Hi Gary, i am currently at college doing my level 2.
Do you know of any books etc that will help me along the way?
many thanks
Colin
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Hi Gary, i am currently at college doing my level 2.
Do you know of any books etc that will help me along the way?
many thanks
Colin
wow.I been doing trailers for five years. Never had info like this. I can take a compressor out and replace it with a new one, go through all the steps to have a good working reefer unit. I have replaced a condenser and an evaporator, pressure tests and evacuation on these things. But I never, never had it explained like this. Just by what you shared it makes me think like I dont know much about these things. Can I be your son?! Thank you very, very much.
Respected Gary Sir
Simple and easily understandable. Thanks a lot for enlightening us.
the makes my job simpler to make the architects and other new entrants easily.
Regards Sridhar
Thanks Gary. This has been very helpful. I definitely needed it.
Hi, I'm new to all this. have found the forum amazing usefull, having been sent on a couple of basic courses, which mainly teach you all the legislation, then left a static sight with no guidense or help. I have a slight confusion which is probably easy to resolve. After reading the guide to calculating superheat and subcooling (which made alot make sense) I use my companies service sheets to record the information needed, but instead of asking for liquid line temp. and press. they ask for discharge temp, press to be recorded. I would have assumed discharge would suggest after the compressor, are they the same thing or is this more likely because the sheets are incorrect. This probably seems like I'm being pedantic but untill I found this forum it was causing me all kinds of confusion.
Compressor discharge temp is measured on the discharge line about 6 inches from the compressor.
Superheated vapor enters the compressor and is compressed, which adds to its heat content, which in turn gives us higher discharge temp along with the higher pressure.
In general, the higher the compressor inlet superheat, the higher the discharge temp as they go up and down together.
However, if the discharge temp rises without a corresponding rise in inlet superheat, this would indicate a possible problem with the compressor.
So... we might say that the discharge temp, in combination with other indicators, gives us a very general feel for the overall health of the system.
That said, I prefer to look much closer at system performance and do not view discharge temp as an important indicator. I very rarely bother measuring it.
now only i become the member & i am so happy to see how Gary has made the refrigeration subject so simple & interesting .I will like to see many more knowledgable issues in future .Once again i appreciate the gary's effort.very well done.
cheers.
Thanks for you help gary, it all helps when trying to apply the theory to practical application. My next question is about high pressure and low pressure cut outs. How do you go about testing these safety features, on both courses we were told to check these but noone has ever said how.
Pressure switches can be tested with a nitrogen via a regulator/gauge, Raise pressure until switch changes. make a note of actual pressure, then slowly release until switch changes back. Adjust until you reach desired set points. "Note" the scale are indicators only, for rough adjustment.
On site, you sort of break a few rules, for HP (discharge) you "slowly" close discharge valve, keeping a very close eye on your gauge. Hp switch will trip (at some set point). (if manual reset then no other settings to check) if auto reset then watch as the pressure drops note switch change, for LP similar process but switch is is opposite direction
hi garry very nice thread should answer a lot of newbies questions!!!
Don't forget to click the reputation button. :D
It's really useful, Garry. After 1 year of self-learning, you give me have a chance to review what I have been done and believe were right or not.
Can you write something about system balancing (using captube) and how to get the max cooling capacity out of the component we have? Or say how to tune a unit?
How the excessive Cond airflow and/or Evap airflow can bring the Capacity down? It looks like I have more SC, lower HP, so I can add more charge to control SH after drawing the Capacity line against charge amount. But it made no sense as I did not get what I had.
Capacity has always been a problem of mine since I started playing :confused:
Thanks, Gary
Insufficient (not excessive) airflow brings down capacity.
In Freezer with capilary as metering devices, how to determine if the system is overcharged or less charged with a refirgerant? Can we decide this base on the suction line temp., discharge line temp./ before filter dryer temp.?
Hi Gary,
I've a question for you. In Freezer system, how we can determine whether the system is overcharged or less charged base on the suction line temperature (evaporator in / out), accumulator out temperature, before filter dryer temperature, discharge line temperature? Let say the system is unsing capilalry as the metering device. Hope you can give me some hints regarding this.
Before/or filter dryer temperature will tell the difference.
In a system that is short of refrigerant the condenser would have a gradual change in temperature from the top all the way down to the strainer. In fact the strainer will be slightly above room temperature.
In a system that is overcharged strainer will be at same tamperature as lower part off condenser.
http://www.supco.com/images/pdfs/Man...g%20Manual.pdf
Most accurate would be to weigh in the charge.
thanks for directing me to your thread on the basics. It really brings it all together for me in plain simple language. Much appreciated!
Hello,
Here is a question from a newbie of both the forum and the world of refrigeration!
You see the terms evaporating temperature, condensing temperature in the literature. My question is where exactly these values are measured from? For example if we take the evaporating temperature; is it measured from the entrance or the exit of the evaporator?
Thanks in advance!
