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Post by coldspaces on Feb 14, 2014 4:47:34 GMT
I covered this some in my thread about the N & R relay modernization I did. My 52 International Harvester chest freezer came to me with a bad solid state start relay on it. I have no were to look up what I need by the model # of the box or compressor. If I had the part # off of the original relay that is long gone I might have found it in the Marrs cross reference. I don't even know for sure what the horse power rating of the compressor is. This is how I will determine what to use. First I hooked a test cord to common and run connections on the compressor. Nothing is hooked to the start winding. I then plugged it in long enough to see what the locked rotor amps are of only the run winding. In this case the run winging LRA is 13 amps. Next I hooked up the start winding and started the compressor to check the normal running amps. Right after start up it was drawing 3 amps This tells me that my relay must close the contacts (pick up) at less that 13 amps. It then must open the contacts (drop out) higher than 3 amps. The closest Marrs relays are the 27003 Pick up 6.8 amp drop out 5.8 amp or the 27004 pick up 8.3 amp drop out 7.1 amp. Since I have an NOS Kilxon relay equivalent to the 27004 that will bolt on same as the original that is what I am planning to try. I will let you know how it works.
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Post by cablehack on Feb 14, 2014 22:48:57 GMT
Those figures seem to be close to those of a 1/8HP GE compressor. I can't find which manual it was in, but the LRA was also quoted as 13A. Drop out currents listed in the Scotch Yoke manual aren't too far off either.
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Post by coldspaces on Feb 15, 2014 2:15:57 GMT
Those figures seem to be close to those of a 1/8HP GE compressor. I can't find which manual it was in, but the LRA was also quoted as 13A. Drop out currents listed in the Scotch Yoke manual aren't too far off either. Interesting, I tried the equivalent relay to the Marrs 27004 last night and it picks up and engages the start winding but does not drop out. I don't have the 27003 on hand but do have a 27002 ( same one I have used on the 1/8 hp in the 38 flat top). I will be trying it next to see how it works. This freezer is only 7 cu ft so it may only be an 1/8 HP. By the way it uses R-22 so could be higher amp draw that an R-12 unit? Coldspaces
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Post by cablehack on Feb 15, 2014 2:36:28 GMT
Sounds very plausible. I just assumed it was R12.
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Post by coldspaces on Feb 17, 2014 4:16:13 GMT
Well The 27002 Marrs relay did just as I thought. Its drop out amps are too low, it will engage the start winding but does not drop it out properly. I really thought the first relay I tried was going to work. It is old stock that I am pretty sure is new,but could be faulty. I will be ordering the Mars 27003 & 27004 and trying them next.
Coldspaces
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Post by coldspaces on Feb 20, 2014 5:47:00 GMT
Those figures seem to be close to those of a 1/8HP GE compressor. I can't find which manual it was in, but the LRA was also quoted as 13A. Drop out currents listed in the Scotch Yoke manual aren't too far off either. Interesting, I tried the equivalent relay to the Marrs 27004 last night and it picks up and engages the start winding but does not drop out. I don't have the 27003 on hand but do have a 27002 ( same one I have used on the 1/8 hp in the 38 flat top). I will be trying it next to see how it works. This freezer is only 7 cu ft so it may only be an 1/8 HP. By the way it uses R-22 so could be higher amp draw that an R-12 unit? Coldspaces Realized tonight that you must be taking about LRA of the 1/8HP GE compressor with the run and start winding both energized. On my 38 flat top I believe the run winding by itself only drew about 8 amps. Considerably less than the 13 amps of this compressors run winding. Anyway I tried a Marrs 27003 tonight and it would also pick up and energize the start winding but did not drop out. The 27004 how ever works great,it starts and runs just like it should. The old NOS relay I tried first can be replaced by the 27004 per Marrs cross reference but it did not drop out,don't know it original drop out spec though. Looks like the pick up needs to be at least 2/3-3/4 of the run winding's LRA and drop out should be approximately double the RLA. Coldspaces
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