PDA

View Full Version : High discharge pressure but discharge pipe is not hot !







A.Mortezania
06-04-2017, 08:44 PM
Dear Friends,

I have a shop at my country and I sell refrigeration parts at my country by this I should be able to inform and lead my customers.

During a year, two of my customers called me and they had this problem :

They told me their system charged with R22, They check discharge pressure, Pressure was 270 ~ 290 PSI but discharge pipe was not hot and they could able to touch it by their hand.
Also sight glass was full but they complained cold room temperature didn't go down and didn't go less than for example -5C but they wanted for example temp. -18C.

What do you think about this ? What kind of problem you think was on these systems that made this situation ? Discharge pressure is high on R22 but discharge pipe temperature not be hot ?!

Sincerely yours.

Grizzly
06-04-2017, 10:25 PM
Hi
I would question the quality of the R22 if indeed the refrigerant being used is R22.
Have you considered Non- condensables in the system?
I.E. Air.
Air in a condenser (Where it normally collects ) will reduce the surface area of the condenser causing higher discharge pressures.
Air purging may be necessary?
If enough air is in the system then moisture will be present to.
Therefore the quality of the refrigerant could be compromised also!
Grizzly

RANGER1
06-04-2017, 11:45 PM
Liquid floodback!
what is superheat?
Could be air, but definitely would think discharge would be hot.

PaulZ
07-04-2017, 12:14 AM
Hi A
There are several things that could be wrong some mentioned by Grizzly. Others could be the TX valve could be blocked, if the sight glass is before the drier the drier could be blocked.
A lot more information is required.
Regards
Paul

RANGER1
07-04-2017, 01:00 AM
Require pressures, room temp, suction superheat, ambient, refrigerant type, liquid line subcooling or liquid line temperature exiting liquid receiver.
Like going to the Doctor, need all the information for any type of diagnosis.

Grizzly
07-04-2017, 07:26 AM
Good answers guys.
You were obviously more awake when replying than I was!
Grizzly

A.Mortezania
07-04-2017, 10:55 AM
Dear friends,

Thanks for all of your replies. Yes, All of you are right. When same as we go to doctor, Doctor should see symptom then take decision about illness. I understand your mean that you should now pressures, Superheat and ….. .

Just I have very small question, As you know discharge of compressor is at Superheat area on PH diagram, Would it be possible (for any reason such as air inside of condenser or system, low quality of R22 and …) we have 280 PSI on R22 at discharge pipe but temperature of discharge pipe not be hot ?
It could be or it is not possible ?

Just my question is it.

Sincerely yours.

Grizzly
07-04-2017, 03:52 PM
Hi.
Read the following which is taken from a USA trade Magazine. it describes how to prove or disprove the presence of Air or non condensable's in a system.
it is possible to
check for the presence of NCGs in the con-
denser: isolate refrigerant in the condenser,
take the compressor offline, and run the
condenser fan. When the refrigerant in the
coil has come to air temperature, measure
the air temperature and the pressure of
the refrigerant inside the condenser. If the
measured pressure matches up with the
pressure indicated on a pressure/tempera-
ture chart, then there are no NCGs in the
coil. If the pressure is more than a few psi
higher than the chart, then NCGs are prob-
ably to blame.
Grizzly

RANGER1
07-04-2017, 11:31 PM
Dear friends,

Thanks for all of your replies. Yes, All of you are right. When same as we go to doctor, Doctor should see symptom then take decision about illness. I understand your mean that you should now pressures, Superheat and ….. .

Just I have very small question, As you know discharge of compressor is at Superheat area on PH diagram, Would it be possible (for any reason such as air inside of condenser or system, low quality of R22 and …) we have 280 PSI on R22 at discharge pipe but temperature of discharge pipe not be hot ?
It could be or it is not possible ?

Just my question is it.

Sincerely yours.

I'm more practical & when system is not pure crazy things can occur, so would simply check all the basics first.
Maybe there are several issues at once, but as we no nothing yet we can speculate or theorize.
Does compressor run continuously with cool discharge?
If compressor was turned off, does discharge pressure drop quickly, maybe restriction like in discharge stop valve seat a drift, check valve, same if turned on pressure increase very quickly!
What is the actual discharge temperature reading?
Is gauge reading discharge pressure correct/accurate?


10 minutes of checks can eliminate a dozen possible problems.

Grizzly
08-04-2017, 07:49 AM
Wise words Ranger.
I still cannot give you rep points.
I need to find some more worthy recipients first.
It's more a process of elimination firstly as you say.
Grizzly

thebrockenshire
08-04-2017, 11:47 AM
blockage or floodback will cause your symptoms