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  1. #14
    Quote Originally Posted by Tommy knocker View Post
    Check SH at comp and evap. Is there a suction filter?
    I haven't been able to have it running long enought to check the superheat. I will asap though.

    Thank you

  2. #15
    Hello, sorry I haven't replied sooner. I was pumping fuel all day yesterday and didn't have a chance. I have an update on my situation. Last night I tried to run the compressor again. The noise was louder and it sounded like it was coming from the HP head. I removed the head and valves and replaced them with the head and valves and unloader from the other compressor that won't run. To my surprise, it is running smooth and quiet with no excessive heat. I didn't see any problems with any of the parts I removed but there must be something wrong. Also, the compressor that I took the head from that trips right away on motor overload, the pistons seem to be seized up in the cylinders. I can't move them at all. So that explains the overload tripping but not what caused it to seize up.

    The compressor ran overnight with no issues and the boxes are down to normal operating temps. I do have some questions though. First I would like to say that I am a tug boat engineer and unfortunately I am not great with HVAC, so if the questions seem very basic, that's why.

    1) The oil level was good on the bullseye when I started the compressor but now after it ran overnight, it is above the top of the glass. Is it harmful to be a little high, and if so, is there a way to drain some oil without shutting down, isolating the unit and bleeding off the pressure?

    2) I'm not sure if the charge is correct. The boxes are down to temp but the pressures are low I think. Suction is 15psi and discharge is 225psi. There are some bubbles in the liquid line to the coolers. There is a lot of ice building up on the suction line in the cooler and near the compressor especially where there isn't any insulation. I am reluctant to add refrigerant because I'm afraid to overcharge. Is it harmful to have not enough charge?

    3) I am embarassed to say that I don't remember how to calculate superheat. I know it is important and I am going to try to read about it on this forum asap.

    There were some questions asked about how the controls for the system are set up. I don't know enough about it to give a good explanation but I will tell you what I do know: There are two identical compressor/condenser units with isolation valving. The unit off line needs to be isolated. They cool a walk in freezer to -20*C, a walk in cooler to 5*C and a provisions stores room to 15*C. Each compressor has solenoid operated unloader valves for start up and load control. The liquid line goes into the cooler and splits three ways, one line going to each evaporator and the return lines come back from the evaporators and come together again in the cooler and back to the compressor. There is valving in the cooler that controls the flow to these lines. some solenoid operated and some thermal operated. I'm sorry that I don't know exactly how it works. I took some pictures but I wasn't able to post them on here for some reason. If any one wants them I could email them.

    Thanks again to everyone for their advice and support. It is really appreciated.

  3. #16
    Join Date
    Nov 2008
    Location
    Hudson Valley, NY
    Posts
    201
    superheat=temperture on suction line next to sencing bulb- then get a presure reading next to sencing bulb convert to temp from a pressure - temperature chart subtrack the two numbers then you will have your superheat --- for cooler 12 is good for low temp 6 is good - it sonds like you might be flooding back not good it will wash the oil out the crank case -all the exter oil in sight glass - after the other compressor ran for 24 hours. Good luck .

  4. #17
    Join Date
    Jun 2009
    Location
    DFW, TX
    Posts
    661
    Am I the only one that is really impressed with the fact that this guy fixed the freezer, and doesn't have formal training? Granted, we still don't know what caused the failure, but at least it's up and running again! Good work! This system is over my head, sounds pretty complicated. Good luck with it. Let us know what you find.

    Quote Originally Posted by anchorman2001 View Post
    Hello, sorry I haven't replied sooner. I was pumping fuel all day yesterday and didn't have a chance. I have an update on my situation. Last night I tried to run the compressor again. The noise was louder and it sounded like it was coming from the HP head. I removed the head and valves and replaced them with the head and valves and unloader from the other compressor that won't run. To my surprise, it is running smooth and quiet with no excessive heat. I didn't see any problems with any of the parts I removed but there must be something wrong. Also, the compressor that I took the head from that trips right away on motor overload, the pistons seem to be seized up in the cylinders. I can't move them at all. So that explains the overload tripping but not what caused it to seize up.

    The compressor ran overnight with no issues and the boxes are down to normal operating temps. I do have some questions though. First I would like to say that I am a tug boat engineer and unfortunately I am not great with HVAC, so if the questions seem very basic, that's why.

    1) The oil level was good on the bullseye when I started the compressor but now after it ran overnight, it is above the top of the glass. Is it harmful to be a little high, and if so, is there a way to drain some oil without shutting down, isolating the unit and bleeding off the pressure?

    2) I'm not sure if the charge is correct. The boxes are down to temp but the pressures are low I think. Suction is 15psi and discharge is 225psi. There are some bubbles in the liquid line to the coolers. There is a lot of ice building up on the suction line in the cooler and near the compressor especially where there isn't any insulation. I am reluctant to add refrigerant because I'm afraid to overcharge. Is it harmful to have not enough charge?

    3) I am embarassed to say that I don't remember how to calculate superheat. I know it is important and I am going to try to read about it on this forum asap.

