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Fifty Years
Some of you have followed me on this blog, and I have even been lucky enough to have helped some of our most seasoned vets at our profession. I just want to relay some of my observations over the last 50 years of being a service tech.
A few years ago I was asked to repair a cheese case in a Cheese sales operation .The store set on a creek with a water wheel and little did I know that I had to go up in the foundry barn and climb down through a 2ft by 2ft hole on a hand made ladder into a unlighted hole that the soil was constantly falling into the creek. There was a pile of old compressors in the corner, wind blowing up from the creek, Snake skins everywhere, rat and raccoon sign all over the place. The case I was in to repair was a federal open top 12 ft long with 4 storage doors underneath. It had a 3/4 hp. Tecumseh condenser with 3/8 liquid lines and 5/8 suction. line routing was about 4 ft. upward, thru the wall, across the floor and then 90 degrees left and into the cooler. Upwards in the cooler to the other end and to the Expansion valve. Total line length of about 30 ft. R12 system converted to R-401 A. Customer complaint is compressors only last 5 years. Case not cooling. Three condensers in the hole. one for a 2 door reach-in, one 6 ft.for a deli case, And one for the cheese case. Most of the compressors where frigdares and GE. Yea I know, I’m dating myself. Shop was heated with wood daytime and none at night. Anyone care to guess why the compressors would either ice up the case, or not start. Better yet why compressors only survive 4 to 5 years.
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5 Replies
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Your story is written like it’s a riddle. I’m sure everything you said needs factored in to determine the problem.
MY DISCLAIMER: I did a mere twelve years in refrigeration repair – of which I wore that hat maybe 15% of the time (so 85% hot-side stuff). Other than knowing the basics of a refrigeration cycle and its components when I started (trained only while in the military on mobile ACs used in the aviation support community), I was TOLD I would start doing refrigeration as well. So…I learned THAT by trial & error in the field…and by doing some reading. And NOW…for four years now…I don’t do any refrigeration at all. -DISCLAIMER OVER
None of our other frequent few have spoken up. I guess I will. I had to think about your riddle for a day (while at work on a project-oven) before feeling bold enough to speak up. I have a feeling I’m fixin’ to get schooled…
So, in your RIDDLE, you didn’t offer any pressures, temperatures…or what type of control is being used. I think I get why.
Certain things stand out to me in your scenario:
THREE CONDENSERS IN A HOLE – Maybe inadequate air circulation to remove the heat rejected from all three condensers? COMPRESSORS WOULD ICE UP THE CASE – Lends to another question. Did the suction line and compressor ice up as well? LINE ROUTING – 30 ft. long. As long as some walk-ins. Although the increase in elevation you’d stated didn’t justify a need for a oil trap, I still wonder if one might be needed.The compressor size looks good. The line sizing looks good.
Well…I tend to think that the TXV setting was opening too much and flooding the compressor with refrigerant. The liquid refrigerant (being heavier than the oil) settled to the bottom of the crankcase. As it flashed, it carried oil with it into the discharge lines and components. The compressor therefore was starved of adequate oil for lubrication. Along with those circumstances, the line-set design may have been less than adequate to properly return oil back to the compressor.
Additionally, the higher-density mixture of refrigerant w/oil caused higher discharge pressures, so the compressor had to work harder. The rejected heat from two OTHER condensers further aggravated the situation by keeping higher ambient temps than normal at the condenser coil – further escalating the discharge pressures. That could result in excessive amp draw, still MORE heat from the motor windings…and thus overheat the compressor and tripping the compressor’s internal overload. The compressor then wouldn’t start on cue because it hadn’t cooled down yet.
Am I CLOSE?
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Ranco suction pressure control with case temp and solenoid for control.
Total rise from compressor to coil of 6 ft, no loops or sag, lines are uninsulated.
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I’m probably the worst guy in the world to answer this question.
If I was there in person to see it, hear it, feel it, I might be able to take a guess.
But when I’m reading a story from print, it’s difficult for me to comprehend and understand.
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No concerns about the line rise then.
I’m a little confused on the rest, though. But…that’s what you’d intended.
So I know that a low pressure control ( as opposed to a thermostat) is generally only used in self-contained systems (where I’m at) In my geographical region, we have four seasons, low pressure controls aren’t used for remote systems. That may not be the case where you’re at.
Then again – a condenser in a hole might not be exposed to the ill effects of frigid temperatures on a refrigeration system.
The lack of line insulation is a concern when thinking in the OTHER direction regarding the TXV setting. The superheat at the compressor could THEN be too high (after 30′ of line) and cause the compressor to be adequately cooled.
But then…that negates my first theory that I’d stated above. Instead of overfeeding, the TXV would be underfeeding. My hangup being that the case freezes up. It wouldn’t freeze-up in an underfeed condition. Maybe the TXV would…but not the entire evaporator!
GOOD GOLLY! I’m with alnelson. I’d need to see it, hear it and feel it – but that ain’t happenin’.
SO…you didn’t answer me. Was I CLOSE the first time?
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You both are correct on having to see it. With the open hole below the units over the creek and the wind coming in, (Adirondacks of NY) the condenser hole vairies from 30 below to 90 degrees.. But the kicker is that the shop being wood heated also varied from 75 daytime to below freezing at night. With the uninsulated lines, there is no way suction control would work with a refrigerant that has the glide of R401B. Also the compressor lifespan was due to line routing. Refrigerant will always migrate to the coolest part of the system during off cycles. At night there was no need for cooling as the shop got cold too. At startup in the morning there would be a liquid slug to a cold compressor. We all know what that does. I cut one of the failed compressors apart out of curiosity and found the cylinder head blown apart.
Solution, Covered the creek over and shoveled dirt over it. Added a heat lamp to the hole. Added suction accumulators and insulated the suction lines. This was in 1994 and 1995, both are still running today. This was before R409 as a interim replacement. The glide is mush better on 409. Installed a electric panel so I could depower the units with-out having to climb out on a ladder and go upstairs to a panel. Stayed with suction control, Todays electronic gauges are great to adjust them. Back then I always kept a accurate low side gauge just for calibration of controls. Tested the gauge monthly. Spring requires uncovering the hole with cool weather the covering. .
FYI there was another condenser in the hole for a deli case 15 ft toward the back that the lines only had to go 3 ft. though a wall to a deli case. It’s compressor was quite old and running fine. Short run, near same height, light always on in case. Different room in building with residual heat. Around 2000, a car went into the waterwheel and sluiceway. Never was replaced.
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