HVAC 103 Scenario Dirty Condensing coil 

Yes! That's great! My friend Chris calls it big picture diagnostics! Well done!

Yes but don't look at pressures! Superheat and subcooling will tell you what's happening. The TXV will try to maintain superheat depending on how bad it is. The cooling capacity will drop. Also the liquid line will exert an opening force on the TXV,. So if the condensor is really dirty it will push the TXV open.

@@love2hvac and suction pressure will be normal? Thanks Ty you are awsome!

There is no such thing as normal suction pressure. TXV has no way of controlling suction pressure. Pressure changes with temperature, humidity and airflow. If you have a tire look at pressure, if you have an HVAC unit look at superheat and subcooling

@@love2hvac mind blown indeed! I’ve never thought of it that way. Always looked at what typical coil temps operate at. High temp 40 , coolers around 20, freezer 0 down to low temp. Thanks Ty I enjoy learning something new every day!

I never said the capacity would go up

@@love2hvac At 5:00, you said it's possible for the evaporator's delta T (temperature differential) to increase, meaning a larger temperature difference between the return air and the supply air. Did I misunderstand what you intended to communicate? Assuming the evaporator airflow remains constant (which it would if condenser airflow is the only variable), a higher temperature drop across the evaporator would mean a higher capacity (more BTUs of heat removed per hour of runtime).

@averyalexander2303 That DOES NOT mean an increase in capacity. When the suction pressure rises you loose dehumidification transferring laten removal to sensible removal. DELTA T IS NOT CAPACITY. !!!! To calculate capacity you need the specific information of the compressor performance chart with superheat subcooling suction saturated and liquid saturated. To differentiate capacity of the evaporator you need the exact CFM, return air wet bulb and supply air wet bulb

@@love2hvac Great point, thanks for correcting me! A higher delta T with the same evaporator airflow, humidity, etc would mean a higher sensible capacity, but as you said, latent capacity depends on humidity removal and total capacity is latent + sensible capacity. Same thing can happen with too much airflow through the evaporator since a warmer coil condenses less moisture. I'm curious under what conditions you have seen the evaporator delta T increase with less airflow through the condenser though?

@averyalexander2303 With a fixed orifice metering device, When the head pressure rises, there is more vapor pressure pushing against the liquid column. That means more liquid is pushed into the evaporator coil but also raises the suction pressure. This reduces laten heat removal and increases sensible heat removal. You also have more liquid to boil away to a vapor. This was expanded in previous videos and demonstrated. If you look at a target superheat chart, you will see it. You can compare conditions and completely flood the evaporator coil under one set of conditions and completely starve the evaporator coil under another. Just because you flood the evaporator coil does not mean that it is system capacity. The compressor still has to move the refrigerant and is suspectable to the compression ratio. All the heat has to be rejected in the same space meaning higher head pressure. You will eventually reach a point where all the liquid is pushed out of the condensor and you are pushing liquid and vapor into the metering device. The videos are in order to explain this. Jumping to the end of the videos means a lot of misunderstandings and confusion. This is the reason they are in order. One lesson builds for the next and so on.

That exceeds my knowledge. That falls into engineering

sciencing.com/uses-temperature-sensor-5997997.html

www.engineeringtoolbox.com/heat-condenser-evaporator-d_881.html

Michael Hernandez, my handwriting is far worse, my teaching skills are ok, however my knowledge, especially compared with Ty, is terrible. Lol

My handwriting is terrible and my spelling is worse. Lol. One day I will get to graphics.

What makes a good teacher is #1 caring, #2 willing to learn. You are here so that shows you probably have both. That makes you a good teacher. I recorded some teacher segment tips. I'm debating on where to publish them.

There is a point where the head pressure will force the TXV to open. There will be a point the compressor floating seal for scroll will relieve or the internal pressure relief valve will open. There is also a point where the condenser can't reject enough heat to condenser to a liquid. Under those scenarios the schooling would not build up.