Compressor Pump Down

[KETTLER]

:confused: I need to replace a combination pressure (high & low) switch on a compressor.

I realize that the refrigerant must be pumped into the LIQUID RECEIVER and isolated before I open the system.

Q: Do I pump ALL the refrigerant into the liquid receiver (i.e. open the suction service valve)?

Q: Will the compressor trip the high pressure switch if the refrigerant is trapped in the liquid receiver?

Q: What is the procedure to recharge the compressor with refrigerant?


Thanks,
KETTLER

[Dan]

Yes. Close the liquid outlet valve of the receiver and let the compressor run. Details:

Have your gauges connected to both the low and high side of the compressor.

Watch the high side to insure that the receiver does not fill up with liquid and cause your discharge pressure to rise above a reasonable level because it is rising into the condenser.
Relieve the high side pressure into the suction and do another pump down cycle. If all is well, you have a small amount of vapor to recover with your recovery unit.

I am sure there are other techniques used by others. I will read their responses to see if there are better ways.

[KETTLER]

Thanks Dan,

So it appears you're telling me to keep the SUCTION SERVICE VALVE open and close the SERVICE VALVE on the liquid receiver?


If the head pressure rises too high (350 psi+) I should bleed off some gas from the liquid receiver into the evaporator? Should I close the SUCTION SERVICE VALVE before I bleed the gas?

Do I pull a 500 micron vacuum on the compressor head and then charge it with some refrigerant after I install the new pressure switches?


Thanks,
KETTLER

[taz24]

Thanks Dan,



Do I pull a 500 micron vacuum on the compressor head and then charge it with some refrigerant after I install the new pressure switches?


Thanks,
KETTLER

Where is the hp / lp switch fed from.
You need to be careful because if they are fed from the service valves then it is important to know how the valve is seated.
If the switches are fed straight from the comp body then just isolate the comp, valve off the comp from the pipework and then remove the gas from the comp. Change the switches and pressure test. Then vac the body of the comp. Open system up and run on test.

taz.

[KETTLER]

Thanks Taz,

The pressure switches are attached to the COMPRESSOR HEAD cover.

:confused: Will I be able to save refrigerant if I pump it into the LIQUID RECEIVER before I isolate and open the compressor?

:confused: Can the compressor pump all the refrigerant into the LIQUID RECEIVER and CONDENSER without undergoing a high pressure failure?



:eek: KETTLER

[Brian_UK]

:confused: Will I be able to save refrigerant if I pump it into the LIQUID RECEIVER before I isolate and open the compressor?You should be able to, it depends on the size of the system charge in relation to the capacity of the receiver etc.


:confused: Can the compressor pump all the refrigerant into the LIQUID RECEIVER and CONDENSER without undergoing a high pressure failure?Hopefully, try and keep the condenser fan running at high speed to minimise head pressure rise if possible.

Also, bypass the low pressure switch the allow the compressor to run as the suction pressure drops during the pump down.

As an afterthought it might be worth while trying to fit schraeder valves to the compressor head before you recconnect your new pressure switches. This will allow easier access next time.

[taz24]

Thanks Taz,

The pressure switches are attached to the COMPRESSOR HEAD cover.

:confused: Will I be able to save refrigerant if I pump it into the LIQUID RECEIVER before I isolate and open the compressor?

:confused: Can the compressor pump all the refrigerant into the LIQUID RECEIVER and CONDENSER without undergoing a high pressure failure?





:eek: KETTLER


I would just shut the suction valve while the comp is running. Then when the comp shuts down shut the discharge valve. The amount of gas in the comp will be minimal. To get the pressure even lower short out the lp switch and let the comp run into a vac. When all valves are closed vent the discharge gas from the comp head back to the suction and that will reduce further any gas loses.
Change the switches and then test like normal.

taz.

[Brian_UK]

I would just shut the suction valve while the comp is running. ..........Well done Taz, trust you to spot the most obvious solution:D

I feel such a ****:o

[KETTLER]

:p Thanks All!

