Results 1 to 11 of 11
  1. #1
    Join Date
    Jul 2004
    Location
    NJ
    Posts
    1,783
    Hallo everyone.(caution ,its a long one.)
    One of my boss`s costumers referred us to another deli.My boss handed me a condensing unit about two weeks ago,with the address hour and a half away from shop.
    Before I go on let me give the specifics:
    Box;8 feet long,Kysor\Warren,mn;539vj1-8u
    R22
    old condensing unit;f3ah-a078-Iaa-001
    old compressor;rs47c2-iaa-101
    new condensing unit;aka9446exaxc
    new compressor;aka9442exa
    lines 1\2",1\4" ,80 feet long.
    solenoid valve on liquid line.
    the bottom grill is covered with paper costumer says that`s the way it always worked.Tells me in three years no body touched the unit.(yaa right..)

    I checked the compressor;internal relief is blown.Sold the new condensing unit on the spot and a fan control and an LPC.When I opened the box I called my boss to tell him that it looks smaller than the old one especially the receiver.He tells me the supplyhouse crossreferranced it.I put everything together.Meanwhile while charging the unit I realize that one of the two fans in the salad show case is not working.Took care of it.
    Here`s the saga;
    first the box wouldn`t go below 44*F.expansion valve has no cap so I suspected it was mingled with.there is flooding back.tried to increase the superheat couldn`t.next day brought 1\2 ton valve with ext.equ. installed it.flooding back.gave it half a turn solved the problem.recovered the excess R22.showed the costumer 25*F to convince him.meanwhile since the first day I know system can not pump down on solenoid; head pressure skyrockets.so left the cut out setting high enough to enable turn off.made my boss aware of it.had a call-back first in three months in this job.found that expansion valve leaks from the header.fixed it and left.had a call- back saturday morning,.that compressor is very hot its clicking and no cooling.went there to see the internal relief blown,or leaking internally.told the costumer will be back monday,supplyhouse is closed ,boss is hunting.he bags me.i enable the compressor to start and run provided he opens the doors to prevent salad from freezing.because it can not stop.turned the thermostat all the way down.he survived weekend that way.monday I pick up another compressor under warranty and install it.jumped out the thermostat adjusted the LPC for temperature control.with no pump down hoped there will be no crazy jump in head pressure.sure enough when the low side reaches 35-37 psi (box is about 36*F)all of a sudden head pressure skyrockets before I pull the breaker off.adjusted LPC little higher not to see this situation before I come back with a new expansion valve.( my boss suspected that the leaky expansion valve was taken apart by previous mechanics)next day replaced the expansion valve.gave boss the good news and left.(I am not getting into the business aspect of this saga).This morning had a call-back..compressor is dead.internal relief open.couldn`t even get the compressor run this time after all the tricks that I know.I forced the costumer to admit that two weeks before the origenal compressor failed he had freon put into it.because he was asking me how come in three years there was no high head pressure problem.(by the way I showed him the date scrached on the origenal condensing unit 6.12.2002)My explanation to him was maybe someone put air inside the system or overcharged it till the oil broke down and coated inside the condenser(these parts are actually my question to you guys)or are you sure someone didn`t add some kind of oil or put wrong refrigerant to screw up the oil?)the origenal compressor died of high head pressure.either the condensor was dirty,we can`t know it now because its clean at the moment,or it was over charged I could not know it,or in time the oil broke down because of air in system and insulated the condensor coil.so he was left with these options from my boss;take another one of the same compressor in its box we`re not installing it.or upgrade the condensing unit preferably the piping also for a cost and labor charge.If I was the costumer I would buy a whole new system.So what do you think,besides that it a long story.sorry I couldn`t help.



  2. #2
    Join Date
    Jul 2004
    Location
    NJ
    Posts
    1,783
    Originally posted by altan
    [/B]

  3. #3
    Join Date
    Sep 2004
    Posts
    8
    the head pressure should never "skyrocket" , this is probably caused by non - condensibles in the system. Remove refrigerant and pull a deep vacuum on system (below 500 microns and holds). This may take some time. With a lack of temperature and pressure readings it is hard to advise on anything else right now.

  4. #4
    Whenever you suspect that receiver is gonna be too small .... go with your instinct!
    You can replace the factory supplied receiver, for the cost of an hour's labor and the price of the new larger capacity one.
    Also, I looked at two diferent manufacturer's air cooled condensing units. The Tecumseh unit had a noticably smaller condensor on it than did the same sized Copelaweld condensor.
    This was something a previous employer pointed out to me.
    (just one more advantage of having such a diverse background to draw from )

    Possibly your new condensing unit has a small condensor.
    It has not always worked for me, but I usually try this whenever I encounter your circumstances; Call Manufacturer! Ask for BTU load of evaporator. Ask for BTU load/ at what back pressure, they recomend for that particular piece of equipment.

    However, there are a couple of guys here who just KNOW what they do.

    I had a case I had to gutt. I contacted one of these guys here, I believe it was Yuma and he recomended the models of evaporator coil and condensing unit.
    I ran with those and it all came together like it was designed to be that way.
    Imagine that?

