Arkansas HVACR NewsMagazine January 2023

HVACR NewsMagazine January 2023

Tech News

condensate backup. In cases where a condensate pump or secondary overflow pan is part of the system, breaking R is usually ideal. Breaking R ensures that the furnace itself will be turned off if there's a condensate leak. Once the system has been running at its max output for about 20 minutes and has stabilized, you can calculate the temperature rise. Just like the delta T in heat pumps and air conditioners, the temperature rise of a furnace is the difference between the supply and return air temperatures. (When you take the supply air temperature, try to do it a few feet away from the furnace so that your reading doesn't pick up additional radiant heat.) On the data tag, you will usually see a range that spans over 30 degrees or so (such as 45-75°F). In general, it's better to be close to the middle of the posted range than close to either end of it. You may have had to install some test ports and shut off valves to do tests and make necessary adjustments. Now is the time to make sure that you leave the system the way you found it. 18. Plug all test ports in the ductwork where you may have taken readings. 19. Verify that all gas pressure test ports are sealed. 20. Remember to turn the gas cock and gas valve back on. 17. Calculate the temperature rise. Teardown from testing

15. Do your combustion analysis.

The combustion analysis will tell you about your excess air and carbon monoxide content. Most importantly, you can tell if a system is a safety risk based on the combustion analysis results. You'll want to do combustion analysis for each cell under the draft hood, as you want to test the undiluted flue gas. Acceptable results will generally be 31-91% excess air with as little CO as possible (under 100 ppm CO air-free).

16. Gather all of your electrical measurements.

Check to make sure that the low-voltage circuit to the thermostat is doing everything it should be doing. Remember, there should be 24v of electrical potential between the thermostat and circuit board at the furnace. If you have a high-efficiency furnace, check to make sure that the float switch is wired to break R (or sometimes Y) in the case of a