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Post by ChrisJ on Nov 23, 2020 16:35:48 GMT
These machines have a big problem with methyl formate condensing in the oil sump even in a warm environment. This is why they needed the crankcase heater. The last thing I would do is run one when it's in a near freezing ambient. Oil floats on top of methyl formate so you could end up with the compressor being starved of oil.
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Post by rodamala on Nov 23, 2020 20:36:23 GMT
These machines have a big problem with methyl formate condensing in the oil sump even in a warm environment. This is why they needed the crankcase heater. The last thing I would do is run one when it's in a near freezing ambient. Oil floats on top of methyl formate so you could end up with the compressor being starved of oil. Noted.
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Post by turbokinetic on Nov 24, 2020 15:12:02 GMT
It seems to me that all of the high-side dome machines, such as the DR, CA, and even other makers units like the Frigidaire meter-Miser; they all suffer in very cold ambient temps.
One of the things we may forget in today's times is that they were sold new in an era where things were different in many ways. For instance, in the block-ice era, during winter; people would move the icebox out to the porch to keep foods in without the need to buy ice. People were familiar with, and in the habit if storing store food in an icebox (without ice) outdoors in winter and would not see the need to run a refrigerator in a cold environment. After all, you just don't need it. Any storage cabinet will stay cold if it's already freezing cold out. Therefore, the makers didn't engineer the compressors with low ambient operation in mind. Now that things are different we have to understand that sometimes we unintentionally go outside the original design limits in ways the original designers didn't predict would happen.
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Post by elec573 on Nov 25, 2020 18:55:32 GMT
Congratulations I’m glad you got it to run, like you said one thing at time .
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Post by rodamala on Nov 27, 2020 17:29:35 GMT
Just a short update.
Now that the machine is running, and because I am told here that the refrigeration system (when operating correctly) is in vacuum, I am performing the NCG bleed as per the manual. 3 off, 1 on, hot water in trays.
Yes the ambient air temperature is in the mid-40s, but this is what I have noted.
As the unit came up to temperature (dome becoming warm) the wattage was noted to be in a pretty consistent cycle.
Initially, it was cycling at a low of about 270W. The load draw would slowly increase to around 300W where I could hear an ever so slightly distinguishable rattle (barely noticable... but I could just "tell" the compressor was loading more... and the Kill-a-Watt followed.
It would then slowly reduce load and that very minor rattle would go away.
The compressor has been running continuously. Thermostat set to coldest setting, but I have doubts about the thermostatic control's performance... which I will get to when I get to it... hopefully when I am confident the top may go back on top of the cabinet.
<i>If</i> I were datalogging the load being drawn over time the graph would be a sawtooth increasing steadily. At one point the peak was 386W, dropping back down to 340W(ish). I bled gas and the load would come down... still cycling as stated.
There is condensate on the evaporator tanks, but it is not frosting... and no distinct "frostline" on the tanks. After a few bleed cycles, the "load cycling" was 270W to 300W.
At one point it "seemed" the gas pressure had reduced to zero, but I let it cycle a few times and continued to check and bleed so long as there is bubbling. MF odor the whole time is noteworthy.
I still have doubts/worries about bleeding all the MF gas off to atmosphere so I only vented a few cycles, but I can tell it does affect the load on the compressor.
I need to get an IR gun to check temperatures. The machine has been running without stopping for 45 minutes.
Eventually I can find help to put the top back on the cabinet and bring the machine into the house so the low ambient air temperature of the front porch is not a distracting issue, but right now I am just looking for performance as a refrigerating unit. I hear "waterfall sound" so I know something is happening, and the dome and topmost circuit of the condenser coil is warm to the touch (not "hot", warm... as in warmer than ambient).
I just do not want to vent off MF. I will continue to purge... but at some point it would be nice to validate the thermostatic control relay. I would figure that I "should" be able to dial it slowly to the warmer settings, and if operating properly, it would open the contact and turn off the compressor, but as of now, in its current disassembled on the front porch for major overhaul condition, when dialing the temperature control from coldest to warmest, the compressor just keeps running.
As of yet (today) the compressor has not stalled or tripped on overload the way it did that last time I was spending time on the machine.
Before posting, I looked at the load cycling again... it seems to be more "steady state" down in the 209W to 217W range with a shorter cycling... AND...
...the evaporator had fully developed frost!
Just did another NCG bleed... and it went about 30 seconds and seemed to stop bubbling so closed it... verified it 3 minutes later and she's gone from blow to suck! The load now seems to be steady state (not sawtoothing) at around 150-153W.
The temperature control relay does not seem to be doing anything... I dread having to remove it again... especially if I get the top back on the cabinet and get this unit inside the house.
Getting there, guys. One baby step at a time.
