Heated Makeup Air Unit
AssigneeCaptive-Aire Systems, Inc.
InventorsWilliam Brian Griffin, Brandon Charles Wellington
Life of this patent
Estimating the term…
Abstract
A heated air makeup unit comprising a heating chamber with a modulated furnace one or more non-modulated furnaces air temperature control and efficient furnace operation over a wide heating rate range. The utilization of indirect fired furnaces in the heated air makeup unit is disclosed. A control system is included to provide control of heated air temperature to within +/−1 F.° using continuous control of the heating rate of the modulated furnace and stepwise activation and de-activation of the non-modulated furnaces in response to heating demand. A programmed combustion air flow controller programmed to provide optimal airflow for any gas flow in a flow range of a modulating gas valve is provided to assure combustion efficiencies of at least 83%.
Claims16
A heated air makeup unit for heating outside air and directing the outside air into an interior space, the heated air makeup unit comprising:
- a. a housing;
- b. a heating chamber disposed in the housing;
- c. a furnace unit disposed in the housing and including a modulated gas furnace and one or more non-modulated gas furnaces;
- d. wherein each of the one or more non-modulated furnaces is operative to function at a generally constant heating rate and wherein the modulated furnace is operative to function at a varying heating rate;
- e. a combustion air blower and a modulating gas valve associated with the modulated gas furnace, and wherein by controlling the combustion air blower and the modulated gas valve, the heating rate of the modulated furnace can be varied and controlled;
- f. an air inlet for directing air into the heating chamber;
- g. an air outlet for directing heated air from the heating chamber;
- h. wherein air is directed into the air inlet and past the one or more non-modulating furnaces and the modulating furnace where the air is heated;
- i. a control system for controlling the furnace unit, the control system operative to provide coarse control of the furnace unit by selectively activating or deactivating one or more of the non-modulating furnaces, and operative to provide fine control of the furnace unit by varying the heating rate of the modulating furnace, the control system including:
- 1) a speed control unit operatively connected to the combustion air blower associated with the modulated gas furnace for varying the speed of the combustion air blower and varying the flow of combustion air into the modulated gas furnace;
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- 2) a controller having a command signal input for receiving a command signal and for:
- a) actuating and de-actuating the one or more non-modulated gas furnaces;
- b) controlling the modulating gas valve associated with the modulated gas furnace and varying the flow of gas to the modulated gas furnace;
- c) controlling the speed control unit which, in turn, is operative to control and vary the speed of the combustion air blower associated with the modulated gas furnace;
- and
- d) wherein the controller is operative to provide course control of the furnace unit by providing on/off control of the one or more non-modulated gas furnaces and to provide fine control of the furnace unit by controlling the gas modulating valve and combustion air blower associated with the modulating gas furnace.
The heated air makeup unit of claim 5 wherein the controller is programmed to control the flow of gas from the modulating valve to the modulated gas furnace and to control the speed of the combustion air blower so as to generally maintain the combustion efficiency of the modulated gas furnace at approximately 83% or higher.
A method of utilizing a heated air makeup unit to heat outside air and direct the heated air into an interior space, the method comprising:
- a. directing outside air into and through a heating chamber having a modulated gas furnace and one or more non-modulated gas furnaces;
- b. controlling the heating of the air by varying the heating rate of the modulated gas furnace and from time-to-time actuating or deactuating one or more of the non-modulated gas furnaces wherein each of the one or more non-modulated gas furnaces is operative to function at a generally constant heating rate and the modulated gas furnace is operative to function at a varying heating rate;
- c. controlling the heating of the air including directing a control signal to one or more of the non-modulated gas furnaces where the control signal is operative to actuate or deactuating the one or more non-modulated gas furnaces;
- d. controlling the heating of the air further including directing a second control signal from the controller to both a speed control unit and a modulating valve wherein the modulating valve is associated with the modulated gas furnace and the speed control unit is operatively connected to a combustion air blower for controlling the flow of combustion air to the modulated gas furnace such that by varying and controlling the combustion air directed to the modulated gas furnace and varying and controlling the flow of gas passing from the modulating valve to the modulated gas furnace, the heating rate of the modulated gas furnace is controlled;
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- e. wherein the control of the one or more non-modulated furnaces provides coarse heating control and controlling and varying the heating rate of the modulated gas furnace provides fine heating control.
Dependencies are inferred from the claim text.