure facility  7 . For example, the enclosure  10  can be bolted or otherwise affixed to a portion of the exterior  8 . 
     The enclosure  10  can include a base  14 . The base  14  can have a first base opening  24  and a second base opening  25 , which can both be configured to receive prongs of a forklift, allowing the enclosure  10  to be easily transported and installed. 
     The enclosure  10  can include a condenser compartment  16 , which can be mounted to the base  14 . 
     The enclosure  10  can include one or more lifting eyes  142   a  and  142   b . The lifting eyes  142   a  and  142   b  can be configured for lifting the enclosure  10  as a one piece unit, such as by using a crane. 
     The condenser compartment  16  can have an air inlet grill  21 , which can cover a side of the condenser compartment  16 . 
     The condenser compartment  16  can have a condenser coil  18  disposed behind the air inlet grill  21 . 
     A fresh air intake section  90  can be formed in the enclosure  10 . The fresh air intake section  90  can be configured to bring in fresh air  89  from outside of the enclosure  10  into an evaporator compartment of the HVAC system  6 . In operation, the fresh air intake section  90  can bring in the fresh air  89  from outside of the enclosure  10  into the evaporator compartment. 
     The fresh air intake section  90  can have a filter holder  92  for supporting an air filter  94  over the fresh air intake section  90 . 
       FIG. 2  depicts a side view of the enclosure  10  with the lifting eye  142   a  showing a detail view of an interior portion of the condenser compartment  16 . 
     The condenser compartment  16  is shown mounted to the base  14 , and can include an air venturi  20 . 
     The air venturi  20  can be mounted to the condenser coil  18  opposite the air inlet grill  21 . 
     The air venturi  20  can pull the surrounding air  19  through the air inlet grill  21  and across the condenser coil  18  to allow for easy viewing of particulate build up on the air inlet grill  21 ; thereby ensuring that maintenance and cleaning occurs as needed for proper air flow in the HVAC system. 
     The condenser compartment  16  can include a condenser motor  28  connected with an interior portion of a wall  32  of the condenser compartment  16 . For example, a condenser motor bracket  30  can support the condenser motor  28  within the enclosure  10 . 
     Fan blades  22  can be mounted to the condenser motor  28 . 
       FIG. 3  depicts the enclosure  10  showing a detailed view of an evaporator motor compartment  34  and a compressor compartment  67 . The compressor compartment  67  can be connected with the evaporator motor compartment  34 . 
     The evaporator motor compartment  34  can include at least one evaporator motor  36  mounted therein. 
     An evaporator flexible electrical conduit  58  can convey power through a junction box  64  from a power supply to the evaporator motor  36 . 
     A condenser flexible electrical conduit  62  can convey power through the junction box  64  from the power supply to the condenser motor. 
     A compressor flexible electrical conduit  66  can convey power through the junction box  64  from the power supply to the compressor  68 . 
     The compressor  68  can be mounted in the compressor compartment  67 . For example, a compressor mount  72  in the compressor compartment  67  can support the compressor  68 . 
     The compressor  68  can be connected between a refrigerant suction line  48  and a refrigerant discharge line  74 . 
     A low pressure transducer  78  can be in communication with the refrigerant suction line  48 . 
     A high pressure transducer  76  can be in communication with the refrigerant discharge line  74 . 
     A shut off valve  80  can be in communication with the refrigerant suction line  48 , and a hot gas bypass valve  82  can be in communication with the shut off valve  80 . 
     A refrigerant site glass  84  can be in communication with a refrigerant liquid line  46 . 
       FIG. 4  depicts the enclosure  10  showing a detail of the evaporator compartment  38 , the heater compartment  96 , and the return air compartment  106 . 
     The enclosure  10  can be secured to the exterior  8  of the positive pressure facility, and the enclosure extension  12  can extend into the interior of the positive pressure facility. 
     The evaporator compartment  38  can include an evaporator fan  40 , which can be connected with the evaporator motor. 
     The evaporator compartment  38  can include an evaporator coil  42  mounted therein. 
     The evaporator coil  42  can be configured to receive a refrigerant through the refrigerant liquid line  46  to cool the fresh air and form a conditioned air. 
     A refrigerant  50  can then flow from the evaporator coil  42  through the refrigerant suction line  48 . 
