HVAC 104 Scenario: Overcharged system Fixed vs TXV TEV

Overcharged system
Fixed orfice Low Superheat (flooded evap) High Subcooling (flooded Condenser)
TXV EEV ( good Superheat, Good evaporator) (High Subcooling (flooded condenser)
There are many other factors that affect this, its just getting you to think about the refrigeration cycle and some of the effects.

[@s.j.5850]

You should write a book on HVAC if you haven't done so already Ty. You explain the concepts so thoroughly it gives us a greater understanding of what is going on inside an A/C system. This allows us to troubleshoot with better accuracy instead of just making assumptions. Your expertise is greatly appreciated. I enjoy your videos tremendously. Keep them coming!

[@deanmartin1966]

Nothing better than a Saturday morning, cup of coffee and Ty teaching. Great video. Thanks for sharing.

[@lynncomstock1255]

Well done. Diagnosis absolutely one to know what the metering device is. The placement of the txv bulb and a good thermal connection that is insulated should also be mentioned.

[@electricboyo]

Excellent explanation! Very helpful for my current project.🎉 I recently checked my home AC system and (unless the gauge manifold I borrowed is way inaccurate) my system is overcharged. It is R410A. Condensing unit is rated for 10° subcooling. But I’m observing 25° of subcooling. Also the condensing temp of 105° (342 PSI) is 25° above outdoor ambient temp today (80°). I think the evaporator is controlled by a TXV but it’s located inside the coil cabinet so I need to pull the cover off to confirm that. This system was professionally installed so I’ll be a bit surprised if it turns out to be overcharged by as much as what I just measured. If I confirm the overcharge I will slowly transfer some refrigerant into a recovery tank until the subcooling drops to perhaps 15° or so.

[@davidmorrone8783]

Great! Once again you have increased my knowledge on the refrigeration cycle and how it works and what conditions affect it's operation. Hope you're proud of yourself because if your not i'm proud of you! Thanks mr ty.

[@majharulislam5950]

Extraordinary teaching. Absolutely perfect explanation. Would be good, if u can explain with Compressor Power consumption. Hop, itcwill increase significantly.

[@mbahcarrier1629]

Thank you for the knowledge, success for "Ty Branaman" ... Pekalongan, Central Java, Indonesia attended

[@love2hvac]

Thanks for watching, I have not been to Indonesia yet!

[@mbahcarrier1629]

@@love2hvac Thanks for watching, I have not been to Indonesia yet!...please visit Bali...always success

[@alirahal5900]

Thank you TY. I Am watching your videos again and again. When you are taking a break, I feel a missed something. It’s always appreciated what you do Sir.

[@shine-cg9uf]

Started my day at 4am working on 2 reach-in coolers n ending my day watching tyb 💪👍. Thanks Great information

[@vinceed9]

Thanks for the lesson here! This is top notch information!

[@jkbrown5496]

Been trying to help out a family member on hard times. His heat pump went out in August, condenser fan running but the compressor just buzzing. 19 yr old R22 2 ton Carrier package unit. The compressor would only run for a few seconds. The HERM capacitor was low so I replaced it, the indoor fan cap and the rough looking contactor just to get things as best as they could be. After the compressor would run about 40-60 seconds. Discharge pressure was high, 294psi with AT in the mid-90s. Verified no significant voltage drop when compressor running. Indoor coil was in reasonably good shape, brushed and sprayed with no-rinse cleaner. Outdoor coil also not terrible, not cleaned yet. All this is good for learning. Compressor RLA 11.4 amp. Runs at 13-15 amps before shooting up to 30 amps where the internal cut off kicks in, tries to restart but at that point the amps shoot right back up. So always just cut the power. When Ambient temps dropped into the 80s, tried again and it ran for 20-30 minutes before cut off on high current. Obviously, compressor on last legs. Compressor is hard to reach but I got to it, contacts are in good shape. Assuming my resistance test of the windings was good enough, they are about 0.5 ohms high from what I found online for the Copeland scroll model number. I paid for a service call in expectation of verification of overcharge and compressor not long for this world. Tech found that the system had been wired sometime the past with the O and Y tied together. Best I can gather likely before the house was bought. He also found a bent pin on the thermostat and sorted that out so that now the system isn't hot wired. Did agree the compressor is failing but didn't mention overcharge. This hot wiring may explain what I found a couple winters ago when high electric bills showed up. When I opened the "indoor" side, there was a huge chunk of ice in corner of the indoor coil, after months of being used for heating in a mild winter. Found in late Feb/March. Beyond me at that time. He had a young tech, a friend of his nephew who worked HVAC for his father's company who said the system was working, this would have been a month or two after I found the ice so the ice was probably melted. So a disaster that has been cooling while set to heat for years. Likely what contributed to the compressor failing. I'm thinking high winter bills that shot up even more when the compressor started over-amping. I'm going to clean the outdoor coil just to be thorough and see if the amps come down. May try to evaluate overcharge now that the system runs for a significant amount of time. But if the compressor stays at 15 amps, it's almost cheaper to run 5KW heat strips. Looking into replacement/alternative costs for the coming heating season. Quote for replacement by last tech is a price too far. Not looking for tech help, just an adventure in learning.

