PDA

View Full Version : superheat



hvacgreen
20-03-2008, 01:37 AM
hey everybody, im new to the site but have a bunch of questions about calculating superheat and what the purpose is of superheat and what it tells me when i figure out how to do so, thanks

nike123
20-03-2008, 02:25 AM
Did you try to search this board for that?

The MG Pony
20-03-2008, 02:37 AM
Oh goat not another one of these threads!

Us ethe search function and if you survive the first multipage thread we'll give you a cooky and your brain will melt down with an over load of info on the subject!

US Iceman
20-03-2008, 03:26 AM
...im new to the site ...


And to the business also. Have you had any training or schooling in this industry at all?

Your information says you are a service tech.

powell
20-03-2008, 04:34 AM
hey everybody, im new to the site but have a bunch of questions about calculating superheat and what the purpose is of superheat and what it tells me when i figure out how to do so, thanks

Well, this thread can get quite detailed so I'll start my post with the simple explanations.

Superheat definition: Refrigerant vapor whose temperature has risen above the saturated temperature. There is no liquid refrigerant present.

P/T charts do not apply, there is a temperature rise without a rise in pressure.

The operating superheat setting for a refrigeration system depends on the temperature difference between the refrigerant and the medium being cooled.


Calculating: Measure the suction pressure and then convert that pressure to a temperature using a P/T chart. Then measure the actual suction line refrigerant temperature using a good thermometer with the sensor strapped and wrapped to the suction line. Then subtract the converted temperature from the actual measured temperature and you will have your superheat value.

Purpose and what it tells you: If these procedures are measured at the evap outlet it tells you if the metering device is working properly and if the evap coil is removing heat efficiently. If measured at the compressor inlet, usually the easiest to measure, you'll get a quick idea of what is happening at the evap outlet and if the compressor is in danger of liquid floodback or overheating.

Here are a few links you should view and read.;)

Sporlan: http://www.parker.com/literature/Literature%20Files/Parker.com/Literature/Sporlan/Sporlan%20pdf%20files/Sporlan%20pdf%20010/10-11.pdf

Copeland; http://www.hvacrinfo.com/cope_ae_bulletins/TAE1260.PDF

All Copeland AE bulletins: http://www.hvacrinfo.com/ae_index.htm

Gary
20-03-2008, 04:36 AM
Just click on the search forum button near the top of this page and type in "superheat". You will find everything you ever wanted to know about the subject... and much much more.

Grizzly
20-03-2008, 10:08 PM
hey everybody, I'm new to the site but have a bunch of questions about calculating superheat and what the purpose is of superheat and what it tells me when i figure out how to do so, thanks

Welcome to the forum hvacgreen

If the majority of the answers you have received
seem a little non committal to you.

It is nothing personal it's just that as you spend time on the forum.

You will begin to realise that every two or three weeks maybe.
Someone new joins and innocently asks about
The most basic but fundamental principle... Super Heat!

So take the advise and do a search.

Also don't be put off.. contribute and what you get back will be worth it!

Grizzly

marc5180
20-03-2008, 10:50 PM
Try
http://www.refrigeration-engineer.com/forums/showthread.php?t=5135&highlight=superheat

It explains all you need to know about superheat.
Thanks

Brian_UK
20-03-2008, 10:55 PM
Aw, come on Marc, he didn't even have to 'search' now that you've done it for him ;)

marc5180
20-03-2008, 11:19 PM
'cos i'm such a nice person:D

Gary
20-03-2008, 11:22 PM
By all means, don't take any of these remarks personally.

Do a little reading and feel free to join in the ongoing discussion.

And welcome to the forums. :)

hvacgreen
21-03-2008, 01:02 AM
And to the business also. Have you had any training or schooling in this industry at all?

Your information says you are a service tech.
yes i do have 3 years of schooling and about 2.5 years in the feild. i see more refridgeration than centerals but im looking to changes companys from appliances to split systems and heating, im 22 years old so i have alot of catching up to do with you senior techs, but thanks for the insult buddy;)

US Iceman
21-03-2008, 02:29 AM
My comments were not meant as an insult. More as a skeptical set of statements of how a service tech does not know what superheat is or used for.

I must admit I was more than slightly surprised that an instructor or mentor had not mentioned this subject to you before.:confused:

powell
21-03-2008, 03:28 AM
hvacgreen,

Ask all the questions you want. I realize that sometimes the education in HVACR classes can be quite overwhelming. This forum is a good source for knowledge and you will get an answer from most without prejudice. ;)

Welcome to the industry.

Regards.............Powell

The MG Pony
21-03-2008, 03:30 AM
Ahf 13 posts! you see what you've started now! ;)

Larry2
21-03-2008, 04:01 AM
I think we need to be patient with this sort of question. I hate to admit, but in the late 60's and early 70's I helped comission a lot of A/C units without knowing what superheat or subcooling was. We just sort of knew what to expect for gauge pressures and temperatures on a hot July day. Energy was cheap. If the system cooled the home, everyone was pleased. We had a good feel for system performance and we had lots of satified customers. Even more embarassing... we assembled a lot of systems without owning a vaccum pump. Owners and even seller didn't appreciate the cost of this for a long term system ownership. It was not until a system could not be made to work that the business bought a vaccum pump for us. I hate to think about the R22 vented before then.

