US 20060174560 A1
A multi-zone HVAC system, including: (a) a hollow curb to be mounted to a building roof, (b) a hollow base mounted on or in the curb, the base having a paratition thereacross; (c) a hollow working unit mounted on the base, the working unit containing a cooling coil, a fan, and a heater so that return air from the building can pass through the curb and base to be heated or cooled in the working unit and then directed through the base and curb into the building, the portion of the base below the working unit having height of less than 24 inches.
1. A multi-zone HVAC system, comprising: (a) a hollow curb to be mounted to a building roof; (b) a hollow base mounted on or in the curb, the base having a paratition thereacross; (c) a hollow working unit mounted on the base, the working unit containing a cooling coil, a fan, and a heater so that return air from the building can pass through the curb and base to be heated or cooled in the working unit and then directed through the base and curb into the building, the portion of the base below the working unit having height of less than 24 inches.
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This application claims priority to U.S. Provisional Patent Application Ser. No. 60/646,346 filed Jan. 24, 2005. The instant invention is in the field of Heating Ventilating Air Conditioning (HVAC) systems.
Roof mounted multi-zone HVAC systems for larger buildings typically blend outside air with building return air, then pass the blended air through an air filter and a cooling coil, then pass the air through a fan, then through a heater, then through a multi-zone damper system so that the air stream is split to flow to a plurality of zones to be heated or cooled in the building. When an older constant airflow volume system needed replacement, it could be retrofitted to the more energy efficient variable airflow volume configuration or the older system could be completely replaced with a new variable airflow volume system. Retrofitting eliminates costly reconstruction, preserves roofing integrity, eliminates field sheet metal work and reduces installation time. However, maintenance and repair of retrofitted systems is more problematic than maintenance and repair of a new variable airflow volume system because many of the components of the retrofitted system are too high for a repairman to reach from the roof deck. Thus, there is a need for a retrofitted multi-zone HVAC system, the components of which are positioned within reach of a repairman standing on the roof deck.
The instant invention is a solution to the above-stated problem. More specifically, the instant invention is a multi-zone HVAC system, comprising: (a) a hollow curb to be mounted to a building roof; (b) a hollow base mounted on or in the curb, the base having a paratition thereacross; (c) a hollow working unit mounted on the base, the working unit containing a cooling coil, a fan, and a heater so that return air from the building can pass through the curb and base to be heated or cooled in the working unit and then directed through the base and curb into the building, the portion of the base below the working unit having height of less than 24 inches.
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Five units (SF-1, SF-2, SF-3, SF-4 and SF-5) are built having the following specifications:
208 VAC 3 Phase 60 Hz Electric Supply
25 Ton Refrigeration Capacity
Variable Volume and Variable Temperature Zoned Control System
10,000 CFM Nominal Air Flow Capacity
400 MBH Input Main Gas Heat
2″ Throw Away Filters
Single Enthalpy Economizer /w Rain Hood
Unit Mounted Disconnect Switch
Barometric Relief Damper—Field Installed
Specific Features: Item SF-1, SF-2, SF-3
Specific Features: Item SF-4
Specific Features: Item SF-5
General Package—The unit cabinet is constructed of G90 galvanized steel, with exterior surfaces coated with a paint finish, certified at 750 hours salt spray test per ASTM-B117 standards. Indoor conditioned air sections are insulated with a minimum of ½ thick insulation, foil faced on the air side. Insulation to be fastened with rigid fasteners. Cabinet panels are removable or hinged for servicing and maintenance. Unit wiring is numbered and/or color coded. Cooling performance is rated in accordance with DOE and ARI test procedures. Unit is manufactured using UL listed components and wired to meet or exceed the NEC.
25 Ton Refrigeration Capacity—The unit is manufactured with scroll compressors, internally protected with internal high-pressure relief and over temperature protection. The compressors have internal spring isolation and sound muffling to minimize vibration and noise. External isolation on a dedicated independent mounting system further reduces noise and vibration. Refrigerant coils shall have aluminum plate fins mechanically bonded to seamless internally enhanced copper tubes with all joints brazed. Evaporator and condenser coils are of the direct expansion—draw through design. Refrigerant circuits are equipped with: Balanced port thermostatic expansion valves with independent circuit feed systems; a filter drier/strainer shall be present to eliminate any moisture or foreign matter; accessible service gage connections on both suction and discharge lines to charge, evacuate, and measure refrigerant pressure during any necessary servicing or troubleshooting, without loosing charge.
Variable Volume and Variable Temperature Zoned Control System—The unit controls provide control of system duct static pressure and support space temperature control in up to 18 separate zones per roof top unit (RTU). The Zoning RTU Controller coordinates the temperature needs of all connected zones and control the HVAC equipment and duct static pressure accordingly. The system functions include separate control of heating/cooling stages or modulating heating/cooling, system fan, economizer, and bypass damper. Individual zone damper controllers modulate open and closed based on the zone temperature versus setpoint and the temperature of the RTU discharge air (heating or cooling). The controller has configurable inputs and outputs as follows: 8 digital inputs, 8 analog inputs, 8 digital outputs and 6 analog outputs.
