What apprenticies need

[damo1206]

Hi Guys

As I am sure all apprenticies will tell you, Collage is a waist of time. The only way we learn is out in the field. My tutor just does not make himself clear. (Not sure if even he knows)

Speaking on behalf of all apprenticies in class 2ref, we need someone to talk us through charging a chiller. We need to learn about superheat, and how to check it. We would like someone on here who has had the years of experience. We need to be able to go to a chiller that is S.O.G and add the correct amount of refrigerant.

If someone could reply to us with the correct step by step instructions, then we can print it off and be our bible. We would like you to give a example of how to check the correct pressures of a display chiller running on R404.

Many thanks for all your help

Damon, Rich, Steve, Paul, Steve B, John, Rob, Trevor
(class 2ref)

[Gary]

You need to know a lot more than that. If you think the only thing (or even the most common thing) that can go wrong is SOG, , then you are already in trouble.

[eggs]

I think you need to club together to buy "Tech Method" by ^Gary^.
Excellent reading, and as near to a bible as you will get. I keep a copy in the van.

Eggs

[US Iceman]

As I am sure all apprenticies will tell you, Collage is a waist of time.

I 'm not so sure that is correct. The purpose of school is to provide you with the understanding of the principles involved and how they interact. Schooling cannot provide experience, it is the foundation on which you increase your knowledge.

The only way we learn is out in the field.

The increase in exposure to the real world helps to provide the experience.

If you do a search on the site for superheat, you will find a lot of posts already presented.

[Brian_UK]

Damo, I am a little confused - you haven't stated your age in your bio but reading an earlier post from you it staes that you have been doing this for over 30 years.

I have been in the refrigeration trade now for thirty years. I have worked for the same company in all that time. I have now realised i have got to move with the times with all these new refrigerants.

I am sorry and ashamed to say that i still charge systems with the touch of my fingers on the suction line. I have never been shown any other way. My company are about to send me on my handling course. I really dont want to look stupid on this course.

Can anyone explain in simple terms about the superheat and how to charge a system the correct way.

Thank you for your time from a man who is feeling his age.

Surely you have picked up something in that time.

Also, if all of you are feeling under trained by the tutor you should approach the college and advise them of this fact. They are taking money under false pretences.

[damo1206]

This is a college sign in. We all use this site. there are ten of us that are studying together. Hope that explains. Couple of older guys on the course.

[Brian_UK]

So it might help if you sign your own posts even if you are logged on as a "corporate".

Then at least we will know who we are reading and writing to.

[Andy]

Hi Guys


If someone could reply to us with the correct step by step instructions, then we can print it off and be our bible. We would like you to give a example of how to check the correct pressures of a display chiller running on R404.

Many thanks for all your help

Damon, Rich, Steve, Paul, Steve B, John, Rob, Trevor
(class 2ref)

I have yet to find a chiller running on R404a, chillers are not supermarket packs.

Was R22
R407c is common and R134a is used on larger chillers.

Kind Regards Andy

[Andy]

Hello Guys,

Charging chillers is mostly by weight. When working on a chiller that has lost charge it is best when you are not experienced to decant all the charge and recharge to the charge on the rating plate.

Basic chiller charging starts with flow, is the flow through the chiller correct?

Clean your pump strainer and clamp test the chiller pump motor and compare this current to a pump curve chart, to at least give you a vague idea what the pump is doing.

Then check the suction superheat, this will be always below 10k.

Sightglasses are usefull but you need to see what the subcooling is off the condenser, I would be looking for 3k, possibly 5k if the subcooling coil was generous on the condenser.

Condensing temperature will vary, but most chiller in the UK are Italian, and will be designed to ambients of 45 deg c, so I would expect a minimum condensing temp of 40 deg c, on standard chillers.

Evaporation will vary, but will be at least 0 deg c but if the water leaving temp is high, anything up to 8 deg c.

I'm sure Gary will give you better advise.

Kind Regards Andy

[icecube51]

if they can read the plate that is attached to the machine,and have a manual for the command module,they find out everything they need to now about chillers. In the command module they will find for what temperatures the engine was build,incomming & outgoing ,the operating hours,and so one. google for some manuals ,Trane have some and Carrier also. suc6 guys.

Ice

[Gary]

In my part of the world, and apparently Andy's also, a chiller is a liquid cooler. But Ive been informed that in some locales a chiller is any medium temp machine. I'm assuming that a "display chiller" is a medium temp display case?

[Gary]

We need to be able to go to a chiller that is S.O.G and add the correct amount of refrigerant.

