marko
7 Cubic Foot
Posts: 141
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Post by marko on Jun 20, 2022 9:35:48 GMT
Well guys, it looks like I have an oil logged evaporator.
The refrigerant is r152a and the oil is 150 mineral.
I fear the worst, in that the evaporator will have to be removed for flushing.
Now I must reconsider the oil and refrigerant choice, or possibly add some provision for oil return from the evaporator and perhaps from the receiver.
Before jumping, I am open to suggestions.
Thanks!
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Post by turbokinetic on Jun 20, 2022 9:49:02 GMT
Well guys, it looks like I have an oil logged evaporator.
The refrigerant is r152a and the oil is 150 mineral.
I fear the worst, in that the evaporator will have to be removed for flushing.
Now I must reconsider the oil and refrigerant choice, or possibly add some provision for oil return from the evaporator and perhaps from the receiver.
Before jumping, I am open to suggestions.
Thanks!
What's actually happening in the evaporator? Can you share a picture? I've always used alkylbenzene in belt drive conversions. However R152A and mineral oil have worked fine for years in other systems, mainly Tecumseh and Frigidaire hermetic units.
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marko
7 Cubic Foot
Posts: 141
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Post by marko on Jun 20, 2022 19:28:04 GMT
What's actually happening in the evaporator? Can you share a picture? I've always used alkylbenzene in belt drive conversions. However R152A and mineral oil have worked fine for years in other systems, mainly Tecumseh and Frigidaire hermetic units. Hi David, I could post a photo, suffice it to say there is a nice even frost on it, just low capacity.
The box was running continuously with a 10 psig suction and a 95 psig head. The cabinet temp was 40F constant, with about 400 fluid ounces of beer and fruit juice in it.
I defrosted it this morning and set the thermostat to the warmest setting and the box has been cycling on the thermostat today The oil seems to be clearing from the evaporator. I have the AXV opened for the highest suction pressure at the moment suction about 12 psig, head 100 psig.
There is slow progress. Time will tell. I think I got over ambitious with the AXV and t'stat. This is the price to be paid. The learning curve is a bit steeper than usual.
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Post by turbokinetic on Jun 21, 2022 0:42:15 GMT
What's actually happening in the evaporator? Can you share a picture? I've always used alkylbenzene in belt drive conversions. However R152A and mineral oil have worked fine for years in other systems, mainly Tecumseh and Frigidaire hermetic units. Hi David, I could post a photo, suffice it to say there is a nice even frost on it, just low capacity.
The box was running continuously with a 10 psig suction and a 95 psig head. The cabinet temp was 40F constant, with about 400 fluid ounces of beer and fruit juice in it.
I defrosted it this morning and set the thermostat to the warmest setting and the box has been cycling on the thermostat today The oil seems to be clearing from the evaporator. I have the AXV opened for the highest suction pressure at the moment suction about 12 psig, head 100 psig.
There is slow progress. Time will tell. I think I got over ambitious with the AXV and t'stat. This is the price to be paid. The learning curve is a bit steeper than usual.
Oh yeah, those AXV systems can be a steep learning curve. I would set the AXV for about a 5 PSI suction so that your evaporator can develop a low-enough temperature. Do you have a sight glass? Be sure the receiver is not low and allowing vapor to reach the AXV input.
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marko
7 Cubic Foot
Posts: 141
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Post by marko on Jun 25, 2022 18:15:02 GMT
Oh yeah, those AXV systems can be a steep learning curve. I would set the AXV for about a 5 PSI suction so that your evaporator can develop a low-enough temperature. Do you have a sight glass? Be sure the receiver is not low and allowing vapor to reach the AXV input. Thanks Dave, lowering the suction pressure now gives a nice cold box, but the pull down rate suffers. I think that is a combination of the one lung compressor (1/10 hp rated motor) and the cabinet insulation (sawdust blocks). I kind of considered a TXV, but no, I'll live with it.
Edit: yes, I put one of those little sg-1 supco glasses in it that you turned me on to (Thanks!), and yes, full column of liquid behind the AXV. I could put the last 8 oz of blowout in it, but if the receiver is not letting vapor, I don't see the point...... On the other hand...... Sometimes my physics and chemistry leave a lot to, well, lets just say, I did not ace those classes.
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Post by turbokinetic on Jun 25, 2022 20:44:32 GMT
Oh yeah, those AXV systems can be a steep learning curve. I would set the AXV for about a 5 PSI suction so that your evaporator can develop a low-enough temperature. Do you have a sight glass? Be sure the receiver is not low and allowing vapor to reach the AXV input. Thanks Dave, lowering the suction pressure now gives a nice cold box, but the pull down rate suffers. I think that is a combination of the one lung compressor (1/10 hp rated motor) and the cabinet insulation (sawdust blocks). I kind of considered a TXV, but no, I'll live with it.
