working on a walk in cooler r22 temp should be at 38d , found unit at 55d and P.S.I. low side 80 psi and 300 psi , removed freon brout it to 45 psi and 225 on th hi side, temp at 38d. i asked the customer if he had called someone els , he did not, got another call found unit low on freon added unit up to par. i double check everything: P.S.I, SOLONOID, FAN CTRL, HI HEAD PSI CTRL, T -STAT. POWER, LINES, I MEAN EVERTHING..... plus i checked to see if compresor would hold psi on pump down, it did not .. unless im checking it the wrong way, . I closed the hi side valve and pumped unit down into the reciver to a vacuum on the low side but notice pressures ascalated up to 20 psi. my question is this once the unit goes into a vacuum should it stay on a vacuum within the low side valves of the compresor.
calling the icemister, pump down
newbeetech
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working on a walk in cooler r22 temp should be at 38d , found unit at 55d and P.S.I. low side 80 psi and 300 psi , removed freon brout it to 45 psi and 225 on th hi side, temp at 38d. i asked the customer if he had called someone els , he did not, got another call found unit low on freon added unit up to par. i double check everything: P.S.I, SOLONOID, FAN CTRL, HI HEAD PSI CTRL, T -STAT. POWER, LINES, I MEAN EVERTHING..... plus i checked to see if compresor would hold psi on pump down, it did not .. unless im checking it the wrong way, . I closed the hi side valve and pumped unit down into the reciver to a vacuum on the low side but notice pressures ascalated up to 20 psi. my question is this once the unit goes into a vacuum should it stay on a vacuum within the low side valves of the compresor.
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How did you close the high side valve to pump it down with out tripping on
head pressure.or do mean king valve at the reciver. is this system a txv?
could be your trouble.it also could have some non condensables in the system
uh newbeetech it sounds like you might be upside down on this. 300 p.s.i ? is this air cooled or water cooled? you say you have taken gas out then came back with a call on low gas? how much Ref does the system hold? if this is air cooled then look through the condenser it maybe plugged,if this is the case then charging will be next to impossible. Pump down test, front seat the suction king valve,making sure the reading you are taking is on the compressor side of the king valve.I recommend you take a deep breath and and start again! also look for what is the ambient temp where the unit is located?
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well i pumped the unit down , clesed the hi side, had gauges on, pumped to a vacuum, held the low psi switch down and got it to the vacuum point, then shut unit down thats when i notice unit psi going to above 10 psi and higher. . . with out doing nothin on the suction valve . did i do something wrong? if so please tell me how to do this,,,,,,
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Newbee...
This initial set of conditions you stated could indicate an overcharged system, which is the apparent direction you took to remedy the situation. It could also have indicated non-condensibles as was mentioned, but let's look at this from the overcharge aspect as it's the more likely scenario of the two.
Since you said this an R22 walk-in cooler system, I'm assuming it has a TEV and a receiver. Does it also have a sightglass? If not, it should. A sightglass is one of your best diagnostic tools when dealing with the refrigerant charge on this kind of system because it can give you a benchmark of where your system charge stands.
Based on what you say you found on the initial call, I wouldn't have suspected a compressor valve problem. The high suction pressure may lead you to think that, but with that high discharge pressure I would believe the compressor to be pumping rather vigorously. An severely overcharged system would be the first thing to check.
To do this, rather than recovering refrigerant to arrive at some arbitrary set of pressures that "look good", you should watch your sightglass as you recover. The SG in an overcharged system will be clear...no bubbles or flashing going on, so as you recover watch for the first sign of flashing in the glass. Then add a little refrigerant until the flashing clears up. This is your benchmark, indicating where you then have a liquid seal in the receiver and a full column of liquid going out to the TEV. At this point, and when the box is at design temperature there is a minimum operating charge in the system. Add about 1 lb or so per HP beyond this point to allow for system load and ambient condition fluctuations. If the system has a Headmaster condenser flooding control, you'll have to add more to allow for cold weather operation. (That's another topic that's covered well all over this Forum.)
I suspect you simply went a bit too far in recovering refrigerant the first time and had to come back due to a low refrigerant charge condition. If you had initially used the sightglass as your guide and assuming all else in the system checked OK, that callback likely wouldn't have happened.