No, you need to be able to tell if it is SOG. Fixing it is the easy part. Finding out what's wrong with it is the hard part.

What should the pressures be? The correct answer is: It depends. Pressures vary according to a long list of conditions... and it isn't about pressures anyway, it's about temperatures. That's why we carry P/T charts. The reason we check the pressures is to find out what the saturation temperatures are.

[Bachuss]

Hi Guys

As I am sure all apprenticies will tell you, Collage is a waist of time.

If someone could reply to us with the correct step by step instructions, then we can print it off and be our bible. We would like you to give a example of how to check the correct pressures of a display chiller running on R404.

(class 2ref)

I'v been told that your superheat should range between 6 - 8 degree Celcius, to calculate

Take temp at evaporator exit, where the TXV bulb is (Exit Temp)

Take temp from center of evaporator (Saturation Temp)

Subtract Exit Temp from Saturation Temp and you have your answer.

Ok you have the Superheat (we will call this SH1 ), but you need to know what superheat should be generated by the gas your using so:

You attach your manifold gauges to the suction line close to the evaporator

Take the pressure and refer to your comparitor to convert the pressure to a Saturation temp

Subtract the Exit Temp from that to get the superheat that your refrigerant should have (call this SH2).

Ok, Compare the two, if SH1 is higher than SH2 thenyou are short on Ref if it is lower then you are over charged.

How my doin old timers?? please tell me if I'm wrong about this.

[Bachuss]

To recharge I would:

MAKE SURE MANIFOLD GAUGES ARE CLOSED

Attach lowside M Gauges to Lowside of system

Attach System valve M Gauges to R404 cylinder

open bottle

open lowside gauges

charge until sightglass runs clear

close lowside gauges/cylinder

check superheat

again oldies, how my doing? oh, by the way damo I too am in class 2ref I think you need to stop farting around in class and pay your tutors more respect because most of them will have made it in there respective feilds long before you were squermin round in your daddys scroat.

[Gary]

I'v been told that your superheat should range between 6 - 8 degree Celcius, to calculate

Take temp at evaporator exit, where the TXV bulb is (Exit Temp)

Take temp from center of evaporator (Saturation Temp)

Subtract Exit Temp from Saturation Temp and you have your answer.

Ok you have the Superheat (we will call this SH1 ), but you need to know what superheat should be generated by the gas your using so:

You attach your manifold gauges to the suction line close to the evaporator

Take the pressure and refer to your comparitor to convert the pressure to a Saturation temp

Subtract the Exit Temp from that to get the superheat that your refrigerant should have (call this SH2).

Ok, Compare the two, if SH1 is higher than SH2 thenyou are short on Ref if it is lower then you are over charged.

How my doin old timers?? please tell me if I'm wrong about this.

You are wrong about this.

SH2 is the proper way to check evap superheat. I have no idea what SH1 describes. And this doesn't tell you if you need refrigerant anyway. You are getting ahead of yourself. First things first.

If you have insufficient airflow through the evaporator, the suction pressure/temperature will drop like a rock and so will the superheat.

If you have insufficient airflow through the condenser, the suction pressure will rise and the superheat may go in either direction depending on other factors.

Delta-T's indicate airflow problems and should be checked first.

[Bachuss]

I admit I was wrong the dirrerence between SH1 and SH2 will not tell you if there is a refrigerant shortage. but what about my recharge procedure? Would that be acurate??Are you telling me that if you know your system is low on charge or SOG as youz like to say that the superheat will not have been effected? I think youll find that due to excess room within the evaporator there will indeed be more heat.If superheat is the temperature above boiling point then superheat is infact the difference in temperature between the liquids flash point and present temp soooo common sence would state SH1 would be the true superheat calculated from the system and SH2 would be the superheat measuered by both system readings and manufacturer data.

[Gary]

There is a list of things to check. Delta-T's are at the top of the list and superheat is on the bottom. You can't go straight to the bottom of the list, because everything on that list will affect the superheat.

[Gary]

The difference between your SH1 method and your SH2 method is the means by which you are determining the saturation temperature. If there is a difference between the two readings, it's because one method of measurement is more accurate than the other. Converting from pressure is more accurate.

[eggs]

Re: What apprenticies need

A feckin good hiding going of my muppets today!!

1, blunt hacksaw
84, lengths of unistrut
16, 100mm x 8mm rod with $h1t cheap nuts to put on 'em

Thats all the feckers are getting tomorrow.

