Sizing Equipment

We often get asked, “What size furnace/AC do I need?” The answer is not as simple as just knowing the square footage. There is a lot that goes into figuring out the right size.

So, what information is needed to figure out the right size? First, we recommend you use the Manual J sizing program. Second, you will need to know some key points.

  • House/building square footage      •  People load
  • Number and size of windows          • Additional load (lights, computers etc.)
  • Outside exposures 
                            • Unconditioned Spaces
  • Amount of insulation throughout the house • Weather info for the area
  • Number and type of doors 
              • Solar Gain
  • Amount of infiltration air 

               • Ventilation
  • Which way the house faces 
             • Humidity

This may seem like a lot of info in order to size equipment, but figuring out the design load is very important. If the system is too large, it can have a very short run time, may not humidify or de-humidify correctly, and the system will be inefficient. If it is too small, it may never satisfy the load of the building, which leads to being uncomfortable, and it is also inefficient. Either way will reduce the life of the equipment. Guessing the size is never the answer. Size the system the right way and keep your customers comfortable and happy!

Jeff Rosenblum
Technical Support
17 Years Industry Experience
Cell (330) 962-2491
jrosenblum@famous-supply.com

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