Walk-in freezer warm

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Hi:
I'm fairly new to the trade. I am employed by a company that owns 40+ McDonalds.
I am having an issue with a Bohn/Heathcraft MAC 8G unit.
The original call was for a warm box. When I assessed the system, I quickly found that the system was off on the HPCO. I reluctantly hoisted a recovery unit on the roof and dropped the head pressure to about 300#. I would have gone lower, but the low side pressure was only at 20# (this is a R404 system).
All went well for about 24 hours. Then I got a call again. This time, the head was at about 350# and the suction was in a slight vacuum. The sight glass thus far has been full and clear.
I attempted to add some gas. The sight glass on my gauges was indicating that gas was transferring, but the head went up very slow and no matter how much gas I tried to put in, the suction pressure always went below zero, usually very slowly.
I checked the EEV, that was opening and closing. Checked the pressures on the other side of filters/driers where possible. There was no difference.
I spoke to our lead technician. he agreed that I checked all that I could and it must be the control circuit board in the box. I changed that. No difference. Previously I had also changed all four sensors in the box as the room temp sensor was giving erratic readings.
Like I said, I'm fairly new to the trade (one year). Anybody have any ideas as to what I might be overlooking?
Thanks Glenn
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Recovery unit to recover refrigerant on a working unit, why???

That's because you masked the real problem. How's the condenser coil?

Post the full set of readings you took (before & after) messing with it.
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wrote:

I know Im going to regret jumping in here but I think we all know me by now...........muhahaha First off, I dont have a clue what box you're working on and Ive never used R-404. That being said....... Why would you suck refrigerant out of a unit? Did you check to see any service record on it prior to when you got there? When you dropped it to 350 on the head and still had a low suction why did you button it up and hope it would fix itself? Then you started adding refrigerant and then found the unit in a vacuum? What made you think the sight glass was full while running in a vacuum? You asked your lead tech and that was the answer he came up with? WOW! You company must be full of dunderheads. Next time you get a chance, pull out your sledgehammer and what that dumbshit over the head with it. I feel for you if you are only a one year tech. You need some training and so does your company. Id be interested in checking out your metering device REAL HARD. Have fun. Bubba
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: wrote: : : >Hi: : > : >I'm fairly new to the trade. I am employed by a company that owns 40+ : >McDonalds.
CY: Yep, they sure do have a lot of refrigeration equipment. Both the walk in coolers, and the portable coolers. Milk shake machine, etc.
: > : >I am having an issue with a Bohn/Heathcraft MAC 8G unit. : > : >The original call was for a warm box. When I assessed the system, I quickly : >found that the system was off on the HPCO.
CY: When a system trips a high pressure cut off, there are several likely causes. Included are..... air in the system, dirty condensor, clogged metering device. Did you check any of the line temperatures? An infared thermometer is a good device to have. I've found it useful to check the liquid line filter drier after the condensor. If it's more than a couple degrees over room temp, you should be thinking dirty condensor, or low air flow through the condensor.
I reluctantly hoisted a recovery : >unit on the roof and dropped the head pressure to about 300#. I would have : >gone lower, but the low side pressure was only at 20# (this is a R404 : >system).
CY: Unless there was some evidence that another tech had over charged the system, I wouldn't be thinking in terms of removing refrigerant.
: > : >All went well for about 24 hours. Then I got a call again. This time, the : >head was at about 350# and the suction was in a slight vacuum. The sight : >glass thus far has been full and clear.
CY: With even less gas, it is still tripping the high head? So, check some temps and see if the system is suffering from dirty condensor. Or, air int he system.
: > : >I attempted to add some gas. The sight glass on my gauges was indicating : >that gas was transferring, but the head went up very slow and no matter how : >much gas I tried to put in, the suction pressure always went below zero, : >usually very slowly.
CY: So, the system is taking the gas out of the low side, and pumping it into the high side. But, the low side never seems to get the gas back. That sounds like a restriction of some kind, the gas isn't going through the evaporator some how. Clogged filter, or bad TXV perhaps.
: > : >I checked the EEV, that was opening and closing. Checked the pressures on : >the other side of filters/driers where possible. There was no difference. : > : >I spoke to our lead technician. he agreed that I checked all that I could
CY: Well, no, you didn't check any of the temperatures of the refrigerant lines. Check the superheat, subcooling, and temp of the liquid line filter drier after the condensor.
: >and it must be the control circuit board in the box. I changed that. No : >difference. Previously I had also changed all four sensors in the box as : >the room temp sensor was giving erratic readings.
CY: I can think of a few more things to check.
: > : >Like I said, I'm fairly new to the trade (one year). Anybody have any ideas : >as to what I might be overlooking?
CY: Yes, I can think of several things. Read what I wrote, following my initials, and that will give you several more things to check. Please let us know how things work out.
: > : >Thanks : >Glenn : > : : I know Im going to regret jumping in here but I think we all know me : by now...........muhahaha : First off, I dont have a clue what box you're working on and Ive never : used R-404. : That being said....... : Why would you suck refrigerant out of a unit? Did you check to see any : service record on it prior to when you got there? : When you dropped it to 350 on the head and still had a low suction why : did you button it up and hope it would fix itself? : Then you started adding refrigerant and then found the unit in a : vacuum? What made you think the sight glass was full while running in : a vacuum? : You asked your lead tech and that was the answer he came up with? : WOW! You company must be full of dunderheads. Next time you get a : chance, pull out your sledgehammer and what that dumbshit over the : head with it. I feel for you if you are only a one year tech. You need : some training and so does your company. : Id be interested in checking out your metering device REAL HARD. : Have fun. : Bubba
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wrote:

You evacuated some refrigerant, still had low suction and thought the system would fix itself? Ok then. Next you ask the lead tech and he told you it was the circuit board? Ok then. What you need to be checking for is a defective metering device, non condensables in the system plugging the metering device, or a restriction in the line set somewhere. But hey, before you do anything I would suggest you and your lead tech go sign up somewhere for some training. Until you do that I suggest you let someone that knows what they are doing mess with it while you watch.
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restriction somewhere , any filter driers in the circuit ?

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Hmm. Filter dryer on the refrigeration system of a walk in freezer. What are the odds of that occurance? I guess that depends who installed it?
--
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Christopher A. Young
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You really don't help yourself sometimes do you?
Cheers
Richard
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I thought the absurdity was clear. That's what happens when I change from serious to absurd, without any warmup.
--
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Christopher A. Young
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LMFAO!!!! you wouldnt know your ass from a hole in the ground ,
STFU idiot!!!!

..Christopher A. YoungLearn more about Jesus http://www.lds.org/portal/site/LDSOrg0 http://www.mormon.org/mormonorg/eng /..v"The Freon Cowboy"
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Nice thing about a public forum, I can exercise my dry sense of humor, here. Regrettably, folks such as yourself are a bit too dense to understand the humor.
Saying a frezer might have a filter dryer is like saying that a production model Lincoln Town Car might have headlights. Understand, now, or shall I explain it a bit more?
--
.
Christopher A. Young
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open mouth, insert foot
give a hoot, don't pollute
take a rock, apply to your brain
then this group will have less drain
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You couldn't explain shit, if you opened your mouth.
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oh, ok, i thought you were trying to be serious , or were you , and just now trying to cover it up ? either way , your not funny ,

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Nice attempt at backtracking there, you fucking jesus freak.
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OMG...
Can you do or say anything that makes yourself look competent?
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On Mon, 24 Sep 2007 15:01:29 -0400, "Stormin Mormon"

Would you like that rock now? Bubba
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Stop posting from the future unless you include stock tips or sports scores, & please include the teams & the points they scored. A Vikings / Packers final of 38 to 3 might seem obvious, but... Besides, the present is troubling enough.
goodluck geothermaljones

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You might be new, but this shit is getting old.
Just shut the fuck up.
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Megatron wrote:

You shut the fuck up.
Why are you replying to a 2-month-old thread?
You think the OP is still reading it?
Moron.
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