Posted: 7/29/2017 2:33:11 PM EDT
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My Trane outdoor unit is becoming louder and louder upon start-up.
I measured 137.3A in-rush current on the compressor L1 with the condenser fan unplugged. And then I measured 144A on L1 with all components connected. The name plate has the compressor LRA as 109A. It is my understanding that scroll compressors don't need a start capacitor is this true? I replaced the run capacitor 60-mF/5mF. I measured 59mF/5.1mF before replacing. It had corrosion on the top so I replaced it anyways. I also used a brass brush to clean all contacts and terminals to the contactor and run capacitor. I then restarted and I'm now measuring 140A in-rush current on the L1 with all components connected. I believe the compressor is still under it's 10-yr warranty. Would these conditions warrant a replacement under the terms of the warranty? What other information might be needed to satisfy Trane warranty replacement? I was thinking an acid test might be needed. Thanks for any help you can provide. All measurements taken using a Fieldpiece SC660 meter. Outdoor temperature was 91°F dry bulb. Did not get a humidity reading however. Trane outdoor unit information: 4TT3048A1000AA 8302TGH4F Date of manfacture 07/2008 Compressor FLA 20.5A, LRA 109 Compressor information: Alliance Compressors SPA041B1RPA S/N 08GE8534N COM 06918 |
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My Trane outdoor unit is becoming louder and louder upon start-up. I measured 137.3A in-rush current on the compressor L1 with the condenser fan unplugged. did you measure the input voltage at startup? i would be very surprised if the compressor isn't seeing a 30Vac+ drop with the 137A inrush. and maybe that is part of the problem, somewhere there is a high resistance connection. check/tighten everything from the two pole breaker all the way out through the disconnect and into the compressor panel. ps this is why i like going one AWG up (bigger) on compressor circuits... ar-jedi |
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Negative, I did not check the input voltage during start-up. Good advice and will do.
I replaced the disconnect whip back in 2008 before I bought the Trane indoor/outdoor units. I upgraded it to 6/2 wiring from the old 8/2. Is it true that scroll compressors should not need a start capacitor? There is a start-up kit I could buy and install if need be. |
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did you measure the input voltage at startup? i would be very surprised if the compressor isn't seeing a 30Vac+ drop with the 137A inrush. and maybe that is part of the problem, somewhere there is a high resistance connection. check/tighten everything from the two pole breaker all the way out through the disconnect and into the compressor panel. ps this is why i like going one AWG up (bigger) on compressor circuits... ar-jedi |
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A hard start kit on a scroll is fine. In fact, I recommend it. Check the run capacitor too and make sure that's within spec. Also check line voltage and make sure you're not dropping out somewhere.
Does the compressor actually run? What is the amp draw while it's running? 140amps is awful high for startup. If this was my service call, I would be using a megaohm meter and testing the compressor windings. I'm willing to bet there's high resistance shorts in the compressor windings. I'd really be surprised if there wasn't. |
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A hard start kit on a scroll is fine. In fact, I recommend it. Check the run capacitor too and make sure that's within spec. Also check line voltage and make sure you're not dropping out somewhere. Does the compressor actually run? What is the amp draw while it's running? 140amps is awful high for startup. If this was my service call, I would be using a megaohm meter and testing the compressor windings. I'm willing to bet there's high resistance shorts in the compressor windings. I'd really be surprised if there wasn't. So yeah, check voltage, check voltage when starting....THEN....check same voltage readings on both sides of contactor. Next ohm out windings....report back results. Also are they any obvious signs of problems like burnt wires? At least performing all of these checks are exhausting all options before calling it that the compressor is on the way out. |
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A hard start kit on a scroll is fine. In fact, I recommend it. Check the run capacitor too and make sure that's within spec. Also check line voltage and make sure you're not dropping out somewhere. Does the compressor actually run? What is the amp draw while it's running? 140amps is awful high for startup. If this was my service call, I would be using a megaohm meter and testing the compressor windings. I'm willing to bet there's high resistance shorts in the compressor windings. I'd really be surprised if there wasn't. Run capacitor was checked and well within specs (see my first post) but I replaced due to the fact it had rust covering the top, not the terminals, just the top. L1 current while running is 15.6A. I checked the subcooling near the end of the season last year and it was right on the money at 10°F subcooling. |
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I had interesting conversations with Trane warranty support yesterday. The first lady told me my equipment was not registered for warranty coverage and that the equipment only has a 5-yr warranty anyways. She said Trane didn't start the compressor 10-yr warranty until 2011. I disagreed with her, I remember the brochure for the equipment I chose advertised a 10-yr Copeland scroll compressor. And I also used a Trane certified installer who I vetted through Trane and the state licensing before hiring. I told her the installer assured me he took care of the warranty processing after installation.
