New with restaraunt refridgeration, need help please!

[a7harkness]

So, I have been in the HVAC industry going on 6 years and was offered a spot in the Refrigeration end of my company. I really want it but I have to prove myself and I feel at a loss with this one. It is a two door under counter 5 deg. (food needs to be 5 degrees but what does the evap need to hit) prep cooler on a Perkins.

Symptoms and problems:
1. High head, low suction
2. I got it running and cooling but only bringing the fridge down to about 20 deg. after that the txv is closing up and dropping my suction and sending head through the roof.
3. Someone has definitely messed with the low cutout and differential settings as well as the high cutout. I need an educated guess as to where these should lay.

Unit is on R-22. I added a pound to the system and it got better but I don't want to do the wrong thing so I stopped. I didn't have all of my tools because I didn't know it was going to be a "working" test. Tomorrow I will have my pipe clamp thermocouples to check temperature on everything but I wanted to go armed with as much info as I can. This would be a $5 pay bump for me and I need it BAD!!!

[matt.yelland]

Hiya,

1: What was the Suction / Discharge Pressures?
2: Did you add the R22 to bring the case down to temp, as adding 1kg of refrigerant may result in the system being overcharged. Is there an I.D plate with the correct charge on?
3: What controller is on the unit?

If you can get them details, then I will be able to help you more.

Regards

Matt

[matt.yelland]

http://www.tpub.com/content/operatormanuals/TM-9-4120-360-14/TM-9-4120-360-140035.htm

[a7harkness]

Matt,

Thank you very much for the reply! Suction was very low... the needle was at about 10 psig and the head was sky high at around 300 psig. Once the txv closed it would pop up to 400-425 and the needle hit 0 on suction. Controller is unknown as of now but it was a very basic set up. Copeland reciprocating compressor and there was no nameplate charge as it is a split system designed on-site.

[a7harkness]

So I went out there today and did well. I felt confident with the Troubleshooting chart that I was given by Matt. Thanks again Matt! I went through the entire chart and nothing. Looked closer and saw that the evaporating T&P's weren't lining up right and at first thought... Hmm.. Gauge must be off. Looked at condensing.... EXACT SAME. Looked again at TP chart.... R-22. Thought I was making a mistake and checked the unit right next to it and that unit was in the right spot. Pulled out R-22 and stuck in 404a. No more problems. :)

One last question....
Is that oil okay? If not what do I need to do?

[monkey spanners]

Had someone previously put R22 in it? I assume it is in fact an R404A system.
A good indicator is the power head on the txv as it will state the refrigerant it is designed for.

If the compressor has ester oil in then it will be ok.

[matt.yelland]

No problem. You can also test the oil to see if it acidic by getting a TKO oil tester, I do belive that thats the correct one.

Regards

Matt

[powell]

Pulled out R-22 and stuck in 404a. No more problems.

One last question....
Is that oil okay? If not what do I need to do?

a7,

Congrats on your new venture into the commercial refrigeration arena.

You will need to be a bit more detailed when servicing these units versus A/C equipment. You're moving from A/C systems that the majority are running at a 45 degree SST using R22/R410A to a host of new refrigerants, suction temperatures, oils, different wiring/controls etc.

In this thread we actually need more info on the compressor model and the TXV number to help you. You should get use to writing down the component part numbers that you find on a commercial refrigeration system.

You said you changed the refrigerant to R404A.......WHY? Was it a guess that happened to be correct? The TXV part number would answer this question. Many TXV's are also colored coded labeled to determine the refrigerant.

Without the model number of the compressor you cannot determine the oil type which means it's a guess again.

Guessing will not help your credibility and it will give you grief in the future.

Good luck!

[a7harkness]

To all,

A follow up...

It was in fact a guess that was indeed correct. Someone had put R-22 in the unit. I tried not to guess but the equipment was old and I didn't know that I could derive the refrigerant type from the compressor model number :o until now at least. Powell is correct that this is a new animal but on the other hand... it is one I feel comfortable with. I am trying to gain some knowledge from this site and everything I have read so far helps a lot. I'm still trying to understand flood back and some things about defrost circuits and why some things are done certain ways. This deal with the Perkins restaurants is proving to be pretty lucrative and I am doing my best not to screw anything up. I changed my first semi-hermetic compressor last week and a faulty temperature control along with it. Today, I was trying to locate a leak in a walk-in freezer to no avail. I think it's in the ceiling between the roof and the freezer.

What is the best way to find a leak like that? Dye?

[Brian_UK]

You say a leak between the roof and the freezer.

Is there a separate roof above the freezer, is there access to the space?

Unless there is a joint in the fabric where the pipes pass through a leak is unlikely. It is also unlikely to have a joint there.

Leak checking can be a s l o o o w process sometimes, try not to rush it.

[a7harkness]

Brian,

Yes. The freezer is in a Perkins Restaurant. The Structure is wooden frame with steel web joists. The Freezer is positioned inside the shell of the restaurant. A drop ceiling meets the top of the freezer and there is a dead space between the actual roof penetration and the freezer penetration. Someone has already injected dye into the system. I cannot figure out why this leak is so hard to find. Also, it sounds like they may want a new system any way. This one is about 25 years old and is constantly needing repairs. The controls are old and outdated and I think the design of the system is a little too out dated as well. They are becoming concerned with energy management and would like to upgrade. The freezer is 10x15x8. Any suggestions as to what I could recommend to them?