[envisioning]

Hello everyone. I want to thank all of you for the wonderful information in this forum. This is my first post so I will give you a background. Please skip to the dotted line to reach the paragraph with technical questions, as this is more of a BIO. My name is TJ, I'm 28 years old, and I'm currently an electrical engineer with a bunch of projects. My father, Ted, was a refrigeration technician / to HVAC tech / to estimator / to Foreman. In the last 5 years he kind of let things go and went out on disability. I recently found an upright freezer for ten bucks, just to bring it home to find it was completely discharged of Freon. Instead of throwing it out, I got my dad out of his hole and brought him out with his old tools. We had a Freon "sniffer" and found the leak and cut out a 12" section of 1/4" tubing and replaced it. We used Sta-Brite since that's what pop had in his bag of tools. We filled the unit with Nitrogen and everything held great. We also sweated on a low side and high side connection (Schrader valves).

We triple evacuated the unit with his two-stage vacuum and put Nitrogen in each time to wick out the moisture (5 minutes evacuation, 55 minutes Nitrogen). After the last time, we evacuated for about thirty minutes to really get things ready for re-charging. The unit information is as follows:

1970's to 1980's AMANA Store-Mor Freezer Cap-Tube
Model No. U18F
Serial No. S234 02456
11.8 oz R-12 Charge
Test Pressure 235 H.S. 140 L.S.
1/4hp 4.7 amps 115V 60 Cycle
About 17 ft^3 of space inside
Evaporator is in direct contact with steel or aluminum shelving

The thermostat was also shot. I purchased one of those temperature controllers (10A rated) for cooling/heating. It included a thermistor which I installed where the old dial was located on the inside of the freezer (middle shelf on the wall). Thing is pretty neat. Totally programmable. Link to the controller is below:
http://www.amazon.com/gp/product/B0..._rd_t=201&pf_rd_i=B0002EAL58&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=0BDS098MB5MNNFNZCE78



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The unit called for 11.8oz of R-12 Freon. I had two cans of R-12 (12oz and 14oz) so I used the 12oz can to prevent overcharging. We filled her up and turned the old beast on. At first, my current reading on the dedicated circuit was about 4.5 amps. Within 10 minutes the ceiling was frosting up so I shut the door and let her run. The low side was about 5psi and high side was about 175psi.

After a few hours, the evaporator was completely frosted all the way down to the bottom, including the accumulator. The low side was reading very close to 0psi and the high side was reading about 145-150psi. We felt that the unit was running great so we shut her down and disconnected the gauges. The low side had next to no loss. We waited 10 minutes before removing the high side and lost a second or so burst of Freon.

I received the temperature controller in the mail a few days later (listed above) and installed it. I immediately filled it with a few 10lbs bags of ice and some containers of water. Within a few hours or so, the water was freezing over and all seemed well. This AMANA freezer has a condenser that runs throughout the inside of the steel shell of the freezer (no condenser can be seen). The freezer was pretty toasty to the touch where the oil cooler circuit and condenser ran... a very good sign I thought. Once the temperatures were approaching 10F to 5F, the unit seemed to stall. I let it run through the night at higher set points (15F to 20F) to stabilize in temperature.

After a day, I changed the temperature settings to -5F to +5F, a 10 degree swing. The unit would run for 91 minutes, and be off for 90 minutes. I put more food into the freezer to help maintain the colder temperatures.

After a day or so, the unit seemed to struggle more. It would run for 90 minutes to hit -5F, and be off for 45 minutes to hit +5. It appears that the more load in the freezer, the more it struggled to reach these lower temperatures.

When the compressor first turns on, I get frost on the suction line back to the compressor for about thirty seconds. It then goes away and after 10 minutes it gets a little warmer to the touch.

My father is coming back out this weekend and we are planning to open another can of R12 to try and top off the unit with an ounce or so of Freon. I feel we may have lost a bit of Freon when I took off the high side gauge. I read that you can lose up to 2oz of refrigerant in a 4 foot length of tubing.

The current readings are 3.7 amps.
The suction line frosts for about 30 seconds on startup, then eventually warms back up after a few minutes.
The unit seems to struggle to maintain 0F.
The evaporator is completely frozen over all the way to the bottom to the accumulator, which also is frozen.

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If we are low on charge, shouldn't some of the evaporator not have frost on it?
What are the typical pressures for a high and low side of an R12 cap-tube system freezer?
Is it possible that I am trying to reach too low of a temperature? I felt that this r12 unit would have no issues reaching 0F.
Perhaps the compressor lost some efficiency over the years?