She then gave me another Trane warranty number to call. The second lady told me Trane didn't require registering equipment for warranty coverage back in 2008. And my compressor and outdoor coil assembly are indeed covered by a 10-yr warranty. She informed me that I can have any licensed HVAC company perform the warranty work, they don't have to be Trane certified. I then asked the conditions under which Trane warrants the compressor replacement and she told me it has to be dead not just on its way out. |
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"I measured 137.3A in-rush current on the compressor L1 with the condenser fan unplugged. And then I measured 144A on L1 with all components connected. The name plate has the compressor LRA as 109A."
"L1 current while running is 15.6A." These numbers do not align at all. A starting current of the size given would be very good for a motor capable of using 109 A at full load. Even higher would not be out of line. The 15.6 running appears way low. Like there is no load on the motor from the actual compressor. How long is the feed? Hard start kits help shorten the start time. They provide more phase shift to the start winding so it can develop more torque. |
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"I measured 137.3A in-rush current on the compressor L1 with the condenser fan unplugged. And then I measured 144A on L1 with all components connected. The name plate has the compressor LRA as 109A." "L1 current while running is 15.6A." These numbers do not align at all. A starting current of the size given would be very good for a motor capable of using 109 A at full load. Even higher would not be out of line. The 15.6 running appears way low. Like there is no load on the motor from the actual compressor. How long is the feed? Hard start kits help shorten the start time. They provide more phase shift to the start winding so it can develop more torque. |
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Do you even know what you're talking about? OP stated that RLA was 20.5. 15.6 is perfectly acceptable, plus you have no idea what the actual load on the system is at the time OP provided this new info. This can vary due to temperatures, humidity, lots of stuff. RIF. Something is very wrong. |
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"I measured 137.3A in-rush current on the compressor L1 with the condenser fan unplugged. And then I measured 144A on L1 with all components connected. The name plate has the compressor LRA as 109A. " RIF. Something is very wrong. LRA is "Locked Rotor Amps." That's amperage the compressor will draw when it's seized up. If you watch your meter when the compressor try's to start, you'll see a very high amp draw somewhere in the range of the LRA rating on the nameplate. It will usually draw LRA and then trip out on overload. A few minutes later, it will try to start and lock out again. Sometimes installing a hard start kit or using a hermetic analyzer will free it up and get you more life out of the compressor. There is something very wrong with OP's compressor, but not in the sense of what you're explaining. Being a commercial HVAC/refrigeration technician, I've worked on some huge compressors. I've never seen or even heard of a compressor or motor with a RLA/FLA in the 100 amp range. Not saying they're not out there, I've just never seen one. Especially not on a residential unit. It's interesting that OP's compressor actually starts and runs after drawing LRA. OP is either dropping voltage out somewhere or windings are fucked. After changing out the contactor, run cap, and start components, and confirming that you're not dropping voltage somewhere, I would be going after the windings on the compressor. Get all the ohm readings on the windings and test it with a megger. If, after all that, it's still drawing LRA, It shouldn't be too difficult for a tech to be creative and get the compressor replaced under warranty. |
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I ordered an insulation resistance meter a couple of days ago. Should arrive the middle of next week. I'll use it to test out the compressor motor windings. I have still not had a chance to check voltage during start-up or voltage drop across the contactor. I have ordered and received a new contactor.