So, my proceedure seems to be as follows:

1. Close (frontseat) the SERVICE VALVE on the LIQUID RECEIVER.
2. Close (frontseat) the SUCTION SERVICE VALVE.
3. Bypass the LOW PRESSURE SWITCH.
4. Run the compressor until a vacuum is achieved.
5. Close the DISCHARGE SERVICE VALVE on the compressor.
6. Remove the existing pressure switch probes and replace them with the new switch probes.
7. Evacuate the COMPRESSOR HEAD.
8. Charge the COMPRESSOR HEAD with a shot of refrigerant (vapor).
9. Open the SERVICE VALVES and run the system.

:confused: I still don't understand how the compressor can run with the SERVICE VALVE closed on the LIQUID RECEIVER and not cause internal damage? Does the compressor discharge pressure drop off once all the refrigerant is condensed and moved to the LIQUID RECEIVER?

:eek: KETTLER

[MRC Guts]

g day kettler
try this, put your gauges on the comp high and low sides... now front seat the suction service valve an let the comp cut out on the LP control.....if it stops above 0 psig short out the LP control and let the comp run till you get to 0 psig [a tiny bit higher is good no crap gets sucked in the system] now turn the comp off....front seat the discharge service valve....bleed the pressure from the high side to the low side....you should now have bugger all pressure in the comp....change the HPLP control... when you have done that close your gauges an crack the suction valve.....purge a puff or two from the high side gauge line to be sure thre is no air left in the comp head....now open both service valves an kick the bugger in the guts...test the operation of the new control an fine tune if needed...dont touch your liquid line service valve... you only need to isolate the comp...now thats done grab a ice beer from the esky.....good luck mate

[KETTLER]

:D Thanks MRC Guts!

:confused: How will my LP gauge read the pressure in the compressor head if I close the SUCTION SERVICE VALVE?

:rolleyes: I really like your idea to purge the air out of the compressor head using the HP gauge hose. Excellent!


KETTLER

[slingblade]

How will my LP gauge read the pressure in the compressor head if I close the SUCTION SERVICE VALVE?


It wont. It will read crankcase pressure.

1. ignore any liquid valves.


2. Close (frontseat) the SUCTION SERVICE VALVE.
3. Bypass the LOW PRESSURE SWITCH.
4. Run the compressor until a vacuum is achieved.
5. Close the DISCHARGE SERVICE VALVE on the compressor.

6.Vent high to low through the manifold set. I.E. cap off the yellow line and open both blue and red wheels. pressure should now be low on both sides (2 to 5 psi maybe). change switches and open valves. run and set switches.
7. pub.

sling.

[frank]

:confused: I need to replace a combination pressure (high & low) switch on a compressor.



Where is the hp / lp switch fed from.



The pressure switches are attached to the COMPRESSOR HEAD cover.


How can you have the high and low pressure tappings connected to the compressor head?

[taz24]

How can you have the high and low pressure tappings connected to the compressor head?


On most semi-hermetic comps there is an access plug to both HP and LP side of the head. they take there pressure from the low side and high side of the cylinder head.
http://img.alibaba.com/photo/50394389/2__3_Cylinder_Compressor.jpg (http://zjcgc.en.alibaba.com/product/50084661/50394389/Refrigerant_Compressors/2__3_Cylinder_Compressor/showimg.html) You can just about see the two plugs on this comp

Cheers taz

[KETTLER]

:D Awesome TAZ!

:confused: How did you paste that pic in your message? What about diagrams, bmp's, etc?


KETTLER

[KETTLER]

6.Vent high to low through the manifold set. I.E. cap off the yellow line and open both blue and red wheels. pressure should now be low on both sides (2 to 5 psi maybe). change switches and open valves. run and set switches.

sling.

:D slingblade,

I really like your quick-and-easy proceedure; however, what's the purpose of venting high to low? All I care about is getting the gas out of the compressor head before I remove the switch probes. Correct?

Then, after the new probes are installed, I can purge out the air through my gauge set by cracking open the SUCTION SERVICE VALVE. Correct?

:eek: KETTLER

[KETTLER]

On most semi-hermetic comps there is an access plug to both HP and LP side of the head. they take there pressure from the low side and high side of the cylinder head.
http://img.alibaba.com/photo/50394389/2__3_Cylinder_Compressor.jpg (http://zjcgc.en.alibaba.com/product/50084661/50394389/Refrigerant_Compressors/2__3_Cylinder_Compressor/showimg.html)

Cheers taz


:confused: taz,

How can the compressore HEAD have a LP access port? Isn't the HEAD the space above the piston?