I think the trade will benefit if the professionals here will take the time to extend their experience to newcomers on this topic, because there is probably no error more frequent than to add even more gas to an overcharged system that is not living up to expectations.

I've read consumer reports that most systems are overcharged. Most reports are that nearly every complaint causes even more gas charge to be added even when the sytem is 10% overcharged or more. The more frequent the consumer complaint is for poor performance, the worse the overcharge condition is. The next mechanic adds a bit more in the hopes of doing something when nothing obvious is wrong.

On a fixed orifice system, this charge condition is pretty critical. On a txv system, a bit over or under has a lesser effect. Those who watch performance closely on a fixed system will be astonished how much difference a few oz makes.

I think one thing that is not adequately addressed is that superheat and subcooling measurements are horribly damaged by poor instrumentation. It doesn't take much error on meaurements to cause wrong choices.

I think this topic is worth more discussion and advice than recommendation to do a search.

US Iceman
21-03-2008, 02:54 PM
...you will get an answer from most without prejudice. ;)


Prejudice has nothing to do with this. At all.:(

My initial comments were intended to be a statement about the lack of education that occurs in this industry. That's everyone who has an opportunity to help instruct a new person. I also feel with the Internet there are a lot of opportunities now where a person can help themselves to certain extent.


Before everyone starts to jump up and down and throw recriminations, think about this. Here is a person who has been in the industry for 5.5 years and doesn't know what superheat is. I am not directing this at hvacgreen, just the situation.

Grizzly
21-03-2008, 03:37 PM
I think we need to be patient with this sort of question. I hate to admit, but in the late 60's and early 70's I helped comission a lot of A/C units without knowing what superheat or subcooling was. We just sort of knew what to expect for gauge pressures and temperatures on a hot July day. Energy was cheap. If the system cooled the home, everyone was pleased. We had a good feel for system performance and we had lots of satified customers. Even more embarassing... we assembled a lot of systems without owning a vaccum pump. Owners and even seller didn't appreciate the cost of this for a long term system ownership. It was not until a system could not be made to work that the business bought a vaccum pump for us. I hate to think about the R22 vented before then.

I think the trade will benefit if the professionals here will take the time to extend their experience to newcomers on this topic, because there is probably no error more frequent than to add even more gas to an overcharged system that is not living up to expectations.

I've read consumer reports that most systems are overcharged. Most reports are that nearly every complaint causes even more gas charge to be added even when the sytem is 10% overcharged or more. The more frequent the consumer complaint is for poor performance, the worse the overcharge condition is. The next mechanic adds a bit more in the hopes of doing something when nothing obvious is wrong.

On a fixed orifice system, this charge condition is pretty critical. On a txv system, a bit over or under has a lesser effect. Those who watch performance closely on a fixed system will be astonished how much difference a few oz makes.

I think one thing that is not adequately addressed is that superheat and subcooling measurements are horribly damaged by poor instrumentation. It doesn't take much error on meaurements to cause wrong choices.

I think this topic is worth more discussion and advice than recommendation to do a search.

Larry
As they say around here! "You fill your boots"

Which basically means If you feel like it you carry on!

But likewise if others get tired of explaining the same old questions.
You can't blame them can you.

lol Grizzly

SteinarN
21-03-2008, 04:05 PM
Before everyone starts to jump up and down and throw recriminations, think about this. Here is a person who has been in the industry for 5.5 years and doesn't know what superheat is. I am not directing this at hvacgreen, just the situation.

It don't surprice me that much. People are different. I can only speak for my self and those I know of. I'm in the lucky situation that I take the teoretical stuff quicly. When I, at age 31, for the first time studied a log P-h chart and read it's explanation, I got a good understanding of it and what it really ment already the first day. Super heat and sub cooling seemed obvious.
I had an apprentice a couple years ago. He had two years in school, one year general mechanics and the second year refrigeration. He was accurate and careful when installing pipes and other equipment. Showed up every day, took good care of the van, had it tidy and clean innside and was a polite and co-operative guy. But he had very hard to understand the physics taking place innside a refrigerating system. He should have learned it in school, but had obviously not been able to get a clear understanding of it. I tried several times to explain it to him, but after a few weeks he could ask again.
He now works at an other ref company. He has now got a better grip on the physics innside the system, and is doing well.

What I'm trying to tell with this little story is that it's a huge difference between people in how quicly one learn different things in our business. I think many in our business is inclined to the practical work, installing pipes and equipment, welding and soldering etc. Those of us in this business which (hopefully) has a better understanding of the more teoretical fundamentals have a responsiblity to try to do our best to bring that understanding to our colleagues. I think this is a field where many companies maybe have a job to do.