     The refrigerant liquid line  46  can be connected with the evaporator coil  42 , and a thermostatic expansion valve  52  can be connected with the refrigerant liquid line  46 . The refrigerant suction line  48  can also be connected with the evaporator coil  42 . 
     Evaporator compartment insulation  54  can be affixed within the evaporator compartment  38 . 
     The evaporator compartment  38  can include a drain  56 , which can be configured to allow a condensate from the evaporator coil  42  to exit the evaporator compartment  38  via the drain  56 . 
     The heater compartment  96  can be disposed adjacent a conditioned air grill  140 . The conditioned air grill  140  can separate the heater compartment  96  from the interior  9  of the positive pressure facility. 
     The conditioned air  99  can flow from the enclosure extension  12  through the conditioned air grill  140 . 
     The heater compartment  96  can include one or more fin heaters  98   a - 98   f . Each fin heater  98   a - 98   f  can be connected with the power supply. 
     The heater compartment  96  can include a conditioned air temperature sensor  100  configured to monitor a temperature of the conditioned air  99  and transmit the monitored temperature to a process control unit. 
     The heater compartment  96  can include a plurality of resistive temperature detectors  102   a - 102   f . Each resistive temperature detector  102   a - 102   f  can be connected with and monitor a temperature of one of the fin heaters  98   a - 98   f  for transmission to the process control unit. 
     Heater compartment insulation  104  can be mounted within the heater compartment  96 . 
     A mechanical thermostat switch  105  can be connected with each of the fin heaters  98   a - 98   f  and in communication with the process control unit. 
     The return air compartment  106  can include a return air grill  108 , a return air filter  110  mounted behind the return air grill  108 . Return air  107  can flow through the return air grill  108  and return air filter  110 . 
     In one or more embodiments, the return air  107  can be mixed with the fresh air to form the conditioned air  99 . Also, a portion of the conditioned air  99  can be re-mixed with the fresh air to form additional conditioned air. 
     The return air compartment  106  can also include a plurality of opposed blade dampers  112 , a humidistat  114  for measuring a humidity of the return air  107  for transmission to the process control unit, and a return air resistive temperature detector  116  for measuring a temperature of the return air  107  for transmission to the process control unit. 
       FIG. 5  depicts a front view of an embodiment of the enclosure extension  12 . 
     The enclosure extension  12  can protrude through the exterior and into the interior of the positive pressure facility, and can attach to the interior. 
     The conditioned air grill  140  can be disposed on the enclosure extension  12  for transmitting conditioned air into the interior. 
     The return air grill  108  can be disposed on the enclosure extension  12  receiving return air from the interior. 
     A human machine interface  144  having a display  179  can be disposed on the enclosure extension  12  for presenting real-time information to users in the interior, and for allowing the users to control one or more functions of the HVAC system. 
     The human machine interface  144  can be connected with or otherwise in communication with the process control unit for receiving data and information therefrom. The human machine interface  144  can be used to control the process control unit for controlling various portions of the HVAC system. 
       FIG. 6  depicts a detail of the electrical compartment  118 , which can be connected with the return air compartment. 
     The electrical compartment  118  can include electrical compartment insulation  120  mounted therein. 
     The electrical compartment  118  can include an electrical control box  124 , which can be configured to receive power from the power supply  60 . 
     The electrical control box  124  can include a relay  125 , a connector  127 , and an overload protection circuit  129 . The relay  125 , connector  127 , and overload protection circuit  129  can operate on the at least one evaporator motor, condenser motor, and compressor. 
     In one or more embodiments, the electrical compartment  118  can have a back panel  122 , and the electrical control box  124  with the relay  125 , connector  127 , and overload protection circuit  129  can be mounted to the back panel  122 . 
     The electrical compartment  118  can include a process control unit  136  connected with the electrical control box  124  for controlling electrical flow through the electrical compartment  118 . 
     The electrical compartment  118  can include a pressure transducer  138  for determining a differential pressure between a pressure outside of the positive pressure facility and a pressure of the interior of the positive pressure facility. The pressure transducer  138  can be connected with the process control unit  136 . 
     The electrical compartment  118  can include control wiring  128  to control power flow through the electrical control box  124 , a control power transformer  130  connected with the control wiring  128 , and a D/C power supply  132  connected with the control power transformer  130  through control power fuses  134 . 