We will be putting gauges on this weekend and get some temperature readings to find Superheat, etc. I am just trying to find what an optimum setting should be. Unfortunately, I can not find any information on R12 cap tube pressures anywhere. We have a bunch of SAM binders, service books and technical books (TRANE, COPELAND) but many of these are for commercial units.

Any help would be greatly appreciated. God bless you.



FYI:
The following is written on the compressor
E:E12-69 541295
8749-14-2M AT43

 

[VTP99]

I feel we may have lost a bit of Freon when I took off the high side gauge.If we are low on charge. What are the typical pressures for a high and low side of an R12 cap-tube system freezer?

Pick up a low loss hose fitting at a supply house. Then next time you will be able to remove the liquid from your high side (charging) hose.
If it's a 10* TD system then your evaporator coil needs to be 10* lower then your desired temperature. A -20* coil should read 0.6 psig. Your ambient temperature is going to dictate your high side pressure. I would expect to see about 25* over your ambient. So say it's 70* ambient plus 25 is 95* or 108 psig. Per a P/T chart using R12.

 

[rayr]

A very long time ago I used to work on domestic refrigeration. If it were mine, I would add refrigerant until there was frost on the suction line 6" from the compressor when it reached the set point. This can be time consuming but is a tried and true method by old timers. Commercial has been my cup of tea for a few decades. Good luck. You did not mention if you changed the filter drier.

 

[envisioning]

First and foremost, thanks for the quick replies: VTP99 and Rayr

If it were mine, I would add refrigerant until there was frost on the suction line 6" from the compressor when it reached the set point.

This is exactly what pops and I were planning to do this weekend. When you say frost on the suction line, you mean consistently correct? As in frost throughout the running of the compressor. Also, the "set point" you are talking about, you mean when my freezer hits -5F, the frost should still be present?

You did not mention if you changed the filter drier.

Unfortunately, I was relying on my father for all of the tips, and he told me we didn't need to. After much reading of refrigeration books, it appears that I should have done so. Now that I am charged, I don't think we should do it.

Pick up a low loss hose fitting at a supply house. Then next time you will be able to remove the liquid from your high side (charging) hose.

I was just reading about these. I am heading there tomorrow to pick some of these up. Thanks!

 

[IRBH]

Envision... you'll have to donate that freezer to the Smithsonion.

45 years on that old AT43 and still going!

With a perforated line & zero freon, that freezer would have been inhaling & exhaling moist air with every cloud passing the sun.

You must change the filter!

Forget about adding more R12.

What's with the 5 min evacuations?

 

[envisioning]

You must change the filter! Forget about adding more R12.

In hindsight, I realize this. My father just told me we were fine. After reading his old tech manuals, I found that this was heavily suggested / required. I will look into finding a replacement. I'm guessing this will help remove additional moisture/particles in the system and improve performance?

What's with the 5 min evacuations?

Again, I should have done some reading. I just followed my father's instructions. He seemed to be on a roll so I let him at it (it was nice to see him in action). His background changed early on from Refrigeration to HVAC units. He seemed absolutely positive that 5min cycles was the process (with 55 minute of Nitrogen). I read that an hour or more is definitely the way to go when evacuating. Do you recommend anything in particular for these freezers? Since it is R12, I was just going to use Nitrogen in between a much longer evac.

Since I have absolutely NO documentation on this thing, are drier/strainers just common by size? I was able to find a replacement on a Sears website, but they wanted $50. I thought that was high. Part number B2150504. Found one on amazon for 11 bucks. Is it definitely worth taking this apart to replace drier too? I have one last can of R12, so it is possible.

 

[IRBH]

Get a spun-copper filter/drier c/w access valve.
Guessing about 12 bux, may be almost give away in good old US of A!

Evacuate from both valves.

 

[Snapperhead]

The filter absorbs "some" moisture and holds it captive. Its ability to continue absorbing it a finite number , its not infinite , which is why we replace them like spark plugs

Moisture in the system could turn into acid after time , and eat away that unit from inside out

What caused the pinhole in the first place ? Did it rub against the wall ?

I ask because it may have been acid

Your local supplier has cheap test kits for acid testing .... real easy

 

[envisioning]

Get a spun-copper filter/drier c/w access valve.
Guessing about 12 bux, may be almost give away in good old US of A!

Thanks. I found the exact replacement on Amazon cheap, but if we want it this weekend, I will look for these at the local supply shops.