    On such a small coil, do you really need a TX with an external line?
    No loss using it though. Just a thought.

    Everything gets matched/ rated/ balanced off your load. Once you know your load, then you size your evaporator(s). From there you size your TX valves. From there you size your condensing unit.

    Some of this you already know, but I am including it for the benefit of those who have yet to walk in your shoes.

    Using a T-stat with a pump down solenoid valve is the way to go. Some guys cheap-out the job. Bad move.
    Pump down will assure good oil return.

    You know your compressor has a need for cold refrigerant gasses to come back and take the edge off it's tremendous load.
    Too hot of a gas return temp and the compressor overheats as it operates.
    Too cold of return gas and the oil washes out of the unit and the bearings go bad.

    You want warmer than 25F degrees and cooler than 40F degrees measured six inches from the compressor itself.

    Do all this and the unit will live a long and healthy life.

  5. #5
    Join Date
    Aug 2004
    Location
    MICHIGAN
    Posts
    12
    R12 has you on the right track,but that 80 feet of piping really raised a red flag.Your Copeland condensing unit capacity @ a +25 degree suction is approx. 6200 btuh.for R-22,roughly the same for the Tecumseh.That 80 feet is probably linear feet,once you add all the fittings required to get from condensing units reciever,to txv,your probably in the area of 125-150 feet or more, this is referred to as equivalent feet,this is the figure you use to design refrigerant piping.At a +25 suction 75-200 equivalent feet of piping, your suction line should be 5/8,and liquid line 3/8.You can use linear feet measurements to determine how much R-22 lines will hold,add in what cond. unit and evap. holds.then size reciever accordingly.Your sudden rise in hesd pressure may have been caused by txv throttling down,backing up refrigerant into condenser,and flooding it.HEATCRAFT supplies a piping manual that can be helpful,check at http://www.heatcraftrpd.com..TRANE Co.publishes the best piping manual,and is the one I refer to.

  6. #6
    Join Date
    Jul 2004
    Location
    NJ
    Posts
    1,783
    [QUOTE [/B][/QUOTE]

    I just installed a new condensing unit that`s bigger ,3\4 HP.I think I found out what was making my high side gauge go to the end all of a sudden once the liquid flow in that 1\4" pipe stopped.whether the solenoid closed or txv closed..After I put the new condensor I went under the box to cut the solenoid out.when I grabbed it it was considerably warm.I left killing the power to it for later.so it was on the floor while I was working on the piping.the plastic part of it started burning.I know somebody recently installed a defrost clock.I found in the box too many neutral wires put together with a wire nut.Now my theory is that the solenoid coil was drawing too much amps it was heating up,so long as there was liquid flow in the 1\4" line it didn`t matter,once the flow stopped it heated up the liquid r22 in the pipe,and my gauge would hit the end.

  7. #7
    Join Date
    Jul 2000
    Location
    Guayaquil EC
    Posts
    10,078
    According to my old, dusty and now somewhat waterlogged Kysor/Warren Databook, an 8 ft S39VJ Deli requires 2600 BTUH @+20 Deg F SST, so the unit you have is a bit oversized for the job, but not the root of the problem.

    I would tend to agree that the receiver isn't big enough for a pump down and as such would either go with a larger, adequately sized receiver or possibly switch to a suction cutoff solenoid in lieu of the liquid line solenoid. Tyler did this a lot and it works quite well.

    It sounds like this system had been running for several years either cycling off on the overload protector or since it's an RS Copeland (which doesn't have an internal pressure relief) it likely just blew out the discharge valves.

    What a mess.

  8. #8
    Join Date
    Apr 2003
    Posts
    139
    I see the 80ft of lq line as a big problem but cant see it
    making the head ski like that.I would have ran 3/8 or 5/8 min. Sounds ODed and that could also be the deal with to
    small of a recver. Let us know when you solve the problem.

  9. #9
    Join Date
    Jul 2004
    Location
    NJ
    Posts
    1,783
    Originally posted by temp tech
    I see the 80ft of lq line as a big problem but cant see it
    making the head ski like that.I would have ran 3/8 or 5/8 min. Sounds ODed and that could also be the deal with to
    small of a recver. Let us know when you solve the problem.
    I think you didn`t see my reply,above.the way that head pressure in a second rised after the liquid flow stopped tells me it was boiling off inside the liqiud line by the solenoid.it went up from 180 or so psi to the end of the gauge in a second or two that I would rush to the breaker in panik.even if I blocked the condensor coil I don`t think I could rise the pressure in that manner.

  10. #10
    Describe your piping. Is it all horizontal? How much is vertical?
    Does any of the tubing cross any extremly hot surfaces or hot attics?

  11. #11
    Join Date
    Jul 2004
    Location
    NJ
    Posts
    1,783
    Originally posted by R12rules
    Describe your piping. Is it all horizontal? How much is vertical?
    Does any of the tubing cross any extremly hot surfaces or hot attics?
    its horizantal.no hot surface or attic.the only heat source was the solenoid.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event