Capacitor query

[Coolie]

Does anybody know if a capacitor that has cracked open and has it's di-electic fluid all over the place will cause a single phase condenser fan motor to rotate in the wrong direction?

I've had advise from a few good engineers and even the manufacturer can't decide.
I know that as a rule, single phase motors can only spin one way, that is why I find this most intriguing!

[chillyhamster]

Only single phase shaded ple motors are directional. Single phase with capacitor start will run in the easiest direction, ie if rotating through a draft or airflow from another fan.

[mrchatts]

It's your capacitor that helps the motor start, if you have a week or faulty capacitor the motor will start in any direction or in a direction the blade is turning at the time the motor gets its power.

when you change the capacitor the motor should only run in one direction, switch of power and spin the motor in the opposite direction and switch on while its spinning, the motor should slow, stop and start to spin in the direction when you first changed your capacitor. hope that makes sense lol

if its a large motor then obviously you'll not be able to try the spin start test above.

usually you can only change the rotation of single phase motors by changing the wiring configuration in the motor.

[Coolie]

Thanks guys, I had already ordered the motor and the cap before posting here.when I do the job I'll change the cap first and test it, then send the fan back, and the customer will love me to bits!

[Gary]

The capacitor pushes the motor in the proper direction, and it then takes off and runs in that direction. Without the capacitor, and given no directional push, it will simply lock in place, not knowing which way to go. Given the slightest directional push, e.g. air movement over the fan blade, it will take off and run in whatever direction it is being pushed.

It is highly likely that you will only need to replace the capacitor.

[Coolie]

Well it is the secondary fan on a Daikin VRV condensor. So the negative pressure caused by the primary fan innitialises the incorrect rotation of the fan, so when the fan kicks in it will just continue running that way. The strange thing is that the operating pressure and temps all seem fine to me. It was only by chance that I discovered the incorrect operation. ( I put my notepad on top of the condenser and when the fan kicked in the note pad stayed put, instead of flying off)
So, when the parts arrive, I'll fit only the cap and see the results.

[Gary]

The pressures/temps would be effected to the extent that warm condenser leaving air is recirculated, and the volume of air flowing through the reversed side is greatly reduced. The effects would be most noticeable in very hot weather.

If a large proportion of leaving air is sucked back through the opposite side of the condenser on a hot day, the high side pressure is noticeably elevated. Otherwise, it can go unnoticed, although it reduces system capacity and increases energy usage.

Good catch.

[Gary]

Does anybody know if a capacitor that has cracked open and has it's di-electic fluid all over the place will cause a single phase condenser fan motor to rotate in the wrong direction?

This would not be an accurate statement. It's not that it causes the fan to run in the wrong direction. It is that it no longer causes the fan to run in the right direction. The direction it runs may very well depend on whichever way the wind blows.

[Coolie]

The direction it runs may very well depend on whichever way the wind blows.

It is a Daikin VRV condenser, so it should only run in one direction, ie. discharging the air up, and away! So, no matter which way the wind is blowing it is imperitive that the motor rotate correctly!

[Brian_UK]

Try thinking.. the wind may be blowing up or down through the fan nozzle depending on conditions.

[Peter Mitchell]

If the capacitor that has cracked open and has it's di-electic fluid all over the place then it is most definetly faulty. if the capacitor is faulty then the fan may well run backwards as it is the capacitors function to start the fan motor in the right direction.
with a faulty capacitor the fan will run in the direction it happenes to be turning when switched off. which may be backwards
But a faulty capacitor does not cause the fan to run backwards. the running backwards is a symptom of having a faulty capacitor. a faulty start winding or a broken wire to the start winding or capacitor could also result in a fan running backwards.
If everything was working fine then the fan would have to be wired wrong for the fan to run backwards; but as you have a faulty capacitor.

[Coolie]

Try thinking.. the wind may be blowing up or down through the fan nozzle depending on conditions.

As I have seen in all my experience installing and servicing Daikin units, all the motors run in the same direction and they all discharge the air up-wards, no matter what the conditions are like!
I'm not trying to be picky, but all I'm saying is I now understand what my problem is. The weird thing is, I actually knew everything everybody has posted here, it's just that I tend to forget things that I don't use very often. But once I started reading, It started coming back to me. I supposed that is why this site is such a good thing.
Keep up the good work guys, I know I'll be making use of a lot of the posts here!

[Peter Mitchell]

that is what the fourm is for to exchange information. Most people do know this stuff but have now forgotten and just need a push in the right direction

[Coolie]

Was only the capacitor. As soon as I replaced the capacitor the motor ran the correct way. Thank you everybody

[coolkev]

all these ansers are spot on seen it many times. if cap is open circuit fan generally runs at reduced speed and some over heat and trip int O/L this depends on on motor The effect on operating press depends alot on wether the fans hve a baffle between thn if no baffle effects alot as air from 1 goes strait out other thats y on multi fan units with no baffling i always remove and blank off empty space to allow operating fans to get max flow through coil this is with evap or conds think logically