:eek: KETTLER

[MRC Guts]

g day kettler
i dont want to be rude or offend but this is basic friggie stuff mate....how service valves work an whats in comp is first year stuff...i am concerned for your safety and the safety of others...if you dont have a clear understanding of the equipment you are working with get someone who does to help you and teach you...sorry if this sounds a bit hard but you can get hurt if you do it wrong

[KETTLER]

:o Thanks MRC Guts. I'm educated, experienced, and certified in refrigeration; however, I don't know EVERYTHING. I like to thoroughly think things through before I start turning wrenches.:rolleyes:

:cool: I think you can see from this string that there are many ways to 'skin a cat'.


:D KETTLER

[LRAC]

g day kettler
i dont want to be rude or offend but this is basic friggie stuff mate....how service valves work an whats in comp is first year stuff...i am concerned for your safety and the safety of others...if you dont have a clear understanding of the equipment you are working with get someone who does to help you and teach you...sorry if this sounds a bit hard but you can get hurt if you do it wrong

For all the forum members sanity and thoughts stop giving Kettler advice he's going to kill himself or the poor person next to him. Next he'll be asking which way the wires go on?

Regards
Lrac

[LRAC]

:o Thanks MRC Guts. I'm educated, experienced, and certified in refrigeration; however, I don't know EVERYTHING. I like to thoroughly think things through before I start turning wrenches.:rolleyes:
:cool: I think you can see from this string that there are many ways to 'skin a cat'.
:D KETTLER

Certified in refrigeration i think you meant Certifiable.

Lrac

[US Iceman]

I have been following this thread with interest. I choose not to respond to this initially because of the nature of the basic question. One of the members mentioned this is "first year stuff" and he is exactly right.

If a person has been working on refrigeration systems for some time and does not know how to pump down a compressor, something is wrong with this picture.




I think you can see from this string that there are many ways to 'skin a cat'.


Never, ever assume this. Just because you get multiple opinions on how to do something does not mean they are all correct. That's a dangerous way to service systems I'm afraid.

[abdulazman]

Cheers to ya all,:eek:

Iceman n LRAC are definitely right.
We don't need schools, university and educator now do we.:D
This guy says he has had knowledge and experience and oh my god, ''CERTIFICATE'' :rolleyes:
And yet he can't perform pump down, maybe, he may be able to conduct liquid transfer.;)
As sherlock says, ''Elementary my dear Watson''.:p

Good luck ya all
Adios Amigo

[abdulazman]

Maybe I don't skin a cat.
Because I smell a rat.

[Dan]

Quote:

Originally Posted by: taz24



I would just shut the suction valve while the comp is running. ..........


Well done Taz, trust you to spot the most obvious solution

I feel such a ****

Of course. Those who suggested simply isolating the compressor have the best method. :)

[hhbref2003]

hi there!
Option 1. recover all the refrigerant if you are familiar with the process.

If there is a shut-oof valve on both inlet and outlet of receiver then apply this procedure
Option 2. Pumpdown the refigerant. meaning
1.-connect your gauges to the compressor valves while both on back seat.

2.-Front seat(close) the valve after the liquid receiver.
3.-adjust cut-out pressure on LP switch to cut at
pressure below vacuum.
4. connect your gauge manifold to the compressor valves (HP and LP). Use a vacuum pump to remove air from the gauge lines with the compressor valves front- seated(close).
5.Then open the valves to almost intermediate position which will allow reading to be registerred on the gauge scale and also allow you to quickly close them later.
6. Run the unit and pumpdown will begin if the compressor cut-out too early on the LP swith , then readjust the cut-out pressure to cut out at a pressure under vacuum. Close (Frontseat) inlet of receiver.You will not be able to recover the left over a 100%. Then the decision is left with you
7.When the compressor cuts-out on a pressure below vacuum, then quickly front-seat both compressor valves

[KETTLER]

:o Thank you. I appreciate the CONSTRUCTIVE advice.


