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Post by ckfan on Jan 30, 2018 15:26:06 GMT
Ever since I started appreciating these old Meter Miser compressors I have been frustrated with the rattle that I hear from them. It always seemed that the rattle got worse when it was cold vs. at the end of the cycle when it warmed up. I also remembered someone from here stating that they used a high side dome. Rattle, high side dome, sound familiar? So I talked to Travis about it and he suggested to put a lamp under the compressor to heat it up. I did just that and it worked! At first I tried a 65 Watt flood light which came very close to the bottom of the compressor. It seemed to get a little hot for my taste but it made it run very quiet. For fear of overheating it i swapped in a 40 watt spot light bulb which is much smaller and therefore further away from the compressor. The light fixture I put it in is one of those metal "bell" shaped fixtures that has a clamp that holds it in place. Perfect! I could articulate it exactly where I wanted it. After letting it sit all night I was greeted with a gentle purr instead of a loud and random rattle. Now it just sounds sweet and happy! The bottom of the compressor is just barely warmer than the surrounding room temp. No chance of overheating it now. To make it even more quiet I decided to stuff some rock wool insulation around the front opening. It is so gentle now, not flat top gentle, but close! I'll have to keep an eye on it when the temps start to rise but I think it will be ok since it is just a little warmer now. I'm so happy with this that I thought I would share it with you all. Sure, it negates the efficiency of the compressor but it sure beats doing permanent damage to it. I think Frigidaire should have taken a lesson from GE and stuck a heater on the compressor, or made it a low side dome. I have some video clips that show just how silent it is. I will post them later!
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Post by Travis on Jan 30, 2018 16:51:35 GMT
In a properly heated house they’re near silent.
Every old theater had a light bulb in the cabinet under the popcorn machine to keep the oil warm enough to start the next day.
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Post by ckfan on Jan 30, 2018 18:13:34 GMT
In a properly heated house they’re near silent. Every old theater had a light bulb in the cabinet under the popcorn machine to keep the oil warm enough to start the next day. That makes sense. I had always noticed that they got quieter as the room warmed up. My house is set to a balmy 64 right now! |
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Post by jake on Jan 31, 2018 5:14:43 GMT
Thanks for the info, ckfan! My '50 Frigidaire does the exact same thing. During the day when I'm not home I keep the heat set at 60°. It rattles along until the end of the run cycle, just like you said. Once I come home and the kitchen starts to warm up it runs perfectly quiet.
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Post by ckfan on Jan 31, 2018 14:12:49 GMT
Thanks for the info, ckfan! My '50 Frigidaire does the exact same thing. During the day when I'm not home I keep the heat set at 60°. It rattles along until the end of the run cycle, just like you said. Once I come home and the kitchen starts to warm up it runs perfectly quiet. Try what I tried. A 40 watt bulb seems to work great. It made a huge difference and I’m sure it’s much happier now. |
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Post by blackhorse on Feb 1, 2018 5:31:31 GMT
You should get one of those PTC crankcase heater cartridges that are used on some heat pump compressors, and clamp it to the suction line stub on the bottom of the compressor. Or slide it up between the fins on the side. They are nice because they only draw the current needed, not the same constantly. So don't heat the compressor as much when it's running, more when it's cold.
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Post by ckfan on Feb 1, 2018 14:49:32 GMT
You should get one of those PTC crankcase heater cartridges that are used on some heat pump compressors, and clamp it to the suction line stub on the bottom of the compressor. Or slide it up between the fins on the side. They are nice because they only draw the current needed, not the same constantly. So don't heat the compressor as much when it's running, more when it's cold. Thank you so much! That is a brilliant idea. I’m so impressed how much a simple light bulb has made to this machine but that solution is much more elegant. It won’t have the halo glow coming from underneath it anymore though! |
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Post by blackhorse on Feb 1, 2018 21:02:27 GMT
It won’t have the halo glow coming from underneath it anymore though! That should be a benefit; you won't have all the foot traffic from the guys from Ghost Hunters waltzing through trying to contact the Great beyond! |
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Post by Dave on Mar 11, 2018 17:42:52 GMT
I too have noticed the "tinking" rattle from cold Meter-Miser compressors. Like you, I assume it's because of condensed liquid refrigerant in the compressor that pumps through on startup.
The idea of a crankcase heater makes sense, however I had another idea which could also be worthwhile. In industry, we keep large electric motors warm so that they stay dry. Different reason, but the way they are sometimes kept warm is interesting. When the motor is off, a low DC current is passed through the stator winding. This keeps it warm. With the small motor in the Meter-Miser, with 2.1 amps full load running current, a small power supply would be adequate. It would be a trade-off. You would be able to hide the relay and DC supply in the shadows; such as in the corners of the fridge bottom compartment. The compressor its self wouldn't have anything attached to it. Also the heat would be inside the compressor and might be more effective. Just a thought!
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Post by ckfan on Mar 12, 2018 10:37:02 GMT
Very interesting idea. I would like to learn more about this. My only fear would be damaging the windings.
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Post by turbokinetic on Mar 12, 2018 21:01:28 GMT
Very interesting idea. I would like to learn more about this. My only fear would be damaging the windings. True. you would have to do some figuring first. I think I read that the Monitor Top has a 12 watt heater in it. In my theorizing; will use that as a goal; to make 12W of heat, using the motor winding resistance as a heating element.
To generate the same 12W of heat using the motor winding, you would need to use Ohm's Law, with Power and Resistance known. This works with DC only since it won't take inductive reactance into account if AC were used.
To start out, measure the DC resistance of the winding which will be used to generate the heat. Just pulling theoretical numbers, lets say the motor winding has 3Ω of DC resistance. To make 12 watts of heat with a 3Ω winding, calculate current and voltage; with power and resistance known.
I=√(P/R) I=√(12/3) I=√(4) I=2 --- so we will need 2 amps flowing, of DC current.
For the voltage required to do this:
V=√(P*R) V=√(12*3) V=√(36) V=6 --- so we will need a 6V DC source.
In other words a small transformer producing 6V, with a diode bridge to make it DC would be a good power source.
Thinking of the Frigidaire setup; it would need a relay to select between the motor winding connected to power; or connected to the DC warming source. That would require 3 components, transformer, relay, and diode bridge. All could be discretely hidden under the fridge.
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Post by ckfan on Mar 13, 2018 22:22:16 GMT
Very interesting concept. I just wonder if the heat would just rise to the top though and not heat the oil since the motor is up top.
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Post by turbokinetic on Mar 13, 2018 23:18:15 GMT
Very interesting concept. I just wonder if the heat would just rise to the top though and not heat the oil since the motor is up top. You know; I was thinking the same thing. With the Frigidaire, the compressor is really small and the motor is pretty close to the sump. I think the shell would carry some heat down.
Looking at the Monitor Top compressors I have seen open on this forum, the motor seems to be much further from the compressor oil sump.
I plan to make up a temporary setup and try it to see if it eliminates the startup rattle.
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Post by ckfan on Mar 14, 2018 0:11:25 GMT
That is true. The compressor shell is much smaller and therefore easier to heat up with the motor up top. I was just thinking from the point of the monitor tops having the heater in a little hole in the bottom of the sump to heat the oil up.
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Post by coldspaces on Mar 14, 2018 0:47:14 GMT
Rheem used to use a dual run capacitor in their central ac units. The 1/2 was in circuit with the contactor open and bled a controlled amount of power through the start winding to warm the compressor and keep from adding a heater. I always though it would not work as good since the motor was on top but the metal of the motor and pump must conduct the heat well enough.
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