If you are making a refrigerant circuit repair, weighing out and weighing in makes perfect sense, especially since microchannel condensers and scroll compressors make pumping down less viable anyway. But there are many cases where you just need to check the charge to make sure the system is working properly, and in these cases, weighing in and out is just plain silly.
When the liquid temperature (liquidus) of the alloy (rod or wire) you are using is 840°F or lower, the process is considered soldering. Brazing occurs when the liquid temperature of the alloy is above 840°.
For the quick, cut to the chase version, turning the adjustment on the bottom of an adjustable valve clockwise equals higher superheat while turning it counterclockwise equals lower superheat. However, before you start messing with the adjustment, I suggest you read on.
Before we convert temperature scales, let’s take a step back and think about what temperature is in the first place.
Temperature is proportional to the average kinetic energy of the random microscopic motions of the constituent microscopic particles, such as electrons, atoms, and molecules.
I live in Central Florida, and while it can get pretty hot in the Summer we also tend to get afternoon thunderstorms that come and go in a flash. I have been connecting gauges, checking charges and even pulling vacuums in the rain as well as under umbrellas or cardboard boxes most of my career and only recently did I stop to think if this was a good idea.
I see techs in the field get the most frustrated when they have a low-voltage short they can’t seem to locate. The challenge techs face with low voltage diagnosis is a combination of poor process and some root misunderstanding about what they are looking for.
Dew point is one example of a very useful measurement to understand, design for and test for in an HVAC/R system. Take an evaporator coil, do you know how to calculate the exact temperature at which that evaporator coil will start to condense moisture? can you tell the exact temperature at which a surface inside of a space will start to condensate and possibly grow mold? These are both cases where a basic understanding of a psychrometric diagram can help a technician.
We’ve installed and serviced a lot of ductless systems (often called mini splits) over the years. They are great in several applications and offer many benefits, including high efficiency and no duct losses.
Refrigerant circuit restrictions can be common things like a plugged filter drier or a restricted metering device. They can also be more difficult to diagnose and exotic issues like a kinked liquid line, blocked evaporator feeder tube, or a compressor connected improperly with a discharge line full of solder (I’ve seen it).
To start with, let’s talk about the symptoms.