:mad: KETTLER

[KETTLER]

:o Hi All,

Many thanks to those of you who have CONSTRUCTIVELY participated in this THREAD! I realize some of my questions and comments have been simplistic, and, I appreciate your POSITIVE indulgence.

:rolleyes: My research has led to the adoption of the following procedure:

1. Check that both SUCTION & DISCHARGE SERVICE VALVES are back-seated and connect service gauges.

2. Close (front-seat) the SUCTION SERVICE VALVE.

3. Jumper the LP switch.

4. Run the compressor until a slight vacuum is achieved on the SUCTION side of the compressor head.

5. Front-seat the DISCHARGE SERVICE VALVE.

6. Equalize the HP/LP pressures through the gauge manifold (center gauge line capped).

7. Replace the combination LP/HP switch.

8. Crack open the SUCTION SERVICE VALVE and purge the compressor head through the gauge manifold (center line open).

9. Backseat both SERVICE VALVES and remove the gauges.

10. Run the compressor.


:) KETTLER

[monkey spanners]

Make sure the Lp and Hp parts of your dual Lp/Hp switch are the same way round if you are replacing it with a different make of switch. Ive seen danfoss ones replaced with ranco and on one the lp is on the lefthand side and on the other it was on the rigthhand side, so when changed it had the Lp hose going to the Hp switch and vice versa.
And any connections you disturb really need pressure testing with OFN to be sure you have no leaks and the evacuating.

Cheers Jon

[KETTLER]

:) Thanks Jon,

I appreciate the heads-up!

I'll add the following step to my procedure:

8a. Leak test the LP/HP fittings.


:D KETTLER

[taz24]

:) Thanks Jon,

I appreciate the heads-up!

I'll add the following step to my procedure:

8a. Leak test the LP/HP fittings.


:D KETTLER

Set the switches up with a hand pump or OFN before you connect them up.
It will save you a lot of time latter on.
taz.

[KETTLER]

:o Thanks Taz.

:confused: What's an "OFN"?


:rolleyes: KETTLER

[taz24]

:o Thanks Taz.

:confused: What's an "OFN"?


:rolleyes: KETTLER

In the UK we use OFN for pressure testing, purging while brazing, blowing condensers clean and things like that.

OFN = oxygen free nitrogen.
It is also dehumidified so OFN can be known as dry nitrogen.

Cheers taz.

[KETTLER]

:) Hello All,

The compressor pump down was a success! Thanks for your help.:o


KETTLER

[LRAC]

You must be one of the most fortunate forum members who has scrapped through on the information supplied to carry out out a simple pumpdown on a compressor. Do yourself a favour and get some proper training in this trade, if you have a certificate it must have been done on your computer.

from the first post on the 14/02/07 its took you 16 days to carry out the procedure, you must also be fortunate to have the most understanding customer in the WORLD.

Lrac

[Brian_UK]

:o Hi All,

Many thanks to those of you who have CONSTRUCTIVELY participated in this THREAD! I realize some of my questions and comments have been simplistic, and, I appreciate your POSITIVE indulgence.

:rolleyes: My research has led to the adoption of the following procedure:

1. Check that both SUCTION & DISCHARGE SERVICE VALVES are back-seated and connect service gauges.

2. Close (front-seat) the SUCTION SERVICE VALVE.

3. Jumper the LP switch.

4. Run the compressor until a slight vacuum is achieved on the SUCTION side of the compressor head.

5. Front-seat the DISCHARGE SERVICE VALVE.

6. Equalize the HP/LP pressures through the gauge manifold (center gauge line capped).

7. Replace the combination LP/HP switch.

8. Crack open the SUCTION SERVICE VALVE and purge the compressor head through the gauge manifold (center line open).

9. Backseat both SERVICE VALVES and remove the gauges.

10. Run the compressor.


:) KETTLERAnd still he gets it wrong :mad:

Kettler after ALL OF YOUR SARCASTIC comments aimed at people who are concerned for your safety and the environment you still do it wrong, I am amazed:eek:

Re-read your list above and tell us ALL why you performed No. 8 instead of doing it properly.

