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Joined: Jan 2006
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I am stuck with 208V, 3 Phase, 4 wire WYE.
I do know that voltage and HZ is not what is needed but one of the strange things is that some of the units have been in service for 6+ months and are working fine, and some others are failing over a few days/weeks.
I sent in some pictures of the units, hope they get posted.
Thanks, Roger
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Joined: Sep 2003
Posts: 650
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At some level we are all grasping at straws here. You are unfortunately in a situation where you need to make do with equipment that is being applied outside of its specification range.
It may simply be luck that some units work and others don't.
Perhaps the difference between the units that work well and the units that fail is the cycle time on the thermostat.
When an air conditioner first starts up, all of the Freon is at the same pressure throughout the system. The compressor starts and builds up the pressure difference that makes the system work. Once the compressor stops, the pressure bleeds back down to equilibrium.
If you try to _restart_ the compressor while there is still a pressure differential, the motor has to start against a significant load.
Combine this with the low voltage and excessive frequency, and the compressor motor might simply stall.
Perhaps some of the thermostats are cycling off and on too frequently.
-Jon
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Joined: Oct 2004
Posts: 135
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I for one would like to know what exactly is failing? I assume the compressors. There are a few reasons compressors fail, poor installation and charging mistakes are one big reason. Has the superheat at the compressors been checked, if so what is it? What about the sub-cooling? Delta T? Low voltage is never a good thing for ac compressors. Maybe a buck/boost transformer would be warranted here or you may try and see if some hard start capacitor kits would help. The hard start cap will help a compressor start that is either suffering from excessive vd or starting to fail. Obviously, keeping the condensor coil and evap. coil clean is necessary as well as other basics. I doubt the hertz issue is causing your problem, undervoltage much more likely as well as poor installation practices.
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Joined: Dec 2000
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Posted for Afghan Roger1) Wiring Diagram: 2) Fan Motor: 3) Condensing unit with covers removed: 4)Complete condensing unit:
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Joined: Jul 2004
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Since you posted the condenser fan pix I am guessing that is what is going. I put my money on the fan blade having too much pitch. The blade is matched to the motor ... at it's rated speed. If you are running 20% over speed, the blade is working beyond the design load. Try the next lowest pitched fan blade, maybe two sized down it it is close.
e; What is the current on the fan when it is running?
[This message has been edited by gfretwell (edited 02-09-2006).]
Greg Fretwell
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Joined: Feb 2003
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i quickly relized that when i did see the nameplate i say to myself oh oh 208 v 60Hz dont work with this unit at all one thing the relay might not able to pull in right and second thing you will blow the capaictor during starting cycle due low voltage and wrong HZ too that why it keep blowing out the other way is readjust the genny from 1800 rpm to 1500 rpm and change voltage connection go with hi volt 'wye ' connection the voltage between line and netural will fall to right spot after fine tuning the regulator [ i am oringally from France so i know this system pretty well ] the same with fan motor too it will affect it too
Merci, Marc
Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)
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Joined: Jul 2002
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Hi Roger, I've done quite a bit of Air Con work in my time. Mainly with the Carrier systems. Sure the fans will run slower as will the compressor, but considering that the compressor motor is immersed in refrigeration oil cooling won't be a problem. Derating will be an issue though, by this I mean it will have a lesser range of heating or cooling. I was under the impression that the newer A/C units with the inverter technology could withstand a 20% difference in frequency with all the fans on the indoor (Condensor) and the Outdoor (Evaporator) units using DC motors.
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Joined: Sep 2002
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Mike,
with an inverter (variable frequency drive) it would have 3-phase motors would it not? (I agree that they should work independently of frequency)
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Joined: Sep 2005
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You can run 50Hz motors on 60 Hz provided that you keep the V/Hz ratio the same. If you increase the frequency, you must increase the voltage by the same ratio. In your case, 230/50 = 4.6 Therefore at 60Hz, you voltage should be 60 x 4.6 = 276. If you operate at a lower voltage, the flux in the iron will be reduced and the maximum power of the motor wil also be reduced. You must also be careful that the increase in speed does not overload the motor. With a pan or a pump, a small increase in speed can give a large increase in power. see http://www.lmphotonics.com/faq/faq_qanda.php?id=12 Best regards, Mark Empson http://www.LMPhotonics.com | http://www.LMPForum.com [This message has been edited by marke (edited 02-10-2006).]
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Joined: Oct 2004
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It would also help this discussion along if Afgan Roger would chime in and tell us what specifically is failing on these units....
Stupid should be painful.
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Joined: July 2013
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