The evaporating temperature is the saturation temperature which corresponds to the low side pressure on a pressure/temperature chart.
The condensing temperature is the saturation temperature which corresponds to the high side pressure on a pressure/temperature chart.
yes! I have one of Gary's TECH books and they cut to the chase to real t/s, a great purchase if u can!!!
Respected Gary
Where I can get the books Tecch method troble shooting? Is there any agent in India?
This thread is a wealth of good information. It is a shame that the people who need this info the most do not look at / subscribe to free sources of education such as this web site.
Thanks
From the west side of the pond.
Hi, I have a quick question about connecting gauges, don't think it has been asked before. I always seem to release alot of gas when connecting guages to split A/C systems. Is there a nack to it, like pumping down a system before hand. Is it best to connect when the system is running or off, both high and low sides.
Turn unit on cooling, close partially valve on smaller pipe and when pressure falls to around 1 bar disconnect your gauge. Open valve fully and put valve caps.
Or buy Refco Quick Couplers.
Hi gary sir
Before 25 years ago self diagnosing systems are in market!! Ex: carrier 30 GT chiller. Now all commercial chiller manufactures are designing self diagnosing based refrigeration fundamentals. Some sample alarms such as- low suction super heat, high saturation suction temperature, low discharge superheat…………….etc.
Your 101 is very useful, thanks a lot
Moideen-dubai
;)
Something like e.g. - low suction superheat - is a symptom, not a diagnosis. In my opinion, these systems are not self-diagnostic.
When they can say things like - insufficient evap airflow, or liquid restriction, or refrigerant overcharge, or inefficient compressor, etc, etc. etc... then I will be impressed.
Gary,you're a legend.I always follow your post since i become a member and your ideas are great.
I'm a legend in my own mind... lol
Something like this:
http://www.ecotechnics.it/en/product...lock-2000.html
Yep... something like that.
I had a couple diagnostic programs that I marketed on floppy disks back in the early 1990's. One for refrigeration and the other for A/C.
Crude but effective. Programmers would have a good laugh, but it told you what was wrong with the system.
Then they started putting USB connectors on printers and the printer function no longer worked. Started getting complaints that my programs wouldn't print the results, so I discontinued the products. I'm a service tech, not a programmer.
i thnk a cooling effect on d finger will appear...due to d reason- d water on d finger will absorb latent heat of vapourization nd will vapourize...as a result d temp. of d finger will fall nd a cooling effect will b produced...
good explanation welldone
hi guys this is a great idea love it:):) i will have to read the technical stuff again cos some of it leaked out my head already an i have learned some things as well an only been in game 20 plus yrs if i may be so bold as to make a small contribution even though most of you are super technical more than me not enough engineers stop and actually look at what there working on an do the stuff i was taught look at it listen to it and feel it there the most important tools we have you can see a design floor in a system and adjust for it you can hear a compressor straining under excessive load and you can feel if an evap is fully wet all the way accross and then ya can break out the super tools to fix it ;)
There seems to be a great deal of confusion about subcooling, so let's take a closer look:
The vapor loses its heat and turns to liquid as it moves very rapidly though the condenser. This does not happen all at once, it is a gradual process.
There is a point where the last vapor bubbles disappear and the mixture becomes solid liquid. Let's call this the "solid liquid point" or SLP.
Technically, if there is enough refrigerant to modulate the superheat at the evap outlet, then the system will function properly, but this is not the full story. Vapor bubbles travelling through the TXV orifice over a long period of time will wear out and distort the orifice, so to ensure long life for the TXV we want solid liquid at its inlet.
So... our minimum charge would have the SLP at the TXV inlet.
At the other extreme, we do not want liquid backing up into the condenser as this takes up condensing space and drives up the high side pressure.
So... our maximum charge would have the SLP at the condenser outlet.
The problem with the minimum charge is that changing conditions could have vapor bubbles at the TXV inlet. The problem with the maximum charge is that changing conditions could have liquid backing up into the condenser.
So... the ideal charge would have the SLP somewhere in between the TXV inlet and the condenser outlet. Thus, we want the SLP to be at the receiver outlet... which is why the sightglass is normally placed there, and why we want to measure subcooling there.
If we monitor the subcooling while observing the sightglass, on a wide variety of systems, we will find that the last vapor bubbles disappear at about 10-15F/5.5-8.5K subcooling. Thus we can identify the SLP by measuring the subcooling at the receiver outlet, ensuring that (with all else functioning properly) we are neither undercharged, nor overcharged.
Respected Gary,
Thank you very much for your "Refrigeration 101", the highly informative article.
May I ask you how can we check the heat absorbing capacity of a fin and tube evaporator, if we do not have any product details on it? Just we have the physical size of tube diameter, distance between end fins, fin spacing, fin thickness, number of tubes, number of elbows, fin width, refrigerant temperature, and cabinet temperaure. Also we know the fin and tube material, refrigerant and its properties. (forget about the oil film on the inner wall of the tube).
Wishing you all the very best:)
Thank you
Rayin