Need some walk in cooler help

[TECH01]

Well fellas........here is my situation. Ive been doing residental for quite a while now, and recently was asked to do some walk in work. I was pretty reluctant to do so because of not having the experience, but agreed only to take a look at it, not to fix it. That didnt last to long though and here is my situation. The system is 42 years old. Did a compressor check, (amps, volts, pump down) and everything checked fine. Unit doesnt get operated but maybe 4 or 5 times a year. Unit is primarly used for home butchering purposes. Today, what I did is this. It was an existing R12 system, recovered that and added 409a. What temp should my evaporator be to maintain around 37-40F in the Cooler. Would 35 be alright? What should my pressure controls be set at? What should my differential also be set at? I live in Ohio, and this is used sometimes in the winter, so i know I need some sort of control for low ambient temps also. Ive been doing residential for just about 8 years now, and know my way around residential AC work pretty well, but this cooler thing is a little different, not sure what i should expect from a 42 year old system, and what kind of temps i should be working with. Any help would be GREATLY appriciated. Thanks alot.

[k-fridge]

Wow, that's an oldie alright.

Good choice in R-409, it will work well. Ok.....pressure control setting....is tit a pump down system with a solenoid valve, or is the pressure control the primary means of temperature control? If it's a pump down system I'd set the control for a cut out of about 2 and a cut in of about 12. If the pressure control is controlling the temp, go with about a 15 cut out and 35 cut in. Tweak as needed to maintain temp. In the latter configuration you'll have problems in the winter.

Evap temp will vary with box temp. Just make sure your superheat at the coil is about 8*.

[TECH01]

The unit has a pressure control as a means of controling the temp. If I may ask K Fridge, would you reccommend a pump down system? Ive seen a few of these pump down systems installed before, so know just about enough to be dangerous, however, if this will work better in the winter, then I would rather fix it right now then have problems later. You also said something about making sure that I have 8* superheat to my coil. Forgive me if I sound stupid, but my mind set is residential where we want 8-10* superheat to the compressor. And 8-12 Subcooling to the evaporator. Is this not the same in refrigeration. Again, i am a residental guy for right now, please forgive my ignorance. Thanks alot

[sarpanch2001]

The unit has a pressure control as a means of controling the temp. If I may ask K Fridge, would you reccommend a pump down system? Ive seen a few of these pump down systems installed before, so know just about enough to be dangerous, however, if this will work better in the winter, then I would rather fix it right now then have problems later. You also said something about making sure that I have 8* superheat to my coil. Forgive me if I sound stupid, but my mind set is residential where we want 8-10* superheat to the compressor. And 8-12 Subcooling to the evaporator. Is this not the same in refrigeration. Again, i am a residental guy for right now, please forgive my ignorance. Thanks alot

superheat at out let evap coil .if you control your temp with low presure switch not problem just follow k firdge advise . make sure set your superheat when your system close to desighn temp i mean close to 40 deg box temp

[powell]

Ok.....pressure control setting....is tit a pump down system

Hmmmmmmmmmmmmm., having a good Saturday k_fridge?

[k-fridge]

The unit has a pressure control as a means of controling the temp. If I may ask K Fridge, would you reccommend a pump down system? Ive seen a few of these pump down systems installed before, so know just about enough to be dangerous, however, if this will work better in the winter, then I would rather fix it right now then have problems later. You also said something about making sure that I have 8* superheat to my coil. Forgive me if I sound stupid, but my mind set is residential where we want 8-10* superheat to the compressor. And 8-12 Subcooling to the evaporator. Is this not the same in refrigeration. Again, i am a residental guy for right now, please forgive my ignorance. Thanks alot

If the condensing unit is outside or exposed to varying temps, by all means a pump down. That way it will keep a fairly consistent temperature.

I don;t think you want 8-10* SH at the compressor even in residential A/C, maybe 10-12* at the coil. Typically the SH at the compressor should be 20-30*. But yes, typical SH at the coil in a cooler is 8*. Forget about subcooling for now, in this type of system it isn't that important.

Good luck

[k-fridge]

Hmmmmmmmmmmmmm., having a good Saturday k_fridge?

Well, now that you mention it...........



:D:cool::D:cool:

[Burnerfixer]

Well, now that you mention it...........



