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Mechanical Contractor
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Discussion Starter · #1 ·
Ok, well since Im new to this forum let me give you a little background on myself. Im 26 years old and have been doing HVACR since I was 16. I have just recently passed my mechanical contractors test and business test and have now sent my application to the state. Over the pass 10 years I have invested my own money to educate myself to be as knowledgable as possible. I feel its very important to learn based on theory rather than repitition. With all that being said, as we all know customer service and relationships (as a service tech) is very important when your wanting work out of a customer. So here it is!

About three weeks ago I was working at one of my best customers who will be switching to my company when I get my license. They had just bought a plant that had a blast freezer the was R-502. The blast had a leak so I was called out to find it. After a few short minutes I had discovered that the HPR was leaking. So after running over the rest of the components I explained to the customer where it was. Now this customer is a very good friend and from time to time will fix his own problems with my direction. I do it to save them a little money. I also explained to them that we could do a retrofit to R-404A and they decided to go for it. So at this time it was late so I explained that I would be taking my mechanical contractors test in the morning and to have it reclaimed and in a vacuum by the time I got there the next evening to add the refrigerant. So when I got there I threw my micron guage on it and it was below 500 so I was satisfied that there was no more leaks and the system was dry. I filled the reciever with as much refrigerant as it would take and opened the feed valve. The blast drop almost instantly. To make a long story short, the blast is having problems now. After talking to one of the guys and mentioning how unlikely a leak was after seeing it below 500 microns he says that all they pulled down was the compressor and reciever. Shocked I replied " No, we did a retrofit and all the refrigerant was suppose to be out of the system" which his story changed after that. Now its in the back of my mind that a mixed refrigerant is a possible problem. After reviewing that night in my head, after I charged the reciever me and the customer opened the valves so I dont know if he had the system completely pumped out. I realize that I should have done the complete job myself so please keep the flaming to a minimum, but I did check suction pressure and the headpressure and subcooling and all seems fine. Any suggestion on how to more accurely check for mixed refrigerants. I honestly never have ran across that problem.
 

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I think you need to reclaim the refrigerant and start over.
Did you weigh the refrigerant you installed?
What pressures (suction and discharge) are you running at with the new refrigerant?
Is this a split system?
 

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Mechanical Contractor
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29 Posts
Discussion Starter · #4 ·
I think you need to reclaim the refrigerant and start over.
Did you weigh the refrigerant you installed?
What pressures (suction and discharge) are you running at with the new refrigerant?
Is this a split system?
Yes its a split system, the problem is its a blast freezer thats 34 tons with 2 evaporators. The system holds about 130 lb of R-404A which as you would assume is rather expensive. The problem I have is how to address the customer and explain that he is (maybe) the cause of the failure. I of course would like to know 100% that Im correct but as explained in the original post he said he only pulled a vacuum on the compressor and HPR, but when requestioned his story changed. Suction and head pressure was normal everytime I checked. Also, in Industrial Refrigeration its a very rare instance to see a tech weigh in a refrigerant. Its not critically charged.
 

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This is a tuff one, the owner is a friend and you thought he knew what he was doing.
I think if I was in your situation i would explain to him what you suspect might have happened and take it from there.
Your gut feeling is the entire system was not evacuated. Did they have the compressor valves closed when they evacuated?
If they were open both sides of the system would have been evacuated. If they were closed then you have a real problem. You would have noticed that (The valves closed) as soon as you put your gauges on and at that time considered the entire system was not evacuated.

It is obvious if the refrigerant is mixed you will have to remove all and re-charge.
You said the pressures when operating looked good and the temp was OK then a problem developed. What is the problem that developed.

Are there sight glasses on the system?

What are your pressures when the problem developes.
Are you sure there are no other refrigerant leaks?
I assume you checked the evaporator and condenser coils etc..
 

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I didn’t see a lot of details as to what was done. Did the retrofit include a POE oil change and filter/dryer replacement?
 

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Mechanical Contractor
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Discussion Starter · #7 ·
I didn’t see a lot of details as to what was done. Did the retrofit include a POE oil change and filter/dryer replacement?
Yes the filter dryer was changed along with the POE. The unit does have a sight glass on it and from time to time has bubbles in it but for the most part stays clear. One of the most important details I left out is that this building they bought is brand new so I have no idea what temperatures in ran before. The unit itself is old and beyond a shadow of a doubt, even if there was something not obvious, I would have found it by now. However, I did not consider doing a heatload calculation yet to see if temperatures are possible. The unit did run -9 with no product or employees entering and exiting. Now its running -3 to 0 F. Im having troubles with the whole plant not reaching temperatures expected by my customer but after looking at it today Im wondering if they even have the tonnage to achieve them.
 

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Is what you working on actually a blast freezer?
We service a blast freezer at a meat packing plant and it runs at minus -40F the blast freezer is located in the middle of a very large freezer that is kept at -15F.
 

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Mechanical Contractor
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Discussion Starter · #11 ·
Is what you working on actually a blast freezer?
We service a blast freezer at a meat packing plant and it runs at minus -40F the blast freezer is located in the middle of a very large freezer that is kept at -15F.
Yes its actually a blast but the problem is what the blast was used for, I dont know. The purpose the new company wants it to serve is to flash freeze meat, but that may not have been its purpose in the past. I have blast that run 20F to cool down ham quickly striaght out of an oven. Im really wondering if I have a lack of tonnage. Now that Ive been thinking about it the temperature problems have been showing up the more production has increased. See as explained before this is a customer of mine that has recently purchased a new facility. The history of it is unknown and the employees that transfered over to the new company have been of no help. I think I will end up doing a load calculation to make sure they have the tonnage to produce the temperatures they want.
 

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-9 degrees F seems too high for a blast freezer. I think you should do a load calc.
Is the compressor old?
Are there unloaders on it?
Is there a suction pressure regulator?
Is it air cooled and is the condenser clean and running correct?
What suction pressure and head pressure do you have when the unit is pulling temperature?
Was the compressor ever replaced?
 

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Mechanical Contractor
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Discussion Starter · #13 · (Edited)
-9 degrees F seems too high for a blast freezer. I think you should do a load calc.
Is the compressor old?
Are there unloaders on it?
Is there a suction pressure regulator?
Is it air cooled and is the condenser clean and running correct?
What suction pressure and head pressure do you have when the unit is pulling temperature?
Was the compressor ever replaced?
-9 would be beautiful to flash freeze meat. It just didnt stay there. A blast freezer can be any temperature you want it to be. Everything else is fine. No unloaders and no regulators. Not sure what you mean by "air cooled" unless your talking about cooling fan for the oil cooler. I have carefully looked over every aspect and my conclusion is either mixed refrigerant or not enough tonnage.
 

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Energy mover
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side note* if you intend on running a business a clear line needs to be drawn between friends and customers. the difference may a liability you'd assume by allowing them to do your job and you then having to own it. an old boss once taught me that if a break needs to be granted on costs, the old B to B barter systems works well. you do a complete job and charge accordingly. but instead of cash, an equal value of "their" probuct can be received as payments. it's win win.
 

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Sidenote #2 I have had customers try to help me on many occasions

I tell them I can't afford to pay them and myself. Good lesson learned here do everything yourself that's why they called you.
 

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An old boss once taught me that if a break needs to be granted on costs, the old B to B barter systems works well. you do a complete job and charge accordingly.
 

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I think you need to reclaim the refrigerant and start over.
Did you weigh the refrigerant you installed?
What pressures (suction and discharge) are you running at with the new refrigerant?
Is this a split system?
If you doubt the prior work then reassure yourself and start over!
 
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