Do not siphon refrigerant by mouth, avoid spilling liquid refrigerant on the skin, use gloves and safety goggles when working with liquid refrigerant ( all of the above) Show
I often see new techs asking how to recover or experienced techs asking how to recover faster, so let’s take a look at both. If looking to connect with a strong culture of HVAC technicians, check out the subscription-based HVAC Know It All app. This all originated from some personal trial and error when an air conditioning manufacturer I worked for had a recall, a missing Schrader core at the receiver service valve (king valve) of all things. This was a possible disaster for an unsuspecting tech. Remove the cap expecting a valve core, and well... Not fun. So it was time to install a single valve core in 50 operational units in critical spaces, each holding between 50 and 100 pounds of R-410A. I had a reasonably repeatable situation on my hands, and I had the opportunity to try all sorts of things: recovery cylinder size, hose size, hose type, etc. I’ll cover all this at the bottom of this article, but we’ve got to start with the basics! How do we recover?There are two typical methods, direct recovery and push/pull. You should always familiarize yourself with the equipment you are working with, but I’ve included a simple diagram of how to connect the required equipment and a “step-by-step” guide for the newer techs. Direct RecoveryThis is our typical recovery method, which will be how every recovery task will finish. 1. Start with all valves closed (recovery cylinder, recovery machine, manifold, hoses.) 2. Setup hoses as shown in the diagram. 3. ZERO/TARE the refrigerant scale. 4. Open hose valves, core removal tool valves or service valves. 1. ---The below steps will vary with your recovery machine--- 5. Set the refrigerant recovery machine to recover. 6. Open the high side of the manifold for liquid recovery. 7. PURGE THE HOSES OF AIR, loosen and unseat the hose connected to the recovery tank until the refrigerant is present, and then retighten. 8. Fully open the vapor valve on the recovery cylinder. 9. Turn on the recovery machine. 2. ---The below steps should be standard for most recovery machines--- 10. The manifold high side valve may need to be adjusted to throttle refrigerant flow into the refrigerant recovery machine to avoid liquid slugging. 11. When the liquid recovery is complete, fully open both the high side and low side manifold valves. 12. Many recovery machines will turn off once the system reaches a vacuum. 13. PURGE THE RECOVERY MACHINE – this one can be pretty specific – so check your manual if you’re unsure. 14. Close all valves and recovery is complete! Push/PullThis will be your faster option if the system has 15 or more pounds of refrigerant. The more refrigerant the system holds, the more time you’ll save. Tip: Using an inline sight glass during push-pull recovery will allow you to visually determine when the liquid flow has stopped. 1. Start with all valves closed (recovery cylinder, recovery machine, manifold, hoses.) 2. Setup hoses as shown in the diagram. 3. ZERO/TARE the refrigerant scale. 4. Set the recovery machine to recover. 5. PURGE THE HOSES OF AIR (this is done slightly differently than in direct recovery.) 6. Turn on the recovery machine. 7. When liquid recovery is complete, switch to Direct Vapor Recovery. Now, let’s speed it up...Valve Core Removal Tools• If you were only going to change one thing – this is it! If you’re stuck pulling through valve cores, get two of these. They’ll even help speed up your evacuation. Recovery Cylinder• Make sure the cylinder is clean and has been evacuated to 500 microns or less. And NEVER fill beyond 80%. This allows for the expansion of the refrigerant. Hoses• Avoid hoses with “anti-blowback” or “low loss” style fittings. • Standard hoses are ¼” – using larger diameter hoses will get you faster recovery. They’re often marketed as “heavy duty,” “charging,” or “vacuum” hoses. • Use hoses that are as short as possible. Temperature• Cool down the recovery cylinder– this will drop the pressure of the recovery cylinder. • With many recovery machines, you can use the fan to draw air over the recovery tank. • Water will work even better, but you’ll need water flow. • Cool down the refrigerant! This one tends to be your best bet if you’re dealing with large volumes of refrigerant – there are heat exchangers available for just for this purpose. Filter It!• If you suspect the system refrigerant to be dirty, use an inline filter drier at the inlet to the recovery machine. With methods ranging from nothing new required to a whole new rig for recovery, you’ve got choices to speed up your recovery in just about all applications. Give some of these a try and see how they work for you. Dan Reggi Humber College Professor Follow HVAC Know It All on Instagram, Facebook, YouTube and LinkedIn and LISTEN to the HVAC Know It All Podcast Save 8% on purchases at TruTech Tools with code knowitall (excluding Fluke and Flir products) BACK A recovery machine contains a compressor to suck out the refrigerant during recovery. Water-Cooled Recovery Units are most common while recovering refrigerant from a chiller system. The advantages of these units are:
