Arkansas HVACR NewsMagazine May 2021

HVACR NewsMagazine May 2021

Tech News

confident that you can recover all the refrigerant and stay within a safe capacity range. Recovery is not a good task for playing the guessing game; it could quickly turn into Russian roulette. A scale will allow you to keep track of what you put into a cylinder and take out of it. The best practice is to use the scale during recovery, too. When you do that, you can observe the weight increase as the refrigerant goes into the tank. If you want the refrigerant to enter the tank as a liquid when there's no dip tube, invert the tank on the scale.

an excellent standard medium for comparisons. One crucial comparison is the measure of specific gravity , which divides a substance's density by the density of water. The refrigerants we use have different densities than water. We can use the specific gravity ratio to determine our capacity using the WC value given. To determine the capacity in terms of a given refrigerant instead of water, you would multiply the specific gravity of a refrigerant at the maximum temperature you'll be exposed to (SG) by WC and add it to the tare weight (TW) to get the total tank weight. It should fit into an equation like this: We don't want 100% capacity because the refrigerants expand under high- temperature conditions. When you increase the temperature in a closed space, you will also increase the pressure; we refer to this as hydrostatic pressure buildup. When you increase the pressure, explosions can happen. These explosions will fling recovered refrigerant all over the place and can hurt or potentially kill you. That doesn't sound like a fun time, so you don't want to fill the tank any more than 80% full. Therefore, we would rewrite the previous equations to account for that 80% capacity (0.8): SG x WC + TW HOWEVER, that would tell us 100% capacity. Filling the tanks to 100% capacity could be a costly and even fatal error.

Figure out your maximum capacity, and DO NOT exceed it!

We already touched on capacity when we talked about WC (or water capacity). We said two main things: (1) we don't use water as a refrigerant, and (2) we NEVER fill cylinders to 100% capacity. Water is a poor refrigerant because it has a high boiling point, making it ineffective in the refrigeration cycle. Therefore, we use refrigerants with low boiling points. However, water is a stable, abundant compound that's easy to measure, so it's

0.8 x SG x WC + TW

That's a lot of math, but there's an easier way to calculate your tank fill. HVAC School has an app with a recovery tank fill calculator that can do all the math for