[@love2hvac]

Cooling mode? R22? Superheat? Subcooling? If cooling mode Wash out the condensing unit. Then keep the condensing coil wet, and watch the pressures and the amps. Let it run past the 15 minute mark. If it keeps running good then remove the water. It will start to dry out. As it does the head pressure and amos will rise. Superheat and subcooling will start to change. Before the pressure relive valve opens, let me know what the head pressure and suction pressure is at least. Would like to also have superheat and subcooling at that point.

[@jkbrown5496]

@@love2hvac Thanks. I've only run the system in cooling and it is an R22 system. Happenstance has delayed the cleaning of the coil, but I did verify that I could see light and the airflow our of the fan wasn't bad. I'd kind of given up but your checks will be at least a good learning opportunity. Eventually I need to pull and clean the blower wheel as well. I lost the data I collected when I did get it to run due to a computer glitch. I need to sort out how to cap the indoor air section while keeping access to the service ports and compressor wiring. Also, the service ports are right off the compressor so I need to trace the piping to find a proper spot on the liquid line for the temp sensor. What I do know is when it would only run for 40 secs, the pressure when it went to 30 amps was 294 psi (130F) condensing sat with 95 outside temps. When it ran for 20 minutes in outside temps in the mid-80s, I remember the condensing sat temp being 120 F so that's about 260 psi for R22 and relatively stable at 15 amps I buttoned it up and on restart ran for about 20 minutes closed up before the compressor went out on high current (from sound). Raining a lot here so it may be the weekend before I can clean the coil and get more data.

[@gustavoinsoluperez_218]

Thank you, an awesome expalanation

[@coldfinger459sub0]

Every day I wake up with a cuppa coffee as a stimulant at the same time stimulate the brain with refreshed or new knowledge.

[@honestman276]

Thanks from Bangladesh.

[@hvactechwanttobe1499]

Thank you Lots of good information to help me understand

[@musakavalci9470]

Excellent as always. 👍🏼👍🏼

[@realestateservicessaleshea99]

🙂👍🏻 Thank you again!!! 🥃🥃🍺🍺🍺🍇🏌🏻‍♀️ Stay safe.

[@victorhugorengifomera6517]

Excelent video my friends

[@salehabdullah399]

Awesome

[@Brian_541]

You’re the man Ty 🤙

[@ozziewelcome5612]

Good 👍 👍 👍

[@robertling9872]

Thank you Ty 👍

[@antoniol1267]

Hello, really nice video! But I dont understand how the Evaporator AT increases... If evaporator pressure and saturated liquid temperature increases, the refrigerant boils at a higher temperature. Therefore it will remove less heat from the ambient, wont it? Regards and thank you.

[@theaustinite5320]

Mr Ty , I appreciate your help and what you are doing to Help, HVACer nation , I have an carrier 12.5 tons condenser with lines of 50 feet to the 4th floor attic, it’s reading very good high side pressure, temperature and 10 f degree of subcooling, the suction line low pressure, low evaporator temperature (24-27), f degree and psi converted temperature (35-38) degree, air flow is good, I fixed some fire dampers, I checked factory charge 9.5 ib plus 50 feet of line charge 3 ib, but still same. Your advice sir😀.

[@love2hvac]

what is your metering device?

