Winter Airflow

Technicians often hear how critical airflow is in the cooling season, but we sometimes forget that it is just as important in heating as well. Just as poor airflow can be a major source of problems in the cooling season, poor airflow in the heating season can cause inefficient operation, high utility cost, and system failures.

Gas and Oil Furnaces
Gas and oil furnaces will operate with a higher than normal temperature rise if the airflow through the furnace is inadequate. While the air leaving the registers will be toasty, this can actually result in less heat being delivered into the house. The limit switch on a furnace with inadequate airflow will typically cycle the burners on and off  - reducing the amount of heat being produced. The cycling causes poorer operating efficiency, increasing the cost of operating the furnace.

Electric Strips
With electric furnaces and strip heaters, poor airflow will eventually result in open fusible links, bad thermal limits, and open heat strips. Like the gas and oil furnaces, the thermal limits may cycle the strips on and off, reducing the amount of heat.

Heat Pumps
Heat pumps with poor indoor airflow will operate at excessive head pressures because the indoor coil is the condenser in the heating cycle. This reduces system capacity by increasing the compression ratio while the compressor is operating.  Eventually, the compressor will cut off on the high pressure switch. Usually, the high pressure switch will need to be manually reset, meaning no compressor heat until the service tech arrives. Systems without a high pressure switch will shut off on the compressor internal overload. Once that happens, the compressor may not come back on for a couple of hours. Either way, the compressor is taking a beating and the system is using more electricity to produce less heat.

So if you run into furnaces that are cycling on the limit, electric strips with open fusible links, or heat pumps with tripped high pressure switches – check out the system airflow. Remember those are all symptoms – not the root cause. Fix the cause of the problem – poor airflow.

Short Refrigerant Cylnders

Recently Mr. Simmons, one of our air conditioning instructors at Athens Technical College, noted that a new cylinder of refrigerant felt light compared to the others. A quick check with a scale confirmed his suspicion – the “30 lb” cylinder only weighed 22 lbs including the cylinder and outer cardboard packaging. However, it had never been used. The plastic seal was still intact.  It made me wonder if there were other cylinders that we have used and did not catch. We checked a few others, and it seemed that one cylinder was the only “short” cylinder. Obviously, a cylinder that holds 30 lbs of refrigerant should weigh more than 30 lbs. How much more should it weigh? Generally, the whole package including the box should weigh around 36 lbs. The empty DOT 39 cylinder weighs around 5 lbs and the box weighs approximately 1 lb. I don’t know if our experience is unique, or if it is common for refrigerant cylinders to be short, but I will most certainly be checking from now on. I recommend that you weigh your cylinders before opening the seal to make sure you are getting what you are paying for. A great deal on refrigerant is not a great deal if they don’t actually give you the full amount you are paying for. In our case, I called the company that we purchased the refrigerant from and they quickly replaced the cylinder with a full one. I weighed it to make sure.

Where Are You Headed?

Where are you headed? With the new year, many people ponder what their new year’s resolution should be. One suggestion would be to determine a goal, lay out a plan to reach that goal, and then start working towards it. I read that the legendary quarterback Archie Manning encouraged his sons to write down their goals. Peyton Manning writes his on notecards. I don’t know what was on the cards, but having specific goals and working towards them seems to have worked pretty well for the Mannings. Sometimes students get discouraged by the length of many HVACR programs. The simple truth is nobody can make you a successful technician, or anything else for that matter, in a couple of weeks. The only person that can really make you successful is you. So let me ask you, what are you planning for the next couple of years? Time will pass whether or not you work towards a goal. So where will you be in two years – graduating from a program of study and embarking on a new career, or will you be exactly where you are today?