HVAC 100 A compression Ratio part 1
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- Опубліковано 26 лип 2024
- Part 1 of 2 Compression ratio introduction and how to calculate it. Also includes some examples to follow along and comparing how changing conditions will affect compression ratio. you will need a pressure temperature app and a calculator.
Video Ulises Palacios shows how an R22 compressor is smaller pump action than a R410A
Comparison of a R22 scroll compressor to a R410A scroll compressor • What's the difference ...
Engineering tool box barometric pressure to PSIA
www.engineeringtoolbox.com/ba...
The Atmospheric meter I use (Not necessary i just like gadgets) www.trutechtools.com/5600511
Part 2 coming up!
The way he ever so fluently delivers his knowledge always blows my mind! Thanks Ty!
Thank you!
Man, this is the Best class on compressor’s ratio value that I’ve seen! Thank you VERY MUCH! I would be very interested to see other classes you did.
Knowing what I know now after watching your video I can easily explain to my customers why appropriate air ducts are the MUST of you want your HVAC system to be more efficient and to last longer!
Thank you again, great job!
Thank you! More coming soon!
Thank you Ty, this is beyond gold, you are an HVACR National Treasure.
Ty definitely has a way to be able to break big complexing and difficult problems and explain them to regular people in a way that they can understand.
Your illustration of reaching refrigerant from lower to bring it up over the head (work harder) makes me easily to understand about what compression ratio is. Thank you.
Hey I have to say this is one the best instructional series
Great teacher. Love the way you giving samples. Easy to understand
Wow! you just blew my mind when you were talking about compression ratio and indoor temp at 70F. It makes so much sense now. Great analogies Thank you sir!
Wow! great info, super interesting, all the information and the comparison between the high efficient larger condensing units VS. the smaller units, etc., all very important info. Thank you!
Your better then any tech teacher and I should know
Thanks just got my EPA 608 because of you
Thanks!
It was absolute / absolute basically but that's why I love watching!
🍺🍺🍺🥃🥃🍇🏌🏻♀️
Stay safe.
Retired (werk'n)keyboard super tech. Wear your safety glasses.
Hi Ty,
Thank you for the awesome review about the compression ratio calculation. I just went through this a few days ago while on vacation. Haha The information I was reading said to add 15 to PSIG.
Yes rounding to 15 is normal .3 is unlikely toake much difference I'm just prepping people for the quizes.
In relaity you want to use the atmospheric pressure your actually at.
Wow! Ty thank you so much for what you are doing for this trade. you make everything so easy to understand
Thanks Isaac!
Very good explanation. Thank you
Thank You very much for this Update:
These is my take away
1. I can be more conscious of energy consumption in my system by paying attention to my CR.
ie I can select an higher CFM condenser fan through a lower Condenser Split so my CR can be reduce.
The suction side has greater affect on CR than the high side. Keeping the home warmer has the greatest affect.
This can still feel cooler by using a fan only in the room you ocupy and making sure you control humidity.
Great explanations 🎉. I have a question about absolute pressure. HVAC systems are vacuum before adding refrigerants and Refrigerant is circulated in a closed circuit. How atmospheric pressure reacts on this system then?
Great question. When you star your in a vacuum wich is bellow atmospheric pressure. You add refrigerant to the system just to get it to 0psig. So that refrigerant is now accounted for in the calculation.
Think of industrial LP chillers. The suction side runs in a vacuum. Even if you removed all the liquid out of a chiller, and had vapor at 0 psiG (at sea level ) there would bee 14.7 pounds of refrigerant still in the system. That vapor only at I psig (14.7) psig would be over 100/phosical pounds of refrigerant.
@@love2hvac Thank you.
Great subject!
Can you do a video detailing explanation of condenser and evaporator design specifically. How the engineers and what math formulas they use.
Automotive have aftermarket condenser manufactures that sell cheap condensers instead of having the factory 21 fin per inch. They will cut the fin count down to 16 or 14 fins per inch saving money.
They will cut the refrigerant passage tube from 58 tube down to 48 tube in Pastis cheaper aftermarket condenser off as a direct replacement.
Can you explain in detail exactly what are the negative consequences of installing such condensers in place of a original design system.
I know the answer but many people do not in a detailed explanation that I know only you can get across using the correct verbiage
I know exactly what your talking about. I don't currently have that only list. I'm so behind on recording and editing it will take a while before I can get to it.
@@love2hvac I know by watching your accountant the amount and adding you do takes a lot of time that’s why I do not edit my videos
I’ll be waiting for the day you make that video and I’ll probably be saving it to my favorites watchlist and recommend list
This video provides exactly the information I've been seeking. Is there a way to know what temperature difference my unit is designed for 15 or 30 degrees? It's a 2010 Trane 5 Ton SEER 14 heat pump.
