A newbie question


T

Tony Hwang

Hi,
Once in a while AC unit needs refrigerant top up at the beginning of
season during annual check up. Are they consumed or if there is no leak,
how come it needs top up? Where does it go?
 
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T

The Daring Dufas

Hi,
Once in a while AC unit needs refrigerant top up at the beginning of
season during annual check up. Are they consumed or if there is no leak,
how come it needs top up? Where does it go?
There is a microscopic black hole in every AC compressor that sucks in
Freon molecule by molecule expelling the Freon into another universe
parallel to our own. ^_^

TDD
 
T

Tony Hwang

Stormin said:
Slow leak, some where. The system is under pressure, after all. Goes into
the atmosphere. The sunlight breaks the chemicals into simpler chemicals,
where they are absorbed by plants.

Christopher A. Young
Learn more about Jesus
www.lds.org
Hmmmm,
So is this quite usual thing?
In three years they topped up once so far.
(Puron system which has higher pressure?)
 
S

Steve

Stormin Mormon said:
Yes, it's usual. Most systems I've worked on, need top off now and again.
A/C refrigerant systems are sealed systems.... if they need topped off, then
there *IS* a leak. If the system is correctly installed, and a proper 400
micron vacuum is pulled, and holds for 30minutes, you should never need to
"top off" the system unless there is a leak.
 
T

The Daring Dufas

A/C refrigerant systems are sealed systems.... if they need topped off, then
there *IS* a leak. If the system is correctly installed, and a proper 400
micron vacuum is pulled, and holds for 30minutes, you should never need to
"top off" the system unless there is a leak.
I often replace the Schrader valves with the highest quality valves I
can find. I've been using those having a polymer seal instead of rubber.
The valves are inexpensive and I often find leaks at the service ports.
Anyone who services AC/refrigeration should have the tool to replace
the valves when a system is under pressure. ^_^

TDD
 
S

Steve

The Daring Dufas said:
I often replace the Schrader valves with the highest quality valves I can
find. I've been using those having a polymer seal instead of rubber.
The valves are inexpensive and I often find leaks at the service ports.
Anyone who services AC/refrigeration should have the tool to replace
the valves when a system is under pressure. ^_^

TDD
Core tool and replacement cores are standard equipment on my truck. With a
lot of new customers, I also routinely find cores that are just plain loose
so the previous "tech" has job security. Yes I tell the customer all of the
things I find when I do a complete system assesment as I do for any seasonal
service.
 
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S

Steve

A vacuum test should never be used as a pressure test. Too many
contractors purchase nitrogen test guages of 0-250lbs. This is not
enough even for an R-22 system let alone a 410A. The high side should
be isolated (not always possible) and tested at 450lbs (R-22) A small
piece of debris can be sucked into a hole and provide a satisfactory
vacuum only to be blown back out when positive pressure is on the
system. The only idea that "nature abhors a vacuum" does not apply to
our situation. Should always be careful testing a unit with a high
pressure guage. A low side test of 100 lbs should be enough for a
satisfactory test. I've found leaks in condensors that held 100lbs
but at 200 lbs began to leak.
I pressure test R22 systems to 350psi, and R410a systems to 500psi with N2
before I pull a vacuum. Only twice in 17 years have I found any leaks in a
condenser that were not caused by stupidity(dropping crap in the fan when it
was running), and only once have I had a leak in a *NEW* condenser.
 
T

The Daring Dufas

Core tool and replacement cores are standard equipment on my truck. With a
lot of new customers, I also routinely find cores that are just plain loose
so the previous "tech" has job security. Yes I tell the customer all of the
things I find when I do a complete system assesment as I do for any seasonal
service.
Steve, do you use the cores with Teflon seals? They cost a little more
but I've never had them leak. I've seen so many AC/refrigeration techs
ignore the darn things or even check whether or not the cores are tight.
I like the home AC units that are manufactured with commercial
type service valves because those don't leak unless the valve packing is
loose. o_O

TDD
 
S

Steve

The Daring Dufas said:
Steve, do you use the cores with Teflon seals? They cost a little more but
I've never had them leak. I've seen so many AC/refrigeration techs
ignore the darn things or even check whether or not the cores are tight. I
like the home AC units that are manufactured with commercial
type service valves because those don't leak unless the valve packing is
loose. o_O

TDD
I prefer teflon, but pretty much have to buy what the supply house has in
stock.
 
S

Steve

Solid practice. The leak I found in the condenser was on a 180° bend.
I doubt it was hit by anything. The leak was on the weld itself. I
spent hours on a 450T Dunham Bush machine where 95/5 solder was used
instead of silver. Over the years, we run into many interesting
things manufacturers let slip by.