[@theaustinite5320]

@@love2hvac Mr Ty my metering device is avTXV, but I found the problem with the attic air handler blower motor belt was crazy loss, that’s still air restriction. Thanks

[@Financialwiz4567]

I didn't read all comments, and perhaps you believe people will draw the proper conclusion from higher compression ratios, but simply put, the greater the difference in pressure the more energy that is required to compress the cool gas into a hot gas at unnecessarily high pressure in an overcharged system. So even with a TEV or TXV, efficiency is harmed by over charging (too much pressure differential) or under charging ( too much super heat and failure to pick up a full load of heat as designed per watt consumed),

[@syedbasheer8210]

🤩🤩🤩👌

[@samersarah957]

Hi Ty! System utilize with TEV so when braze suction line close to evaporator then the TEV will be to close is a rag will help or is there another way could protect TEV?🌷Thank you.

[@alfaomega8824]

Please help me understand. Why is there automatically more subcooling when you add more refrigerant? why isn't it instead more vapor that doesn't have time to cool down because the air flow has to cool down a larger surface. So that there is less subcooling instead? How should I think? Thank you again for charing your knowledge!

[@kamozoren]

Thank you for an eye opening explanation of this anomaly. One thing I can not understand: With fixed metering, how can the Evaporator Delta T go down if TD goes up? it looks to me like a paradox. If the temperature difference between the coil and the air is lower, there will be less heat exchange. Isn't it so? I can see why the excess molecules will cause pressure raise by the PV=nRT formula. But on the other hand, there's more flash gas dropping in temperature due to expansion. So to me it looks like that with small overcharge, the Delta T will go up. But with severe overcharge, the opposite. In each case the TD and DT should be in the same trend, otherwise it defies the laws of thermodynamics.

[@love2hvac]

Let's say the return air temperature and airflow is a constant for this example. To get a larger TD only way to do that is with a lower suction pressure that will give us a lower saturated temperature. We are going to get a lower suction pressure by having less refregerant and less refregerant molecules bouncing around inside the evaporator. This created is how the temperature between the air and the refregerant saturated will be farther apart or larger TD number. However less refregerant in the evaporator coil means less liquid refregerant able to change state from a liquid to vapor. It's the latent heat of the refregerant changing state that gives us the cooling capacity. So less refregerant in the evaporator coil changing state means we are absorbing less heat energy. Because we are absorbing less heat energy we don't have enough BTU capacity to make a change in the delta T of the air in vs the air out. So the Delta T of the air will be less of a change or a lower number. Does this help?

[@love2hvac]

Now on the reverse let's look at overcharge. Again with the return air temperature the same, and the same airflow. We now have more refregerant in the evaporator coil, more molecules bouncing around, giving us a higher suction pressure. The Return air temp being the same, and a higher suction pressure means a higher saturated temperature. So the TD becomes closer together or a lower TD. Now that we have more refregerant in the evaporator, there is more refregerant able to change state from a liquid to a vapor, more latent heat available. This means we have . Ore capacity to absorb heat. That extra capacity means we have more BTU available to absorb more heat. That extra capacity means we can have a larger change in the temperature of the air in vs the temperature of the air out. So more refregerant changing state means more heat absorbing to make a bigger change to Delta T or higher delta T.

[@love2hvac]

I think where your getting confused is the PV = nRT. This is a gas law, and if we had only gas it would work but it compley leaves out latent heat, the change of state, Wich is the THE key behind refregeration. For this we need the refregerant enthalpy chart. This will cculate how many BTU of heat will be absorbed for how much change of state we have with the associated pressure. After we know howa y BTU we have we can apply that to the air temperature to see how much it changes the temperature (deltaT) the manufactures actually give us this data with performance charts. I have an introductory video on that

[@love2hvac]

Check out HVAC 098 Delta T and I have included an introductory to performance data. Hopefully that helps

[@kamozoren]