:D:cool::D:cool: That will be the last "Hooters" lunch break for you. :D:D

[crackertech]

That will be the last "Hooters" lunch break for you. :D:D

:D:D:D:D:p

[k-fridge]

What can I say, I was a breast fed baby.:p

[Burnerfixer]

What can I say, I was a breast fed baby.:p Nothing like a good "Bust" in the mouth.:D:D:D:p

[TECH01]

On these pump down systems, let me see if I understand these things. Basically you install a solenoid inside the liquid line to so that when the box reaches its setpoint (38*) then basically the solenoid will deengenergize, shutting down the liquid line, making the compressor pull alll the refrigerant back into the condenser. Then, when the compressor has complete its pull down, you shut the power for the compressor off with a pressure switch monitoring the suction line pressure, say 5 or 10 psi? if I may ask, what is the benefit of this, and also, should there be a crankcase heater on the compressor? again, any help would GREATLY be appriciated

[k-fridge]

On these pump down systems, let me see if I understand these things. Basically you install a solenoid inside the liquid line to so that when the box reaches its setpoint (38*) then basically the solenoid will deengenergize, shutting down the liquid line, making the compressor pull alll the refrigerant back into the condenser. Then, when the compressor has complete its pull down, you shut the power for the compressor off with a pressure switch monitoring the suction line pressure, say 5 or 10 psi? if I may ask, what is the benefit of this, and also, should there be a crankcase heater on the compressor? again, any help would GREATLY be appriciated
Close, the refrigerant should pump into the receiver. Make sure it has a receiver.

I would set the pressure control to cut off about 2-3 PSI, back on about 10-12 with that refrigerant.

The benefits are several;

-More consistent temp control
-Less affected by outdoor temps
-Less slugging on start up
-Possibly improved oil return
-Helps protect compressor from flooded starts

And yes, you need a crankcase heater if outside in cold weather.

[TECH01]

This unit does not have a thremostat currently. (I meant it when i said it was really messed up!). I ordered on and got it today. I am going to put in this pump down system like you reccommended. I was looking at the T-stat, and it said the thermostat should control the solenoid valve. This correct? It also said that I should install a motor starter, which would monitor the suction like pressure and start and stop the compressor like wise. I understand this, just wondering if you would do it this way. One last thing before I get into this thing, looking into the compressor oil sight glass, didnt see any oil. I am pretty sure that it should be half full when running at stable conditions. Is "AG" oil what i need to add. When it comes to adding this, am i recovering all the refrigerant? Didnt know if the oil sump was sealed from the refrigerant side of things. Again, appriciate any and all help.

[yotaman16]

This unit does not have a thremostat currently. (I meant it when i said it was really messed up!). I ordered on and got it today. I am going to put in this pump down system like you reccommended. I was looking at the T-stat, and it said the thermostat should control the solenoid valve. This correct? It also said that I should install a motor starter, which would monitor the suction like pressure and start and stop the compressor like wise. I understand this, just wondering if you would do it this way. One last thing before I get into this thing, looking into the compressor oil sight glass, didnt see any oil. I am pretty sure that it should be half full when running at stable conditions. Is "AG" oil what i need to add. When it comes to adding this, am i recovering all the refrigerant? Didnt know if the oil sump was sealed from the refrigerant side of things. Again, appriciate any and all help.

Wire the solenoid in series with the t stat so that when the stat satisfies and opens the power is killed to the liquid line solenoid, causing a restriction which pumps the unit down into the reciever.

[Burnerfixer]

TECH01 I highly recommend this book, it will explain things clearly.:)

[k-fridge]

This unit does not have a thremostat currently. (I meant it when i said it was really messed up!). I ordered on and got it today. I am going to put in this pump down system like you reccommended. I was looking at the T-stat, and it said the thermostat should control the solenoid valve. This correct? It also said that I should install a motor starter, which would monitor the suction like pressure and start and stop the compressor like wise. I understand this, just wondering if you would do it this way. One last thing before I get into this thing, looking into the compressor oil sight glass, didnt see any oil. I am pretty sure that it should be half full when running at stable conditions. Is "AG" oil what i need to add. When it comes to adding this, am i recovering all the refrigerant? Didnt know if the oil sump was sealed from the refrigerant side of things. Again, appriciate any and all help.
Install the solenoid and wire the thermostat in series with it. The thermostat is just a switch, just break one side of power to the solenoid.

If the compressor is operating from a pressure switch now, you can leave it as is. You don't have to add a contactor assuming it's single phase. But you need to set the low pressure control lower than it is now. Set it to cut out about 1-2 PSI and cut back in about 10-12 PSI.

[bob_scheel]

Most manufacturers recommend that the oil level be between 1/8th and
3/8th of the sight glass.

If you are going to have the system in a vacuum you can add the oil by letting it suck into a schrader on the sump of the compressor. Be careful not to overfill. Then continue your evacuation until you get the desired micron level.

If you have to add when the system is charged you will need a pump. They cost about $100 or so and work like a bicycle air pump except they attach w a charging hose and have a built in check valve to prevent the refrigerant from blowing back.

Make sure you purge the air by carefully pumping until you start getting oil out the end of the hose, then attach it to the compressor sump schrader. (You may need to add one if the compressor doesn't have a valve or a schrader already present.)

Make sure the oil is the manufacturers recommended viscosity for the compressor and evaporator temp range you have.