I can't remember how long ago or from who I heard this reference, I can only assume Bryan Orr of the HVAC School. The ABC of heating and air is Airflow Before Charging. This article is going to expand on that concept and help you understand if your getting the appropriate service and being charged for the right repair.
In a typical air to air cooling/heat pump we move air over two different coils to exchange temperature. These coils are the outdoor coil (condenser coil) and the indoor coil (evaporator coil). The temperature and the volume of air moving over these coils not only dictates the capacity of the equipment, but drastically effects the refrigerant density and state. What does that mean? When we as technicians look at a running system to determine the refrigerant operation and level we are looking for the physical state and temperature of the refrigerant. Refrigerant exist in two states in a typical system and that is liquid and gas. The state is a reflection of the amount of heat being absorbed and rejected by the refrigerant as it passes through these coils and air is being moved over the coil. You have to be familiar with that to understand where this is going. Basically know that without the designed volume of air in the system, the refrigerant level and operation becomes irrelevant.
Let's say it's summer time and your ac isn't performing properly so you call a service company. The technician tells you that the system is low on charge and that you need refrigerant added. We need to stop right there and ask some good questions such as; "have you checked to ensure I have good airflow over the coils?". That's because a system with low indoor airflow will give very similar symptoms and readings as a system that is low on refrigerant. A few tell tell signs that we as technicians look for when diagnosing a low refrigerant charge is overall low refrigerant pressure (volume), but most importantly high superheat. Superheat being the amount of heat picked up in the indoor coil by the warmer air from the home circulating over that coil. This is the one metric that many techs fail to check as it's the defining difference between low refrigerant level and low indoor airflow. Superheat on every system is going to vary, but an average rule of thumb is that the superheat should be above 6 degrees and below 14 degrees. Ask your tech what the superheat was, if your superheat is already below 6 degrees, adding refrigerant is not going to fix the issue and actually it's going to cause you more problems.
The best part of being thorough especially when it comes to the issue of airflow, typically speaking low airflow problems ARE A CHEAPER FIX THAN LOW REFRIGERANT REPAIRS. We all like saving money right? If your tech has not been to the air handler, they did not visually check airflow and if they can't tell you and show you the superheat, they didn't thoroughly investigate the issue prior to diagnosing. A visual inspection of the indoor coil and blower assembly is necessary to ensure that air can be moved at the right volume, also it's important to go ahead and make sure that the system has an appropriate blower motor installed. I've seen some crazy stuff out there to include the wrong blower motor which causes a bunch of problems.
We have to check airflow before charging a system or we can cause way more damage than you can imagine. I'll tell you a scarier situation that often plays out over something like this that could be a very easy fix. The summer of 2022 I got a call from a panicked homeowner who tells me that she had another company out earlier that day who told her that her system was low on charge, given the age it wasn't worth fixing and that she needed a new system. This is a very young military family that didn't have the money for that at the moment and with summer kicking into high gear she was becoming concerned. I went out to their home and immediately checked the refrigerant side operation. I found the refrigerant operation initially suggesting a low charge, except I noticed the superheat was 3 degrees. I asked her if she noticed low indoor airflow and she wasn't sure. I went inside and found an extremely dirty air filter (they didn't know about changing air filters because they were young new homeowners) as well as I found the settings for the blower motor to be set on a lower speed than what I would have recommended for that application. I pulled the filter, adjusted the blower motor, and the system was working perfect. I told her to get a new filter immediately and to let us know how the system was doing over the next couple of days. 2 Years later now and that client is a routine customer of mine, they still have the same unit in there home, and the only repair she has needed since is a drain line cleaning. Someone almost convinced her that she needed to spend thousands of dollars because she had a dirty air filter ($5 from walmart?). It pays to be involved and have quality service.
As always I hope this helps someone at some point and as always, thank you for taking the time to read this blog.
Kenneth Casebier
Comments