Which is the best Copeland scroll compressor to replace the Trane one? Emerson's cross reference calls out 8 models for Trane SPA041B1RPA: 1. ZP41K3E-PFJ 2. ZPS40K5E-PFJ 3. ZPS40K5E-PFV 4. ZP42KSE-PFV 5. ZP42K5E-PFJ 6. ZPD42K5E-PFV 7. ZHI14K1P-PFV 8. ZP42K5E-PFE I believe the -PFJ models are the voltage I need. |
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I can call my distributor tomorrow if you want me to. See what they recommend as a replacement. But you'll have to pay for that one. If you want Trane to cover it, it's gotta be an OEM compressor.
As for the voltage, you need 230 single phase. I don't have my Copeland book handy to decode the model numbers. |
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RLA is "rated load amps." That's the nominal amp draw of the compressor while it's running. In my experience, about 80% of RLA is what they draw. If it starts dropping way below 80%, there's less load on the compressor. For example, there may not be enough refrigerant or the compressor has a mechanical failure where it's just free-wheeling. If it starts drawing over RLA, that's usually a problem with the run capacitor or the windings. High resistance shorts in the windings will cause it to draw over RLA, but not trip the breaker immediately. LRA is "Locked Rotor Amps." That's amperage the compressor will draw when it's seized up. If you watch your meter when the compressor try's to start, you'll see a very high amp draw somewhere in the range of the LRA rating on the nameplate. It will usually draw LRA and then trip out on overload. A few minutes later, it will try to start and lock out again. Sometimes installing a hard start kit or using a hermetic analyzer will free it up and get you more life out of the compressor. There is something very wrong with OP's compressor, but not in the sense of what you're explaining. Being a commercial HVAC/refrigeration technician, I've worked on some huge compressors. I've never seen or even heard of a compressor or motor with a RLA/FLA in the 100 amp range. Not saying they're not out there, I've just never seen one. Especially not on a residential unit. It's interesting that OP's compressor actually starts and runs after drawing LRA. OP is either dropping voltage out somewhere or windings are fucked. After changing out the contactor, run cap, and start components, and confirming that you're not dropping voltage somewhere, I would be going after the windings on the compressor. Get all the ohm readings on the windings and test it with a megger. If, after all that, it's still drawing LRA, It shouldn't be too difficult for a tech to be creative and get the compressor replaced under warranty. "L1 current while running is 15.6A." These two things do not align. While starting current (around locked rotor current typically) is often a couple times operating current he would appear to be reading 9.2 times. That is a little excessive to say the least. "LRA is "Locked Rotor Amps." That's amperage the compressor will draw when it's seized up." And also when it is starting. The rotor is not 'locked' at startup except by it own momentum and that it has not started to move. Within a few rotations the starting draw has decreased since the now rotating motor is generating its 'back EMF.' While often missing from hermetic refrigeration units larger electric motors have a "kvA per Horsepower with Locked Rotor" code letter associated. This number allows estimating the starting current based on the Horsepower and operating voltage of the motor. This number is used to determine contact ratings in the feed switches and how to enlarge feeders for the starting loads. While the actual load is not known a 230 V, 3 HP motor has an LRA of ~17 amps. Not indicated is the length of the cable run from panel to unit. Both resistance and inductance here can start to cause problems. If they unit has an older massive copper lug type contactor that is not great either. Newer equipment uses a single pole relay with a higher quality contact. Control relays are not disconnects so there is no requirement to open both legs of the 240 V. It can be a PITA to check contact voltages drop under starting load but it ends up being required sometimes. I have a home built setup that allows me to check FOUR junctions at a time and records their voltage. A 4-channel system similar to an oscilloscope. Hook up across each junction, set a trigger level, force a system start, each switch (or junction) has voltage recorded at 1,000,000 samples/second to 12 bits of accuracy. Each input channel can ride at any voltage up to about 2 kV. Everything is protected against over-voltage. It does not have much problem showing contact bounce on mechanical switches. |
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I can call my distributor tomorrow if you want me to. See what they recommend as a replacement. But you'll have to pay for that one. If you want Trane to cover it, it's gotta be an OEM compressor. As for the voltage, you need 230 single phase. I don't have my Copeland book handy to decode the model numbers. Is there a place I can order an acid test kit online? |
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There's some misinformation floating around in the thread, but let's get back to the original subject.