I have a video on TD and Delta T. (They are not the same)
Each manufacturer will provide performance data for a system matchup. It will be a graph that you can select specific conditions. One day it could be at 15, while another it could be 25
Hi Ty. I do have some question regard compressor ratio. How about compressor with 2 or more cylinders? is the calculation for ratio formula still the same?
Yes, it is still the same for the total compressor compression ratio.
👍👍👍
Hi thanks for your nice video.
It is good idea place the link of the video that helping to understand this video in your description.
Thanks.
Great point
The HVAC 000 series is meant as a continuing class in consecutive order. One video builds upon the next. This is the same course that school charge several thousands for .
Here is the complete class in order.
ua-cam.com/play/PLc7QlzR-srBgknwzlXjoESxNbzHQJ-TIq.html
@@love2hvac Thanks for your fast response and being kind to share spread of your great knowledge. 🤗
Great content? Can u knw a compressor ratio on a mini split unit
Yes, yes you can.
Hi Ty. Just wondering why atmospheric pressure is involved/required in the calculations. Seems to me the refrigerant system is in a rigid conduit and as such isolated from atmospheric pressure. Conceptually what am I not understanding?
Great question.
When we charge a system we first pull it into a vacuum. Below atmospheric pressure. We measure it is "hg bit it can also be considered in PSIa. We remove atmospheric pressure from inside the rigid piping. We then replace the atmospheric pressure with refrigerant. So we add 14.7 psi of refregerants to get it to 0psi guage. Then continue to add refregerants to what ever pressure.
We have to account for that refrigerant that is in there below the 0psi because it is still acting against the compressor.
So if your in Denver Colorado the atmospheric pressure may be only 12psia.
If you where to pull a vacuum, you can only remove the atmospheric pressure.
Since it is at altitude there is less pressure in the air. So we account for that. After a vacuum is pulled we replace it with refregerants 12psi to get it back to 0 and then what ever psi we end up with above that.
@@love2hvac Alhamdulillah, someone asked the question, and Ty answered it!!
Thanks, both of you!
Question.....for residential style equipment. You are reading liquid pressure and not discharge pressure. Would the math still work or would it be skewed. On most RTU'S you can get discharge pressure so the math works. Just curious about how it works if you read liquid pressure.
That's a great question. There will be a difference in discharge vs liquid. I will get those numbers shortly.
Discharge is best and refregeration is much more criticle for compression ratio and that's where we also have access to a discharge port. It
Residential liquid will be close enough.
does gravity affect compression ratio like having evap on 2nd floor?
Great question!
Since we are taking a compression ratio at the compressor, gravity will not affect it.
However the piping itself can affect system performance. Different piping configurations have restrictions that affect system capacity.
Great thing about digital gauges, you can zero them to atmospheric pressure.
Pluss mearuquick calculates compression ratio and used the GPS to figure atmospheric pressure and altitude.
One thing I don't understand is how does the compressor maintain the 15 or 30 F difference between sat. temp and the outdoor ambient temp? How does it know to increase or decrease the compression ratio? I understand that the compression ratio changes depending on the heat load inside, if the refrigerant is more or less dense when it reaches the compressor, but I don't understand how it maintains the 15/30 F difference regardless of the indoor heat load. Thank you
This is where all the previous videos come into play.
The compressor does not do co TROL the condensor TD or the compression ratio. It just uses positive displacement to move a set volume under giving conditions. You can track the displacement via a performance chart for the compressor with a given set of conditions.
As the temperature of the air outside goes up, more heat will be reacting against the coil, and that heat energy will transfer through the copper to the refregerant. The heat energy will excite the refregerant molecules faster causing higher pressure and thus a higher saturated temperature.
As the outdoor temperature goes up or down the pressure in the condensor will go up and down.
Now if we slow the fan down, we end up with less heat transfer. The heat builds up around the condensor and that heat raises pressure and then raises the compression ratio.
If we move more air across the condensor, the heat transfer is faster and more effectively cooles the coils, the molecules move slower, this less pressure, lower compression ratio and a lower saturated temperature.
The problems is moving more air requires a motor that uses more energy.
Alternatively we can use a larger condensing coil to transfer heat better.
The larger coil allows more air across more air across the metal. The better heat transfer allows the molecules to move lower and this lower pressure and a lower compression ratio and a lower saturated temperature.
It's all about the heat transfer from the air and the refregerant.