A water-cooled recovery unit uses a condenser coil that cools down the recovered vapor refrigerant and converts it into a liquid. The recovery unit’s condenser coil is similar to the condenser coil in a refrigeration appliance. Local municipal water supply is continuously passed over the condenser coils to cool it. Other recovery machine types heat up after some time due to the large amount of refrigerants. A water-cooled recovery unit is generally used to recover large amounts of refrigerant in comparatively less time. Recall that any low-pressure chillers have a ruptured disc. The rupture disc might burst if the pressure exceeds 10 psig at any time in the recovery process. All recovery units used for recovering from a low-pressure chiller have high-pressure cut-out control that does not allow the pressure to rise above 10 psig. Recovery ProcedureDuring refrigerant recovery, if there are confirmed leaks in the system, the water from the condenser and evaporator barrels must be drained from the drain valve. Recall that the pressure in the chiller barrel is decreasing continuously during the recovery process. The low pressure created by the recovery machine can suck the water from the chiller tubes via the leak openings or holes. Recall that water is an impurity when mixed with refrigerant. If there are no leaks in the system and the recovery is made for other purposes, the water in the chiller tubes need not be drained out. In such conditions, the water in the evaporator and condenser tubes must be circulated throughout the process. Recall that the water-circulating pumps always circulate water. Recall that a reduction in pressure due to recovery will also reduce the temperature in the chiller system. The water is circulated continuously during the recovery process so that it does not freeze inside the tubes. If the water is in circulation, there is no freezing chance, and ice formation is prevented. The water in the chiller tubes is never allowed to stay stationary and is either circulated or drained out. Ice formation is very dangerous as it can burst the copper pipes and damage the water circulation pumps. Recovery MethodsThe refrigerant can be recovered in liquid form or vapor form. It is necessary to recover both liquids as well as vapor refrigerant from the system for complete recovery. Let us discuss this a bit more. While recovering, liquid refrigerant is recovered from the liquid line in the system. Refrigerant is first recovered in liquid form for faster recovery. As refrigerant oil is mixed with refrigerant, liquid recovery causes loss of refrigerant oil. After liquid recovery, the remaining refrigerant is recovered in vapor form. Vapor recovery is slow & consumes more time. So to save time, the recovery process is started by removing the liquid part first. While recovering, vapor refrigerant is retrieved from the vapor line in the system. A lower amount of refrigerant oil is mixed with the vapor as compared to liquid refrigerant. So vapor recovery minimizes the loss of refrigerant oil from the system during recovery. An average 350 ton R123 chiller at 0 psig still contains 100 pounds of vapor after all the liquid refrigerant has been removed. So it is important to recover the vapor refrigerant after liquid recovery. Tonnage is the cooling capacity of any appliance. For example, we commonly say a 5 ton AC referring to its cooling capacity. Recall that atmospheric pressure is the pressure of the surroundings. Sometimes, leaks in the appliance cause air to leak inside during recovery, and a complete recovery cannot be made. In such cases, recovery from the appliance is only possible till atmospheric pressure. Note that depending on the question, the EPA exam may use the word Evacuation in place of Dehydration or in other questions in place of Recovery. Recovery TimeRecovery time is the time it takes to recover a refrigerant. Generally, we want to recover refrigerants in the least possible amount of time. Recall the factors affecting the time it takes to recover refrigerant:
A higher ambient or room temperature leads to a faster recovery. The shorter the length of the recovery hoses, the faster the refrigerant flows through it. As already discussed, liquid recovery is faster and reduces the recovery time. Recall that the pressure inside the liquid side is higher. The higher pressure pushes the liquid out of the system into the recovery tank more quickly. In this module, we discussed the different refrigerant recovery methods. We walked through the pieces of equipment used for the recovery process. We also learned a couple of techniques for faster recovery. Question #1: What is a typical advantage of a water cooled recovery unit?
Scroll down for the answer... Answer: Faster recovery of large quantities of refrigerant. A water-cooled recovery unit is generally used to recover large amounts of refrigerant in comparatively less time. Question #2: A typical setting for the high pressure cut-out control on a recovery unit used for evacuating the refrigerant from a low-pressure chiller is;
Scroll down for the answer... Answer: 10 psig. The rupture disc might burst if the pressure exceeds 10 psig at any time in the recovery process. All recovery units used for recovering from a low-pressure chiller have high-pressure cut-out control that does not allow the pressure to rise above 10 psig. Question #3: What should be on and what should be off during vapor removal from a low-pressure refrigeration system?
Scroll down for the answer... Answer: Commercial refrigeration EPA classifies appliances used in retail food and cold storage warehouse sectors as Commercial Refrigeration System. Question #4: What precaution should be taken prior to recovering refrigerant from a chiller suspected of having tube leaks?
Scroll down for the answer... Answer: Drain the watersides of the evaporator and condenser. During refrigerant recovery, if there are confirmed leaks in the system, the water from the condenser and evaporator barrels must be drained from the drain valve. Question #5: Why must water be circulated through a chiller during refrigerant evacuation?
Scroll down for the answer... Answer: To prevent freezing of water in the appliance. Recall that a reduction in pressure due to recovery will also reduce the temperature in the chiller system. The water is circulated continuously during the recovery process so that it does not freeze inside the tubes. If the water is in circulation, there is no freezing chance, and ice formation is prevented. Question #6: Refrigerant removal from a low-pressure system starts with;
Scroll down for the answer... Answer: liquid removal. While recovering, liquid refrigerant is recovered before the vapor refrigerant in the system. This saves a lot of time during recovery. |