[Josip]

Hi, Brian_UK :)


And still he gets it wrong :mad:

Kettler after ALL OF YOUR SARCASTIC comments aimed at people who are concerned for your safety and the environment you still do it wrong, I am amazed:eek:

Re-read you list above and tell us ALL why you performed No. 8 instead of doing it properly.

See my sig;)

Best regards, Josip :)

[Brian_UK]

So true, oh so true ;)

[KETTLER]

And still he gets it wrong :mad:

Kettler after ALL OF YOUR SARCASTIC comments aimed at people who are concerned for your safety and the environment you still do it wrong, I am amazed:eek:

Re-read your list above and tell us ALL why you performed No. 8 instead of doing it properly.


First off, I made no sarcastic comments. It was YOU folks who used my inexperience and simple questions to validate yourselves by shamming me.

Second, step 8 is intended to purge the air from the compressor head, and, was given to me by someone else on this thread.

I actually purged the air from the head using an R22 bottle. I fed the refrigerant through the suction service valve access port and bled it out from the discharge service valve access port.


:mad: What kind of people are YOU? I thought this was a dignified website!
Do you conduct business in the manner I experienced? Very poor.

:cool: I think you people are the amatures!


KETTLER

[monkey spanners]

Hi Kettler

Your opinion of me is'nt me, its just your opinion:)
Out of the six billion people on the planet surely one will think i'm an idiot, now he's got a name:D

Cheers Jon

[LRAC]

:mad: What kind of people are YOU? I thought this was a dignified website!
Do you conduct business in the manner I experienced? Very poor.
:cool: I think you people are the amatures!
KETTLER

Well that last statement has been your problem all the way. You are completly incompetent at what you are doing and do not deserve any help from forum members in the future.

In your tiny mind you may think that you can do the job but honestly you are the pits,your skills are none existent and your attitude stinks.

Enough said to a complete looser
Lrac

[Andy]

First off, I made no sarcastic comments. It was YOU folks who used my inexperience and simple questions to validate yourselves by shamming me.

Second, step 8 is intended to purge the air from the compressor head, and, was given to me by someone else on this thread.

I actually purged the air from the head using an R22 bottle. I fed the refrigerant through the suction service valve access port and bled it out from the discharge service valve access port.


:mad: What kind of people are YOU? I thought this was a dignified website!
Do you conduct business in the manner I experienced? Very poor.

:cool: I think you people are the amatures!


KETTLER

KETTLER:)
It is illegal to knowingly vent refrigerant, you should have used a vacumn pump. If the EPA comes accross this post they will have fun putting you through the courts.

I'm sorry but after one year working at refrigeration any apprentice should know you.

If someone posted on this thread inviting you to purge refrigerant I would say shame on them:mad:

KETTLER please go and get training so that you can work at refrigeration without ruining the enviroment for all of us:mad:


Kind Regards Andy:)

[Josip]

Hi, Kettler :)


First off, I made no sarcastic comments. It was YOU folks who used my inexperience and simple questions to validate yourselves by shamming me.

All said was with intention to help you and sometimes some joke is inevitable;) , NHF, please


Second, step 8 is intended to purge the air from the compressor head, and, was given to me by someone else on this thread.

There are teachers and teachers...


Just because you get multiple opinions on how to do something does not mean they are all correct.

It was possible to ask HOW if you were in doubt.



I actually purged the air from the head using an R22 bottle. I fed the refrigerant through the suction service valve access port and bled it out from the discharge service valve access port.

:eek: This is forbidden way, you should use vacuum pump for this to contribute to care about your environment and your family, neighbors, etc.


:mad: What kind of people are YOU? I thought this was a dignified website!

So we are bad people, because we tell you what you did wrong. What about so many answers trying to teach and help you to do your job properly:confused:


Do you conduct business in the manner I experienced? Very poor.
:cool: I think you people are the amatures!
KETTLER

Don't know what to say, but coming here asking maybe some "silly" questions getting relevant answers:


g day kettler
i dont want to be rude or offend but this is basic friggie stuff mate....how service valves work an whats in comp is first year stuff...i am concerned for your safety and the safety of others...if you dont have a clear understanding of the equipment you are working with get someone who does to help you and teach you...sorry if this sounds a bit hard but you can get hurt if you do it wrong

where people take care about you I do not think this can come from some amateurs but you do:confused:

Please think again, about all, and admit your mistakes (at least to yourself) and you'll see we are not so bad guys.