Specific control functions include: individual setpoint for duct static pressure in tenths of an inch water column; modulating (4-20 mA) or floating (relay open and close signals) control of system bypass damper to control duct static pressure. For floating control, the controller selects the floating bypass actuator motor speed from 30 to 1200 seconds; the system has a bypass default position used for system start up or duct pressure sensor failure with a range of 0 to 100%. Intermittent or continuous fan operation in the occupied mode; proportional plus Integral (PI) control of modulating heating and cooling valves, or up to four stages of heating or cooling; individual programmable minimum on and off times and individual interstage times for heating and cooling; outdoor air temperature are used to provide a programmable mechanical cooling lockout or mechanical heating lockout with a 2 degree F. differential.
A discharge air temperature sensor is used as an input to the heating and cooling control loops and to provide discharge low limit control and discharge high limit control. Control of the unit economizer is accomplished by interfacing with a packaged economizer system or by floating or modulating control of the economizer damper actuators. Three options of enabling the economizer: from a digital input such as dry bulb changeover, single enthalpy changeover or differential enthalpy changeover; outdoor Air Temperature; outdoor Air Enthalpy; Demand Control Ventilation (CO2) are provided as an option. A 2-10 vdc CO2 sensor is mounted in the return air duct or a selected zone. The controller continuously compares the CO2 level against the CO2 setpoint. If the measured value exceeds the setpoint, the controller increases the outdoor damper position to let more outdoor fresh air in.
Programmable space temperature setpoints and comfort ranges for each zone for the occupied mode are optionally available. If the space temperature wall module has a setpoint knob, the setpoint knob high and low limits are configurable. An occupied setpoint deadband between heating and cooling is configurable between 0 to 20 degrees F.
Unoccupied heating and cooling setpoints for each zone are optionally available. Each zone has the following individual configurable options: damper minimum position; damper maximum position; stages of zone reheat or floating reheat; zone fan; reheat damper position; unoccupied zone override selectable from 0 to 1440 minutes. Bypass of unoccupied mode for each individual zone is initiated by a pushbutton digital input in the zone. Up to 3 occupied and unoccupied schedules per day are optionally available. Holiday programming is also optionally available. Zone priority High or Normal or none (up to 5 high priority zones) is optionally programmable for enhanced control strategies.
10,000 CFM Nominal Air Flow Capacity—The unit fan is a belt drive assembly and included a variable pitch pulley. The job site selected brake horse power (BHP) should not exceed the unit motor's rated horsepower, plus service factor. The fan wheel is a double inlet type with forward curved blades, dynamically balanced to operate throughout the entire range of operation. The bearings of this portion of the unit are are sealed and permanently lubricated.
400 MBH Input Main Gas Heat—This portion of the unit is designed with induced draft combustion with post purge logic and energy saving direct spark ignition, redundant main gas valve. The ventor wheel is constructed of stainless steel for corrosion resistance. The heat exchanger is a tubular type, constructed of T1-40 aluminized steel for corrosion resistance and allowing minimum mixed air temperature of 25° F. Burners are of the inshot type, constructed of aluminum coated steel and containing air mixture adjustments. All gas piping enters the unit at a single point. An integrated control board provides timed control of evaporator fan functioning and burner ignition.
The heating section of the unit is provided with the following minimum protection: primary and auxiliary high-temperature limit switches; induced draft motor sensor; flame roll out switch; and flame proving controls. The unit preferably has two independent stages of capacity.
2″ Throw Away Filters—Two inch [50.8 mm] throwaway filters are used in the unit.
Single Enthalpy Economizer /w Rain Hood—An economizer is installed in the unit. The assembly includes: 0-100 percent fully modulating dampers, minimum position setting, preset linkage, wiring harness, and fixed dry bulb control. Changeover from compressor to economizer operation is provided by an internal electronic enthalpy control that feeds input into a basic module. The outdoor opening is covered with a rain hood. Water/Mist eliminator filters are provided. Simultaneous economizer/compressor operation is optionally possible. The damper is set to fully close on a power loss.
Unit Mounted Disconnect Switch—The unit is equipped with a disconnect switch.
Barometric Relief Damper—A field installed barometric relief damper is optionally used on each unit.
In conclusion, while the instant invention has been described above according to its preferred embodiment, it can be modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the instant invention using the general principles disclosed herein. Thus, the instant application is intended to cover such departures from the present disclosure as come within the known or customary practice in the art to which this invention pertains and which fall within the limits of the following claims.