     In one or more embodiments, the electrical control box  124  can have a plurality of explosion resistant seals  126   a - 126   c  disposed on an outside surface of the electrical control box  124 . The explosion resistant seals  126   a - 126   c  can be configured to surround inlet and outlet conduits connecting to the electrical control box  124 . 
       FIG. 7  depicts a diagram of refrigerant flow in the HVAC system. 
     The compressor  68  can be in communication with the condenser coil  18  through the refrigerant discharge line  74 , and a high pressure transducer  76  can be disposed along the refrigerant discharge line  74  between the compressor  68  and condenser coil  18 . 
     The compressor  68  can be in fluid communication with the evaporator coil  42  through a hot gas line  81 . The hot gas line  81  can have a shut off valve  80  and a hot gas bypass valve  82 . 
     Also, the compressor  68  can be in fluid communication with the evaporator coil  42  through the refrigerant suction line  48 . The refrigerant suction line  48  can have a low pressure transducer  78 , a low side service port  79 , and a sensing bulb  53  disposed between the evaporator coil  42  and the compressor  68 . 
     The condenser coil  18  can be in fluid communication with the evaporator coil  42  through the refrigerant liquid line  46 . 
     The refrigerant liquid line  46  can have a refrigerant shut off valve  88  and a refrigerant liquid line dryer  86 . 
     A high side service port  83  can be disposed between the refrigerant liquid line dryer  86  and the refrigerant shut off valve  88  in the refrigerant liquid line  46 . 
     The refrigerant sight glass  84  can be disposed between the refrigerant liquid line dryer  86  and a thermostatic expansion valve  52 . 
     In one or more embodiments, the refrigerant shut off valve  88  can be connected with the hot gas bypass valve  82 . 
     A refrigerant distributer  85  can distribute refrigerant from the refrigerant liquid line  46  into the evaporator coil  42 . 
     An equalizer tube  51  can engage with the hot bypass valve  82 , refrigerant suction line  48 , the thermostatic expansion valve  52 , and the sensing bulb  53  on the refrigerant suction line  48 . 
       FIG. 8  depicts an embodiment of the human machine interface  144  having a display  179  presenting a home display screen for monitoring the HVAC system. 
     The display  179  can be configured to present: real-time temperature values  146 , real-time humidity values  148 , and a real-time building pressure  150 , which can be reported in inches of a water column. 
     The display  179  can be configured to present: a home control button  152 , a control button  153 , a health control button  154 , a set points control button  156 , a values control button  158 , and a heating, cooling, and dehumidifying indicator  160 . The heating, cooling, and dehumidifying indicator  160  can be presented as a color, such as the color blue to represent cooling. 
     The display  179  can be configured to present an operating indicator  162 , which can be presented as the color green to provide an online indication that system is operational. 
     The display  179  can be configured to present a building pressure OK indicator  164  and system OK alarm  166 , which can both also be the color green or another color. 
     The display  179  can be configured to present time  176 , which can include: a day of week  168 , a month  170 , a day of month  172 , a year  174 , and a time of day  177 . 
       FIG. 9  depicts an embodiment of the human machine interface  144  with the display  179  showing a health display screen for monitoring the HVAC system. 
     Health screen computer instructions in the process control unit can cause real-time health information to be presented on the display  179 . The health screen computer instructions can be linked to the health control button  154 . 
     The real-time health information can be updated in one to five second intervals. 
     The real-time health information can include: rotation OK  180 , fire smoke  181 , gas detection OK  182 , 100% recirculate off  183 , condensate level OK  184 , low building temperature OK  185 , high building temperature within a first building set point  186 , and high building temperature within a second building set point  187 . 
     The real-time health information can include: building pressure OK  188 , humidity OK  189 , communication OK  190 , redundancy OK  191 , a stage 1 low refrigerant pressure alarm  192 , a stage 1 high refrigerant pressure alarm  193 , a stage 1 #1 heater high temperature OK  194 , a stage 1 #2 heater high temperature OK  195 , a stage 1 #3 heater high temperature OK  196 , a stage 2 #1 heater high temperature OK  197 , a stage 2 #2 heater high temperature OK  198 , and a stage 2 #3 heater high temperature OK  199 . 
     The real-time health information can include: a compressor malfunction alarm  200 , compressor amps OK  201 , condenser amps OK  202 , evaporator #1 amps OK  203 , an evaporator #2 amps OK  204 , and an alarm reset  205 . 
