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Post by cablehack on Sept 29, 2014 10:56:57 GMT
I do not like the PTC relays for all of the reasons mentioned, and because they have been much more prone to failure than the mechanical relays. They can fail from the conductive coating on the disc failing, the disc can shatter, they can short out and never disconnect the start winding. They have been the subject of recalls for setting the kitchen cabinets on fire. And these are the factory-spec ones the refrig's came with, not maybe-misapplied replacements. I have replaced a boatload of them. Now I will make some enemies. I put a run capacitor and a Klixon overload in the original relay housing of my CK in the kitchen over a year ago, when the relay heater burned up the terminal mounting. No relay. It runs as a PSC compressor, like air conditioners. Most refrigerators now have a run capacitor, it shaves about an amp off the run current. It sounds a bit different on startup, instead of "Clickwhirr" , it's more of a soft start "Click-whirr", with about 1/4 second between the sound of the control closing and the motor at speed. With the compression release, it restarts immediately and repeatedly. Amp draw falls below 2 amps when the box is at about 32F (1/6 Hp motor). And as mentioned above, I put on a 3-wire cord with grounded plug, while I was at it. I'm sure there's the feeling that I should keep it original, but that ship has sailed. Sailed, made port, and offloaded it's cargo, when the float valve decided it would make a better tubing stopper than orifice. The TXV, receiver and 134a are nowhere near original, but keeping a great machine going for it's original purpose suits me better than preserving a museum piece. I've seen enough failed PTC thermistors in my electronic repair work to know they're not 100% reliable. Apart from the thermistor discs breaking in half, I've seen some that have burnt the plastic housing. They're not my personal choice for a fridge, but others like them and that's fine by me. I doubt you'd make enemies as a result of your mods. Both my CA's have their float valve seat removed and a cap tube and filter installed. One has a homemade heater, the other has polystyrene cabinet insulation. The story is the same with other members here. It's a choice of do some mods or have it remain an inoperative museum exhibit.
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Post by ChrisJ on Sept 30, 2014 13:18:15 GMT
I do not like the PTC relays for all of the reasons mentioned, and because they have been much more prone to failure than the mechanical relays. They can fail from the conductive coating on the disc failing, the disc can shatter, they can short out and never disconnect the start winding. They have been the subject of recalls for setting the kitchen cabinets on fire. And these are the factory-spec ones the refrig's came with, not maybe-misapplied replacements. I have replaced a boatload of them. Now I will make some enemies. I put a run capacitor and a Klixon overload in the original relay housing of my CK in the kitchen over a year ago, when the relay heater burned up the terminal mounting. No relay. It runs as a PSC compressor, like air conditioners. Most refrigerators now have a run capacitor, it shaves about an amp off the run current. It sounds a bit different on startup, instead of "Clickwhirr" , it's more of a soft start "Click-whirr", with about 1/4 second between the sound of the control closing and the motor at speed. With the compression release, it restarts immediately and repeatedly. Amp draw falls below 2 amps when the box is at about 32F (1/6 Hp motor). And as mentioned above, I put on a 3-wire cord with grounded plug, while I was at it. I'm sure there's the feeling that I should keep it original, but that ship has sailed. Sailed, made port, and offloaded it's cargo, when the float valve decided it would make a better tubing stopper than orifice. The TXV, receiver and 134a are nowhere near original, but keeping a great machine going for it's original purpose suits me better than preserving a museum piece. I'm a bit confused. I thought the start windings in these were too small to leave connected all of the time such as a PSC setup? One of our engineers where I work actually had told me to do just this a few years ago and I assumed he didn't know what he was talking about because I've been worried about burning the start winding up. I'm assuming this basically turns it into a 2 phase motor with the capacitor giving you the shift you need. What I really don't get is if you can use a cap in this way then why do a lot of motors have a relay or switch to disconnect it?
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Post by blackhorse on Sept 30, 2014 17:33:10 GMT
First of all, you are absolutely right, if you leave the start winding connected or the relay sticks, it will burn out if the overload doesn't disconnect it. That would be awful. I think the manual says not to leave it connected more than a minute, that would be about 50 seconds longer than I would suggest.
But with a 15 uf capacitor in series with it, the current is very limited, way less than it normally draws. And I mention the 15 uf because I measured the characteristics of the motor starting and running with capacitors from 5 uf to 35 uf, in 5 uf increments, and that's where the null (lowest current) was for my particular motor (1/6 Hp CK).