Evacuate from both valves.

We did this, as I did read about how the cap tube restricts the evacuation process heavily. Thanks for the tip.

What caused the pinhole in the first place ? Did it rub against the wall ? I ask because it may have been acid

The pinhole was located in the tube as it passed through the bottom of the unit to enter the compressor compartment. They loaded the area with caulk but did not use a grommet or anything to protect the tube from rubbing (it was a tight fit). The tubing appeared to have a white paint on it and it look like it rusted away (I know copper doesn't rust but the paint was like a metallic type)

Your local supplier has cheap test kits for acid testing .... real easy

Thank you for the tip. I will pick one of these up. I read about moisture causing acid, I just didn't realize they had an easy test kit.

I have no problem changing out the drier and doing an acid test, but I would still like to figure out why I am having the conditions that I have. I will have all the gauges and equipment this weekend to be able to get accurate pressure and temperature readings of the suction line, superheat, etc.

If I am going to evacuate and fix some of this stuff, I want to make sure I do all the proper prep work and testing. I have been reading manuals and books for the last two weeks and I can't seem to find a situation quite like mine.

Would the old drier cause a drop in efficiency in heat removal?
Is it normal to have a drop in amperage once the unit is on? It seems to start at full amps (4.5ish) and then quickly drops down to about 3.9amps.

I can't seem to find anything on cap-tube amperage readings. Should the compressor pull close to full amperage when the door is opened or does that number only apply when the thing is being started at room temperature.

Thank you all for the help. God Bless you.

 

[IRBH]

Your readings of 0/150 are ok.

As far as holding at 4.5A, that would be at full load & highest allowable ambient & min voltage.

Don't set it to -5f with 10 diff.

It's taking 3 full hours for one cycle!
Try -2 to +2.
I would not be surprised that you're slightly overcharged already.

Don't chge with "frost line 6" from compressor". It has an accumulator, different story. The only way to charge is weigh-in, period.

Ignore the inital start frost back... all ref is in the cold evaporator.

This is domestic refrigeration...ditch the N, the acid test (what would you do with a positive- install a 162HH?

 

[envisioning]

Try -2 to +2.

I was thinking that the diff was a little high. Thank you for the recommendation.

I would not be surprised that you're slightly overcharged already.

Do you think that is possible if we used a 12oz can and the specs called for 11.8oz, and had 4' hoses on high/low side? We lost barely any refrigerant on the low side, but lost a burst for a few seconds on the high side removal. I thought you could lose quite a bit on the high side with regular hose/gauge setup (no low-loss valves)

If the refrigerant was only slightly undercharged, would the evaporator still be fully frosted along with the accumulator? We will get gauges on this thing on Saturday morning, so I will report back with the data.

Ignore the inital start frost back... all ref is in the cold evaporator.

Thanks, I figured this could be the case.

This is domestic refrigeration...ditch the N, the acid test (what would you do with a positive- install a 162HH?

This has only became a project to see how much I can get out of this thing. It's been interesting thus far. I would not get a 162HH filter and fix it at that point.

 

[captaincompressor]

A very long time ago I used to work on domestic refrigeration. If it were mine, I would add refrigerant until there was frost on the suction line 6" from the compressor when it reached the set point. This can be time consuming but is a tried and true method by old timers. Commercial has been my cup of tea for a few decades. Good luck. You did not mention if you changed the filter drier.

i did one here at home. i changed mine over to 134a with a new embraco 1/4 hp compressor.
i took the superheat at the compressor suction after the box temp went -5F. i charged to 10 degrees superheat. mine cools and freezes great.

 

[envisioning]

i took the superheat at the compressor suction after the box temp went -5F. i charged to 10 degrees superheat. mine cools and freezes great.

Did yours have an accumulator as well? If you read further on, you will understand why I am asking.


UPDATE:
So, the oil cooling loop had a leak at one of the couplings we put in. The old copper tubing wasn't playing very nice with the Sta-Brite. We got it fixed, put in a new Drier/Filter (SUD111) and hooked up the vacuum pump for about 5 hours. I wasn't going to let any moisture sneak by this time.

I had one last 14 ounce can of R12. The new drier was slightly longer and larger than the stock one, so we put most of the can in. We did not have a way to measure our charge so we are left to do superheat / subcooling / pressure checks.

This thing has no problem going down 2"mg on the suction (as the freezer gets down to the -5*F mark) and the head pressure is around 130 psi. The strainer is pretty warm still but the suction line is sweating since it is pretty cold (around 50*F the last time I checked).

