Zero is NOT Nothing!

Many times people have remarked that even though they recovered a system to 0 psig or lower, when they opened the system, there still appeared to be some refrigerant. Often the presence of some refrigerant was most noticeable when they started brazing on a system that supposedly has nothing in it, and noxious green flames come out of the joint. This is because zero is not nothing. And no, that is not my “casual” grammar coming out. Don’t assume that because you have recovered a system down to 0 psig, or even into a vacuum, there is no refrigerant remaining. In fact, there can be quite bit of refrigerant in the compressor oil even under a vacuum. Since the refrigerant oil and the refrigerant are miscible, refrigerant dissolved in the refrigerant oil leaves the oil very slowly. The attached video shows refrigerant boiling out of oil removed from a compressor that was removed from a system which was recovered down to 28” of vacuum. The oil continued to boil for hours after being removed.



 This helps explain why system pressure can rise in a system which is left under a vacuum. This also explains why you should make sure the compressor oil sump heater(crankcase heater) is on before recovering refrigerant. If you are planning on recovering refrigerant from a system that has an operable compressor, run the system until the compressor is warm before beginning recovery. The compressor can draw out the refrigerant from the oil faster than your recovery machine. A heat gun applied to the bottom of the compressor can also help a great deal. While you are heating places that trap refrigerant, go ahead and heat the bottom of accumulators, receivers, and filter driers as well. A little time spent warming these areas trap oil and refrigerant will save time during recovery and evacuation. Remember, zero is not nothing!

New EPA Rules

On September 26, 2016 the EPA issued a new Final Ruling updating the regulations for handling refrigerants. Don’t panic, there is plenty of time to prepare. For technicians, the first important enforcement date is not until January 1, 2018 and some parts do not take effect until January 1, 2019. However, you do need to prepare. There are more changes than I can list in a short blog post, but I will provide an overview and plenty of links to the information.

Mostly about Global Warming
Most of the changes have to do with limiting global warming by reducing the use and release of HFC refrigerants. Some of the more significant changes include requiring certification to purchase and handle HFC refrigerants, reducing the allowable leak rate for ozone depleting and global warming refrigerants, specifying regular leak inspection for equipment which has exceeded the allowable leak rate, and requiring record keeping when disposing of systems with more than 5 pounds of refrigerant.

Technician Certification
Staring January 1, 2018 technicians must be certified to purchase and handle nearly all refrigerants, not just ozone depleting ones. One curious exception is that sales of small cans of refrigerant for use in car air conditioning systems will not require certification. The cans will be required to have a valve, but sales to the general public will still be allowed.

Leak Rates Lowered
Starting January 1, 2019, the leak rates will all be lowered and will apply to HFC and replacement refrigerants as well as ozone depleting refrigerants. A few specific refrigerants are exempted from the venting prohibition and the leak requirements. These exempted refrigerants include carbon dioxide, nitrogen, water, ammonia, chlorine, hydrocarbons, and R441A. The leak trigger rates which require repair are now 30% for industrial process refrigeration, 20% for commercial refrigeration, and 10% for air conditioning and “other” uses. Note that the refrigerant charge level for these trigger rates remains at 50 pounds or more.

Leak Inspection
Beginning January 1, 2019, the new rules require regular leak inspection for systems that have reached the “trigger rate” requiring leak repair. The frequency of the required inspections is determined by the type of system and the size of the system charge. Quarterly inspections are required for commercial refrigeration and industrial process cooling systems which hold 500 pounds or more refrigerant. Commercial refrigeration and industrial process cooling systems holding at least 50 pounds of refrigerant but less than 500 pounds require an annual leak inspection. Air conditioning systems holding at least 50 pounds require annual leak inspections. When leaks are repaired, an initial system tightness verification is required before adding refrigerant. A second system tightness verification is required after the system is up and operating. Records of all of these tests are required.

System Disposal Record Keeping
Starting January 1, 2018 technicians disposing of systems with at least 5 pounds of refrigerant must keep records regarding the equipment and the refrigerant charge. Specifically, you must keep
The location, date of recovery, and type of refrigerant recovered for each disposed appliance
The quantity of refrigerant, by type, recovered from disposed appliances in each calendar month;
The quantity of refrigerant, and type, transferred for reclamation or destruction, the person to whom it
was transferred, and the date of the transfer. Note that you are not required to report the quantity of refrigerant recovered from each individual system, but rather, the cumulative quantity of refrigerant recovered each month.

Links to EPA Documents
This is just an overview. To really understand all the details you should consult the information published by the EPA. Here is a list of links to some of that information.