I would also mention for everyone's safety and happiness, that most motors (I never went there with this motor) have a "Huge Smoking Crater" null point with a much larger capacitor, typically above 50 uf for fractional horsepower motors. When the capacitive reactance of the start winding is the same as the inductive reactance of the run winding, a parallel resonance will occur. The current draw on the line cord will be very small, but the current flowing in the windings will be huge. And the overload won't stop it because it's not between the windings where the high current flows. When you are setting one up as a PSC motor you always want to check the current on each winding separately, and both together (line current). If either the run or the start winding separately is drawing more current than the total line current, stop immediately; they should always be less. But the apparent total will be more than the line current. Example: 1.6 A run winding, .65 A start winding, 1.9 on the line cord. This is because they are out of phase, and totally expected. And use good sense. Modern 5 Hp compressors usually have 50 to 80 uf run capacitors. Modern refrigerator compressors usually have 12 to 20 uf run capacitors. If you get results outside of that, reconsider your work.
I am totally not trying to scare the crap out of anyone or imply it is dangerous to do so, I'm just hitting the "do not do" points. :-)
I plan to make a detailed thread on the process involved, but need to see what size the 1/8 Hp motors like best, make some drawings and photos, etc.
As to why "if you can use a cap in this way then why do a lot of motors have a relay or switch to disconnect it?" , let me clarify: I'm talking about a run capacitor. A lot of motors use run capacitors. A start capacitor is a completely different critter. It, like the start winding itself, will fail in a blue flame and a cloud of chemical smoke if you leave it in the circuit for more than a few seconds. They are of a much higher uf value, and draw much higher current. Many motors have both a start capacitor and a run capacitor, leaving only the run capacitor on during run time. This particular CK monitor had a start capacitor as original equipment, the original one failed decades ago and I replaced it then.
Most air conditioner compressors are PSC motors, they only have start capacitors and relays if there's a hard starting issue. Most refrigerator compressors have start relays of some sort because most refrigerator compressors don't have a compression release, which was G.E.'s brilliant answer to using float valves, which would not equalize and would be very hard to start the compressor otherwise. All the float valve machines have a compression release and start under no load, so start very easily as a PSC motor.
Also please understand that I am not referring to the DR machines, some of which use a complicated arrangement of resistors, multi-tap transformers, capacitors, chokes, to manage the starting current. One day, I may bravely go where no man has gone before, and see about simplifying the start controls on one of those. But I haven't found a compelling reason to do so yet.
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Post by coldspaces on Sept 30, 2014 19:30:30 GMT
First of all, you are absolutely right, if you leave the start winding connected or the relay sticks, it will burn out if the overload doesn't disconnect it. That would be awful. I think the manual says not to leave it connected more than a minute, that would be about 50 seconds longer than I would suggest. But with a 15 uf capacitor in series with it, the current is very limited, way less than it normally draws. And I mention the 15 uf because I measured the characteristics of the motor starting and running with capacitors from 5 uf to 35 uf, in 5 uf increments, and that's where the null (lowest current) was for my particular motor (1/6 Hp CK). I would also mention for everyone's safety and happiness, that most motors (I never went there with this motor) have a "Huge Smoking Crater" null point with a much larger capacitor, typically above 50 uf for fractional horsepower motors. When the capacitive reactance of the start winding is the same as the inductive reactance of the run winding, a parallel resonance will occur. The current draw on the line cord will be very small, but the current flowing in the windings will be huge. And the overload won't stop it because it's not between the windings where the high current flows. When you are setting one up as a PSC motor you always want to check the current on each winding separately, and both together (line current). If either the run or the start winding separately is drawing more current than the total line current, stop immediately; they should always be less. But the apparent total will be more than the line current. Example: 1.6 A run winding, .65 A start winding, 1.9 on the line cord. This is because they are out of phase, and totally expected. And use good sense. Modern 5 Hp compressors usually have 50 to 80 uf run capacitors. Modern refrigerator compressors usually have 12 to 20 uf run capacitors. If you get results outside of that, reconsider your work. I am totally not trying to scare the crap out of anyone or imply it is dangerous to do so, I'm just hitting the "do not do" points. :-) I plan to make a detailed thread on the process involved, but need to see what size the 1/8 Hp motors like best, make some drawings and photos, etc. As to why "if you can