Is it normal for these things to sweat like that? My R134 fridge has a relatively warm suction line.

So, since this freezer has the condenser located inside the shell of the freezer, I have no access to the suction line as it exits the accumulator/evaporator. However, the cap tube and suction line are soldered together as they just enter the shell and go inside. About 18 inches away, I have an access hole I made to leak check and I can see the suction line/cap tube are frosted up pretty good.

Is this a sign that I am overcharged? Since I have an accumulator, should I not have any frost inside where the cap tube and suction tube are connected? Or is this a normal situation, where the cap tube and suction line are frosted, but not within 18 inches (or further) from the compressor?

If I am to read superheat at the suction line (6inches from the compressor), what's a good number?

 

[captaincompressor]

Did yours have an accumulator as well? If you read further on, you will understand why I am asking.


UPDATE:
So, the oil cooling loop had a leak at one of the couplings we put in. The old copper tubing wasn't playing very nice with the Sta-Brite. We got it fixed, put in a new Drier/Filter (SUD111) and hooked up the vacuum pump for about 5 hours. I wasn't going to let any moisture sneak by this time.

I had one last 14 ounce can of R12. The new drier was slightly longer and larger than the stock one, so we put most of the can in. We did not have a way to measure our charge so we are left to do superheat / subcooling / pressure checks.

This thing has no problem going down 2"mg on the suction (as the freezer gets down to the -5*F mark) and the head pressure is around 130 psi. The strainer is pretty warm still but the suction line is sweating since it is pretty cold (around 50*F the last time I checked).

Is it normal for these things to sweat like that? My R134 fridge has a relatively warm suction line.

So, since this freezer has the condenser located inside the shell of the freezer, I have no access to the suction line as it exits the accumulator/evaporator. However, the cap tube and suction line are soldered together as they just enter the shell and go inside. About 18 inches away, I have an access hole I made to leak check and I can see the suction line/cap tube are frosted up pretty good.

Is this a sign that I am overcharged? Since I have an accumulator, should I not have any frost inside where the cap tube and suction tube are connected? Or is this a normal situation, where the cap tube and suction line are frosted, but not within 18 inches (or further) from the compressor?

If I am to read superheat at the suction line (6inches from the compressor), what's a good number?

Took superheat at the inlet of the compressor. I do believe they run the liquid cap tube together to get extra subcool.
Mine freezes all the way to the compressor but is not flooding.
Mine does not have an accumulator but it would be a good idea.

 

[ICanHas]

The thermostat was also shot. I purchased one of those temperature controllers (10A rated) for cooling/heating. It included a thermistor which I installed where the old dial was located on the inside of the freezer (middle shelf on the wall). Thing is pretty neat. Totally programmable.

The one that controls the AC in your house or the one used in a walk-in is a direct control thermostat. The thing that cycles the compressor in a freezer like yours is called a cold control. It's important to distinguish one from a thermostat since the behavior is quite different. It uses an indirect method to control box temperature as a part of an engineered product.


That controller doesn't even look UL listed, quacks like CHINA MADE and smells like China QC.
I would try ditching that China made microcontroller based embedded wreckthems driven BS and use a real electromechanical freezer cold control installed in the same way the original one was installed. If the original was in zigzag or coiled, the replacement needs to be setup like it too.

The location, orientation and shape of the sensory tube affects the integration behavior and affects the box temperature especially in passive convection evaporator type. Cold control is not a single point sensing. It senses across the entire length.

After a day, I changed the temperature settings to -5F to +5F, a 10 degree swing. The unit would run for 91 minutes, and be off for 90 minutes. I put more food into the freezer to help maintain the colder temperatures.

After a day or so, the unit seemed to struggle more. It would run for 90 minutes to hit -5F, and be off for 45 minutes to hit +5. It appears that the more load in the freezer, the more it struggled to reach these lower temperatures.

It almost seems like the location or shape of the sensor is wrong. A recovery time that long suggests the sensor is thermally too heavy, or that junk controller is messing everything through its Chinese Poorly Implemented Disarray algorithm that's not appropriate for a small freezer.

How are you measuring the temperature? You'd want to freeze a probe into a place in meat or inside a bag of corn to get a better idea of average (integrated) box temperature, but the sensing tube should be very rapidly responding. Thermistor is generally quite slow to respond and can cause excess integration to occur and cause swinging in temperature of stuff inside the freezer.