Now as for checking the compressor, as was mentioned, the valve you need to close off to check pumping efficiency is the suction service valve not the King Valve. When you pump down using the King Valve, you're pulling down all the refrigerant from that point all the way back to the compressor and that requires boiling off all the liquid in the liquid line and the filter-drier which can take a relatively long time. (I suspect the slow rise in suction pressure you observed was simply the residual cold liquid boiling off in the LL and FD.)
Although closing off the suction service valve is a common check for bad valves, it really will only tell you if your discharge valves are holding. You could have one bad suction valve and the compressor will still pump down into a good vacuum and hold it. The preferred method is to use the compressor manufacturer's performance data to determine if the compressor is doing what it's supposed to be doing at those conditions. Copeland's Compressor Performance Calculator is an excellent program to use for all of their compressors and is available for free download on their website. Tecumseh has tabular compressor performance data available online as well. If you don't have online access in the field, call your wholesaler and they should be able to do a quick check for you over the phone.
Also, when you check a compressor's performance and find that it's not up to where it should be, don't automatically assume that it's just bad valves. Of course, if it's a fully hermetic can, it's time for a new compressor, but if it a semihermetic before you run out for a new valve plate you should pop the head and do an inspection of not only the valves, but of the pistons. You could have a broken rod or piston. You should also check that the pistons come all the way up flush with the deck. Piston and rod wear can also cause serious loss of capacity and a call for a new pump.
This initial set of conditions you stated could indicate an overcharged system, which is the apparent direction you took to remedy the situation. It could also have indicated non-condensibles as was mentioned, but let's look at this from the overcharge aspect as it's the more likely scenario of the two.
Since you said this an R22 walk-in cooler system, I'm assuming it has a TEV and a receiver. Does it also have a sightglass? If not, it should. A sightglass is one of your best diagnostic tools when dealing with the refrigerant charge on this kind of system because it can give you a benchmark of where your system charge stands.
Based on what you say you found on the initial call, I wouldn't have suspected a compressor valve problem. The high suction pressure may lead you to think that, but with that high discharge pressure I would believe the compressor to be pumping rather vigorously. An severely overcharged system would be the first thing to check.
To do this, rather than recovering refrigerant to arrive at some arbitrary set of pressures that "look good", you should watch your sightglass as you recover. The SG in an overcharged system will be clear...no bubbles or flashing going on, so as you recover watch for the first sign of flashing in the glass. Then add a little refrigerant until the flashing clears up. This is your benchmark, indicating where you then have a liquid seal in the receiver and a full column of liquid going out to the TEV. At this point, and when the box is at design temperature there is a minimum operating charge in the system. Add about 1 lb or so per HP beyond this point to allow for system load and ambient condition fluctuations. If the system has a Headmaster condenser flooding control, you'll have to add more to allow for cold weather operation. (That's another topic that's covered well all over this Forum.)
I suspect you simply went a bit too far in recovering refrigerant the first time and had to come back due to a low refrigerant charge condition. If you had initially used the sightglass as your guide and assuming all else in the system checked OK, that callback likely wouldn't have happened.
Now as for checking the compressor, as was mentioned, the valve you need to close off to check pumping efficiency is the suction service valve not the King Valve. When you pump down using the King Valve, you're pulling down all the refrigerant from that point all the way back to the compressor and that requires boiling off all the liquid in the liquid line and the filter-drier which can take a relatively long time. (I suspect the slow rise in suction pressure you observed was simply the residual cold liquid boiling off in the LL and FD.)
Although closing off the suction service valve is a common check for bad valves, it really will only tell you if your discharge valves are holding. You could have one bad suction valve and the compressor will still pump down into a good vacuum and hold it. The preferred method is to use the compressor manufacturer's performance data to determine if the compressor is doing what it's supposed to be doing at those conditions. Copeland's Compressor Performance Calculator is an excellent program to use for all of their compressors and is available for free download on their website. Tecumseh has tabular compressor performance data available online as well. If you don't have online access in the field, call your wholesaler and they should be able to do a quick check for you over the phone.