    There were some questions asked about how the controls for the system are set up. I don't know enough about it to give a good explanation but I will tell you what I do know: There are two identical compressor/condenser units with isolation valving. The unit off line needs to be isolated. They cool a walk in freezer to -20*C, a walk in cooler to 5*C and a provisions stores room to 15*C. Each compressor has solenoid operated unloader valves for start up and load control. The liquid line goes into the cooler and splits three ways, one line going to each evaporator and the return lines come back from the evaporators and come together again in the cooler and back to the compressor. There is valving in the cooler that controls the flow to these lines. some solenoid operated and some thermal operated. I'm sorry that I don't know exactly how it works. I took some pictures but I wasn't able to post them on here for some reason. If any one wants them I could email them.

    Thanks again to everyone for their advice and support. It is really appreciated.

  5. #18
    Quote Originally Posted by A1 Burt View Post
    superheat=temperture on suction line next to sencing bulb- then get a presure reading next to sencing bulb convert to temp from a pressure - temperature chart subtrack the two numbers then you will have your superheat --- for cooler 12 is good for low temp 6 is good - it sonds like you might be flooding back not good it will wash the oil out the crank case -all the exter oil in sight glass - after the other compressor ran for 24 hours. Good luck .
    I took the vapor line pressure after the evaps. It read 65psi. which gives me 27*F saturation temp. and the line temp is 32*F. So subtract and I get a 5* superheat. Does that sound correct? I took the readings in the cooler near the evap.

    I also took readings near the compressor on the vapor return line. 20psi suction pressure which gives a -14*F saturation temp and the line temp was 8.6*F. So a 22.6*F temp difference.

    Does that make sense at all? I don't know why it is so different in the cooler and near the compressor.

  6. #19
    Quote Originally Posted by trippintl0 View Post
    Am I the only one that is really impressed with the fact that this guy fixed the freezer, and doesn't have formal training? Granted, we still don't know what caused the failure, but at least it's up and running again! Good work! This system is over my head, sounds pretty complicated. Good luck with it. Let us know what you find.
    Thanks a lot for the encouragement. I do feel like I got lucky with it but I'm very relieved to have it running. I just hope it will stay running.

  7. #20
    Join Date
    Jul 2012
    Location
    Western KY
    Posts
    1,221
    Quote Originally Posted by anchorman2001 View Post
    I took the vapor line pressure after the evaps. It read 65psi. which gives me 27*F saturation temp. and the line temp is 32*F. So subtract and I get a 5* superheat. Does that sound correct? I took the readings in the cooler near the evap.

    I also took readings near the compressor on the vapor return line. 20psi suction pressure which gives a -14*F saturation temp and the line temp was 8.6*F. So a 22.6*F temp difference.

    Does that make sense at all? I don't know why it is so different in the cooler and near the compressor.
    Yep you're checking it rite. 22* at comp sounds good. 5* at Evap is good for a freezer alittle low for a cooler and dry room but with 22 at comp its acceptable, IMO.

  8. #21
    Quote Originally Posted by Tommy knocker View Post
    Yep you're checking it rite. 22* at comp sounds good. 5* at Evap is good for a freezer alittle low for a cooler and dry room but with 22 at comp its acceptable, IMO.

    Ok great. Thanks for the info. I'm relieved that it's in the acceptable range.

    How about the oil level in the compressor? When I started it was half way up the bullseye. Now its above the bullseye. I can't tell how high. Should I be concerned about this? I don't know where the extra oil came from.

    Thank you

  9. #22
    Join Date
    Jul 2012
    Location
    Western KY
    Posts
    1,221
    Quote Originally Posted by anchorman2001 View Post
    Ok great. Thanks for the info. I'm relieved that it's in the acceptable range.

    How about the oil level in the compressor? When I started it was half way up the bullseye. Now its above the bullseye. I can't tell how high. Should I be concerned about this? I don't know where the extra oil came from.

    Thank you
    I'm not a bitzer guy so can't say I'm positive, but never seen a recip with an oil sight glass that wanted more then 3/4 full glass while running. 1/2 or 1/3 more in the normal range. Should be a drain plug or valve at bottom of crank case. Valve out comp recover remaining refrigerant from comp drain oil down to 1/2 glass then a quick vac open valves run and recheck. Repeat as needed. Extra oil usually comes from a comp change out or someone puts it in instead of trying to get oil back from system first. You should remove oil over charge, it will cause problems. Good luck

  10. #23
    Join Date
    Feb 2008
    Location
    California
    Posts
    2,065
    I'd turn the compressor off

    Put a hose on the oil pump.

    Turn the compressor on.

    And use the compressor to pump the oil out into a container, until I was between 1/2 & 3/4 visual level in the compressor.

    Turn compressor off, and remove my hose.

  11. #24
    Join Date
    Jul 2012
    Location
    Western KY
    Posts
    1,221
    Quote Originally Posted by Phase Loss View Post
    I'd turn the compressor off

    Put a hose on the oil pump.

    Turn the compressor on.

    And use the compressor to pump the oil out into a container, until I was between 1/2 & 3/4 visual level in the compressor.

    Turn compressor off, and remove my hose.
    Hell ya. Good idea.

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