The amount of refregerant can also affect this. Less molecules of refregerant means less pressure and more molecules of refregerant means more pressure. This is because the metering device allows so much refrigerant flow. The rest backs up in the condensor.
The manufacture and engineers design all of these factors together. The compressor volume, compressor motor size, fan blade size, fan motor size, coil size, tubing size, metering device size and more for the overall effecency they are trying to achieve.
Is there an app to quickly calculate compression ratio in the field?
Yes, measurquick app does it automatically.
It works with digital probes attached to the equipment and GPS to calculate location, uses weather data and calculates compression rational time!
Apart from the terminology of pressure ratio ( discharge pressure abs / suction pressure abs ), there is also terminology of pressure difference ( discharge pressure - sucton pressure ) , what is the significance of this pressure difference ?
It's how much work the compressor is doing, it greatly affects how much volume of refregerant it can move and the heat buildup in the compressor.
@@love2hvac Thanks for the reply but I still cannot quite differentiate the significance of pressure ratio ( Discharge pressure in abs / Suction Pressure in abs ) and Pressure difference ( Discharge Pressure - Suction Pressure ) coz I am still literally stuck with the understanding and impression that both Pressure Ratio and Pressure Difference have to do with doing the compression work which is to bring the suction pressure up to the Discharge pressure level......? Other than that , I am still not able to grasp the understanding from other / different angle .Please kindly help to clarify in detail... thanks
With regards to the measurement by the pressure gauges in HVAC System, understand that the pressures measured will need to be added by the atmospheric pressure ( 14.7 psig or 1 bar or 1 atm ) if we are to calculate pressure ratios. However I still cannot really understand the real influence and impact that the atmospheric pressure imposes on the measured pressure because it is a close system and not subject or exposed to outside air or ambient pressure.. What is the real logic here ?
We pull a vacuum to remove all atmospheric pressure. Then we add refrigerant into the system. There is refregerant added to the system just to get back to 0 psig. That refrigerant must be accounted for.
You pressure gauge does not aclint for that so we must manually add that back in.
It's only going to be 14.7 at sea level.
If you where in Denver Colorado the atmospheric pressure would besay 12psia. So when you pulled a vacuum, you could only remove 12psia. Then you add refrigerate to get back to 0. So you would add 12 psi to each side to do the compression ratio because that's the true amount of pressure the compressor is pushing against.
"You're under pressure!" - So true! :O
It's really not clear to me why condensers are kept to a minimum size, seems additional heat rejection would require less energy for any system/refrigerant?
I must not be comprehending something.
It is a lot of info, just view the video again, even a few times if you need to.
@@Michael-pz1hc Put another way, I'm attempting to understand the downside (if there's a technical reason) of using an oversized condenser.
That's a great question.
Refrigeration has less room physically, typically. Right space restaurants and limited space are one issue.
The second is control. We run ac in the summer only. Refrigeration has to run all year. They need capacity contol usually by flooding the condensing coil with refrigerant via the fan cycle or headmaster. Larger coils would require significantly more refrigerants to overcome these conditions and build the necessary to build pressure to push into the evaporator coil past the metering device.
As for residential there gets to be limited. The saturated still needs to be so much above ambient so you can achieve subcooling. The lowest liquid line temperature can be ambient. So no matter how many coils you use it just gets to the point of diminishing returns. Not able to gain anything vs the cost of making it larger.
@@love2hvac "The lowest the liquid line temperature can be, is ambient."
Perfect answer, thanks! ;)
I was wondering, do compressors that use variable speed, do they control subcooling? ie, get their feedback from the calculated subcooling?
We have not got to that yet, but no.
@@love2hvac I have been thinking about this, and don't know how else it could control an inverter condenser unit with multiple indoor evaporators. It's only control feedback mechanism would be subcooling? Or should I keep watching and learn... Seriously, I have learned so much from you, and am very grateful. You are by far, the best online Hvacr instructor.
I will get there eventually.
Each head unit determines it's needs based on how far the return air temperature is from the set point temperature. They will also have a coil sensor and sometimes a supply air temperature. It controls the fan speed based on this also. It then sends it needs to a mixing box or the condenser directly depending on model. The mixing box or the outdoor unit will open the EXV (EEV) to send refrigerant to that head unit as needed. It can measure the superheat coming back at that point as well on some models.
The outdoor unit and compressor calculates the refrigerator needs form all the head units and uses an algarethem to determine how much refrigerant volume to pump. Higher demands it pumps more volume, lower demands it moves slower volume, but because the volume is low the velocity of the refrigerant will be low and can loose oil, so the algarethem determines how often and how long the compressor needs to speed up to get the oil return. The outdoor fan is also variable, so the outdoor fan will speed up and slow down to maintain a design TD and also appropriate subcooling. However there are other controls inside also, such as hot gas bypass, and a host of others.