     The alarm reset  205 , when initiated, can clear all alarms displayed on the display  179 , and can reset all alarms that are inactive. 
     Along with the real-time health information, the display  179  can also present the home control button  152 ; the control button  153 ; the health control button  154 ; the set points control button  156 ; the values control button  158 ; the heating, cooling, and dehumidifying indicator  160 ; the operating indicator  162 ; the building pressure OK indicator  164 ; and the system OK alarm  166 . 
     In operation, the health display screen on the display  179  can provide a visual aid to a user as to what caused an alarm to be initiated. 
       FIG. 10  depicts an embodiment of the human machine interface  144  with the display  179  showing a control display screen for monitoring the HVAC system. 
     Control screen computer instructions stored in the process control unit can cause real-time control information to be presented in the display  179 . The control screen computer instructions can be linked to the control button  153 . 
     The real-time control information can include: a first step button  207  for changing a status of the system from off, to auto, to on; a second step button  208  for changing the status of the system from on, to auto, to off; the real-time temperature values  146 ; the real-time humidity values  148 ; and the real-time building pressure  150  in water column inches. 
     In operation, the first step button  207  can be used to turn the HVAC system on or put the HVAC system into auto mode. When the HVAC system is turned on, rather than in auto mode, the HVAC system can operate in a non-redundant mode. 
     Along with the real-time control information, the display can also present the home control button  152 ; the control button  153 ; the health control button  154 ; the set points control button  156 ; the values control button  158 ; the heating, cooling, and dehumidifying indicator  160 ; the operating indicator  162 ; the building pressure OK indicator  164 ; and the system OK alarm  166 . 
       FIG. 11  depicts an embodiment of the human machine interface  144  with the display  179  showing a set points display screen for monitoring the HVAC system. 
     Set points screen computer instructions in the process control unit can cause real-time set points information to be presented on the display  179 . The set points screen computer instructions can be lined to the set points control button  156 . 
     The real-time set points information can include: a login  210 , an alarm history  212 , a temperature set point for the positive pressure facility  214 , a humidity set point for the positive pressure facility  216 , an alarm set point for a low temperature of the positive pressure facility  218 , an alarm set point for a high temperature of the positive pressure facility  220 , a high humidity set point  222 , and a low pressure alarm delay  224 . The low pressure alarm delay  224  can be initiated when personnel enter or leave the positive pressure facility. 
     The real-time set points information can include an update all heating, ventilation, and air conditioning button  225 , which can synchronize all connected set points with one stroke. 
     Along with the real-time set points information, the display  179  can present: the home control button  152 , the control button  153 , the health control button  154 , the set points control button  156 , and the values control button  158 . 
     In operation, the set points display screen on the display  179  can be used to configure various levels of operation of the HVAC system. For example, the low and high temperatures, pressures, humidity levels, and the like at which alarms are initiated can be inputted using the set points display screen on the display  179 . Also, the time can be set within the set points display screen on the display  179 . 
       FIG. 12  depicts an embodiment of the human machine interface  144  with the display  179  showing a real-time values screen for monitoring the HVAC system. 
     Computer instructions in the process control unit, which can be linked to the values control button  158 , can cause real-time values information to be presented on the display  179 . 
     The real-time values information can include a plurality of preset values  159 . 
     The plurality of preset values  159  can include the building pressure, the fan cycle, the amps being used by the system or portions of the system, measured temperatures of portions of the system, and measured temperatures and pressures of supply air, return air, ambient air, the refrigerant suction line, and the refrigerant liquid line. 
     The real-time values information can include a meter button  161 . The meter button  161 , when initiated, can provide a refrigerant pressure status  163 . 
     The real-time values information can include a listing of spare parts  228 . 
     Along with the real-time values information, the display  179  can present the home control button  152 , control button  153 , health control button  154 , set points control button  156 , and values control button  158 . 
     In operation, the real-time values screen on the display  179  can present the current operating parameters of the HVAC system. 
       FIG. 13  depicts an embodiment of the process control unit  136 . 
     The process control unit  136  can have computer instructions to instruct the process control unit to present real-time health information on the display  178 . 
     The process control unit  136  can have computer instructions to instruct the process control unit to present real-time control information on the display  206 . 
     The process control unit  136  can have computer instructions to instruct the process control unit to present real-time set points information on the display  209 . 
     The process control unit  136  can have computer instructions to instruct the process control unit to present instructions to the user to enter a password into the process control unit, cancel, clear, enter new values into the process control unit, or combinations thereof  226 . 
