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primary advantage of installing a pumpdown on a tstat is tighter temperature control. pumpdowns MUST be installed with some form of defrost control. LPC control may or may not since the control can be set to cause the coil to defrost by itself. Pumpdowns are also more able to handle heavy traffic as they turn on quicker when you open the door. In applications where temp is critical - milk etc. pumpdowns are best.

Also, for stats - I sell Johnson Controls A419's.
The additional settings allow for a lot of flexibility
when dealing with 'problematic' icing.

It sounds like this has been a good learning experience for you. Why use the T-stat/LLSV aka pumpdown control? A thermostat will control the temperature better then an LP control will and you won't have to make seasonal adjustments. I like the Ranco ETC stats. They hold their setpoints/differentials better than electromechanical t-stats and you can lock the keypad with a switch under the cover. A pumpdown system controls liquid refrigerant in the low side during the off cycle. This is especially important if the compresssor is below the evaporator coil and is mandatory on a freezer application with electric defrost. One suggestion for this job; if the customers box needs new thermometers, sell them some new ones. I would never tell a customer that it's up to them to get some new thermometers. I can repair that [at a profit of course]. Suggestions for the next time you have to do a job like this-

1. Verify the line sizes for the refrigerant you switch to. Don't assume that the existing lines sizes will be ok.

2. Verify the size of the nozzle in the distributor. I noticed that no one asked about it.

3. Install a door switch. On walk in coolers, the door switch can shut off the LLSV and the evaporator fans or just the LLSV- dealers choice. On walk in freezers, the door switch has to shut off both the LLSV and the evaporator fans.

One other suggestion- invest in a micron gauge and some deep vacuum hoses and isolation valves.

thanks again for info everyone, i explained to the costumer about the pumpdown valve and that it should be installed,the manager said it seems to work fine so well give it some time and if we have trouble well go ahead with it,

i put on a tstat since i bought one anyway, i had one service call prior to this on a walk but some idiot turned turned the tstat down to -30 degrees and left the dooor open because the air conditioning wasnt working and never turned it back up, i had 2 york rooftops to clean the evap and consensore coils, the cooler condensor was on the roof too, it put the tstat back to 35 and it seemed to cycle fine as i was watching while cleaning the coils, and they havent called back yet,

On the cooler i posted with the trouble, i noticed there wasnt a tstat so picked one up when i got all the equipment to have just in case because the prior cooler had one, its in place and cycling the unit off,i told the manager to get new thermometers cause one said 38 and the 52 only 3 feet from one another, defrost timer now on 2 times a day for 60 min after searching for the pins to attach to the clock, everything seems kosher the manager said it held 35-38 with constant door opening all day and i seen minimal frost on the coil and condensation in the drain pan and at 8 am frost on the food so im guessing it was a lil colder than the thermoeter that said 38 but i didnt callibrate the differential on the tstat yet at that point

i've done residential HVAC for 6 years now and learned on the job no schooling, then went to school thru local 399 and put all the pieces to the puzzle together so now on residential is a piece of cake, but refrigeration i havent a clue on the controlls, on a furnace i almost know the problem right away when the costumer explains what is happening

all and all is the purpose of the pumpdown valve is to close off the liquid line at tstat cycling to get all the refrigerant back to the compressor untill the LPC shuts down the compressor ? is the main reason to get the frost and ice off the evap faster by getting the refrigerant out of the suction line?

should i go by the costumer request on the valve(see how it runs) or tell him its mandatory

thanks again all, im so glad i found these forums just take it easy on me, im new to refrigeration so if i ask what you think is a dub question just ignore it

Originally posted by NedFlanders
Dave , you are a patient man

Note that my phone number appears nowhere in that entire post.

Did I actually use the word "abbreviated"????

Dave , you are a patient man

Hey, Bud

If you know how to wire a thermostat to turn the compressor on and off, you ALREADY know how to wire the tstat to control a Liquid Line Solenoid valve.

Pretend that the valve is the compressor contactor, and set your LPC to cut out at about 15, and cut back in at about 25.

When your tstat opens, (Shuts off) the Liquid Line Solenoid coil will deenergize, which closes the valve itself, which will cause the refrigerant in the evaporator to pump into the receiver and condenser, until the LPC "opens" (shuts off) the compressor contactor, turning off the compressor.