Edit: yes, I put one of those little sg-1 supco glasses in it that you turned me on to (Thanks!), and yes, full column of liquid behind the AXV. I could put the last 8 oz of blowout in it, but if the receiver is not letting vapor, I don't see the point...... On the other hand...... Sometimes my physics and chemistry leave a lot to, well, lets just say, I did not ace those classes.
Those automatic expansion valves are very rudimentary! They just don't adapt to anything unless you turn the knob. Lower pressure leads to colder evaporator, but less of the evaporator frosted. In other words, the frosted areas are at a lower temperature, but there is less frosted area. Higher pressure leads to higher BTU moved by the system, and more of the evaporator frosted; however the frosted areas aren't as cold as they should be. It may even frost back to the compressor. The balance to be struck is to get the frost line to stop before the end of the evaporator, when it is down to its coldest cabinet temperature. Once that point is set, you may find that upon startup, it only frosts about the first 1/4 of the evaporator. The frost will progress as the cabinet pulls down to temp. That small HP compressor is going to make it take a while to pull down to temp and cycle off.
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marko
7 Cubic Foot
Posts: 141
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Post by marko on Jun 25, 2022 21:01:29 GMT
Thanks Dave, lowering the suction pressure now gives a nice cold box, but the pull down rate suffers. I think that is a combination of the one lung compressor (1/10 hp rated motor) and the cabinet insulation (sawdust blocks). I kind of considered a TXV, but no, I'll live with it.
Edit: yes, I put one of those little sg-1 supco glasses in it that you turned me on to (Thanks!), and yes, full column of liquid behind the AXV. I could put the last 8 oz of blowout in it, but if the receiver is not letting vapor, I don't see the point...... On the other hand...... Sometimes my physics and chemistry leave a lot to, well, lets just say, I did not ace those classes.
Those automatic expansion valves are very rudimentary! They just don't adapt to anything unless you turn the knob. Lower pressure leads to colder evaporator, but less of the evaporator frosted. In other words, the frosted areas are at a lower temperature, but there is less frosted area. Higher pressure leads to higher BTU moved by the system, and more of the evaporator frosted; however the frosted areas aren't as cold as they should be. It may even frost back to the compressor. The balance to be struck is to get the frost line to stop before the end of the evaporator, when it is down to its coldest cabinet temperature. Once that point is set, you may find that upon startup, it only frosts about the first 1/4 of the evaporator. The frost will progress as the cabinet pulls down to temp. That small HP compressor is going to make it take a while to pull down to temp and cycle off. Yep, getting there. I am trying to keep the box loaded up and not introducing too much extra heat with more product and excessive door opening. I have noticed less ice in the defrost tray.
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marko
7 Cubic Foot
Posts: 141
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Post by marko on Jul 24, 2022 12:07:29 GMT
Update: Although the AXV has had a full column of liquid to it, I decided to put my last 1/2 pound of 152a in the machine. The gauges have been hanging off the lines since I started the refrigerator, so I gave the AXV another 1/2 turn out to bring the suction pressure down to 1 or 2 psig, then removed the manifold. Now the box does not run most the time and stays off for a while. I will check the actual cycle rate over the next few weeks. I now have 3 lbs. of freon in it and it runs better than ever. I wonder why the extra mass of refrigerant has such a pronounced effect. It would seem that enough refrigerant would be enough, but apparently the AXV behaves somewhat like a cap tube. I don't know.
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Post by turbokinetic on Jul 24, 2022 12:40:51 GMT
Update: Although the AXV has had a full column of liquid to it, I decided to put my last 1/2 pound of 152a in the machine. The gauges have been hanging off the lines since I started the refrigerator, so I gave the AXV another 1/2 turn out to bring the suction pressure down to 1 or 2 psig, then removed the manifold. Now the box does not run most the time and stays off for a while. I will check the actual cycle rate over the next few weeks. I now have 3 lbs. of freon in it and it runs better than ever. I wonder why the extra mass of refrigerant has such a pronounced effect. It would seem that enough refrigerant would be enough, but apparently the AXV behaves somewhat like a cap tube. I don't know.
Good to know Those AXV systems are unique in quite a few ways it seems. It's good that you have found a charge level which works for your unit.