Eggs

[Grizzly]

Re: What apprenticies need

A feckin good hiding going of my muppets today!!

1, blunt hacksaw
84, lengths of unistrut
16, 100mm x 8mm rod with $h1t cheap nuts to put on 'em

Thats all the feckers are getting tomorrow.

Eggs

My God Eggs!
Don't tell me you still expect them to learn how to cut with a hacksaw?
You will be telling us next that when they do progress to a chop-saw.
You will expect them to file the burs off!
If you really want to be mean, give them 32 tpi blades.
Grizzly

[eggs]

My God Eggs!
Don't tell me you still expect them to learn how to cut with a hacksaw?
You will be telling us next that when they do progress to a chop-saw.
You will expect them to file the burs off!
If you really want to be mean, give them 32 tpi blades.
Grizzly

Shape like they have today, and they'll be using their mummys best knife and fork.
..................and filing burs with their foreheads.
Thats if the lazy gits can get up in time!!!!

eggs

[Bachuss]

The difference between your SH1 method and your SH2 method is the means by which you are determining the saturation temperature. If there is a difference between the two readings, it's because one method of measurement is more accurate than the other. Converting from pressure is more accurate.

when I messure the superheat, would the best readings come from the txv for temp and as close as I can get to the evaperator? because the guy I work for is convinced that the temperatures will be the exact same.

[Bachuss]

when I messure the superheat, would the best readings come from the txv for temp and as close as I can get to the evaperator? because the guy I work for is convinced that the temperatures will be the exact same.

He wants me to explain that the example I have in my books shows the gauges attached right next to the txv bulb

[Bachuss]

There is a list of things to check. Delta-T's are at the top of the list and superheat is on the bottom. You can't go straight to the bottom of the list, because everything on that list will affect the superheat.

At college th lectures will give you a task and unless that task is to find the fault you do not go looking for one because the system has been setup to have the fault he has told you to fix. If he tells you to recharge a chill that is what you do because all he wants to see at this point is weather you know the correct recharge procedure. If he wants to see if your capable of finding a fault he wont tell you sog he wont tell you he wants you to recharge a chill thats sog, he WILL tell you to find what is wrong with the system. (he may not even wish you to fixit due to the next class needing it)

That said and done, out in the world yes you are ofcourse right as always, when arriving at a system thaat is not running properly there are loads of things to be checked before a diagnosis can be made but please appreciate that despite the way things are done in the real workd, in college they are tought backwards. first how to fix then how to find.

[Gary]

when I messure the superheat, would the best readings come from the txv for temp and as close as I can get to the evaperator? because the guy I work for is convinced that the temperatures will be the exact same.

I'm not sure what you mean by reading temp from the TXV.

[Gary]

He wants me to explain that the example I have in my books shows the gauges attached right next to the txv bulb

The most accurate saturation temp is obtained by converting from pressure... and the most accurate pressure reading is obtained at the outlet of the evaporator.

[Gary]

If he wants to see if your capable of finding a fault he wont tell you sog he wont tell you he wants you to recharge a chill thats sog, he WILL tell you to find what is wrong with the system.

What is your strategy for finding what is wrong with the system? What do you check first?... what next?... etc. etc. etc.?

[Andy]

Re: What apprenticies need

A feckin good hiding going of my muppets today!!

1, blunt hacksaw
84, lengths of unistrut
16, 100mm x 8mm rod with $h1t cheap nuts to put on 'em

Thats all the feckers are getting tomorrow.

Eggs

A swift kick up the backside was what they got when I was serving my time.

Some still need this.

If you want to learn you will learn, no good blaming the College because you can't be arsed to study.

In my everyday work if I need to know something I get a book or look it up on the internet.

Kind Regards Andy

[casstrig]

The trouble with temperature reading is on the accuracy of the thermometer and two if you are not in the medium being measured you must allow for the temperature difference between the refrigerant and the pipe or copper where you are measuring,Gary is perfectly correct measure pressures and convert to temperatures using your P/T chart which is as invaluable as your manifold and gauges.I think the most important thing for an apprentice to lean besides basic principals is the methodology in finding a fault,as Gary says you cannot start at the end.

[cmac]

The trouble with temperature reading is on the accuracy of the thermometer and two if you are not in the medium being measured you must allow for the temperature difference between the refrigerant and the pipe or copper where you are measuring,Gary is perfectly correct measure pressures and convert to temperatures using your P/T chart

If we cant rely on pipe temperature, Would this not give superheat and subcooling readings of 0?

[Bachuss]

I'm not sure what you mean by reading temp from the TXV.

