50HZ compressor on a 60HZ circuit

[dan wong]

What happen if a compressor rated as 50HZ 230vac were hook up to a 60Hz 208/230vac.

does it run slower? faster?, overheat? loss effiecency?, gain efficency? or does it matter... no problem at all?

I never done it, but always wonder what would happen.

[Dan]

I believe faster and with higher amperage. Most likely hotter. If you had a 230/50 compressor hooked up to 200/60, you would run faster but not hotter, which leads me to believe that there would be about the same wattage in the latter case and a higher wattage in the former. These are just guesses. I don't know what the behavior would be with capacitor run motors, for example.

Dan

[karelsdr]

I am from Canada and once on a European fishing trawler I had to install a 3 phase motor I believe it was 60 hp. It ran faster. The compressor was running above the engineered specs for rpm for the compressor(Sabroe).To compensate I used a smaller pulley on the motor.On a hermetic the compressor will run faster as well so the compressor discharge temp will be higher so it could be trouble for the oil carboning up and breaking down.

[Robearbam]

I deal with a lot of overseas equipment here in the US. The newer equipment is 60 hz. The 3 phase 50 hz stuff I have successfully used, however, I was told a very long time ago as long as the use was not continous I wouldn't have a heat problem.

[RAC'ers 98]

Good Day SIr!

Its one of my problem here... But it goes by a Cascaded Syatem using R-404A and R-23. Its a Thermal Shock (Temp. Cycle) machine came from Malaysia at 50Hz and was transferred here in the Philippines and we are operating at 60Hz. At running condition, compressor stop intermittently with an erratic pressure readings. Though it run, still, it couldn't reach the required Temperature Specs of -65 deg. C... Please help what should I need to do...

Thanks in advance,
Rac'ers 98

[ernestlin]

Hi, wong. As I know, some of the compressors can work well at either 50Hz or 60Hz, and the discharge/capacity will be increased of 20%. U can ask the manufacturer about this question.
RAC'ers 98, ur issue could be due to the increase of discharge. the cascade system may need redesign.

[RAC'ers 98]

Thanks Sir!
Would it be helpful if I will only replace the 50Hz compressor with 60Hz rated frequency? Do you think it will solve the issue or I need to redesign the whole cascade system???
Appreciate all the help... and thanks in advance...

[Peter_1]

What do you mean with erratic pressure readings?
LP or Hp and on what side?

We need a lot more of information to help you.
Give us numbers: SH, SC, LP, HP, discharge temperatures and this of both stages.

A cascade system is a very well balanced system which can't be changed very much.
Changing to 60 Hz is in increase of +/- 20%.

[ernestlin]

Thanks Sir!
Would it be helpful if I will only replace with the 50Hz compressor with 60Hz rated frequency? Do you think it will solve the issue or I need to redesign the whole cascade system???
Appreciate all the help... and thanks in advance...
Hi, RAC'ers 98, you're welcome, I consider it's a short cut to replace 60Hz compressors which have the same capacity of these 50Hz ones. If not, the whole system would be redesigned.

[Cofreth]

A 60 hz equipment can run on a 50Hz, but a 50hz equipment cannot run on a 60hz, motor will produce extra heat, thus shorten the life of motor.

[frank]

A 60 hz equipment can run on a 50Hz, but a 50hz equipment cannot run on a 60hz, motor will produce extra heat, thus shorten the life of motor.
Using the fan speed formula
RPM = [[frequency x 60]/pole pairs] - friction factor (4% normally)
we can see that a 50hz, 4 pole motor driven by 50hz would give a speed of
[[50 x 60]/2] - 4% = 1440RPM

Now, if the same motor was driven by 60hz you would get
[[60 x 60]/2] -4% = 1728 RPM, an increase of 20%. This increase will lead to additional current draw and heat being generated which will decrease the life of the motor.

[RAC'ers 98]

What do you mean with erratic pressure readings?
LP or Hp and on what side?

We need a lot more of information to help you.
Give us numbers: SH, SC, LP, HP, discharge temperatures and this of both stages.

A cascade system is a very well balanced system which can't be changed very much.
Changing to 60 Hz is in increase of +/- 20%.


Good Day Sir Peter,

My apology for a lacking info...

Erratic Pressure reading means for me that the gauge display or the pointer movement is not normal. Its a kind where the gauge hand looks like vibrating and its not pointing on an exact pressure value. Anyway, I will try to get all recorded data the ASAP and will get back here for a discussion with your great support likewise.

Thanks also for the rest of the advisers... Sir Ernestlin, Sir Frank and Sir Cofreth... APPRECIATE ALL YOUR HELP...

Regards,
Rac'ers 98

[frank]

Erratic Pressure reading means for me that the gauge display or the pointer movement is not normal. Its a kind where the gauge hand looks like vibrating and its not pointing on an exact pressure value.

This is where the gauge is reading the compressor pulsations. Get a set of damped gauges to stop it.

[dan wong]

Using the fan speed formula
RPM = [[frequency x 60]/pole pairs] - friction factor (4% normally)
we can see that a 50hz, 4 pole motor driven by 50hz would give a speed of
[[50 x 60]/2] - 4% = 1440RPM

Now, if the same motor was driven by 60hz you would get
[[60 x 60]/2] -4% = 1728 RPM, an increase of 20%. This increase will lead to additional current draw and heat being generated which will decrease the life of the motor.

Very Interesting, I am surprise Counter EMF does not come into play.

[kiwireeferman]

I have fitted a number of 50hz fractional compressors into a 60hz situation. (Embraco and Copeland) I have always downsized the compressor to what was originally fitted. Had one failure so far. I don't have a choice about this as there are no 60hz compressors in the country.
Just goes to show that the internals of a motor-compressor are very forgiving!

[The MG Pony]

What does Nz run on? and why are 60Hz scarce?

[Peter_1]

Now, if the same motor was driven by 60hz you would get
[[60 x 60]/2] -4% = 1728 RPM, an increase of 20%. This increase will lead to additional current draw and heat being generated which will decrease the life of the motor.
Frank is right , the speed will increase proportional with the frequency.
But a higher speed of the compressor with the same evaporator connected to it will result in a lower suction pressure, so a reduced motor current which will balance the higher speed.
Is this statement correct? This is some sort of a brainteaser.

[US Iceman]

Peter,

I think you are going in the right direction with your logic.

If the compressor speed increases, it's displacement increases too. That would result in a lower suction pressure and a higher TD to increase the coil capacity to cause a re-balance.

[kiwireeferman]

What does Nz run on? and why are 60Hz scarce?

New Zealand is 230V 50Hz or three phase 400V.
The reason for the 60Hz application is a ferry I look after.
I was asked to fit A/C to two theaters on this ship.
I asked many people what would happen when a 400V 50Hz inverter machine was connected to 60Hz.
"Motor would burn out" / "electronics would not be able to control the temperature" etc.
Finally two knowledgeable people said "no problem"
They were correct, this system has worked A1 since installation.

[Flimsical]

Most 3 phase motors nowadays come rated for both, however, you could always buy a little vfd and knock the freq back down to 50 if 60 is too fast.