WAlK-IN COOLER, R409

[olegmechanic]

Hello. If anybody could help me please.

I ‘m working on a walk-in cooler. 3hp Copelametic KWGI-0075-TAC compressor, r 409, evaporator REFPLUS LSA 0400-1 (4000BTU), water cooling condenser. Unit keeps temperature 36F.
Suction pressure 22 Psig, temperature of suction pipe beside txv bulb is 32F. When pressure drops to 20 psig, compressor stops by cut out pressure control.
Then pressure in suction line rises quick (20sec) up to 36 psig and compressor starts, works 3 seconds, bringing pressure down to 20psig and stops. In 20 -30 seconds the same. Compressor runs for 3 seconds and stops.

After 2-4 “short cycles” pressure in suction line raises slowly, compressor starts and works normally, bringing temperature in walk-in cooler down and after 4-6 minutes of work shuts off by pressure cut out control.
What is wrong with the unit?
Thank You

[crackertech]

You might want to call a pro to look at it.Or put some info in your profile as to
what you do.This is not a DYI site.

[olegmechanic]

Is this the best professional answer i can get on this site? :confused:

[Biblepoet]

Is this the best professional answer i can get on this site? :confused:
Not to be a smart@rse, but Yup!!

We pros are picky about the advice we give. When we know about the person the more likely we are to help. So give us more info about yourself and we will be more than happy to give you the advice you need.;)

[markettech]

I see you have updated your profile...;)

Now, I don't have a PT chart at my disposal at the moment, but it seems to me the cut-in/out pressures are too close together.

My guess is that the unit is short cycling as it pumps down (assuming it is controlled by thermostat and solenoid valve).

- How is the temperature controlled in the box?.......t-stat/solenoid or pressure?

[olegmechanic]

Thank You.
Unit operates by pressure in suction line only. No thermostat or any solenoids in the box.

[Biblepoet]

I think I would install a thermostat and solenoid. Use the pressure control for a safety if the unit runs low or out of refrigerant. As it stands now you might have weak or weakened suction valves.

[jpsmith1cm]

I like t-stat and solenoid control, as well.

Another thing to consider is a minimum on timer.

When is this happening?

If it is after a longer off cycle like a defrost, you have a system at or near equalization. With very little pressure on the high side to push liquid through the TXV, you have no real load.

The compressor cycles on and off to build up a bit of pressure difference. Once it gets that differential, the TXV starts to feed and the suction will stay up.

If you install a minimum on timer to bypass the low pressure control for a minute or so, you will eliminate your short cycling problem.

[olegmechanic]

Thank you, guys. You are awesome.

Special thanks for Markettech: man, I took your advice and, before I did anything else, I raised cut in pressure setting from 36 to 39 psig and cut out from 19 to 21 psig (temperature in box went too low).

I did it at 8 am and was checking around 4pm – compressor is not short cycling and temperature in the box is fluctuating between 34 and 38 F.

Some other problems with this unit – oil dirty brown and probably some air in system. I’m going to clean it tomorrow.
Thanks you guys, again.:)

[crackertech]

Thank you, guys. You are awesome.

Special thanks for Markettech: man, I took your advice and, before I did anything else, I raised cut in pressure setting from 36 to 39 psig and cut out from 19 to 21 psig (temperature in box went too low).

I did it at 8 am and was checking around 4pm – compressor is not short cycling and temperature in the box is fluctuating between 34 and 38 F.

Some other problems with this unit – oil dirty brown and probably some air in system. I’m going to clean it tomorrow.
Thanks you guys, again.:)

I hope you under stand I was not being a smart a$$ yesterday.See what a little
info in your profile will get ya.:)

[markettech]

I hope you under stand I was not being a smart a$$ yesterday.:)


Sure, sure......those of us in the know - know better...:cool:.......................:D

[beachtech]

pro refridgeration is in need!!!

[markettech]

pro refridgeration is in need!!!

Maybe let's come to a consensus as to the correct spelling first:rolleyes:


:D:D




Beachtech, I'm not bustin' your balls.....honest!! I'm just having a little fun is all;)

[Marc O'Brien]

Thank you, guys. You are awesome.

Special thanks for Markettech: man, I took your advice and, before I did anything else, I raised cut in pressure setting from 36 to 39 psig and cut out from 19 to 21 psig (temperature in box went too low).

