Arkansas HVACR NewsMagazine March 2021

S tate, National, Chapter News Tech News

3. Refrigerant Leaks : See #1 for the most common places to find refrigerant leaks. Improperly made and improperly tightened flares seem to account for a large majority of the refrigerant leaks. How do I know if the machine is low on refrigerant? Good question. While superheat and subcooling can’t tell you the whole story, don’t discount the data you can gather from it. Look in the manual and determine how the machine’s EEVs are being controlled (see the above explanation on how target superheat and target subcooling is achieved). Once you have established that, it is possible to determine whether you are low or not. I will typically run the machine in full heat or full cool (whichever the conditions allow) then observe what the superheat is doing. Most machines seem to run between 4-10 degrees of suction superheat in both heating and cooling mode. Remember that in heating mode, the big line leaving the unit is actually discharge gas (so please don’t call it the suction line, because it isn’t). You need to take your pipe temperature exiting the outdoor coil to see what the suction superheat is. Once you’ve established that it is low, the best practice is to pull the entire charge, pressure test, evacuate, and recharge. If a flare is “loose,” please don’t tighten it. Take it apart and remake it; it only takes a few minutes. You save more time by remaking it early than responding to a callback when it leaks again.

flare (using an orbital flaring tool with clutch), checking it with a flare gauge, and tightening it to the proper torque settings are the keys to avoid this from happening. Expansion and contraction put the flare under a huge amount of stress changing between modes. See Bryan’s tech tip for more info. https://www.hvacrschool.com/m aking-flare-quick-tips/ 2. Communication Problems : Communication problems can stem from any number of things. Hit the basics first. Make sure your wiring terminations are correct, as most use a 1, 2, 3 configuration. Ensure any external safety circuit wiring, like a condensate overflow switch, is wired properly, drains are clear, and condensate pumps are in working order. Generally speaking, most manufacturers use the third wire and one of the other high voltage conductors as a traveler wire (or common if you want to look at it that way). You can check between either 1-3 or 2-3 (again, this depends on the manufacturer; refer to the manufacturer for specs). You will typically look for a fluctuating DC voltage signal from 30-100 VDC. If you remove the third wire from the outdoor unit and check for VDC coming from the outdoor unit and the indoor unit, you could narrow your work by seeing if there is one voltage that is not fluctuating. Continue to narrow your work until you can identify the issue or the failed component.