The bulb of the thermal expantion valve

[Gary]

If we cant rely on pipe temperature, Would this not give superheat and subcooling readings of 0?

There is very little, if any, difference between the pipe temperature and the refrigerant temperature.

[Gary]

We seem to be getting off the subject here. The point I was trying to make is that any reduction in airflow through either coil will substantially alter the gauge readings and make it difficult, if not impossible, to get the charge right. For that reason, we should always check the airflow through both the evaporator and the condenser before putting gauges on the system.

Beginners tend to underestimate the importance of airflow and overestimate the importance of pressures. Airflow is crucial. Apprentices should become airflow experts before they are given a set of gauges.

[The MG Pony]

Thats what I treid explaining to my clase mates, first thing, only thing you should do is vissualy check the system look at the coils and check air flows, befor you do any thing ells. if air flows are good and coils clean then proceed.

[Bachuss]

poo a visual check to make sure there is no damage or debre on some thing is the first step in any fault finding exercise no matter what you are working on and for this reason can be ignored in any and all conversations especially when the questions are quite dirrect and to a point. you should not assum that a person does not know because he does not mention and simply answer the question or do not!!but jus so you know.. again... you are right and also I have given up asking because you have such a hard on for dancing around the question at hand instead of bloody answering it.

[Gary]

poo a visual check to make sure there is no damage or debre on some thing is the first step in any fault finding exercise no matter what you are working on and for this reason can be ignored in any and all conversations especially when the questions are quite dirrect and to a point. you should not assum that a person does not know because he does not mention and simply answer the question or do not!!but jus so you know.. again... you are right and also I have given up asking because you have such a hard on for dancing around the question at hand instead of bloody answering it.

You are not the only person reading this thread. Some know and some do not... and some don't know that they don't know.

Nothing can be ignored.

And a direct question doesn't necessarily have a direct answer. Sometimes the correct answer is, "It depends".

You want it to be simpler than it actually is. Sorry, it doesn't work that way.

[US Iceman]

I think it is important to recognize everyone has different levels of skill, experience, and background. In a setting like this forum it is all too often found that questions are asked without sufficient information.

As a result, the posts tend to look haphazard as the various people ask questions in trying to respond to the original questions.

Almost everyone has a different approach to problem solving, so it might be possible to learn something by understanding why the questions are asked.

When this occurs, it is not about trying to make the issuance of an answer first off as this process usually takes a while before the real problem is understood.

People may find this frustrating, but trying to teach skills is a lot like analysis of problems. They occur in small steps.

And... it does not help to respond with negative posts because something does not work the way someone thinks it should. So...let's watch the language and tone, OK?

[The MG Pony]

poo a visual check to make sure there is no damage or debre on some thing is the first step in any fault finding exercise no matter what you are working on and for this reason can be ignored in any and all conversations especially when the questions are quite dirrect and to a point. you should not assum that a person does not know because he does not mention and simply answer the question or do not!!but jus so you know.. again... you are right and also I have given up asking because you have such a hard on for dancing around the question at hand instead of bloody answering it.

Any thing worth mentioning once is usualy not worth mentioning, to me it is worth mentioning many times becuase so many people get hung up on the gas side or electrical side and forget of the simpler things first!

With that said yes I do walk around the question, Just as I walk around a device I am designing or repairing, I can not fix what I do not know, and I will not help you by spoon feeding

Nothing in life is simple or direct, relax enjoy and go with the flow.

[Gary]

We would like you to give a example of how to check the correct pressures of a display chiller running on R404.

Imagine that you have two identical containers of refrigerant sitting side by side.

They are identical except that one container is 25% full while the other is 75% full.

Hooking up your gauges to them will reveal that they are at the same pressure despite the fact that one contains 3 times as much refrigerant as the other.

Pressures do not tell you how much refrigerant is in the containers, nor do pressures tell you how much refrigerant is in a system.

Getting it right is about a lot more than just pressures.

[nh3dude]

What apprentices need!
One of the the best tools for a good basic overview of refrigeration and technics for trouble shooting is the book that most wholesalers have and is called basic refrigeration. I start out all my people with it. I wished i had a copy of that when I started. Not much for ammonia but a good start on troubleshooting and systems. The biggest item you will need is a work ethic that is missing from 75% of the people in the work force. Show the oldtimers your willing to work hard and learn and they will throw the doors open for you!

[CoolMike]

College isn't a waste of time. I think that is a bad attitude. You need college and experience. Also, that is how to get precious qualifications.