OP, I know you're trying your best at troubleshooting this...don't take this the wrong way but I think you don't have the expertise to properly check the electrical health of the compressor correctly. Even if you are able to confirm for a fact the compressor is shot or very close to letting out the smoke, replacing one is no time for amateur hour. You need expensive and specific tools to accomplish such a job and dealing with refrigerant is a whole different ballgame in itself that doesn't carry over from any sort of electrical knowledge. I'd recommend hiring a trusted contractor to get you through the rest of this. |
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Sure I'd be curious to see how much they cost. A local distributor has the Copeland ZP42K5E-PFJ for $695.00 but they won't sell to me. If the HVAC tech quotes me anything more than that to replace the original compressor under warranty (Trane warranty doesn't cover the cost of diagnosis, labor, and freon) I might try to do the swap myself. Is there a place I can order an acid test kit online? |
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I have a four-channel oscilloscope but no high voltage probes for it. Some are reasonably high but a lot are not suitable for 120 VAC ground float. The individual channel grounds are also not always isolated from each other. That leaves you using two channels per device and subtracting them. This often limits the bandwidth. |
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TexasSmooth, thanks for checking back in. You've given good solid advice.
Now Ar15Texan, I made a couple of phone calls this morning. I called up my local Trane distributor. He wasn't able to see if the compressor is under warranty. I'd have to call Trane corporate and have them look it up. Anyway, you have a 4 ton 410a scroll compressor in the unit. In my market, Rochester NY, the price on the OEM compressor is $974.87 plus freight. I also called my main refrigeration distributor and they looked up a Copeland ZR48K5E-PFV-800 compressor for $562.12. But TexasSmooth is absolutely right. Replacing a compressor is not for amateur hour. I'm not sure what equipment you have or the level of your knowledge, but I'll break it down and explain everything involved. You will need thousands of dollars of tools and equipment, including but not limited to: 410a refrigerant manifold Recovery machine Recovery cylinder Torches with brazing rod(preferably oxy acetylene, but a turbo torch will work) Nitrogen tank with regulator New compressor and start components New filter drier- I'd go with a 163 Sporlan drier Miscellaneous copper tubing and fittings Pipe cutters Vacuum pump with fresh oil Micron gauge Virgin(new) 410a refrigerant Refrigerant scale First you disconnect the power to the unit. As you're recovering the refrigerant from the system, disassemble the unit to get down to the compressor and unhook the electrical. When it's done recovering, unsweat the piping from the compressor, remove the mounting hardware and then remove the compressor from the system. Now would be the time to get an oil sample from the compressor and do an acid test. Mount the new compressor in the unit. With an aftermarket compressor, you'll most likely have to redo some of the piping inside the unit to pipe it in. An OEM compressor would most likely drop right in. Now remove the existing filter drier. Sometimes the factory will have one piped inside the condensing unit. I always remove those and put a straight piece of pipe in there so you can braze in the filter drier on the liquid line outside the unit. Be aware of the orientation of the drier. So now you have the compressor and the filter drier piped in. Time to braze. It's proper to flow nitrogen while brazing to help eliminate any carbon buildup. It doesn't take much to plug up a metering device. Also, if the system was acidic or if there was a burnout, you'd have to pipe in a suction filter too. Now you have the new compressor and filter drier brazed in. Time to pressure test. I like filling the system up to 350 to 400 psi of nitrogen and check all your joints with soap bubbles. If there's any leaks, dump the nitrogen, fix the leaks, and then pressure test again. Leave the nitrogen in for a while and watch for any pressure drops. I like leaving pressure on it over night if I can, but that's not always feasible. While it's under pressure, hook up the electrical and install the new start components. Once you're convinced you're not dropping pressure, it's time to evacuate the system. Dump the nitrogen charge and hook up your vacuum pump with fresh oil. You now have your manifold, vacuum pump, and micron gauge hooked up, turn the pump on and wait. Now is the time to put the unit back together. Bring the vacuum down to 500 microns, valve off your manifold and make sure the vacuum holds for 30 minutes. The rate at which the vacuum rises will determine