What determines the static pressure?

[craig1]

As long as the system is physically able to equalize (no hard shutoff TXVs, no solinoids) The system pressure will correspond to the portion of the system that contains liquid and saturated vapor which is usually the coldest point unless the coldest point is already full of liquid.

Imagine the following system:

coil capable of holding 3 LBS in the basement is 70 degrees

Linset capable of holding 2 LBS in the walls is 80 degrees

condenser capable of holding 6 LBS outdoors is 90 degrees


If that system has less that 3 LBS of refrigerant, it should show a pressure that corresponds to 70 degrees.

If it is holding more than 3 but less than 5 LBS it will correspond to 80 degrees

If its holding more than 5 it will correspond to 90 degrees

[beenthere]

I have not seen many non-bleed txv's lately. Maybe they are favored by a brand I don't usually run into.

Pump down systems are usually refrigeration setups, so that would be a unique sector in the industry. I don't think we are dealing with refrigeration in this situation.

Most of the AC systems I see have no trouble equalizing. In fact, many don't use a TXV at all.

I have to agree that if I want to measure "static pressure," it will involve my 510, and not my gauge set.....and I have to admit, this is the first time I have heard someone mention static pressure outside of a discussion of fans and ducts.

Static pressure is mentioned in water systems/piping/plumbing, air planes, and many other things.

Static pressure, is simply the pressure exerted by something in all directions.

[beenthere]

As long as the system is physically able to equalize (no hard shutoff TXVs, no solinoids) The system pressure will correspond to the portion of the system that contains liquid and saturated vapor which is usually the coldest point unless the coldest point is already full of liquid.

Imagine the following system:

coil capable of holding 3 LBS in the basement is 70 degrees

Linset capable of holding 2 LBS in the walls is 80 degrees

condenser capable of holding 6 LBS outdoors is 90 degrees


If that system has less that 3 LBS of refrigerant, it should show a pressure that corresponds to 70 degrees.

If it is holding more than 3 but less than 5 LBS it will correspond to 80 degrees

If its holding more than 5 it will correspond to 90 degrees

I believe what you posted would violate the laws of psychics.

[craig1]

I believe what you posted would violate the laws of psychics.

explain?

[beenthere]

Your basing your saturation on all the refrigerant being in only X part of the system, if it only has X amount left in it.

Even if it only has 3 pounds in it. There will be some liquid in the condenser, and the line set.

[ICanHas]

And what would be the point in knowing this, I wonder? Would the poster state why this is necessary information.

Is it a crime to ask questions without stating the purpose of necessity?

[craig1]

Your basing your saturation on all the refrigerant being in only X part of the system, if it only has X amount left in it.

Even if it only has 3 pounds in it. There will be some liquid in the condenser, and the line set.

Depends how long it sits. After a its off long enough all the refrigerant liquid will be in the coldest part of the system as long as theres room to accept it. If theres not room it moves to the next coldest part.

Thats why if you work on refrigeration you get calls for warm freezers when its 20 below outside. If theres not more refrigerant in the system than the condenser can hold, all the refrigerant will migrate to the condenser during the off cycle, and take on a pressure that corresponds to the outdoor temperature. When the solinoid opens on a call for cooling, the refrigerant will just sit there because it has no incentive to move to a warmer place (the freezer at 0 degrees). The compressor won't start because the pressure in the system is lower than the cut in point on the compressor. There needs to be enough refrigerant in the system so that there is always some in the indoor receiver or outdoor heated reciever if long off cycles are expected.

[DeltaT]

Is it a crime to ask questions without stating the purpose of necessity?

Actually, yes. The HVAC-talk wrong question cops will be by shortly.

There usually is a question behind these types of questions and that is what I'm interested in. It's an educational process. You asked about the sitting pressure inside a sealed system and I'm interested in what you are attempting to attempt.

Maybe there is a better way for you to find out what you are looking for. Or maybe you are on to a new science that all of us could benefit by.

By your defensive stance, I'm assuming you don't want to expose yourself to deeper questioning.

[timebuilder]

Static pressure is mentioned in water systems/piping/plumbing, air planes, and many other things.

Static pressure, is simply the pressure exerted by something in all directions.

I like the give and take with you on these points.

Okay.

All of the things you mentioned do indeed have specific ideas assoociated with "static pressure."

In fact, that is pretty much what I was pointing out.

HVAC has a specific expectation for the words, "static pressure."

RSES Journal has an article on leak prevention in systems, and there are four of five mentions of "standing pressure," in regards to the ability of the system to hold pressure during leak testing.

http://www.rses.org/assets/rses_journal/0710_Leak.pdf

And it is referenced here http://hvac-talk.com/vbb/showthread.php?t=251392 in the same vein.

..and my application of the term is used in this HVAC textbook, on page 563:

http://books.google.com/books?id=gni...anding&f=false

[ICanHas]

RSES Journal has an article on leak prevention in systems, and there are four of five mentions of "standing pressure," in regards to the ability of the system to hold pressure during leak testing.

Though I was asking for the purpose of determining maximum tolerable pressure for testing, what I was asking is the steady state refrigerant loop pressure when it is not running.

[beenthere]

Though I was asking for the purpose of determining maximum tolerable pressure for testing, .

What ever the test pressure is of the indoor coil.

[ICanHas]

I suppose that means not less than 250 psi, unless the indoor coil will rupture if the ambient gets to 110F.

[beenthere]

I suppose that means not less than 250 psi, unless the indoor coil will rupture if the ambient gets to 110F.

No. Just means that is a safe pressure to use for leak testing. Can use less if you want.

[ICanHas]

No. Just means that is a safe pressure to use for leak testing. Can use less if you want.

I meant safe pressure is not less than 250psi. The more pressure you use, the easier it is to find small leaks, isn't it?

[beenthere]

I meant safe pressure is not less than 250psi. The more pressure you use, the easier it is to find small leaks, isn't it?

Generally yes.