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Re: 50HZ vs 60HZ #61967 02/09/06 08:40 AM
Joined: Jan 2006
Posts: 9
Afghan Roger Offline OP
Junior Member
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

Work Gear for Electricians and the Trades
Re: 50HZ vs 60HZ #61968 02/09/06 12:12 PM
Joined: Sep 2003
Posts: 649
winnie Offline
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.


Re: 50HZ vs 60HZ #61969 02/09/06 08:46 PM
Joined: Oct 2004
Posts: 135
BobH Offline
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.

Re: 50HZ vs 60HZ #61970 02/09/06 09:48 PM
Joined: Dec 2000
Posts: 4,283
electure Offline
Posted for Afghan Roger

1) Wiring Diagram:

[Linked Image]

2) Fan Motor:

[Linked Image]

3) Condensing unit with covers removed:

[Linked Image]

4)Complete condensing unit:

[Linked Image]

Re: 50HZ vs 60HZ #61971 02/09/06 11:14 PM
Joined: Jul 2004
Posts: 9,485
gfretwell Offline
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.

What is the current on the fan when it is running?

[This message has been edited by gfretwell (edited 02-09-2006).]

Greg Fretwell
Re: 50HZ vs 60HZ #61972 02/09/06 11:29 PM
Joined: Feb 2003
Posts: 939
frenchelectrican Offline
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?)

Re: 50HZ vs 60HZ #61973 02/10/06 10:20 AM
Joined: Jul 2002
Posts: 8,328
Trumpy Offline
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.

Re: 50HZ vs 60HZ #61974 02/10/06 01:41 PM
Joined: Sep 2002
Posts: 1,497
C-H Offline

with an inverter (variable frequency drive) it would have 3-phase motors would it not? (I agree that they should work independently of frequency)

Re: 50HZ vs 60HZ #61975 02/10/06 11:26 PM
Joined: Sep 2005
Posts: 4
marke Offline
Junior Member
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.
Best regards,
Mark Empson |

[This message has been edited by marke (edited 02-10-2006).]

Re: 50HZ vs 60HZ #61976 02/11/06 02:18 AM
Joined: Oct 2004
Posts: 803
mxslick Offline
It would also help this discussion along if Afgan Roger would chime in and tell us what specifically is failing on these units.... [Linked Image]

Stupid should be painful.
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