I did it at 8 am and was checking around 4pm – compressor is not short cycling and temperature in the box is fluctuating between 34 and 38 F.

Some other problems with this unit – oil dirty brown and probably some air in system. I’m going to clean it tomorrow.
Thanks you guys, again.:)

To fill you in a bit more, you should not have to change the cut-in setting. Unless you change the cut-out (differential) so much that it effects the cut-in. But the cut-in's first purpose here is to defrost the coil and secondly to not let the system temperature rise too far. This pressure is environmentally and seasonally constant. The better the product thermal mass, the enclosing space insulation and the proportional spare capacity of the system the easier this is.

The cut-out, on the other hand, will vary with ambient temperatures around the condensing unit. So this type of control is best used when the system is located in constant temperature climates and little maintenance is required. In varying climates it is a good control philosophy that also ensures that the customer will be forced to call you at least twice a year for maintenance when you will also change the cut-out setting for each new season, winter or summer, lower in winter and higher is summer.

[markettech]

To fill you in a bit more, you should not have to change the cut-in setting. Unless you change the cut-out (differential) so much that it effects the cut-in. But the cut-in's first purpose here is to defrost the coil and secondly to not let the system temperature rise too far. This pressure is environmentally and seasonally constant. The better the product thermal mass, the enclosing space insulation and the proportional spare capacity of the system the easier this is.

The cut-out, on the other hand, will vary with ambient temperatures around the condensing unit. So this type of control is best used when the system is located in constant temperature climates and little maintenance is required. In varying climates it is a good control philosophy that also ensures that the customer will be forced to call you at least twice a year for maintenance when you will also change the cut-out setting for each new season, winter or summer, lower in winter and higher is summer.


Olegmechanic, in complicated engineereze......what Marc said:rolleyes: - in refer mechanic terms.........slap a effin' t-stat/solenoid (and maybe a defrost timer, depending) on the system and walk away.;)

[raveon]

What? A thermostat - Where is the restaurant owner going to put the knife now to adjust the box temp lower? Come on, I love it when he explains how he hardly did anything and he can't understand why the compressor is shot. Even though I am the third contractor to tell him his compressor is shot - we are all a bunch of criminals according to him. Thermostats are perfect - give them what they need to protect them from themselves. I am just a little jaded after today-sorry.

[GsxrMike]

X2 on the solenoid/thermostat. I have a customer with a small walk-in cooler and I was there at each change of season to adjust controls until I convinced her to let me install a thermostat.

[meoberry]

What? A thermostat - Where is the restaurant owner going to put the knife now to adjust the box temp lower? Come on, I love it when he explains how he hardly did anything and he can't understand why the compressor is shot. Even though I am the third contractor to tell him his compressor is shot - we are all a bunch of criminals according to him. Thermostats are perfect - give them what they need to protect them from themselves. I am just a little jaded after today-sorry.

Simple solution is to leave old t-stat on outside of coil and install new one on inside of the coil remote bulb to back of coil set it and forget it. Manager can play with old one all he wants.:D

[GsxrMike]

Simple solution is to leave old t-stat on outside of coil and install new one on inside of the coil remote bulb to back of coil set it and forget it. Manager can play with old one all he wants.:D

I love that trick! I had a few thermostats that we mounted inside the evaporators that kept turning themselves up. I figured it had to do with the tiny amount of vibrations coming from the fans.:confused:

[meoberry]

I love that trick! I had a few thermostats that we mounted inside the evaporators that kept turning themselves up. I figured it had to do with the tiny amount of vibrations coming from the fans.:confused:

Stick tacky tape or cork tape under the cover. Also did it in an office building full of 40 to 50 year old women just one man the office manager. They kept the unit froze up at least 2 to 3 times a month I would have to thaw out the coil. Manager complained that the women tried to freeze him to death daily.
I told him I could solve the problem. He told me to do whatever I had to do.

Disconnected t-stat installed new one with autochangeover in the return duct about four foot in. Could not see it from return. But could see fine from inspection panel. Left old one on wall even had power for the lights to work on the t-stat. (just R and C).:D:D:D

Was about 3 months later. Changed filters went in to get ticket signed. Manager said, "close the door". I was like uhoh what did I do now.
He cracked a big smile and said, Eveytime he turns around someone is tampering with t-stat on the wall all I do is smile. Did I mention that I turned the thermometer on the t-stat down about 10*. Has not froze up since.:D:D