Rod
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Post by rodamala on Nov 27, 2020 17:54:08 GMT
Update... a few minutes later.
Was going to power down unit and go dobother things and in playing with the thermostatic control relay (wanted to see what happens when turned from "ON" to "DEFROST", the knob latched onto DEFROST, not springing back to ON.
Turned it backbto ON and then turned the temperature knob slowly ("up" in temperature) from COLDER, and the compressor shut off! Twisted it back towards COLDER, and the compressor came back on!!!
Gonna line up some muscle to put the top back on cabibet and bring it all inside. I don't care if it needs a fresh coat of paint and a rechrome job on the shelves...
I think I got a new fridge here, boys!
Rod
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Post by turbokinetic on Nov 27, 2020 18:35:52 GMT
Wonderful news! It sounds like you have a runner! The 150 to 175 (ish) power demand is quite normal. It will probably be OK once it runs in the cabinet for a few days. Thanks for the good news!
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Post by ChrisJ on Nov 27, 2020 21:35:02 GMT
When bleeding I usually notice what I believe is the smell of the oil in the system. The methyl formate smells a lot like pvc cement or acetone.
They say to keep your nose a few inches above the valve and not right at it. I think this is to avoid smelling tiny amounts.
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Post by rodamala on Nov 28, 2020 2:59:01 GMT
End of the day checkout of the unit out on the front porch. As info: Outside ambient air temperature is 40° F. Humidity high as it has been rainy here for a couple days. Frost, well developed. Just wanted to show everyone what I got. This refrigerator... is older than most of the steam locomotives I have worked on in my life as a railroader. I am pleased that I have taken this on and it has gone "kinda OK"... so far. youtu.be/Lie7q-2AWEw
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Post by cablehack on Nov 28, 2020 11:36:24 GMT
Frost line looks good - you haven't lost any MF by the look of it. I go by condenser temperature rather than the odour of MF to know when to stop purging.
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Post by rodamala on Nov 30, 2020 3:11:15 GMT
Frost line looks good - you haven't lost any MF by the look of it. I go by condenser temperature rather than the odour of MF to know when to stop purging. I got the head unit back on the cabinet today and brought it inside. Power consumption was higher nearly 350W. Performed more NCG purging... and noted the gas vent bubbles if I keep the dome and condenser warm by covering the top with a blanket; but if I take the blanket off, it gets cooler and find the vent is in vacuum. I bled it a bunch of times. It is running at about 304W. I am really not sure why it is not 150W like last night. If you go by condenser temperature to know when to stop, what should I be looking for? Like I said, I am perplexed why the power consumption is now double. Rod
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Post by cablehack on Nov 30, 2020 11:13:44 GMT
I got the head unit back on the cabinet today and brought it inside. Power consumption was higher nearly 350W. Performed more NCG purging... and noted the gas vent bubbles if I keep the dome and condenser warm by covering the top with a blanket; but if I take the blanket off, it gets cooler and find the vent is in vacuum. I bled it a bunch of times. It is running at about 304W. I am really not sure why it is not 150W like last night. If you go by condenser temperature to know when to stop, what should I be looking for? Like I said, I am perplexed why the power consumption is now double. Rod When sufficient NCG's have been purged, the bottom of the condenser will be the same temperature as the top. Just before purging is complete, the float chamber will be of similar temperature, though maybe a couple of degrees cooler. The important point is it's warmer than ambient. I've never had to cover the top of the unit for purging - I use a container of very hot water sitting in the evaporator. In summer with a room temperature in the mid 20's or above (degrees C), it's not even necessary to do that. Power consumption will be higher on the initial temperature pull down. Once the cabinet temperature has stabilised, it should be around 150-170W. If it's more, I'd expect rattling to be evident, with poor cycling times. There isn't really much beyond NCG's or an oil logged evaporator to cause excess power draw otherwise (except in the unusual cases of where the system has been damaged and left open to the atmosphere, and all the problems that introduces, but that's another story).
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Post by turbokinetic on Nov 30, 2020 21:38:13 GMT
Frost line looks good - you haven't lost any MF by the look of it. I go by condenser temperature rather than the odour of MF to know when to stop purging. I got the head unit back on the cabinet today and brought it inside. Power consumption was higher nearly 350W. Performed more NCG purging... and noted the gas vent bubbles if I keep the dome and condenser warm by covering the top with a blanket; but if I take the blanket off, it gets cooler and find the vent is in vacuum. I bled it a bunch of times. It is running at about 304W. I am really not sure why it is not 150W like last night. If you go by condenser temperature to know when to stop, what should I be looking for? Like I said, I am perplexed why the power consumption is now double. Rod Hi rod. How long did you let it run? The power demand will be very high before the evaporator frosts. There is a lot of heat-load on the system at first startup. It should taper off as a frost line develops.
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