use a cap in this way then why do a lot of motors have a relay or switch to disconnect it?" , let me clarify: I'm talking about a run capacitor. A lot of motors use run capacitors. A start capacitor is a completely different critter. It, like the start winding itself, will fail in a blue flame and a cloud of chemical smoke if you leave it in the circuit for more than a few seconds. They are of a much higher uf value, and draw much higher current. Many motors have both a start capacitor and a run capacitor, leaving only the run capacitor on during run time. This particular CK monitor had a start capacitor as original equipment, the original one failed decades ago and I replaced it then. Most air conditioner compressors are PSC motors, they only have start capacitors and relays if there's a hard starting issue. Most refrigerator compressors have start relays of some sort because most refrigerator compressors don't have a compression release, which was G.E.'s brilliant answer to using float valves, which would not equalize and would be very hard to start the compressor otherwise. All the float valve machines have a compression release and start under no load, so start very easily as a PSC motor. Also please understand that I am not referring to the DR machines, some of which use a complicated arrangement of resistors, multi-tap transformers, capacitors, chokes, to manage the starting current. One day, I may bravely go where no man has gone before, and see about simplifying the start controls on one of those. But I haven't found a compelling reason to do so yet. Thank you for sharing your knowledge of using run capacitors on these and how to size them. Great info to know. I assumed that the stator or rotor would be different on a psc motor and it might not be possible to use a run cap unless the motor was designed for it.
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Post by blackhorse on Sept 30, 2014 21:46:08 GMT
The rotors are pretty equivalent, as long as they are induction-start, induction-run (not wire-wound).
The stators can be fairly different, the biggest differences are rather poor motors where the manufacturer has gone a bit overboard with the very-few-turns of very-thin-wire to keep enough resistance for 110v. There are some aluminum-wound motors that have such thin start windings that they will corrode through on long exposure to sunlight. Biodegradable, I guess you would say. If you try them as PSC, they will take a looong time to get off the dime and come up to speed. Long enough to drop out the overload, even. If loss of the switch mechanism makes it very desirable to use them as PSC, the problem can be solved by putting a PTC start relay across the capacitor terminals. And PSC fan motors, which are meant to have a boatload of slip, even different speeds of slip by using taps that draw less current.
Most motors of fairly high Q factor will work nicely as PSC motors. ("Q" is a measure of relative inductance to resistance, related directly to efficiency.) Compressors tend to be very high Q motors because excessive heat build-up is hard to get rid of inside the shell. Compressor motors will slip less and run just a bit faster with a run capacitor, closer to their synchronous speed (1800 RPM for 4-pole motors) with the additional torque the start winding phase shift provides, which is why the run winding draws less current. The motor will run cooler as well; on compressors that run long cycles, long enough to get hot, I have observed a 15 to 20 degree F drop in shell temperature after adding a run capacitor.
Conversely, motors that run PSC with a start relay will draw more current and run hotter if the run capacitor goes open. They will draw very heavy current and cycle on overload if the capacitor shorts.
Which is why I would suggest you always incorporate an overload with your PSC conversion; some of our machines have been altered over the years and may not have a working overload. I'm not real sure of the calibration on those solder-pot overloads anyway, after all these years. I used a Klixon rated at 10 LRA. Very helpfully, that was the only rating given. I bench-tested it at various currents, it held indefinitely at 3 amps, and dropped out in 3 1/2 minutes at 4 1/2 amps. (My 1/6 Hp CK is rated 3.3 to 5.3 amps).
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Post by Claire Schend on Oct 12, 2014 11:30:34 GMT
I have a 1940s-1950s GE refrigerator I am redoing. I am at the electrical part and figured out quickly, it needs new wiring and relay box. I have a CR. 1057-RIA RELAY G.5 CAT M1A162, V. 110, CYC. 50/60 HP 1/8 AMP 3.2. The compressor works fine. I am not an electrician but was wondering if the relay, overload and new electrical cords you used would work for mine so I can follow your instructions??
thanks
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Post by coldspaces on Oct 12, 2014 13:38:13 GMT
I have a 1940s-1950s GE refrigerator I am redoing. I am at the electrical part and figured out quickly, it needs new wiring and relay box. I have a CR. 1057-RIA RELAY G.5 CAT M1A162, V. 110, CYC. 50/60 HP 1/8 AMP 3.2. The compressor works fine. I am not an electrician but was wondering if the relay, overload and new electrical cords you used would work for mine so I can follow your instructions?? thanks Your relay is the exact same part number as the one I show in the first pic in this thread. The 3.2 amp rated relay was a popular one. You should be good using the same parts and procedures as I did.