Hello Ty. I appreciate your elaborate answer. In the end, from the sensible heat perspective, it’s air (Return) meeting metal (evaporator coil). So, what I meant was that given a higher (sensible) temperature of the coil(metal), where Return air temp. & humidity and airflow being the same, the delta T (Return to Supply air differential) will be smaller. And vice versa. I simply cannot see how there can be a higher (sensible)heat transfer of air if the (sensible)difference between the two medias get smaller. The amount of refrigerant we inject into the coil determines the proportion of liquid to gas inside the coil. When calculating TD, we infer the refrigerant temperature from the suction pressure according to P/T chart. But this is true only for the saturated vapor. This vapor will be superheated as is it travels further up the evaporator. The question is what the Average coil temperature will be for the Return air in order to reliably calculate TD. This, I cannot personally answer as the pressure/temperature relationship of the medium can only be predicted for the saturated vapor. Not for the liquid/flash gas, nor the superheated vapor. I’m sure you’d agree that if I blew, say, a 400 CFM, 80 degrees, 50%RH, air over a 40 degrees metal coil and then use the same air conditions with a 20 degrees metal coil (and hence, higher TD), I’d get a higher delta T (lower Supply air). For a coil containing refrigerant, I think we can measure the result by increasing metering (with TXV it can be done by removing the bulb), then measuring the average temperature of the coil with a temp. probe, at different spots. Then, calculating the new Delta T. Brian Or, for example, claims that Delta T will go down upon severe overcharge of fix metering. He explains it by saying that the evaporator temperature will go up (hence TD is less), and eventually Delta T is going down also. See: kzbin.info/www/bejne/p3rSkJyKbdKmkKM minute 9:33/17:57

[@lindamdaka7832]

Thanks

[@GiannisKaralis]

Great!

[@barronweir123]

You are great do you sit down and spend hours responding to people?

[@love2hvac]

I appreciate the complement. I'm not great, just a guy who has been helped and trying to help others. My wife says I spend a lot of time communicating with people, but a lot of emails, comments and texts I don't get to.

[@vidalrichardson9337]

I always see every video from the angle of running the unit in cooling mode and being overcharged.... but never what the signs of overcharging are in heating mode... I have learned you can get away with more if you are just overcharging a unit in the cooling mode so long as it is not grossly overcharged but this same unit will come to bite you in the rear come wintertime when it is placed in heating mode. because it will start to trip the overpressure switch...

[@love2hvac]

Overcharging in cooling mode leads to long term issues such as compressor flood back shortening the compressor life. You will notice the issue faster with heat pumps Because less refrigerant is needed in heating mode. The indoor coil, now the condensor is much smaller and has no place to store the additional refrigerant. Airflow is also more critical with a heat pump.

[@vidalrichardson9337]

@@love2hvac Would is a sign then be high discharge pressure in heating mode that slowly creeps up and keeps going up... until the unit trips on over pressure? I say this because I once had a unit once where the discharge pressure kept slowly going up, not fast mind you but constantly going up in healing mode... until it should trip the high-pressure switch... yet if you ran it in cooling mode it ran fine .. the tech with me told me it had a reversing value issue but once I set down and drew up a diagram of the system, I realize this made no since because I would have saw symptoms it in more then one area.. I came back a few days later and did a diagnose and decided to remove some 410A from the system.. after removing just under a pound the high pressure stop climbing and started to stabilize .. it was still to high but I notice it cease to just keep climbing with no end in sight .. so then I decided to remove a few more ounces right before my eyes the system went back to normal operating range for the conditions it was it and settled out nicely, after putting it in cooling mode it also work very nicely as well .. that is when I realize one of the symptoms of overcharging is when in heating mode you will get high discharge pressure that can trip the over pressure switch. Yet every where I look people only talked about it in the cooling mode.

[@samersarah957]

If the evp fan or condenser fan speed replaced with higher speed 250 rpm and the system charged correctly what’s can happen? Thank you Mr.Ty.🌱

[@love2hvac]

The condenser, would drop the head pressure, and liquid saruration, drop condensor TD. Drop condensor Delta T More airflow inside: raise suction pressure, raise suction saturated. Father from due point so less dehumidification. Drop Delta T and increase superheat.

[@thisisyourcaptainspeaking2259]

So one reason hvac guys prefer txv/tev is they still appear to operate correctly (for taillight warranty purposes) despite being improperly charged.

[@love2hvac]

Yes!

[@mikestevenson1819]

New txv 22 to 407c Weighed in charge High head Low suction High SH

[@love2hvac]

Open the TXV, turn the pin counter clockwise.

[@arbersh9644]

What about frozen accumulator in heating mode?

[@love2hvac]

It should not be an issue. It should be sized large enough to still protect the compressor.