As the box temp rises, and the tstat "closes", it OPENS the valve, by powering up the solenoid coil, and the whole process starts all over.

Here is an abbreviated list of what you'd need to do:

• Cut in a liquid line solenoid valve (rated greater than the entire system tonnage- REAL easy on a small system like you have.) right before the coil.
• Install a thermostat (Close-on-rise, like a Penn A19) near the solenoid valve, preferably near the BACK (Inlet air side) of the evaporator.
• Find a power source for the tstat and solenoid. (This can come from the evap fans, if no other source is available, although a separate source is much preferred.) It does NOT have to connect in any way, shape or form to the condensing unit.
• Wire the "hot" to one side of the stat, then take this "hot" from the other side of the stat, and get it to the solenoid coil.
• Wire the L2 or "neutral" (depending on the voltage. I'm assuming 115, but 230 is also common...) direct to the solenoid coil. (Other wire in coil, not already occupied by the "hot".)
• Connect the ground whereever there is a place to connect it. (The stat and the coil should have grounding screws already in place.)
• Turn all this shit ON.
• Set the tsat to 35 degrees or so.
• LOWER THE LPC SETTING TO 15-25, like I said above. {NOTE: The LPC is STILL turning the compressor on and off, but only on a "command" provided by a low suction pressure condition caused by the tstat turning the coil off!!!}
• Get paid.
• Go home.
• Repent your sins.

The entire process sounds intimidating, until you've actually done it.

The parts are relatively inexpensive, and you don't have to CHANGE A DAMN THING, other than the setting on the low pressure switch.

I could do this whole thing, vacuum and all, in a real limited-access cooler, in about 2-3 hours, but I've done it a few times before...

Print this out, go unf*ck that thing, and make the customer happy.

You might want to discuss the bill with your boss before you hand it to the customer, as he may want to knock some off of it for all the excess time. That is OK. I'd worry if he didn't. Remember, he THREW your sorry ass into this mess while he was filling up the G-string of some worn out stripper near some airport. He should expect to cover some of that bill.

.Have fun

Originally posted by icemeister
Jeeez.....I wish I had had this kind of educational resource when I was stumbling around in the dark 35 years ago.

Line-jacker.

If you put a T-stat in, trust me, you will want to install a LLSV (Liquid Line Solenoid Valve) or you will be back in a month or less. You can get the valve body to your LL size then, I believe it was Lusk, like he said get a 120v coil. It's 2 seperate pieces for the part. Talk to Johnstone they should know what it is and help you. Leave the LP control in it will still control your compressor operation. The customer might be happy now but if it goes down again due to an iced up coil within a couple weeks you will be right back where you started if not worse with your customer.

Originally posted by refer dude 2479
If you are going to install a tstat set the LP control as a safety say 55/35. I would suggest 4 def per day and start at 30 min. If you choose not to go with the tstat I would set the LP to 58/38 and the adjust the cut out to get the box temp you want (35) Just be aware that with LP control changes in the weather and the condition of the condenser will affect compressor capacity and you will most likely on occasion get calls that the box is too warm or everything froze.

the condensor is in the kitchen on top of the box with constant ambient at like 90 degrees, butt i am going to install tstall and will adjust the defrost timer hopefully this will solve problem for a least a 6 month call back, this is a complete learning experience for me but thanks for all your input

If you are going to install a tstat set the LP control as a safety say 55/35. I would suggest 4 def per day and start at 30 min. If you choose not to go with the tstat I would set the LP to 58/38 and the adjust the cut out to get the box temp you want (35) Just be aware that with LP control changes in the weather and the condition of the condenser will affect compressor capacity and you will most likely on occasion get calls that the box is too warm or everything froze.

hey everyone thanks for your input, i am so glad i found this site and will recomend many to stop by, i dont think im gonna go with the pump down controll on this one not beause i dont want to do it right but because there was never one before and i spent to much time allready and i have no clue to what the hell it is and how it works, i got the cooler to 38* its 100 better than what i started with. i will install a tstat though, and adjust the timer for defrost, but i will definatly look into the upcoming seminars on refrigeration and freezer apps at the local supply houses here in chicago, this was my first time on a cooler i have only done residential HVAC prior and learned on the job half ass i guess, and figured out a lot after learning on the job then going to school, i never knew about SH and SC my boss always just felt the heat coming off of the condenser fan motor but learning on the job then going to school is a way better benefit than going to school and then out in the field

YOU DID

you just didn't want to listen

Jeeez.....I wish I had had this kind of educational resource when I was stumbling around in the dark 35 years ago.