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Post by cablehack on Oct 13, 2014 0:34:13 GMT
I have a 1940s-1950s GE refrigerator I am redoing. I am at the electrical part and figured out quickly, it needs new wiring and relay box. I have a CR. 1057-RIA RELAY G.5 CAT M1A162, V. 110, CYC. 50/60 HP 1/8 AMP 3.2. The compressor works fine. I am not an electrician but was wondering if the relay, overload and new electrical cords you used would work for mine so I can follow your instructions?? thanks Just curious what kind of fridge - can you post a pic? By the sounds of it it's possibly a Flatop or one of the post war models like a Spacemaker. Either way, doing the rewire will be easier than a Monitor Top. The CR1057 relay was a GE favourite, lasting many years on many models.
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Post by learney on Sept 19, 2016 19:18:51 GMT
I have 1949 ge frig. the relay got wet and corroded in our last flood. is there a replacement?
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Post by coldspaces on Sept 19, 2016 19:24:05 GMT
I have 1949 ge frig. the relay got wet and corroded in our last flood. is there a replacement? The Supco Ro81 solid state relay is the easiest to use.
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RAUL -Santiago Chile
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Post by RAUL -Santiago Chile on Aug 23, 2018 21:40:00 GMT
My ancle have GE refrigerator model 1955 she bought in USA when studied there. After 60 years fail the relay CR1057-R48 during storm afect the utility network. Is possible obtain this spare part (used) or suggest replace for connect start winding the compressor motor? my email is servingen@gmail.com
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Post by coldspaces on Aug 24, 2018 1:16:59 GMT
My ancle have GE refrigerator model 1955 she bought in USA when studied there. After 60 years fail the relay CR1057-R48 during storm afect the utility network. Is possible obtain this spare part (used) or suggest replace for connect start winding the compressor motor? my email is servingen@gmail.com Do you know the model # of the refrigerator? Most likely you will have to use a solid state relay but get me the model# and I will search some more.
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Post by coldspaces on Jan 14, 2020 23:23:54 GMT
This one took too long but all the pics that Photobucket blurred have been re hosted and can be seen again. Except for two videos I need to do still.
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Post by iRdchr on Jun 23, 2020 6:26:58 GMT
Hi there,
I'm a total idiot, and I have one of these fridges with a working relay. I have some questions about rewiring it.
Mainly, should I upgrade to new stuff if the old relay is working? Also, I want to wire in an STC-1000 so I can control the temperature more accurately. Can anyone assist me with this? I can't really get my head around the wires coming from the compressor to the relay or what's coming out of it. I have coming from the compressor : 1 White, 1 Green (not a ground) and 1 Black.
I eliminated the light in the fridge to simplify, especially since I'm using it as a kegerator. If anyone could help me get an idea of what needs to go where so I can not burn down my house that would be incredible.
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Post by cablehack on Jun 25, 2020 1:35:40 GMT
Hi there, I'm a total idiot, and I have one of these fridges with a working relay. I have some questions about rewiring it. Mainly, should I upgrade to new stuff if the old relay is working? Also, I want to wire in an STC-1000 so I can control the temperature more accurately. Can anyone assist me with this? I can't really get my head around the wires coming from the compressor to the relay or what's coming out of it. I have coming from the compressor : 1 White, 1 Green (not a ground) and 1 Black. I eliminated the light in the fridge to simplify, especially since I'm using it as a kegerator. If anyone could help me get an idea of what needs to go where so I can not burn down my house that would be incredible. The compressor has three wires since there are two motor windings; one used for the normal running (green wire), and the other being a start winding (white wire) to bring it up to speed. Black is common. When the compressor is first switched on, the run winding current is very high. The relay senses this, and then switches in the start winding so the motor can come up to normal speed. Once the motor is up to speed, the run winding current drops, and the relay disconnects the start winding. The start winding is not designed for continuous use, so if it's left in circuit all the time it's liable to burn out. I'd suggest having a look at the wiring diagrams in the Scotch Yoke manual to see how it's all connected. Looking at the connections of the STC-1000, you'd connect the 120V supply from the mains to terminals 1 & 2 to power the controller. Terminals 7 & 8 are then connected in series with the 120V to the fridge to switch it on and off.
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