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Post by csulaguy on Jul 27, 2018 20:24:55 GMT
Someone suggested a different thread per machine to make things more organized. CA-2-A15 "soup can." Wasn't cooling until I bled NCGs. It looked like it'd never been bled before, as the top screw was welded/soldered, and also rusted shut. Unfortunately, I had to drill out that top screw. Used my bristol key to purge NCGs and it started forming a frost line. In fact, the frost line is all the way to the top of both header tanks. My problem now are run times.
These do not correspond with actual times, but are from logs pulled from my Watts Up Pro. I haven't yet got logging done on my thermometer (BK Precision, and I do have logging options available).
13:53 on
14:21 off
14:26 on
14:46 off
14:51 on
15:11 off
15:15 on
15:38 off
It appears that it runs for 20 minutes and cycles off for 5. This explains why the dome never truly gets cold. Control is set to 3. With the compressor off during an off cycle, and without the door having been opened well over 12 hours, cabinet temp on the top shelf is 37.8, evap is 18.1. Evap is being measured in a small wedge between the top shelf and actual evap. The fridge is filled with aluminum and glass beer bottles, and insulation was redone in all but the door.
I feel like I was making better progress with the CA-2-B16...
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Post by Travis on Jul 27, 2018 21:03:35 GMT
A long purge and a short off cycle likely point to a worn needle and seat.
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Post by cablehack on Jul 28, 2018 0:46:30 GMT
What Travis says. A worn needle and seat won't allow sufficient pressure differential - the liquid is entering the evaporator at too great a rate for the amount of suction which takes the vapour out of the low side. Therefore the evaporator does not get as cold as it should. 18 degrees F is definitely too warm - something like 3F or colder is what's required. When that happens your run and off times will be the reverse of what you get now.
Worn needles and seats are not uncommon with CA's, and appear to be a result of operating with NCG's in the system. The good news is that a capillary tube replacement will restore operation to as good as, or better than, a good float valve, and the problem can never recur. A further advantage of the capillary is that it won't cause the high side flow to shut off when the NCG's start building up, which allows longer periods between purges.
If you are keen and have nothing to lose, you can try carefully crimping the high side tube to create a restriction - measuring the evaporator temperature while you do so. The performance won't be as good as a capillary tube or float valve, but will prove the point.
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Post by birkie on Jul 28, 2018 14:18:01 GMT
Sorry to hear that - your observation that this machine seemed to be running all the time was well founded. So that means all two of your CA machines seem to be suffering from this. Are you interested in doing surgery to add a cap tube?
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Post by csulaguy on Jul 28, 2018 17:09:33 GMT
I am, but I don't know if I'm at the level to accomplish this on my own just yet. And even though the methyl formate otherwise works, I'm even open to experimenting in the future with R124 (or was it R114)? Whatever bhigdon2 experimented with and found favorable. I'm just bummed either way that both machines suffer from the same problem.
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Post by Travis on Jul 28, 2018 21:29:04 GMT
Paul,
I don’t recall the R number that would work. Neither 114 or 124 or it.
Many CA’s suffer from this. It’s why I recommend CK’s for normal use.
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Post by turbokinetic on Jul 28, 2018 22:39:30 GMT
I am, but I don't know if I'm at the level to accomplish this on my own just yet. And even though the methyl formate otherwise works, I'm even open to experimenting in the future with R124 (or was it R114)? Whatever bhigdon2 experimented with and found favorable. I'm just bummed either way that both machines suffer from the same problem.
I believe that R11 and R123 were considered as replacements for the CA's methyl formate. These are liquid at atmospheric pressure / temperature. They were used in centrifugal chillers for large buildings.
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Post by cablehack on Jul 29, 2018 12:05:25 GMT
You can leave the existing methyl formate in the system whilst doing the cap tube installation. As it happens, the ideal charge is slightly less than when a float valve is used, so a small amount evaporating or burned off is something you can get away with. R11 and R123 are the modern replacements if you cant get or don't want to use methyl formate. I should point out that the cap tube characteristics are different for different refrigerants, so the recommended cap tube length for MF doesn't suit R11/R123. While one of the members has used a cap tube with R11, its length had not been optimised.
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Post by birkie on Jul 29, 2018 12:36:07 GMT
Yes, I think jhigdon2 used R123 for a while with great success. There are also some new "environmentally friendly" refrigerants that would probably work well (especially after the 2030 phaseout of R123 in the US) like R1233zd(E) and/or R1366mzz(Z) I should point out that the cap tube characteristics are different for different refrigerants, so the recommended cap tube length for MF doesn't suit R11/R123. While one of the members has used a cap tube with R11, its length had not been optimised. Ah, yes that's right. With a functional float, you could likely try out an alternate refrigerant without much fuss. The cap tube provides the need (or opportunity, depending on perspective) to experiment. If I were in this situation, I'd probably just use cap tube dimensions found by one of the CA pioneers on this form and keep the machine methyl formate. |
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Post by rick on Aug 25, 2018 2:41:08 GMT
This makes me sad. Two unhappy CAs.
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Post by csulaguy on Sept 26, 2018 1:17:03 GMT
As an update - I defrosted the evap with my soup can off, using a heat gun. I also did both my CKs in the kitchen around the same time.
So the next morning, I found the evap was just sweating. I got some pretty hot water in ice cube trays, put them in the evap, bled out NCGs, and the evap got frosty. A few years later, it had a high frost line across both expansion tanks on the evap. Fast forward another 2 days, and it's just sweating. So I bled out NCGs a second time, and now it's getting frosty again.
Should I have to bleed this thing out that much? Or is this still related to the probable need for a capillary tube conversion? And of course, the CKs didn't change except for having an almost frost-free evap.
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Post by ckfan on Sept 26, 2018 16:25:46 GMT
I would think that it’s just a worn out float seat showing itself after having a heavy load put on it. I would think that you shouldn’t get that many NCGs but then again I’ve been surprised at the amount before.
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Post by csulaguy on Sept 26, 2018 19:55:18 GMT
I bled it off once more today, and some more yesterday. The evap is definitely getting pretty cold, but of course, it still runs constantly. Worst case scenario, I have the CA-2-B16 that I got from Herb to use. Oddly, it's the CAs that my mother wants when I put an MT in her house, even when I offered a later CK with an evap door.
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Post by cablehack on Sept 26, 2018 23:22:19 GMT
If the condenser is evenly heated and there is some warmth on the float chamber, the NCG's are sufficiently purged. If the frost line reaches halfway up the header tanks or higher when under load, there is sufficient refrigerant. That leaves a worn needle and seat. Question is, how cold can the evaporator get?
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Post by csulaguy on Sept 27, 2018 3:03:00 GMT
The coldest I've seen it get, as measured midway with a K-type thermocouple, is 14.9. I didn't leave it on long enough to see if it went down. The frost line is definitely at the top of the header tanks.
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