US Iceman
21-03-2008, 04:46 PM
Those of us in this business which (hopefully) has a better understanding of the more theoretical fundamentals have a responsibility to try to do our best to bring that understanding to our colleagues.


This I completely agree with. It's one of the reasons I spend so much time on this site answering questions and discussing topics.

Someone once said "It takes a village to raise a child." The refrigeration business is not much different. Those who know should help and teach.

I still remember what is what like when I asked questions (back when I was younger than hvacgreen;)). The old timers would explain it once and you were expected to figure it out to the point where you could ask for additional explanations.

It made you more independent and self-sufficient. That's part of teaching also....

The MG Pony
21-03-2008, 05:06 PM
We not only have villages but GigaCities in the SH arena! In fundamentals area we have threads you could make an empire out of!

Chunk
21-03-2008, 05:17 PM
And i would just like to say that all you oldies (and some younger ones) do a brilliant job in helping us less knowledgable people.

I have to say that without this site and the technical knowledge within, i would have struggled with a lot of stuff,so keep up the good work.:D

Gary
21-03-2008, 05:23 PM
Back when I was in refrigeration school, about 40 years ago, superheat was something you needed to know about for adjusting TXV's... and subcooling was a little known phenomenon that had no practical use.

Then 20 years ago, when I introduced the TECH Method trouble shooting procedure, which relies heavily on subcooling and superheat, all I got was blank stares and remarks like, "That's not how I was taught to troubleshoot", the implication being that I didn't know what I was talking about.

Not much has changed. The schools are still teaching "frostline" and "beer-can cold". The biggest change is the introduction of weighed in charges, so people don't have to think. If the system doesn't have a charge weight on the label, everyone is lost. How does the factory determine the proper weighed in charge? Subcooling and superheat.

It's frustrating. :mad:

But back to the subject:

It is much easier to just send newbies to one of the many superheat and/or subcooling threads than to rehash the subject every time someone signs up.

It's not that we are unwilling to help and newbies are welcome to read a little and then jump in with their remarks and/or questions. We are here to help.

US Iceman
21-03-2008, 07:03 PM
It is much easier to just send newbies to one of the many superheat and/or subcooling threads than to rehash the subject every time someone signs up.


That is exactly what I have been thinking about also. Instead of having 100's of threads on explaining subcooling and superheat, why not have just one thread for each subject and make it a sticky thread?

The sticky thread would be the definition of each. Any time the topic shifts to: how do I use superheat on something, or how much subcooling should I have in a condenser, etc., etc. then a new thread should be started.

The sticky threads would only be for the definition so that anyone could see them.

hvacgreen
21-03-2008, 11:20 PM
Prejudice has nothing to do with this. At all.:(

My initial comments were intended to be a statement about the lack of education that occurs in this industry. That's everyone who has an opportunity to help instruct a new person. I also feel with the Internet there are a lot of opportunities now where a person can help themselves to certain extent.


Before everyone starts to jump up and down and throw recriminations, think about this. Here is a person who has been in the industry for 5.5 years and doesn't know what superheat is. I am not directing this at hvacgreen, just the situation.
like you said iceman, you can search the internet and usually come out with a answer, but mm the kinda person that would rather discuss a question than read about it. i now brushed up on the superheat questions thanks to the helping people on the site "including you iceman" but i wouldent say i have 5.5 years in the industy, its more like 48hours. see i went to a tech school my junior and senior years of high school and became very interested in electricity and refridgeration so i went to lincoln tech institute and experienced so many things that i couldent possibly remember in a years time, then i graduated and started working for and company that works on a wide range of small end appliances and hvac, so that stuff that i thought i knew a little about suddendly dissapeared. so im tring to brush up on my studies and move to different company that not only pays more but gives me more work and experience, thanks for all the help and expect more questions:)

US Iceman
22-03-2008, 01:24 AM
...so that stuff that i thought i knew a little about suddenly disappeared.

Now that can happen to anyone.;) You will find there are a lot of things you will have to relearn over the course of years. This falls into the category of use it or loose it. Nothing to apologize for...

I hope you know none of my comments were personally directed towards you. I get frustrated with schools that are supposed to teach...

Darc
22-03-2008, 03:35 AM
Prejudice has nothing to do with this. At all.:(

My initial comments were intended to be a statement about the lack of education that occurs in this industry. That's everyone who has an opportunity to help instruct a new person. I also feel with the Internet there are a lot of opportunities now where a person can help themselves to certain extent.


Before everyone starts to jump up and down and throw recriminations, think about this. Here is a person who has been in the industry for 5.5 years and doesn't know what superheat is. I am not directing this at hvacgreen, just the situation.

Its funny that you should say this, I am a 3rd year adult apprentice and I have had to learn just about everything myself by asking questions at the school and by finding answers to my questions on the internet (this site has been a massive help). The tradie teaching me, whilst being an awesome fridgie is either unwilling, unable or doesnt know how to teach me correctly.