Hope you will not misinterpret all of this;)

Best regards, Josip :)

[US Iceman]

Well said Josip.:cool:

[Dan]

I hate to see a good discussion go down the drain such as this one has.

I saw some good advice and I saw you accepting it. Perhaps too much good advice caused the confusion. Let's not be angry with one another. :)

[knight rider]

excellent thread , excellent forum , keep it up

WHY DO I GET THE FEELING KETTLER KNEW HOW TO DO THE PROCUDURE BEFORE HE POSTED THE QUESTION

could he have been testing us ?

DID YOU KNOW HOW TO DO THE PROCEDURE BEFORE POSTING MR KETTLER ?

MANY THANKS

[Peter_1]

I would just shut the suction valve while the comp is running. Then when the comp shuts down shut the discharge valve. The amount of gas in the comp will be minimal. To get the pressure even lower short out the lp switch and let the comp run into a vac. When all valves are closed vent the discharge gas from the comp head back to the suction and that will reduce further any gas loses.
Change the switches and then test like normal.


Same way I do it Taz. The remaining gas will be indeed very small, just the portion above the piston and the very small volume in the discharge valve.
This is something you don't find in schoolbooks but only can learn in practice, which you have.

[taz24]

[quote=taz24;60065]
Same way I do it Taz. The remaining gas will be indeed very small, just the portion above the piston and the very small volume in the discharge valve.
This is something you don't find in schoolbooks but only can learn in practice, which you have.


Thankyou Peter.

Iv'e been at it for 28 years now.
I'm still learning.
I was taught by some good engineers and was taught to leave the system running if possible no mater what the fault.


taz.

[chefid]

dont know how to change a pressure control?? the system pumps down every cycle. and i dont know to many people who pump down the system to change a switch. if you do vent refrigerant not "***** sorry pet peeve" dont advertise the fact

[The MG Pony]

Better yet, slap any A-Hole you see venting with a crow bar hard enough he'll never vent again! I like breathing air, and I like going into the sun with out SPF-2,000,000,456 SunBlock

[chefid]

if refrigerant were killing the planet i would think there would be a harsher punnishment for venting. any ways i have enough carbon credits to vent untill i retire if i did that sort of thing

[chefid]

sorry i cant spell so well me sort of dumm

[Brian_UK]

sorry i cant spell so well me sort of dummYour spelling has been impeccible up till now, I suspect false claims here. :(

[tjk2007]

Hi Guys,

Good Evening,

I am new member to this forum.i am happy to communicate all members.

I am just confused to post a new theads.Kindly mail me the procedures.

Thank you,
Jeyakumar.T

[Peter_1]

Welcome from Belgium. Read once http://www.refrigeration-engineer.com/forums/faq.php?faq=vb_faq#faq_vb_user_maintain
We have a special section for new members http://www.refrigeration-engineer.com/forums/forumdisplay.php?f=72

[wineman]

why dont u ask a fridge guy he will do it in ten minutes

[kr1664uk]

I am also new to the game,but the thing that would give me a scare is the fact you didnt even know what ofn was..thats first wek stuff never mind first year...

Sorry fella but...



:o thanks taz.

:confused: What's an "ofn"?


:rolleyes: Kettler

[Peter_1]

You're replying to a post of more than 3 years old :off topic:
Don't forget that the mother tongue of many posters here isn't English
I bet you don't know what a ratelsleutel is.

[CHIEF DELPAC]

Peter_1 There will not be a lot of interest unless its a Belgium pastry or a bottle of liquid cheer. I wonder if it would help if there was a section on definitions of some of the terms that are common in some countries but are unheard of in others.An example would be TUPE that is use in the U.K. but is not used in my country. C.D.

[penamante]

hi guys,
good day!!

Im new member of this forum and i would like or kindly help how can i start to open regarding refrigeration discussion..

thanks a lot,
philip

[Peter_1]

At the top of each page, you will find the link FORUM.
Click on it, search the right section, don't post an airco related question into the NH3 section. Click on that section an then you ill see on the top of that page NEW THREAD. That's all