     The process control unit  136  can have computer instructions to instruct the process control unit  136  to present real-time values information on the display  227 . 
     The process control unit  136  can have computer instructions to instruct the process control unit to present a listing of spare parts on the display  229 . 
     The real-time health information, real-time control information, real-time set points information, and real-time values information can each be updated in one to five second intervals. 
       FIGS. 14A-14B  depict an embodiment of a method for providing positive pressure to an interior of a positive pressure facility using a heating, ventilation, and air conditioning system. 
     The method can include lifting and moving the heating, ventilation, and air conditioning system as a one-piece unit using a crane and lifting eyes on an enclosure of the heating, ventilation, and air conditioning system, as illustrated by box  1000 . 
     The method can include using a forklift to lift and move a base of the enclosure by engaging prongs of the forklift into a first base opening and a second base opening of the base, as illustrated by box  1002 . 
     The method can include securing the enclosure to an exterior of the positive pressure facility, as illustrated by box  1004 . 
     The method can include conveying power from a power supply to the heating, ventilation, and air conditioning system, as illustrated by box  1006 . 
     The method can include providing overload protection to an electrical compartment of the enclosure, as illustrated by box  1008 . 
     The method can include preventing damage from explosions in an electrical control box in the electrical compartment using a plurality of explosion resistant seals, as illustrated by box  1010 . 
     The method can include regulating a flow of electricity in the electrical compartment using control wiring to control power flow through the electrical control box, a control power transformer connected with the control wiring, a D/C power supply connected with the control power transformer, and control power fuses connected with control power transformer, as illustrated by box  1012 . 
     The method can include pulling fresh air from outside of the enclosure into an evaporator compartment and filtering the fresh air to form conditioned air, as illustrated by box  1014 . 
     The method can include transferring the conditioned air from the enclosure to an enclosure extension attached to the interior of the positive pressure facility, as illustrated by box  1016 . 
     The method can include flowing the conditioned air into the interior of the positive pressure facility, as illustrated by box  1018 . 
     The method can include receiving air from the interior of the positive pressure facility into the enclosure extension, as illustrated by box  1020 . 
     The method can include determining a differential pressure between a pressure outside of the positive pressure facility and a pressure of the interior of the positive pressure facility, as illustrated by box  1022 . 
     The method can include maintaining positive pressure in the interior of the positive pressure facility using the determined differential pressure, a process control unit, the conditioned air, and a human machine interface connected with the process control unit, as illustrated by box  1024 . 
     The method can include determining real-time temperature values and presenting the real-time temperature values on a display using the human machine interface connected with the process control unit, as illustrated by box  1026 . 
     The method can include determining real-time humidity values and presenting the real-time humidity values on the display using the human machine interface connected with the process control unit, as illustrated by box  1028 . 
     The method can include determining real-time building pressure and presenting the real-time building pressure on the display using the human machine interface connected with the process control unit, as illustrated by box  1030 . 
     The method can include presenting a home control button, a control button, a health control button, a set points control button, and a values control button on the display using the human machine interface connected with the process control unit, as illustrated by box  1032 . 
     The method can include presenting a heating, cooling, and dehumidifying indicator; an operating indicator; a building pressure OK indicator; a system OK alarm; and a time on the display using the human machine interface connected with the process control unit, as illustrated by box  1034 . 
     The method can include presenting real-time health information on the display when the health control button is initiated, and updating the real-time health information in one to five second intervals, as illustrated by box  1036 . 
     The method can include presenting real-time control information on the display when the control button is initiated, and updating the real-time control information in one to five second intervals, as illustrated by box  1038 . 
     The method can include presenting real-time set points information on the display when the set points control button is initiated, and updating the real-time set points information in one to five second intervals, as illustrated by box  1040 . 
     The method can include presenting instructions onto the display to the user to enter a password into the process control unit, cancel, clear, enter new values into the process control unit, or combinations thereof, as illustrated by box  1042 . 
     The method can include presenting real-time values information on the display when the value control button is initiated, including a plurality of preset values, a listing of spare parts, and a meter button providing a refrigerant pressure status, as illustrated by box  1044 . 
     While these embodiments have been described with emphasis on the embodiments, it should be understood that within the scope of the appended claims, the embodiments might be practiced other than as specifically described herein.