Old timer needs some help

[damo1206]

Dear all.

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. :rolleyes:

[superswill]

Dear all.

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. :rolleyes:


welcome to RE

search this forum and you will find lots on this topic

here is a few to start you off

http://www.refrigeration-engineer.com/forums/showthread.php?t=13284&highlight=superheat

http://www.refrigeration-engineer.com/forums/showthread.php?t=13311&highlight=superheat

http://www.refrigeration-engineer.com/forums/showthread.php?t=13119&highlight=superheat

[bernard]

Hi

Well the first thing I,d like to say is not what can anyone on here can teach you but what can you teach us.You don,t stay as long in this trade as you without being good at what you do.The amount of times i,ve charged a integral by the book to find the recommened weight to be wrong.So I end charging by back pressure and suction line.As for Superheat well type the word in the search bar and you,ll find many topics on the subject.I,ve learned this back to front but never really had to use it,Ive only had a problem when someone has been fiddling about with superheat because they don,t know what the real problem is,I always put the correct orifice in and set valve back to the central position and it works.Fridges are very reliable and once set up correctly they very rarely break down, its either ambient temperature block condensers overstocking or the most common a crap engineer.Thats why us in the Supermarket trade always like the crap engineer syndrome because this single engineer can create enough out of hours work to keep us all happy.So when you go for your handling course just be honest people will respect you for what you know.

Regards and respect Bernard

[icecube51]

you don't have to be ashamed if there is something you don't now. there is a lot of things we don't now.:o

if you like and love your job, you will end up learning for the rest of your live. :)
he ho claim to now everything, is the most stupid of them all,because he stop learning.:p

Ice

[DaS Energy]

Hello Ice.

Your response to old fella is most sincere.

I too am a old fella, knowing little about refridgeration other than if you compress Co2 through a small orifice into an expansion chamber, the Co2 vapour becomes colder.

I am chasing any figures any one can give me about orifice and expansion chamber? size, plus the temperature decrease, using a flow rate of 1 litre per second.

Cheers

Peter

[chemi-cool]

Looks like we all old timers here.

Like you, damo1206, I also trust my finger tips touching the pipes more than any digital instrument.

And you know what? They haven't invented yet anything as good.

[SUBCONTRACTOR]

I agree with touching the pipes but this is only to establish some cooling.,what if the system has a problem then it really gets tough especially when the system need a little bit of tuning which is nearly there but something small and it will start doing the job ....

[old gas bottle]

thats when the experience comes in,not the other way round,;)

[Peter_1]

Bernard and Icecube 51, nice post.
The fact damo2106 you do it with your hands is not so stupid as youthink
As a matter of fact, I wrote a whole article about it in a Belgium magazine.
You should be amazed how much you can measure with your hands and see with your eyes.
A refrigeration circuit works in our climates around temperatures which can be relative good sensed with your hands. I'm not talking about the climate of Chemi :p
At an ambient of 25°C (77°C), condensing at 35°C to 40°C (95 °F -104°F) are temperatures which can be very good judged with your hands.
same for temperature differences which can be judged many times with your hands.
Spitting - yeah laugh - can give you an idea of discharge temperatures.
Rooms at 0°C, evaporating at -7°C (19.5°F - God bless Uconeer), SH of 6K will give you just a frosted suction line.
Wet fingers can feel the difference between -10°C and -20°C.

One of the first things I'm doing when arriving at a faulty installation is touching some tubes (suction, liquid), looking to some specific points and very important..listen to your customer.

So go for that course.

[Grizzly]

very important..listen to my customer.

"It wasn't Me!"
Sound familiar?
Seriously though, good point peter,
Damo. Experience will of taught you when to believe them.
Steve

[Peter_1]

Steve, you're right but I meant more that even if your client is a butcher or a baker and not a technician at all, sometimes they tell you important things that can direct you to possible causes and eliminate other.

It's also up to you to ask the right questions.

Had a call last Saturday evening: "you have to come because my island is not cooling any longer"

After asking him several questions, liquid felt warm (client said +/- same temperature as his hands), fans were running but his compressor was completely covered under ice.
Fans were running in the cooler.
I said I thought his evaporator was completely frozen up.
Asked him to open some plates and look to his 'radiator' in the cooler and tell me what he sees.
Completely under ice.
Then told him how he could defrost is (old analog timer) and let it there for 45 minutes (forced ventilation defrosting)
Said that he should remember the time on the clock.
I should call him back after an hour. Unit was completely defrosted and I asked him to look to the clock. It was still on the same hour.
Client realized that clock was faulty but the result was that I could postpone my repair till Monday morning.
And he was glad he save a service call (charged him double his clock :p;))

[icecube51]

as you can see Damo1206, you don't need any shame to go on a course.
just keep in mind that the teacher who hasn't nearly any field experience, is going to learn from you. he needs that specific experience to prove his students his a clever man, an is able to answer field questions.
teach him as he teaches you,and you are going to gain a good friend.;)

Ice

[marc5180]

Looks like we all old timers here.
Speak for yourself Chemi :D

[refmech]

;) as being old enough to have blown out condenser coils with r-12 because it was the cheapest compressed gas on my truck. I know where your coming from. my fingers are the first tool in the bag of tricks,sight-sound-touch best tools out there. I started this trade thinking i made things cold, once you get a handle on SH/SC it all makes sense. everyone that posts on this sight is top notch,glad i found this to sound my own pratices and experiences off of. just search within this sight and you'll find your answer. good luck testing.

[Fridgeteach]

I also use my fingers to feel where i cannot see. Are we talking about capillary tube systems or expansion valve systems?

[Gary]

Did someone call for an oldtimer?

Enter a walk-in freezer. Pick up a steel pipe in one hand and a wooden pole in the other.

They are the same temperature, but the steel pipe feels much colder than the wooden pole. Human skin is NOT a good judge of temperature.

What you are sensing is not temperature but rate of heat transfer... and this is a job at which human skin excells.

Is grasping the pipes useful? Yes.

Is it the right way to trouble shoot a system? No.

[nike123]

Did someone call for an oldtimer?

Enter a walk-in freezer. Pick up a steel pipe in one hand and a wooden pole in the other.

They are the same temperature, but the steel pipe feels much colder than the wooden pole. Human skin is NOT a good judge of temperature.

What you are sensing is not temperature but rate of heat transfer... and this is a job at which human skin excells.

Is grasping the pipes useful? Yes.

Is it the right way to trouble shoot a system? No.

Nicely said and explained. I am with you here, Gary!
http://www.physicsforums.com/archive/index.php/t-83623.html

[thebigcheese]

im quite a young engineer and i will admit i dont no everything but ive always used my hands as indicators, i even used them when doing my handling course in collage

[cool69]

to obtain correct superheat, first obtain suction pressure at bulb; convert suction pressure to temp. second, take temp. reading at bulb. third, subtract the bulb temp. reading from the psi conversion temp. that would give you your super heat. Different manfg. recomend diff. super heats. A good super heat for frozen is four degrees superheat. While coolers six to eight degrees for superheat. Check with mangf. while some superheats are negtive. such as minus four degrees to six degrees. Air conditions systems usually require superheat to be in teens. Anywere from twelve to eighteen degrees. That would insure proper charge.