Hvac Pump Down
Kylee Evancho
During my second year in HVAC, the company I worked for was hired to fix some poor work that was done on a multi-head inverter system. The system used flare connections, and many of them were leaking. The system also had a branch box, which meant there were even MORE flares. So we pumped all the refrigerant down into the condenser, remade all the flares on the system, and began a pressure test. Using soap bubbles, we found quite a few flares we needed to tighten.
After that, we watched the gauges and could see that the pressure in the system was still dropping. We checked everything again and could find no problems. It took us a couple of hours to realize that the nitrogen was leaking back through the service valves and into the low side of the condenser.
This is not the only time this has happened to me. This last summer, I was replacing a TXV and realized during my vacuum that my service valves were leaking back into the condenser. I had to recover the charge and pull a vacuum on the condenser as well as the lineset and evaporator coil. Pumping down a system can be a great time saver, but is it always the best idea?
Location of the Filter Drier: if the filter drier is inside the condenser, I have always recovered the refrigerant and replaced the filter drier. I am not 100% sure this is required, but it seems to be best practice.
Overall, I am becoming more convinced that recovering refrigerant on middle-aged to older systems is a good practice. It prevents expensive and time-consuming mistakes, even if it adds precious time to your vacuum procedure.
Pump down systems have a solenoid valve in the liquid line. This solenoid closes once the temperature reaches the prearranged set point. However, the compressor continues to pump refrigerant into the receiver and/or condenser coil, removing it from the low side of the system. The compressor cuts out once the low-pressure switch registers a predetermined pressure. (This setting is directly related to the type of refrigerant being used in the system.)
We at WhisperKOOL strive to make the installation process as easy as possible for the installing technician. One thing we offer is a split system pre-weigh-in charge list. This document comes with every WhisperKOOL split system. It shows how much refrigerant will be needed to charge the system based on the line set length. This charge amount will help the technician complete 90% of the charging process. However, they will still need to top off the system with refrigerant vapor.
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We are planning on having a new concrete patio poured in a couple of weeks and need to move our AC unit to make way for the slab. Is it possible for a layman to pump down the refrigerant and move the unit or do I need to pay someone to do this for me?
Unless you are an abnormally equipped layman, no. Even then, there may be a legal requirement (depending where you are) for this to be done by a licensed A/C service person, as regulations around refrigerants have become much more stringent over the years, trying to limit uncontrolled releases to atmosphere.
The hard part actually isn't pumping down the vacuum on the AC, the hard part is recovering the refrigerant. Auto parts stores will loan you a vaccum pump that will work on a house AC, but this won't allow you to recover the refrigerant. Recovering the refrigerant requires specialized equipment that's quite expensive. Discharging the refrigerant to the atmosphere is definitely illegal.
Seriously to move your AC unit, you don't need any fancy equipment to pump down your refrigerant. You simply need a set of gauges and the know how to trap the refrigerant (pump down) within the AC unit by closing the low and high side at the right time and shutting of power to the unit. Putting back in service is a different matter though.
The process begins with safety precautions. Our technicians don protective gear, including safety goggles and gloves. This is crucial to safeguard against potential contact with refrigerants, which can be harmful if mishandled.
With the valves located, the high side valve is carefully closed using an adjustable wrench. This valve is connected to the thinner copper pipe, and its closure is the first step in the containment process.
Once the high side valve is secured, the AC, or the mini split unit is turned on in cooling mode. This action creates a vacuum pump for the refrigerant from the indoor unit towards the outdoor unit, setting the stage for the next step.
Remember, while this overview provides insight into the process, the actual execution involves a high degree of technical expertise and experience. At Good Guys Heating and Cooling, we have a team of dedicated professionals ready to handle all your HVAC needs with precision and care. Trust us to keep your AC system running smoothly and efficiently.
Regular maintenance is key to the longevity and efficiency of your HVAC system. Our tune-up services include a comprehensive check of all components, cleaning, and necessary adjustments. Regular maintenance can prevent unexpected breakdowns and keep your system running at peak efficiency.
We extend our expertise to commercial properties as well. We understand the unique needs of businesses and offer tailored HVAC services to ensure your commercial space remains comfortable and energy-efficient.
Benefit from our quality workmanship, exceptional customer service, and a 100% satisfaction guarantee. Reach out to us today, and let us handle all your heating and cooling needs. Your journey toward optimal comfort starts here.
In the realm of HVAC maintenance and installation, pumping down a mini-split system is a crucial procedure that ensures the longevity and efficiency of your equipment. This technique involves removing refrigerant from the unit and securing it within the outdoor compressor, a step often undertaken before servicing or relocating the system. This introductory guide by The Trade Table will walk you through the fundamentals of safely and effectively pumping down a mini-split, equipping you with the knowledge needed to tackle this task confidently.
You first need to locate the service valves to pump down your mini split. These valves connect the refrigerant lines to your indoor and outdoor units. The indoor unit typically has two copper lines - a larger suction line and a smaller liquid line. The outdoor unit also has two ports - one for the suction line and one for the liquid line.
The service valves will either be located right where the lines enter the wall or unit or, in some cases, may be inside a covered service panel on the side or bottom of the unit. You may need to remove some screws or a small access panel to access them. The valves typically look like small wheel valves or plunger valves.
Once you've found the valves, ensure your mini split is turned off and off for at least 30 minutes so pressures can equalize. Then, attach your manifold gage set - the two gages that measure suction and liquid pressures. Connect the low-pressure (blue) hose to the suction line valve and the high-pressure (red) to the liquid line valve.
Slowly loosen both valve cores with a valve core tool or pliers until they become loose - do NOT fully remove them yet. The refrigerant may spray out slightly at this point, so be very careful. Have your recovery machine ready to pump the refrigerant into an empty tank. Once the pressures seem equalized, you can fully remove the valve cores to allow maximum flow into your recovery machine.
Continue running the recovery machine until both pressure gages drop to 0 psi. Congrats, you've successfully pumped down your mini-split! Be sure to replace the valve cores before recharging the system with new refrigerant. Following these steps carefully will ensure safe and effective servicing of your mini split.
Now that you've ensured the power is off to the unit and gathered your tools, it's time to attach the manifold gages. These allow you to monitor the pressures in the refrigerant lines to evacuate the system properly.
Fire up your vacuum pump and let it run for a few minutes to warm up. Once heated, attach the low side of the yellow hose to the vacuum pump inlet port. Attach the high side of the yellow hose to the low-side service port on the outdoor unit.
Open the low-side access valve on the outdoor unit to allow the vacuum pump to start extracting air from the system. Monitor the compound gauge connected to the vacuum pump to monitor the pressure inside the lines. At first, the pressure will drop quickly, then start to level off. Let the vacuum pump run for at least 30 minutes or until the compound gauge reads 500 microns or less.
The lower the final micron rating, the better. A lower rating means there are fewer contaminants left behind that could damage the new mini-split or reduce its efficiency. Most HVAC technicians aim for 300 microns or less. Some high-end mini-split systems may require a lower final micron level according to the specifications, so double-check with the installation instructions.
Close the low-side access valve to isolate the vacuum once you've achieved a low enough micron level. Turn off the vacuum pump and disconnect the hoses. Your mini-split system should now be free of any air, moisture, or other contaminants that could have been left behind from the previous refrigerant. It's ready for the final step - releasing the new refrigerant charge into the system.
In this system there is both a solenoid and a low pressure cut-out switch. The cooling thermostat controls a solenoid connected to the liquid line inside the cooler and the low pressure cut-out switch is used to energize and de-energize the compressor.
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