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Post by coldspaces on Aug 17, 2014 18:05:33 GMT
Hey guys. Have checked the power with a power monitor. The service manual says that the average running amp on this model is 2.3amps. From starting up and running it stays around 3.9amp. Shouldn't it start at that then drop down. Sounds not good? That is correct it should drop drown after starting. It may just be that the relay is welding the contacts together at times and not shutting off the start winding. That would make it heat up and should be tripping the overload if it is still working properly. Do you have an amp meter that clamps around the wire? If so placing it around the wire to the start winging would let you see that the relay is sticking on. No power should flow through the start winding after the compressor starts.
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Post by cablehack on Aug 17, 2014 23:49:08 GMT
What are you measuring the current with, and where in the circuit? 240V or 110V? 3.9A at 240V would have cooked your transformer by now, so I assume it's on the 110V side you've measured it. I would expect the compressor motor to be under considerable stress if that were the case. If it really is drawing 3.9A@110V, my first thought is the start relay contacts are stuck. It might be worthwhile to open the relay box and see that the contacts are closing and opening at start up. Make sure you don't apply pressure to them; just do a visual inspection. As Coldspaces says, there should be no current in the start winding once the motor is up to speed (within a couple of seconds). Personally I just find power readings much more meaningful than current when dealing with fridges. The current reading is affected by power factor. If you're using a plug in power meter, then I presume you're measuring on the 240V side. The wattage measured here should be under 220W, less with a well designed transformer. I've tried transformers which waste anything from 6 to 40W of magnetising power. As I've only got CA measurements to go on (which should be similar as both are 1/8hp), typically, the consumption might drop about 10W within a minute.
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Post by karlbrighton on Aug 19, 2014 8:07:09 GMT
Cheers guys. Will do some further checks in the next few days. Used the power monitor before the transformer at 240v. No wonder the transformer gets hot.
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Post by ChrisJ on Aug 19, 2014 13:37:27 GMT
936 watts! Ouch.
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Post by cablehack on Aug 19, 2014 23:24:05 GMT
Ouch indeed! That would imply nearly 8A on the 110V side and a rapid burn out of the motor. Just to explain this, the wattage of a 110V appliance remains the same whether you use it directly on 110V, or 240V via a transformer. (There are some transformer losses but they are small enough to be ignored for the purposes of explaining this). The current is another story. For any given power, the current decreases as you increase the voltage. Take for example, a 120V lamp rated at 240W. Plugged into a U.S. power point, it would draw 2A. Plugged into a 240V socket via a transformer, it would draw 1A. The power is the same, but the current is less. So, if you're measuring current on the 240V side, you should be getting a reading of about half that of the 110V specification. Something in the region of 1.1A @ 240V. I'm wondering if the transformer is wired correctly. Is it an auto transformer or a double wound type? What power does the transformer draw when the 110V side is disconnected? There's some major problem here and we need to be careful your motor doesn't get burnt out.
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Post by cablehack on Aug 20, 2014 23:24:51 GMT
Just for the record, I looked at my CA-2 current this morning using my 240V plug in power meter: volts 235, current 1.45A, power factor 52, watts 176.
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Post by karlbrighton on Aug 21, 2014 7:50:11 GMT
Cheers guys. Have checked power. Watts 920 volts 245 Amp 4.1 power factor 90. Top section of the R relay gets red hot. Only left on for a minute. Motor sounds smooth. So hope no damage has been caused to the motor. Gut feeling is that it's the relay. Waiting for a mate to help. Knows more about electrics than my basic knowledge. Thinking of ordering an RO81 relay. Unless there's something better?
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Post by cablehack on Aug 21, 2014 23:27:49 GMT
Thanks for that most useful information. There's definitely a real fault. From what you're describing, my impressions are that either the transformer is wired incorrectly and putting excessive voltage into the fridge, or the relay contacts are stuck together (sounds a bit more likely given the power factor of 90). Don't be tricked by apparently smooth running of the motor. There was a guy about 18 months ago with a Flatop that was missing the relay altogether. He found it ran smoothly with just the start winding in circuit, and the fridge even got cold. By the next day the motor had burnt out, so that was the end of it. It is most important not to run the motor for more than a couple of seconds until the fault has been located. An RO81 is the easiest replacement for the type R relay. You'll most likely have to order from a U.S based supplier as it must be for 110-125V use. (The other Aussie member here, rambler64, got one from Amazon). Don't use a locally available 240V relay because the motor current is different.
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Post by karlbrighton on Aug 22, 2014 8:17:57 GMT
Have ordered the relay. Shall just have to wait now. Hope this works, really want to save it and restore. Really appreciate the help you guys are giving. Cheers Karl
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Post by karlbrighton on Aug 22, 2014 8:18:20 GMT
Have ordered the relay. Shall just have to wait now. Hope this works, really want to save it and restore. Really appreciate the help you guys are giving. Cheers Karl
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Post by ChrisJ on Aug 22, 2014 10:38:11 GMT
If you're really curious you could just unhook the start wire, touch it to the screw when you turn the unit on and then pull it away. The unit should run normally then.
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Post by coldspaces on Aug 22, 2014 23:57:13 GMT
If you're really curious you could just unhook the start wire, touch it to the screw when you turn the unit on and then pull it away. The unit should run normally then. I have a test cord with a momentary switch in the start wire. It is a great way to see if all you need is a relay. I can't seem to find one like it online to post a link. Mine came from Graingers years ago. They are easily made.
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Post by karlbrighton on Aug 24, 2014 14:55:49 GMT
Hey guys. released the relay to look at the wiring. Looking a bit dry in there. Rigged up the power meter. Switched on, watt 990, released the white wire to the motor. No difference, was still drawing high. Put the wire back, switched on let the start up. Then quickly switched on off on, heard a click in the relay, power dropped immediately, to 210w 185amp 248v pf50. Which looks normal. Compressor motor sounds smooth ran to cold. Compressor lightly warm. It has to be the relay? Looking for to the RO81 now to know for sure.
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Post by coldspaces on Aug 24, 2014 15:02:19 GMT
Sure sounds like it is the relay sticking. Your new relay should get ya working again.
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Post by cablehack on Aug 24, 2014 23:33:48 GMT
Those readings are right on the mark for the kind of transformer you're using. Once you install the RO81 it should stay like that.
It will be interesting to see inside the old relay once you've replaced it. I'm beginning to wonder if it actually does incorporate overload protection. According to the manual it should, but being a UK/US hybrid model it's possible an earlier relay was used. If that's the situation, then it's a prime example of why a modern control should never be put in a pre-war GE without ensuring there is overload protection somewhere else in the circuit. The occasional "missing one knob" monitor top I see on ebay worries me in this regard.
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