A pebble in a shrader valve is what used to irritate me.
FWIW, if you have to repair any braze joints or unsweat/ resweat anything in
a Rheem/RUUD condenser, the factory uses 45% silver. Silphos is not gonna do
it for repairs.
 
H

HVAC

Hmmmm,
So is this quite usual thing?
In three years they topped up once so far.
(Puron system which has higher pressure?)
Topping off a Puron (R-410A) system can be problematic.
410A is an azeotropic refrigerant...A blend of different refrigerants.
When there is a leak, the blend becomes unbalanced.

Fix the leak.
 
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T

The Daring Dufas

Topping off a Puron (R-410A) system can be problematic.
410A is an azeotropic refrigerant...A blend of different refrigerants.
When there is a leak, the blend becomes unbalanced.

Fix the leak.
Zeotropic refrigerant mixtures must be liquid charged. You hit the wrong
end of the alphabet. I do it all the time. ^_^

TDD
 
P

PaxPerPoten

A vacuum test should never be used as a pressure test. Too many
contractors purchase nitrogen test guages of 0-250lbs. This is not
enough even for an R-22 system let alone a 410A. The high side should
be isolated (not always possible) and tested at 450lbs (R-22) A small
piece of debris can be sucked into a hole and provide a satisfactory
vacuum only to be blown back out when positive pressure is on the
system. The only idea that "nature abhors a vacuum" does not apply to
our situation. Should always be careful testing a unit with a high
pressure guage. A low side test of 100 lbs should be enough for a
satisfactory test. I've found leaks in condensors that held 100lbs
but at 200 lbs began to leak.
While what you say is quite true... A deep vacuum in the 15 micron range
or thereabouts will usually indicate at tight system. 5 Microns is used
for airborne attack radar modulators. They are cooled with liquid
refrigerant that loves to leak. Most good vacuum pumps can attain 15
microns. Don't do that to automobile systems though. sucks the seals out
of them.
 
G

Guest

"PaxPerPoten" wrote in message
While what you say is quite true... A deep vacuum in the 15 micron range
or thereabouts will usually indicate at tight system. 5 Microns is used
for airborne attack radar modulators. They are cooled with liquid
refrigerant that loves to leak. Most good vacuum pumps can attain 15
microns. Don't do that to automobile systems though. sucks the seals out
of them.

http://www.jbind.com/technical/faq-micron-gauges.aspx

//Some manufacturers have a micron range that they want their system pulled
down to, so therefore, JB can only suggest a micron reading. Our suggestion
is to pull a system down to 250-300 microns only if you are also pulling a
vacuum on the compressor. Going below 250 microns, you will start degassing
the oil in the compressor and it will not be the same lubricating oil as it
was originally. The oil will only degass and will not suck up into the
vacuum pump.\\

======================

http://www.refrigeration-engineer.com/forums/showthread.php?10919-vacuum-timeline

//This is from CPS:
2000 microns lowest average industrial requirements for A/C systems
1000 microns medium average industrial requirements for A/C systems
600 microns highest average industrial requirements for A/C systems
400 microns lowest average industrial requirements for refrigeration systems
200 microns medium average industrial requirements for refrigeration systems
100 microns highest average industrial requirements for refrigeration
systems
25 microns deep vacuum for special requirements and for testing of vacuum
pump efficiency\\

====================

http://www.jbind.com/pdf/Deep-Vacuum-Principles.pdf


//There are many evacuation level recommendations
including the statement “evacuate the system to below
200 microns.†This should not be considered. Note we
say “system†because it is possible to evacuate piping or
some component other than the compressor to below
this level. Refrigeration oil has a vapor pressure and by
going below 200 microns, you will degas particles of the
refrigeration oil. By changing the makeup of the oil, it will
no longer be a true lubricating oil.
Remember, hydrofluoric and hydrochloric acids, and their
pal, moisture, do collect in the oil. Having nothing but time
on their hands, they effectively destroy pull down and act
as an abrasive on internal surfaces. If left sitting in an idle
pump, these culprits keep busy by rusting and corroding
internal surfaces. Deep vacuum pumps need a fill or two
for every job.
In order for your pump to pull a near perfect
JB\\
 
