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Post by ChrisJ on Jul 6, 2015 3:20:18 GMT
I've been watching my CA-2-A and with a Fluke dmm and thermal couple froze to the center of the bottom shelf the closest I could get to the service manual specs is 10.5 to 11 off and 21 to 22 on which I set to #5. Seems odd because the spec is 13 off 22 on and I'm 2 degrees wider.
Also noticed when it turns on it creeps up to 24 pretty fast before dropping which I assume is just a normal effect of the capillary tube.
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Post by cablehack on Jul 7, 2015 2:07:36 GMT
The out of spec temperature differential just changes the frequency of cycling times, but the total on/off times per hour will still be the same. If you really want to change the cycling frequency, you'll have to go through the trial and error exercise of recalibrating the temperature differential. After 80 odd years, it's still pretty good to have maintained it as well as it has. My CA-2 control was too narrow one degree and correcting that did make quite a difference, slowing down the frequency of cycling somewhat.
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Post by ChrisJ on Jul 7, 2015 14:17:56 GMT
I was concerned because two "refrigerator thermometers" I have from 2011 both claimed 24-26F cabinet temperature and even raising the control enough to start defrosting the evaporator wasn't getting it above freezing.
I used my Fluke DMM + thermalcouple and so far am seeing 34-36F set to #5 on the lowest shelf. To be sure, i placed a small bowl of water on the bottom of the cabinet and will watch it.
As you know, I want this as close to freezing as possible but not below. Definitely not impressed that the 82 year old GE thermostat is more reliable than two 2011 thermometers. It's scary too because if you think your fridge is 38f and it's really 48f that could get people sick.
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Post by coldspaces on Jul 7, 2015 20:58:28 GMT
Only off 2 degrees after all these years sounds pretty good. As for thermometers you don't know how many bad one I have found over the years. Almost all the standard spring type are off at least a little when compared to a good electronic one.
Looks like its time to tell the story of the meat case that no one could get the temp set right back in the 60s. My Grandfather fixed it in 45 min. Butcher said no way did he fix it that fast,owners had already spent over $1500 back then and it still wasn't right.
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Post by cablehack on Jul 8, 2015 12:37:55 GMT
You might need to check the calibration of your refrigeration thermometers just to confirm their operation. Mine can measure room temp so I can check their calibration from that, but if they don't go that high, you could put them in a bowl of melted ice and compare their reading with the thermocouple.
Keep in mind when doing temperature measuring experiments the long time lag between the evaporator and cabinet temperatures. You can have a dripping evaporator with a saucepan of boiling water in it without raising the cabinet temperature for a while. This is why the defrost function works so well, and you can do an NCG purge without having to take the food out. With no compressor running, it takes about 24hrs for my CA-1 cabinet to get up to about 50F from its normal run temp of about 38F.
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