He has a time clock on it but it is set to 60 min x 2 a day. I would like to see 4 x 30 and others would like to see 2 x 30 @ 12 & 12.

The LPC set at 32 and 64 is off. That would equal 10* shut down and 37* turn on. But you have to consider the subcooler effect on the line set too.

Like Ice said. A walk in cooler is no place for a LPC to control temp. Set it at 5 lb cut out and 25 cut in. Install a 120v pump down solenoid and thermostat at the evaporator. Take the 120v power from the fan power supply, run it to the coil and then to the thermostat and back to common. Don't let the fans cycle with the stat. As the stat opens, the valve closes and the LPC will shut down the unit.

Since your time clock in on the top of the walk in, have the clock make and break the LLV as well. Just two little o’l wires

I agree with ice, leave that TXV alone now. Let it do its job. If you haven't insulated the TXV bulb, do it now. It is time to work on the control system and make it a real walk in. That'll impress'em.

No one has discussed your billing for your labor. You addressed it a little but with a customer that has product loss and you are doing "OJT" I would think you would want to reflect a normal billing time. Not sure how others will react but 5 to 7 hours should be close. Another thing, I would suggest doing the stat and LLV at no charge to show him you are looking out for his needs and want to keep him as a customer. (These are my thoughts only and reflect the nature of the beast but not those of your BOSS) if you know what I mean.

Oh yeah... welcome to the site.

Just some advice here.........

1. Stop playing with the TXV as if it were a pressure regulator. Its only function is to control evaporator superheat and that's all it knows.

2. Since you're asking about low pressure control settings to control temperature I assume that you have no thermostat or liquid line solenoid valve for pumpdown. A LP control is good for temperature control in a deli case but not in a walk-in box.....especially with R22. If your boss expects you to do what's right to make this system run work, add a LLS and thermostat for temperature control. Then you won't be married to this box.....and its owner.

3. If you're looking for 34-35 Deg F box temperature you'd best add a defrost timeclock to the above stuff if you don't want to be called back for a frozen-up evaporator.

If this came across as harsh commentary, I apologize. I have seen so many jobs where somebody came in and messed it up royally and didn't care afterward. I commend you for bringing this problem of yours to us here and trying to get the straight info to do it right.

did you check the filter screen in the txv? could be clogged.

ok all seems well now box is holding 38 degrees with constant door opening all day long

im gonna check it again first thing in the morning before antone gets there, if box get down and holds 35 all is well, if it still holds 38, can adjusting the txv fix this and if so would you think to alow more liquid in or less,

would you say my LPC settings are right 32out and 64in for R22

pressures were at 38 suction 245 discharge,box at 38 degrees, the coil temp im not sure of didnt wanna move 14 gallons of milk again to take off the side panel but all seems fine now, just might need so minor tweaking to get to 34-36 degrees inside the box

a low pressure cutoff is controlling the unit set at 32out and 64 in, and a timer to shut unit down for 60 min twice a day leaving the evap fan running, i left the timer settings alone cause manager said defrosting was never a problem, unless systems with different refrigerant require different defrosting settings

i charged unit to clear sight glass, i dont know why i didnt think of that before, i was more worried about the pressure, i got the discharge up to 230psi and suction went up to 60 and with a little tinkering of the txv adjuster the super heat at the coil is down to 9 i got 22 after the txv into the inlet tube of the coil and 31 at the outlet tube just before the txv bulb, but because both lines are attached the rest of the way to the compressor im getting 64 degrees at 60psi at the compressor.

all tubes are now condesating in the evaperator compared to only the first row which i had yesterday, so hopefully it was just undercharged, i gotta back in a couple of hours and check on it.

i was just worried that the pressure at the compressor reading 68 after charging to a clear sight glass it wouldnt cool the box enough, its practically a normal house AC system but the suction eventually dropped to 57,and the discharge stayed at 230

hopefully i can get a check and move on the the next one now

Referdude asked what was controlling the temp, thermostat in box or pressure switch on suction. I feel he asked an excellent question here. No matter how well that unit is set up and running if your controls aren't right you won't hold the proper temp in the box. Just a thought