T

Tony944

"PaxPerPoten" wrote in message



http://www.jbind.com/technical/faq-micron-gauges.aspx

//Some manufacturers have a micron range that they want their system
pulled down to, so therefore, JB can only suggest a micron reading. Our
suggestion is to pull a system down to 250-300 microns only if you are
also pulling a vacuum on the compressor. Going below 250 microns, you will
start degassing the oil in the compressor and it will not be the same
lubricating oil as it was originally. The oil will only degass and will
not suck up into the vacuum pump.\\

======================

http://www.refrigeration-engineer.com/forums/showthread.php?10919-vacuum-timeline

//This is from CPS:
2000 microns lowest average industrial requirements for A/C systems
1000 microns medium average industrial requirements for A/C systems
600 microns highest average industrial requirements for A/C systems
400 microns lowest average industrial requirements for refrigeration
systems
200 microns medium average industrial requirements for refrigeration
systems
100 microns highest average industrial requirements for refrigeration
systems
25 microns deep vacuum for special requirements and for testing of vacuum
pump efficiency\\

====================

http://www.jbind.com/pdf/Deep-Vacuum-Principles.pdf


//There are many evacuation level recommendations
including the statement â?oevacuate the system to below
200 microns.â? This should not be considered. Note we
say â?osystemâ? because it is possible to evacuate piping or
some component other than the compressor to below
this level. Refrigeration oil has a vapor pressure and by
going below 200 microns, you will degas particles of the
refrigeration oil. By changing the makeup of the oil, it will
no longer be a true lubricating oil.
Remember, hydrofluoric and hydrochloric acids, and their
pal, moisture, do collect in the oil. Having nothing but time
on their hands, they effectively destroy pull down and act
as an abrasive on internal surfaces. If left sitting in an idle
pump, these culprits keep busy by rusting and corroding
internal surfaces. Deep vacuum pumps need a fill or two
for every job.
In order for your pump to pull a near perfect
JB\\
Some of guys answers of pulling vacuum on systems got me interest and what
got me most that you believe what manufacture tell you, well gents those
that believe are fools, first of all you need to work for manufacture and go
on seminars to manufacture and see for your self what is done and how is
done. Vacuum should be pull down to 50 microns on any new refrigeration
system. If refrigerant was already in the system refrigerants that use POE
oil it may take hours are days to get down to 50 microns so it is acceptable
if you can get down to 100-300 microns, However it is also necessary to have
system pressurize because there are times that system may leak in one
direction but not in the other. Thec. At site most determined how he/she
will proceed and what he/she will need to do the job right. If system lost
gas on the high side or low side it makes large difference and if system has
pressure safety switches that will shut down system if refrigerant is lost.
There is another phenomena how cold this system is use for we must remember
that all material shrinks with low temperature and expand with high. These
phenomena may cause unit to leak at one temperature but not the other, I
have seen and experience these problems on my own, as some of us may say it
will drive you to drink even so I don't drink. Pressure testing is necessary
but one most take precaution, up to 300 PSI any system can be check, sealed
units you can go up to 400 PSI. Semi hermetic unit I would not advise any
one to go above 300 even so I have. By the way I never heard of 45% silver
on less is on special order so that Manufacture will need to sit bare assed
on fire before I would believe them!!
 
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P

PaxPerPoten

Some of guys answers of pulling vacuum on systems got me interest and what
got me most that you believe what manufacture tell you, well gents those
that believe are fools, first of all you need to work for manufacture and go
on seminars to manufacture and see for your self what is done and how is
done. Vacuum should be pull down to 50 microns on any new refrigeration
system. If refrigerant was already in the system refrigerants that use POE
oil it may take hours are days to get down to 50 microns so it is acceptable
if you can get down to 100-300 microns, However it is also necessary to have
system pressurize because there are times that system may leak in one
direction but not in the other. Thec. At site most determined how he/she
will proceed and what he/she will need to do the job right. If system lost
gas on the high side or low side it makes large difference and if system has
pressure safety switches that will shut down system if refrigerant is lost.
There is another phenomena how cold this system is use for we must remember
that all material shrinks with low temperature and expand with high. These
phenomena may cause unit to leak at one temperature but not the other, I
have seen and experience these problems on my own, as some of us may say it
will drive you to drink even so I don't drink. Pressure testing is necessary
but one most take precaution, up to 300 PSI any system can be check, sealed
units you can go up to 400 PSI. Semi hermetic unit I would not advise any
one to go above 300 even so I have. By the way I never heard of 45% silver
on less is on special order so that Manufacture will need to sit bare assed
on fire before I would believe them!!
Pressure testing and pulling a deep vacuum seem to be 2 different
animals. A deep vacuum seems to insure no leaks ..Where-as many times a
pressure test seems to miss them.
 

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