Arkansas HVACR NewsMagazine January 2024

HVACR NewsMagazine January 2024

Tech News

of the fitting around its perimeter. A concentric exhaust kit is essentially a pipe inside of a pipe, so only one hole is needed in the home. The functionality is very similar to a flush mount kit but takes up less wall space. Concentrics can be used in both horizontal and vertical applications, while flush mount kits are designed for horizontal only use. Speaking of exhaust venting, it’s important to note its location. While a roof mount location might be more susceptible to freezing, a wall mount may be in an area that gets covered in snow. A flue opening next to the condensing unit can cause corrosion of the condensing coil. The vent termination should be installed away from places where people might congregate, such as a back porch or walkway, when possible. If the flue pipe is in an unconditioned space, such as a vented crawl space or an unconditioned attic, it may need to be insulated or even need heat tape applied. Again, check with the manufacturer’s installation guide for the specific requirements. When the gas valve opens, the inlet pressure shouldn’t drop below the manufacturer's rated inlet pressure, but it can definitely drop. Ultimately, that pressure drop shouldn’t be a problem unless it causes the outlet pressure to drop. If there is a significant drop, we can rule out a possible problem with the gas valve by running multiple gas appliances. If the pressure drops below the rated output pressure, then we can be confident that the issue is in the piping or the gas regulator, not the appliance. Gas Pressure

CO Sources

AHRI Guideline X (available for free download on the AHRI website) tells us where to take CO readings (and unacceptable CO thresholds) before it’s necessary to look for cracks in the heat exchanger. Even before we start looking at the appliance, before we go through the five steps laid out in Guideline X, we can start looking for CO in the home. If we see CO on our personal monitors, we’ll want to rule out sources like a backdrafting water heater, car exhaust in a nearby garage, or even the occupants’ lifestyle choices (like smoking). And, for the 5,000th time, please invest in a personal low-level CO monitor to protect yourself. (Let your customers know about the benefits of low-level CO detection, too.)

Flame Rectification

Flame rods are small parts that play a vital role in furnaces. For them to work as intended, they need to be kept clean, and the system needs to be properly grounded.

Flame Rods: Clean or Replace?

It’s best to measure the DC microamp signal before deciding to clean or replace the flame rod. If the signal is weak (usually less than 1.5 microamps), then we can take a closer look at the flame rod. Most dirty flame rods that don’t show signs of damage (cracks or even melting) can be cleaned and put back into service. It’s best to use steel wool to clean these, not sandpaper or a grinder. If you still don’t read an acceptable signal after cleaning the flame rod, then replacing it would be the next logical step.