Bryan teaches a class about how to identify and rectify HVAC problems that stem from overcharge with refrigerant.
When we charge systems, we typically add refrigerant via the suction line when the system is running. (You can only add refrigerant when the system is off if the system is under vacuum and has no refrigerant at all.) It's easy to overcharge systems with accumulators, as the accumulator may store liquid refrigerant before it gets to the compressor. People also may overcharge systems if they don't let the system equalize, if it's cold outside, or if the airflow is poor.
You can't tell if a system is low on refrigerant from suction pressure alone, and some technicians may overcharge a system with refrigerant if they see low suction pressure. Technicians are also more likely to overcharge a system if they don't weigh in the charge with a scale and don't give a system time to equalize. Systems that have different stages of operation also need to be run at the highest stage during charging; failure to do so may lead you to overcharge a system.
When you add refrigerant, it boils in the suction line and goes to the compressor, where it becomes pressurized. It becomes a subcooled liquid in the condenser and goes to the metering device. As the pressure drops in the metering device, some of the refrigerant will boil off. The metering device ensures that the evaporator is fed with refrigerant (and maintains superheat in the case of a TXV).
When there is too much refrigerant in the system, some of that refrigerant will back up against the metering device and "stack" in the condenser. So, the head pressure increases, and the condenser becomes less efficient. As a result, the main symptoms of refrigerant overcharge are high head pressure and high subcooling. (However, a clogged condenser coil may also result in high head pressure and high subcooling. A visual inspection will often allow you to distinguish dirty condensers from overcharge; finding the differential between the liquid line temperature and the ambient temperature can help.)
Low suction pressure is NOT a telltale indicator of low charge and likely indicates a restriction or poor airflow. So, we need to focus on multiple refrigerant readings and focus on the state of the airflow if we come across low suction pressure. Suction pressure is also not a good charging indicator.
Read all the tech tips, take the quizzes, and find our handy calculators at https://www.hvacrschool.com/.
When we charge systems, we typically add refrigerant via the suction line when the system is running. (You can only add refrigerant when the system is off if the system is under vacuum and has no refrigerant at all.) It's easy to overcharge systems with accumulators, as the accumulator may store liquid refrigerant before it gets to the compressor. People also may overcharge systems if they don't let the system equalize, if it's cold outside, or if the airflow is poor.
You can't tell if a system is low on refrigerant from suction pressure alone, and some technicians may overcharge a system with refrigerant if they see low suction pressure. Technicians are also more likely to overcharge a system if they don't weigh in the charge with a scale and don't give a system time to equalize. Systems that have different stages of operation also need to be run at the highest stage during charging; failure to do so may lead you to overcharge a system.
When you add refrigerant, it boils in the suction line and goes to the compressor, where it becomes pressurized. It becomes a subcooled liquid in the condenser and goes to the metering device. As the pressure drops in the metering device, some of the refrigerant will boil off. The metering device ensures that the evaporator is fed with refrigerant (and maintains superheat in the case of a TXV).
When there is too much refrigerant in the system, some of that refrigerant will back up against the metering device and "stack" in the condenser. So, the head pressure increases, and the condenser becomes less efficient. As a result, the main symptoms of refrigerant overcharge are high head pressure and high subcooling. (However, a clogged condenser coil may also result in high head pressure and high subcooling. A visual inspection will often allow you to distinguish dirty condensers from overcharge; finding the differential between the liquid line temperature and the ambient temperature can help.)
Low suction pressure is NOT a telltale indicator of low charge and likely indicates a restriction or poor airflow. So, we need to focus on multiple refrigerant readings and focus on the state of the airflow if we come across low suction pressure. Suction pressure is also not a good charging indicator.
Read all the tech tips, take the quizzes, and find our handy calculators at https://www.hvacrschool.com/.
Overcharged systems compressors will also draw more current, and in extreme cases trip on HP or even I have seen a Rooftop trip a breaker because of overcharge
Also, subcool will go down when the house is hot. If you charge to 10° subcooling when the house is 90° and go back when the house is 70° the subcooling will be much higher. The TXV will throttle back when the heat load across the indoor coil drops.
👍👍👍
Keep your heating blanket close to your recovery rags.
Great video as always 👍
Would an overcharged heat pump in summer cause water to drip from underneath condenser onto the concrete pad?
Thanks 🙏 bro
At about the 13 minute mark you state the increased pressure of the liquid stacking up behind the txv has an influence on it.
Why?
The txv bulb on the coil manifold, or suction line, is opening and closing based on the temperature of the refrigerant exiting the indoor coil.
Is it your position that the increased pressure of an overcharge drives more liquid refrigerant through the txv opening than a properly charged system? If so wouldn't it only be for the amount of time it takes for the txv to react, because it is based on SH.
If so, then a dirty coil or failed/failing condenser fan motor would produce the same effect, as would high ambient temps.
Just think of how, you would have a hangover in the morning and thirsty, thats how the coil feels when the txv is starving the coil.
I don't work on HVACs, will never work on HVACs, have no interest in every working on HVACs, but find these videos' fascinating to watch lol. Really enjoy learning how it works. Are you in Kanata ?
Very informative. Good teacher. Excellent techno speak.
You can also add refrigerant when the system is off by using your recovery machine in reverse. 410a i use a charge compensator with filter driers on the inlet and outlet ( if recovered refrigerant is being re-used ) or if its virgin refrigerant just hook your tank of refrigerant on the inlet and the equipment on the outlet. It'll get it all in there quickly. On commercial equipment this is done a fair amount of time.
Heating blanket lol. Sure..
Excellent videos as always. Just watching a plumber on YouTube changing a compressor on video.
He can’t understand why and was literally boasting how the amount of Attar charge that he had to add that he felt was correct was literally more than the entire condensing units factory refrigerant charge.
I was literally ripping my hair out and wanted to say something but this particular famous YouTuber makes so much money Office plumbing business and just recently got into air-conditioning and sells new units all the time when they don’t need to be replaced he takes offense to being told what he should do or should not do so I said nothing.
I just guess they’ll be replacing another compressor next year or two. He could buy more gold chains.
What is a refrigerant in hvac Service area Ottawa??