Gas Appliances – Preparing for Heating Season Part 1
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Most systems in Florida use 80% open combustion furnaces, which is different than other parts of the country that use 90%+ high-efficiency or condensing gas furnaces.
The main tools we use with gas appliances include a combustible gas leak detector (to find leaks), combustion analyzer (to test the flue gases for commissioning), manometer (to adjust gas pressure at the gas valve, also used to measure static pressure), and low-level CO monitor (for personal safety). Since we typically have metal flues in our market, drilling a hole into the flue for combustion analysis is difficult; we may alternatively stick the probe into the outlet of the flue. Low-level CO monitors measure ambient carbon monoxide levels (NOT carbon dioxide / CO2) to protect HVAC professionals when they work.
The top skills you will need to work on gas appliances are carrying out a thorough visual inspection, examining the surrounding areas (not just a furnace), using a manometer to measure gas pressure (on either a standard or Gemini gas valve), using and selling low-level CO monitors, and using a combustible gas leak detector to find gas leaks.
The gas furnace sequence of operation begins with a W call from the thermostat, which prompts the board to confirm that the pressure switch is open. If the pressure switch is closed, the inducer fan will start, which leads to the pressure switch closing. The board will confirm that the safety circuit is closed, which is an ongoing process, before the ignition sequence begins. The gas valve then opens to allow natural gas to come through, and then a flame should propagate. From there, the flame rod (or flame rectifier) will prove the flame. (The furnace must be well grounded, and the rod must be clean and immersed in flame.) The blower turns on as the final step in the sequence of operation.
Topics covered in this video include:
- Uses of tools like combustion analyzers, personal CO monitors, and gas leak detectors
- Caps and leaking gas lines
- Common issues to look out for, including gas line leaks, corrosion, improper burner alignment, improper combustion air, etc.
- The importance of thorough visual inspections on gas appliances
- Some gas pool heater practices
- Practical skills like setting gas pressure, checking for ambient CO, and leak testing
- An in-depth look at each step of the gas furnace sequence of operation
- Silicon carbide vs. silicon nitride ignitors (for HSI modules)
- Flame rectification
- Signs of problems like scorching or heat damage
- What really causes back drafting and CO spillage
Above all, it is important to be attentive to potential safety issues, protect the client, and use opportunities to suggest upgrades that keep the customer safe.