From inside (document excerpt):
Product Data ® 58MXA Deluxe 4-Way Multipoise Fixed-Capacity Direct-Vent Condensing Gas Furnace Series 131 Input Capacities: 40,000 thru 138,000 Btuh 4-Way Multipoise Design Allows More Applications. The model 58MXA is a must for your product line. This high-efficiency furnace allows more applications with its reliable 4-way multipoise design. The model 58MXA is available in 12 heat/airflow combinations and with the 4-way multipoise design can be installed in upflow, downflow, or horizontal positions covering up to 48 different applications.
With the exception of the 140 size unit, all 58MXA models can be installed in a manufactured (mobile) home when the optional kit is used. The furnace is factory configured for upflow application. This versatile unit utilizes hot surface ignition (HSI) which ignites the burners directly. HSI eliminates gas waste that typical continuous-pilot designs can bring. Hot surface ignition provides reliable start-up and operation. Take a look at the control center on model 58MXA. Control of ignition, inducer, and blower operation is all handled in 1 central printed circuit board. The status indicator on the control signals when a fault has occurred and identifies where the problem is. This, along with the component test feature, makes the 58MXA one of the easiest gas furnaces to troubleshoot. High efficiency is achieved by maximizing heat transfer. The model 58MXA uses 100% outdoor air for combustion in a sealed-combustion system. The result is energy-saving efficiency, 92% Annual Fuel Utilization Efficiency (AFUE) on all models except the 140 size, and reduced operational noise. The model 58MXA is 1 of the quietest furnaces in the industry. A unique feature of this unit is the patented polypropylene-laminated Form 58MXA-6PD ® ® Carrier Corporation heat exchanger. This secondary heat exchanger ensures that all available heat is properly transferred to the airstream and throughout the home. Using the exclusive flow-through design, the secondary heat exchanger reduces the pressure drop in the furnace which leads to lower electrical usage, an important part of this unit’s efficiency. Carrier heat exchangers are backed by a Limited Lifetime Warranty. (See Warranties section for details.) When we put it all together, the model 58MXA combines quality and design to bring high efficiency and comfort. You will enjoy the versatility and ease of installation of this unit. The model 58MXA is equipped for either left- or right-side connections. Blower speeds are easily adjustable with speed-taps conveniently located on the control center. An updated, more efficient inducer allows for more use of 2-in. vent and combustion-air piping, keeping installation costs low. As with other Carrier furnaces, this model is designed to work as a part of the total home comfort system which includes elements for cooling, air cleaning, humidification, ventilation, and zoning. Certifications — The 58MXA units are A.G.A. and C.G.A. design certified for use with natural and propane gases. The furnace is factory-shipped for use with natural gas. An A.G.A./C.G.A. listed gas conversion kit is required to convert furnace for use with propane gas. The efficiency is GAMA efficiency rating certified. The 58MXA meets California Air Quality Management District emission requirements.