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marko
7 Cubic Foot
Posts: 141
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Post by marko on Dec 2, 2022 1:15:50 GMT
Well, this ol gal has been performing admirably for a few months now. She will cause ice crystals to form in my fruit juice. The evaporator will frost thickly over a few weeks. I have not implemented my Norge defrost clock, but I did do a defrost. After that the evap did not frost well, so I opened the AXV and got flow back. The evap frosted, but the cycle on was always. I pinched back the AXV and after a couple of weeks, she started cycling on setpoint again. To me, it is an oil problem. Shouldn't the oil be miscible in the refrigerant? Or soluble? What am I missing here? What, other than refrigerant velocity, will carry the oil out of the evap? Correct me where I am wrong, but experience has taught me that an unloaded compressor will pump oil, thereby making the problem worse by reducing the effective evap surface area. Am I using the wrong oil?
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Post by turbokinetic on Dec 2, 2022 11:46:14 GMT
Well, this ol gal has been performing admirably for a few months now. She will cause ice crystals to form in my fruit juice. The evaporator will frost thickly over a few weeks. I have not implemented my Norge defrost clock, but I did do a defrost. After that the evap did not frost well, so I opened the AXV and got flow back. The evap frosted, but the cycle on was always. I pinched back the AXV and after a couple of weeks, she started cycling on setpoint again. To me, it is an oil problem. Shouldn't the oil be miscible in the refrigerant? Or soluble? What am I missing here? What, other than refrigerant velocity, will carry the oil out of the evap? Correct me where I am wrong, but experience has taught me that an unloaded compressor will pump oil, thereby making the problem worse by reducing the effective evap surface area. Am I using the wrong oil? Sounds like worn parts in the expansion valve. The AXV regulates based upon low-side pressure. If there is anything worn which results in a sticking of the valve, it will be inconsistent. If the seat is worn from years of use, the moving part of the valve can become jammed in the seat when the system is shut down. The pressure rises in the low side and causes the diaphragm to put a lot of pressure on the seat, forcing the valve closed. If the parts are worn they can get stuck together. Then, when the compressor runs again, the valve doesn't move off the seat until it's "disturbed" by something. The valve would work the same whether or not there is oil or liquid refrigerant there. There's no way the oil will cause the AXV to malfunction.
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marko
7 Cubic Foot
Posts: 141
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Post by marko on Dec 2, 2022 23:27:04 GMT
Thanks David, The machine is being very well behaved at the moment. It is keeping the Thanksgiving turkey gumbo fixins cold right now. This is a much better machine than my brand new Whirlpool with r600 or whatever in it, I already replaced an evap fan on it, and that one failed as well, the box only two years old.
Look, I'm not totally adverse to putting a TXV on the old girl, but I do not know at the moment, what bulb charge/powerhead would kinda match r152a. I suppose I should look into that.
The itty-bitty compressor takes alooong time to pull down a hot box. After a load is cooled, she performs very well.
Thanks again, David!
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Post by turbokinetic on Dec 3, 2022 13:31:04 GMT
Thanks David, The machine is being very well behaved at the moment. It is keeping the Thanksgiving turkey gumbo fixins cold right now. This is a much better machine than my brand new Whirlpool with r600 or whatever in it, I already replaced an evap fan on it, and that one failed as well, the box only two years old.
Look, I'm not totally adverse to putting a TXV on the old girl, but I do not know at the moment, what bulb charge/powerhead would kinda match r152a. I suppose I should look into that.
The itty-bitty compressor takes alooong time to pull down a hot box. After a load is cooled, she performs very well.
Thanks again, David!
That's good it's working well for you! Those tiny compressors just can only do so much it seems. I've had good success with "vintage" R12 Sporlan TXV's and also newer R134A ones. You just have to adjust the superheat range until it works well. R152A is between R12 and R134A so most any adjustable TXV would be able to work with it. My Sparton has an AXV and it seems to still be in good shape. Never had any issues with it. Same for my older Kelvinator with its brine-filled evaporator. Those both seem to still be in good order. Hopefully they stay in good order LOL!
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Post by douro20 on Dec 7, 2022 16:09:52 GMT
I wish that I had a drum of F-11 to warsh these parts in... A drum of that stuff nowadays is over US$1000.
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Post by douro20 on Dec 7, 2022 16:11:37 GMT
I think that an over zealous mechanic over tightened the bolt in that hole trying to stop a leak. I know from first hand experience that old iron like this just is not as strong as more modern iron (it is hard to "wet" when brazing, as well). Also, I draw file all the flat machined gasket surfaces to even them up, and I noticed quite a few bolt holes had been "pulled up" just a bit, not bad, just enough that the file cut around the hole the first few ten thousandths, like a contour map of the surface.
Here is the repair, not perfect, but it will seal to a gasket.
Beautiful. That will last decades! You're so right about mechanics and overtightening things..... they often don't have sense enough to simply replace the gasket! Thanks for the update. My father is a MACHINIST and he has a tendency to overtighten things.
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