 

[envisioning]

I would try ditching that China made microcontroller based embedded wreckthems driven BS and use a real electromechanical freezer cold control installed in the same way the original one was installed. If the original was in zigzag or coiled, the replacement needs to be setup like it too.

The original cold control was routed inside the aluminum walls of the freezer. I can not and will not be able to find the original routing or the final location of the bulb (whether it was on or near the evaporator).

The location, orientation and shape of the sensory tube affects the integration behavior and affects the box temperature especially in passive convection evaporator type. Cold control is not a single point sensing. It senses across the entire length.

I wish I could have seen the original routing of the sensory tube so I could rig this thing up properly.

How are you measuring the temperature? You'd want to freeze a probe into a place in meat or inside a bag of corn to get a better idea of average (integrated) box temperature, but the sensing tube should be very rapidly responding.

Fortunately, this thermistor has a rapid response. When the door is opened, the temperature on the display responds almost immediately and updates every two to three seconds accordingly. I like your idea of freezing it into a bag of corn or something similar to get a better average temperature. The thermistor is sticking past the wall about three inches. I was hoping this location would help it get air temperature, and not the wall temperature. It may just be too close to the door and is reacting to the heat gain/loss through the old insulation.

I'm still in the process of trying to find the sweet spot for the refrigerant charge. I feel that I am still slightly overcharged, but I do not want to go under since I am all out of R12.

 

[ICanHas]

On my upright, the sensing line is attached on the bottom side of second from top shelf/evaporator. It's not touching, but suspended under a small plastic spacer so it's not actually touching the evaporator coil. Refrigerant enters at the top, then suction at the bottom. It's in the center horizontally, then towards the back.

Maybe try that position. You got me curious, so I got data logging going last night. I"ll post it later.

The only right charge is the nameplate charge. If you're having to add beyond your filter drier size difference, it means your cap tube is restricted.

 

[ICanHas]

Mine runs at about 1 cycle per hour. 30min on, 30 min off.

Here's what it looks like with a very fast responding thermocouple where the cold control is:

The bottom one is from a different time. Temperature setting might have been different, but the cold control differential is the same. I used a sensor that was much heavier thermally.
As you can see, there's quite a difference in swing as seen by the sensor depending on sensor's thermal mass.

I logged the resistance of one of the eart buds of 16 or 32 ohm earphones from the dollar store as a copper RTD since copper is pretty much linear. The unit is in °C, because, the equation was more readily available. That huge spike is from when the door was opened.

 

[envisioning]

On my upright, the sensing line is attached on the bottom side of second from top shelf/evaporator. It's not touching, but suspended under a small plastic spacer so it's not actually touching the evaporator coil. Refrigerant enters at the top, then suction at the bottom. It's in the center horizontally, then towards the back.

You, sir, are a gentleman!! Thank you so much for this information. I don't have a way to connect it in that exact spot, but I did get the probe right next to the evaporator at the back left corner. I need to find a way to attach this thing (a little difficult with a -5*F freezer).

I think moving this probe to the new location will help greatly! And thank you so much for your temperature/time plot! This is some seriously rock-solid data to work with. Now I can adjust my temperature controller to behave in a much similar way to the original cold control.

I have been reading the SAM manuals, Copeland Manuals, Fridge/Freezer Repair Tech manuals (from the 70s) all trying to find some hard data for temperatures.

With your chart, I can make this POS temperature controller behave in a way that is close to the original settings.

Thanks again

 

[ICanHas]

I dunno. paper clips? Post pictures of interior.

A freezer that old was quite inefficient to begin with even in perfect conditions. If there's anything less than optimal, it only goes down hill. To name a few, degrading insulation, partially clogged capillary, worn compressor, worn gasket and incorrect charge level.

If this is just some crappy old freezer and not some kind of iconic vintage, I'd be careful. Updating semi-modern freezer won't do much, but many from something that old guzzles power. It's not uncommon for something that old to use 1,400 kWh/year... and the cost is whatever your power rate is. At the national average, that's gonna cost you about $170 a year in power or about 3 times what modern ones use.

As much as I dislike a lot of today's China made stuff, 30-40 years is getting to the end of useful life.

Capillary obstruction problems are quite common. I had an R12 freezer. Worked good for a few months. Capillary clogged up, which made it not equalize and preventing compressor from starting. It thawed out. about $200 loss in food and I thought I saw hell taking out the rotting mass inside.

Mine's about half the cu.ft size of yours, quite new, manual defrost, quite new and Energy Star and its doing about 0.85kWh/day.