A Direct Gas-Fired Air-Handling Unit AHU may be used as a primary or secondary source to warmth a building area. When used for this application, a room thermostat controls unit outlet air temperature.
On a call for warmth, a space-heating unit will provide air on the desired room temperature. An airhandler can also be designed to boom outlet temperature while room temperature is low. A duct stat or probe at the opening of the unit prevents outlet temperatures from exceeding the most allowable cost.
When a unit blower runs continuously, room air is monitored and the opening air temperature is modulated to keep the temperature.
Systems are typically designed for either Space Heating or for Make-Up Air use. However, popular Make-up Air Units may be provided with a room thermostat that video display units indoor minimum set factor, a sign is sent to the unit to override outlet temperature set factor and turn the unit to full fire. When minimum room temperature is happy, unit returns to outlet air temperature control mode.
Return Air Units are a layout that includes a damper to deliver room air lower back into the unit. These re-circulate indoor air thru a unit with a minimal of outdoor air delivered. This kind of unit is capable of provide air motion for indoor comfort and reduced temperature stratification, however with at the least warmth added to the building.
Manufacturers of direct fuel-fired makeup air gadget must show that their device will “adapt” thru its complete running variety to within five% of laboratory measured out of doors airflow. This has been a substantial undertaking. Many manufacturers have tried to use a few form of outside air damper function indication as a manner to show the amount of out of doors airflow.
All go back air must be brought in downstream of the burner and no longer recirculated thru the burner. This is to save you buildup of waste merchandise from the combustion process inside the constructing. It additionally prevents contaminants originating in the building surroundings from being surpassed via the direct fire burners. The combustion of unknown contaminants may be a serious Safety or Indoor Air Quality problemArticle Submission, and so must be avoided.