if you're still leaking somewhere or if you still have non-condensibles in the system. Correct whatever you need to and just make sure your vacuum holds. Once it holds, it's time to charge the system. Valve off your manifold and unhook your pump. Get out your scale and hook up your refrigerant tank. Make sure you bleed your middle charging hose. Since 410a is a blended refrigerant, you must charge the system with liquid by flipping the tank upside down. Now weigh in the factory charge. That will be listed on the tag on the side of the unit. If you can't get it all in at once, you'll have to turn the compressor on continue charging carefully through the low side. Meter it in carefully so you don't slug the compressor. Once the factory charge is in, let it run for a few minutes to stabilize. Look at your pressures and temperatures and adjust the charge according to manufacturer specs. There should be a chart either on the the outdoor unit or in the installation manual. Verify all your pressures, temperatures, superheat, and subcooling. Verify your system voltages and amp draws. And now you're done. Easy peasey!!! Enjoy your air conditioning. Not trying to scare you off, but it's not typical DIY project. It takes years of experience for a technician to get to this point. It's essentially heart replacement surgery for your AC system. And once again, TexasSmooth is correct about the pricing. Figure $1500 -$2000 for a technician to come in an replace a warranty compressor. If this is something you really want to do, then I'd be more than happy to help you. But I would strongly encourage you to hire a professional to do it for you. |
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I appreciate the advice and I'm not trying to excoriate the HVAC technician and his trade. I know enough to be dangerous and to make costly mistakes, I realize that. But once we cross the $2,000 threshold I can buy brand new delivered condenser units via the Internet.
I have quite a few tools already. I would need a recovery machine, recovery cylinder, and R410a gas. And gas for my oxygen/acetylene tanks. I would have to determine how to connect the compressor fittings to the line. It looks like the OEM compressors has couplings at the line connections. I already have: Robinair 2-stage vacuum pump with oil Nitrogen cylinder Low pressure nitrogen valve for purging Robinair 410a manifold set Extech psychrometer with pipe clamp thermocouples Extech anemometer CFS refrigerant scale Digital micron vacuum gauge Fieldpiece SC660 Valve core removers with port and shutoff Snapon leak detector So plenty of equipment to get myself in deep. And I could always try to hire out the system evacuation and save the expense of a recovery machine and cylinder. |
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There's some misinformation floating around in the thread, but let's get back to the original subject. OP, I know you're trying your best at troubleshooting this...don't take this the wrong way but I think you don't have the expertise to properly check the electrical health of the compressor correctly. Even if you are able to confirm for a fact the compressor is shot or very close to letting out the smoke, replacing one is no time for amateur hour. You need expensive and specific tools to accomplish such a job and dealing with refrigerant is a whole different ballgame in itself that doesn't carry over from any sort of electrical knowledge. I'd recommend hiring a trusted contractor to get you through the rest of this. |
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You might be right about that, but why would it be difficult for me to perform an insulation breakdown test on the compressor? It only has three connections. Way back when in the Air Force I would perform insulation breakdown tests on TWT's with a Telsa coil generating up to 100kV. Quoted:
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There's some misinformation floating around in the thread, but let's get back to the original subject. OP, I know you're trying your best at troubleshooting this...don't take this the wrong way but I think you don't have the expertise to properly check the electrical health of the compressor correctly. Even if you are able to confirm for a fact the compressor is shot or very close to letting out the smoke, replacing one is no time for amateur hour. You need expensive and specific tools to accomplish such a job and dealing with refrigerant is a whole different ballgame in itself that doesn't carry over from any sort of electrical knowledge. I'd recommend hiring a trusted contractor to get you through the rest of this. Higher end digital meters can often detect badly leaking coils. Their input impedance is extremely high allowing them to at least indicate lower impedance. My good one is over 100 MOhm. Manufacturers will sometimes share specs but not often with a homeowner. |