Also, when you check a compressor's performance and find that it's not up to where it should be, don't automatically assume that it's just bad valves. Of course, if it's a fully hermetic can, it's time for a new compressor, but if it a semihermetic before you run out for a new valve plate you should pop the head and do an inspection of not only the valves, but of the pistons. You could have a broken rod or piston. You should also check that the pistons come all the way up flush with the deck. Piston and rod wear can also cause serious loss of capacity and a call for a new pump.
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let me give you a little more info icemister, this unit is a tucumsi scroll compressor, not a sami hermatic unit, , yes it does have a txv and a slonoid t-stat ctrl, and and the unit is workin fine 45 on the low side and 225 on the hi side , however, i have been monitoring the unit and at times the psi are to hi like today 80 on the low side and 300 on the hi side. fan is working clean coils, then after while the unit start to work up to par. im getting frustrated with this , all being equel , if i had bad compressor valve would this be the reaction i would be getting, the unit has a reciever i shut the the hi side goes into a vacuum while holding the pressure ctrl, a couple of times hoping i get aal the reseduel freon then when in vacuum i shut the unit down , then the unit slowly creeps up on the suction side. should this accure. queston should the compressor hold in a vacuum or not , if the answer is yes then i have a bad compressor , right ?
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A Scroll?
I wasn't aware that Tecumseh offered a scroll compressor in their commercial refrigeration unit lineup, but if it is a scroll then you don't have to worry about bad valves....because it doesn't have any.
Scrolls should never be run into a vacuum anyway, so don't try that any more.
You now say that this system is randomly reverting to the high suction/high discharge conditions all on its own? Does this system have a Headmaster on it? If it does, the Headmaster valve may be getting stuck in bypass intermittently. That could cause the conditions you're seeing.
With a Headmaster on R22, the valve should be wide open with the bypass port closed above 180 psig. At normal operating conditions and ambients above about 70 Deg F all flow should be through the condenser, through the Headmaster and on to the receiver. There should be no flow through the bypass line. If you find the system at high suction and discharge again, check the bypass line to see if it's hot and if the liquid leaving the Headmaster is warmer than the liquid entering. If so, the valve is stuck in bypass.
I wasn't aware that Tecumseh offered a scroll compressor in their commercial refrigeration unit lineup, but if it is a scroll then you don't have to worry about bad valves....because it doesn't have any.
Scrolls should never be run into a vacuum anyway, so don't try that any more.
You now say that this system is randomly reverting to the high suction/high discharge conditions all on its own? Does this system have a Headmaster on it? If it does, the Headmaster valve may be getting stuck in bypass intermittently. That could cause the conditions you're seeing.
With a Headmaster on R22, the valve should be wide open with the bypass port closed above 180 psig. At normal operating conditions and ambients above about 70 Deg F all flow should be through the condenser, through the Headmaster and on to the receiver. There should be no flow through the bypass line. If you find the system at high suction and discharge again, check the bypass line to see if it's hot and if the liquid leaving the Headmaster is warmer than the liquid entering. If so, the valve is stuck in bypass.
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im sorry , icemister to tell you the true, iwas just guess what brand the compressor was , since i have not gone back, however, i will make it a point to go back today, iv been doing lots of commecial kitchen, but this just prove your knoledge verses mine lots to learn still., however, this unit does not have a headmaster it does have a fan ctrl, mainly hot weather in houston tx, thank and i will get back with you.
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643 Posts
New BEE M#? S#? condensing unit
Evap coil M# S#?
TXV #
just post you will get good help
Evap coil M# S#?
TXV #
just post you will get good help
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2,032 Posts
Icemeister,
Let's you and me put the money together and bet that: It is a Copeland compressor AND there is a head master control on this unit locating on the left hand side corner, which is hard to be located.
Let's you and me put the money together and bet that: It is a Copeland compressor AND there is a head master control on this unit locating on the left hand side corner, which is hard to be located.
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13,539 Posts
Yeah....like on a Heatcraft outdoor unit with that little Sporlan LAC gizmo tucked way in there behind the tall black thingamajig.Icemeister,
Let's you and me put the money together and bet that: It is a Copeland compressor AND there is a head master control on this unit locating on the left hand side corner, which is hard to be located.
Of course, Newbee did say this had a fan cycle control, so this probably isn't the right unit.....unless somebody added one.
Yep, the model numbers would be real handy about now, Newbee.