Advance Copy of Final Rule
https://www.epa.gov/sites/production/files/2016-09/documents/608_final_rule_pre-publication_copy.pdf

Subpart F—Recycling and Emissions Reduction
http://www.ecfr.gov/cgi-bin/text-idx?SID=085a41355598f2919b6655098a466757&mc=true&node=sp40.21.82.f&rgn=div6

Fact Sheet on New Regulations
https://www.epa.gov/sites/production/files/2016-09/documents/608_fact_sheet_technicians_0.pdf

EPA Page on Revised Regulations
https://www.epa.gov/section608/revised-section-608-refrigerant-management-regulations

EPA page on leak requirements
https://www.epa.gov/section608/stationary-refrigeration-leak-repair-requirements

Keeping Your Cool!

Hot weather is coming, and that can mean slow refrigerant recovery. It is common to have high recovery tank temperatures and pressures shut you down as the temperature rises. The condensing temperature of the refrigerant in the recovery unit has to be higher than the outside temperature, and so the refrigerant leaving the recovery unit can be hot, especially on a hot day. This raises the recovery cylinder temperature and pressure, which in turn makes the pressure leaving the recovery unit climb even higher since it must be higher than the cylinder pressure. You often need to cool the recovery cylinder to keep going. There is the old stand-by: ice and a bucket. It works great, but involves the extra bother of carrying ice and a large bucket to the job site. You can use the recovery machine to cool off the cylinder.

Connect the vapor valve of the cylinder to the inlet of the recovery unit and the liquid valve of the recovery cylinder to the outlet of the recovery cylinder. Purge both hoses of air. Start the recovery unit with both cylinder valves open. After the unit gets started, turn the liquid valve on the recovery cylinder clockwise to create a restriction. Be careful NOT to completely close it off. You have just made a refrigeration system with the refrigerant recovery cylinder acting like a flooded evaporator.

The recovery unit is provides the compressor and condenser, and the partially closed liquid valve on the cylinder acts like a metering device. Liquid in the cylinder boils as vapor leaves, cooling off the remaining liquid. The returning liquid is at a lower pressure and temperature, thanks to heat being removed by the recovery unit and the pressure drop at the liquid valve. It takes a bit of practice to learn where to set the liquid valve, but you can monitor the two pressures on the gauges of the recovery unit. You should see both pressures drop as the unit operates.

I have made cylinders frost on the bottom using this technique. One caveat – if you wait until the high pressure switch on the recovery unit opens, you can’t use this method to cool the cylinder down since the recovery unit won't run at that point. You need to make sure and cool the cylinder before that happens. One manufacturer used to make a recovery unit with this feature built in. You connected two lines from the recovery unit to the cylinder, and anytime you needed to cool the cylinder down you would just set the recovery unit valves to subcool. This kept you from having to move your hose connections after the cylinder was cooled down. However, I don’t think it is available any more.

Zero is Not Nothing!

The other day a technician asked me why there appeared to be refrigerant coming out of a compressor that he was de-brazing. He had recovered the system refrigerant, so where was this refrigerant coming from? First I asked now deep a vacuum he pulled with his recovery machine. He had pulled down to 0 psig. I pointed out that 0 is not nothing. Even though I am from Georgia, “0 is not nothing” is in fact not a double negative. Remember that there is still 14.7 psia worth of pressure in the system at 0 psig, so 0 is really not nothing. Something is still in there. You would have to pull a deep vacuum to get close to nothing. Additionally, the compressor oil holds lots of refrigerant. So if you want to reduce the refrigerant coming out of the system, you need to go lower. For a system that has an operating compressor, operate the system until the compressor gets warm before starting recovery. No recovery machine can pull refrigerant out of the oil as fast as you can by operating the compressor. However, if you are changing the compressor, that probably won’t work. Instead, get out your hair drier and heat up the bottom of the compressor with hot air. While you are at it, heat the accumulator and filter drier as well. If you don’t plan on dining out while the recovery machine operates, use core removal tools to take the Shrader valve cores out to reduce restriction. Trying to recover through a Shrader valve with the core in is like drinking a milkshake through a coffee stirrer –not impossible, but really slow. But back to the 0 is not nothing story. 

I have done an experiment several times now that shows how much refrigerant can be left in the compressor oil. After recovering a 2 ton R22 packaged unit down to approximately 5” hg vacuum, we let it sit to see that it would not rise above 0 psig. Convinced that we had achieved 0, we operated the unit. After a few minutes of operation, the system was operating at 150 psig on the high side and 25 psig on the low side. There was a lot of refrigerant in the compressor oil. Now I must warn you that compressor manufacturers would frown on my experiment – so don’t do this at home – use someone else’s compressor! Operating a compressor on “nothing” is a sure way to kill it. One last safety tip: instead of de-brazing the compressor, try cutting it out. No fumes, no flames, and far safer if you mistakenly left a lot of “not nothing” in the system.