@@love2hvac I'm referring specially to mini splits for my example. If multiple evaporators are running from a single condenser unit, surely the superheat of each individual evaporator would be managed by their own txv's? Therefore, the load on the condenser could only be managed by monitoring the subooled refrigerant and altering compressor speed accordingly? I don't know what other purpose a variable speed compressor would serve? In mini splits, do the indoor evaporator units use solenoid valves to cut off refrigerant flow when no demand is called for? At least when multiple indoor units are used?
The last example was specifically for multiple head ductless (mini split) to 1 condenser.
At 12:40 I'm sure I'm not the only 1 that realized the 390 psig (or am I the only 1 listening?) 😉
And that's after in double checked it! Haha the first video I did the math while recording. The editing was just to much so I did this.
@@love2hvac this is awesome either way. I use measure quick and I see compression ratio on there but I never understood it so clearly. thank you
[Edit: this is dumb, see my reply below] So why does it matter if you're using psia or psig? As long as you're using the same on both sides, it shouldn't matter. It's just like a regular fraction in math class. If you add 14.7 to the numerator and then add it to the denominator as well, you should immediately cancel it out to simplify. You can even add a dinosaur to the top and bottom. If the same dinosaur is on the top and bottom, both dinosaurs cancel each other out.
Ok so this is actually strange. I just set out to prove that the 14.7 doesn't matter but I actually proved it does matter. 226 divided by 76 is 2.97 but 240.7 divided by 90.7 is 2.65. Huh.
Why was I wrong?
So I think this is because when you add a dinosaur to the top and add a dinosaur to the bottom of a fraction, you don't get to cancel them out. You only get to cancel them out when you multiply them by the numerator/denominator.
So for example, if there was a fraction 2 over 1, or 2/1, that would obviously reduce to just 2. But if you add 2 to both numerator and denominator, you get 4/3, which definitely does not reduce to 2. However, if you instead multiply numerator and denominator both by 2, you get 4/2, which does in fact reduce to 2.
So I asked ChatGPT about this and it appears as though I was misusing "the multiplicative property of fractions". It doesn't apply to addition or subtraction.
Yep, math!
Also, if we where at sea level 14.7 we pull a vacuum below atmospheric -14.7. to get back to 0 we must add in 14.7 psi of refregerant just to get back to 0.
When the system is running, the suction side will have a larger impact on compression ratio than the high side. Keeping the house a few degrees cooler requires more work than the outdoor temp being a few degrees warmer.
It's also important to note it's not always 14.7, at altitude the number will be less and the compression ratio has to account for that.
For example Denver Colorado we would add inly 12.4
Who told you refrigeration equipment was poorly designed in the OLD DAYS of the 80s Lol, if anything it’s worse today with the cheap crap these techs have to deal with, cheaper thinner coils, crazy refrigerant blends, power saving fan motors at the expense of proper air flow, computers replacing simple reliable controls, if anything i’d worry more about the equipment design of these days. I started in this trade in the 70s and this video dissing the equipment of the “OLD DAYS” is totally off the wall, i’ll take the old reliable equipment over this new crap any day! Please explain to me how building a piece of refrigeration equipment that has to be replaced three times to equal the life expectancy of the same piece of equipment of the OLD DAYS is supposed to be environmentally conscious.
#1 I reached the entire video and nowhere in there did I say equipment was poorly designed in the old days.
#2 this video has nothing to do with all that rant you gave. It was about compression ratio.
Fact a larger designed condensing coil will provide a lower compression ratio.
I'm the 80's it was designed for a 30TD meaning the head pressure was 30 degrees higher than the ambient.
As time progressed we figured out, increasing the condensing coil size transfered the same amount of heat with a smaller TD. The lower saturation temperature the lower the head pressure the lower the compression ratio.
I will not acknowledge the rest of your rant because it is irrelevant to the topic of this video about compression ratio.
Bro what is up with you today?
All of this anger has nothing to do with what I said in the video.
Are you alright?
Haha dyslexia here too. I actually almost cost my company a few thousand dollars because of it 🙈
Oh no! I was always so nervous with bids. I had a guy who wanted to give me his commercial company. It was all big bid work. I turned it down, the anxiety was just too much. One bad bid and it's all done. Haha I'm glad you made it threw.
@@love2hvac was actually a license for a well known unit and you get one shot. I gave the wrong serial number. Usually it's to bad and you have to pay again. Thankfully I was able to get it. Phew