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308 Posts
got some more info icemister, unit is tecumshi 15000 btu hermatic compressor m#awg5515exn.... without headmaster, with a head pressure ctrl, in houston tx. called tech sopport thay said that it could be the txv sticking. i had performed the tested that tech sopport sugasted i do , pump down, holding, and how fast the unit reaches the desire psi, thay said that the compressor was good .,,,,,,,i was not/ am not sure how the valves on the low side held the psi in a vacuum? is there seals that close when uint is of? please a explaine and how does one check the scroll compressor .
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13,539 Posts
How To Check A Tecumseh Compressor:
Go HERE, enter the model number and click on "search". Then on the page that comes up, click on the highlighted compressor model number. That'll take you to the specs page for that compressor. At the top of that page, click on the "Performance Data" tab and you'll get a performance table that gives you the capacity and amp draw for any condition.
Go back to the job and get a reading on the suction & discharge pressures along with the amp draw. Compare your numbers with this table's numbers. You should be with 5% or so. If it's way off, you have a bad pump.
Again, if you insist on doing the pumpdown efficiency test, close off the suction valve, not the King Valve to see if it'll pull a good vacuum and then shut off the compressor to see if it holds. That's the right way for doing that test....simple as that. But as I said earlier, it's not always a good test if you happen to have one broken suction valve reed.
The performance data is the best test.
Now as for you weird pressures, since you don't have a headmaster that theory is out the window. The TEV is a long shot IMHO, but it's easy to check. Just monitor the suction superheat and see if the TEV is doing what it's supposed to do. If the SH is OK then it's not the valve.
On your next visit, get some hard numbers on the suction superheats at the evap and at the compressor along with the subcooling leaving the condenser. Get these numbers when it's running good and again when the pressure shoot up. The answer will be in that info.
Go HERE, enter the model number and click on "search". Then on the page that comes up, click on the highlighted compressor model number. That'll take you to the specs page for that compressor. At the top of that page, click on the "Performance Data" tab and you'll get a performance table that gives you the capacity and amp draw for any condition.
Go back to the job and get a reading on the suction & discharge pressures along with the amp draw. Compare your numbers with this table's numbers. You should be with 5% or so. If it's way off, you have a bad pump.
Again, if you insist on doing the pumpdown efficiency test, close off the suction valve, not the King Valve to see if it'll pull a good vacuum and then shut off the compressor to see if it holds. That's the right way for doing that test....simple as that. But as I said earlier, it's not always a good test if you happen to have one broken suction valve reed.
The performance data is the best test.
Now as for you weird pressures, since you don't have a headmaster that theory is out the window. The TEV is a long shot IMHO, but it's easy to check. Just monitor the suction superheat and see if the TEV is doing what it's supposed to do. If the SH is OK then it's not the valve.
On your next visit, get some hard numbers on the suction superheats at the evap and at the compressor along with the subcooling leaving the condenser. Get these numbers when it's running good and again when the pressure shoot up. The answer will be in that info.
service AE Bulletins are readily available for Copeland Scrools
both online abd tru your Copeland wholesaler, they give a lot of
service info
However, that Tecumseh AWG is not a scroll, it's a hermetic, also
known as a weld pot. you can get Tecumseh infor at: http://203.196.151.124/nacg/
both online abd tru your Copeland wholesaler, they give a lot of
service info
However, that Tecumseh AWG is not a scroll, it's a hermetic, also
known as a weld pot. you can get Tecumseh infor at: http://203.196.151.124/nacg/
those conditions seems strange that high suction and high suction the would think the txv.. If ur valve was closed off the most it could u may see higher head but i would expect to see low suction.. And the other way if the valve was wide open id think low head and high suction.. Id use the site ice linked up and test the comp that way i think u will find u have a bad compressor
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I still think it's the txv.Or non condesabiles.
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643 Posts
another vote
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My vote is "get another tech out thers to diagnose it so you can learn better"
Since you make mistake between a scroll and hermetic compressor. It was like you make a mistake between "Larry Bird" and "Magic Johnson".
Since you make mistake between a scroll and hermetic compressor. It was like you make a mistake between "Larry Bird" and "Magic Johnson".
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308 Posts
blank you! my opinion . thats just my opinion
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