Most forget this crucial area when doing heating equipment check-ups. Are you?

Temp Rise

As the summer heat slowly begins to fade, the cool breeze of fall will meander into the area. Many of us will begin to shift our focus to heating equipment check-ups. These can be a bit monotonous in the early days of fall, but the most important time to check a heating system is before it endures regular run time through the winter.

A crucial area that is often overlooked on a gas furnace is the temperature rise. The temperature rise across a gas furnace is like ensuring that your vehicle has plenty of coolant in the radiator. Furnaces, much like engines, do not like to run hot!

A good temperature rise will come down to two factors:

  1. The amount of fuel burned.
  2. The amount of air moved.

Every manufacturer lists the acceptable range of temperature rise across the gas furnace. This will usually be in a range close to 30-60 degrees. The ideal “sweet spot” is the middle of the given range. Maintaining a good middle range temperature rise provides the following benefits:

  • Good, warm air flowing from the ducts.
  • Good fuel burning efficiency.
  • Proper operating temperature of the furnace.
  • Good even cycling.

Setting the Temperature Rise

  1. Find the nominal gas pressure listed on the furnace’s data plate. A classic example would be 3.5″ w/c for natural gas.
  2. Set the airflow to closely resemble the cooling airflow.
  3. Cycle the furnace for roughly 15 minutes to allow temperatures to stabilize.
  4. Take a temperature reading in both the supply and return duct trunks. Ensure that the supply reading is taken “out of line of sight” from the heat exchanger.
  5. Once the temperature rise is known, make adjustments to either outlet gas pressure or airflow to set it to your desired rise.
  6. Take care to keep adjustments within manufacturer specifications.

Author: Matt Rutland

Matt is our Director of Technical Services and has been with East Coast Metal Distributors since March 2016. He is devoted husband and father to three boys in the Charlotte, NC area. He stumbled into HVAC completely by accident and is now climbing within the industry to be the best he can be.