Motor randomly reversing 1

[enigmapaul]

Hi Folks,

I have a pool heat pump where the fan motor is acting erratically. The fan will engage either clockwise or counterclockwise on different attempts, seemingly at random. Occasionally it will also hum and not turn at all, unless assisted by a screwdriver, in which case it will run in the direction assisted. The motor is supposed to always run CW.

Any ideas what the problem might be?

Thanks!

 

[itsmoked]

If there is a capacitor involved it has failed.

If there is a centrifugal start switch involved it could have failed. That is the standard failure mode of single phase induction motors - the centrifugal start switch.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

It could be a broken shading coil but Keith's suggestion is several thousand time more likely.
I have seen many failed capacitors over the years as well as many failed centrifugal switches and only one broke shading coil.
And further, the broken coil was on a contactor and not a motor and shaded pole motors typically have two shading coils and one should be enough to start a fan in the proper direction, albeit slower than normal.
Follow Keith's advice.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[enigmapaul]

Thanks guys.

The motor is a CF-9622:

https://www.alltemp.ca/product/cf-9622/

Can we tell if that has a centrifugal switch?

I could easily test the capacitor - I think - just by measuring the resistance change, and by verifying the capacitance with a DMM?

Thanks!

 

[EdStainless]

It is easier to just replace capacitors. They get leaky (electrically) and can give you all kinds of odd readings.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[waross]

Permanent Split Capacitor, no centrifugal switch.
With a blown capacitor and a little back draft on the fan, this will start in reverse.
The textbook resistance of a perfect capacitor is infinite, and the resistance of a blown capacitor may be infinite.
But,
When you try to measure the resistance of capacitor with an Ohmmeter, the ohmmeter measuring current charges the capacitor.
The Ohm reading depends on the current in the measuring circuit.
As the capacitor charges, the current drops and the indication goes upscale towards a very high resistance.
Once the capacitor becomes charged, the reading stabilizes at a high resistance value.
If you then reverse the Ohmmeter leads and test again, the meter will initially pin at zero Ohms as the stared charge is dissipated in the ohmmeter circuit. The reading will then drift upscale again.
If you have an analog meter, the moving needle shows this much better than the rolling digits of a digital meter.
If the DMM has a capacitor check function that may work, but I have been disappointed more than once by DMMs that did not have the capacity to check large motor circuit capacitors.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[che12345]

Dear Mr. enigmapaul
1. Capacitor failure is the first (very likely) suspect. Look out for leakage or tank being bloated; but some times without any external physical deformation, (dry out=open circuit) internally.
2. The replacement capacitor may be from any manufacturer, physical shape/size that suits the bracket, metallic or plastic tank.
3. It is important that the replacement capacitor shall be of equal or slightly higher voltage (Vac) and capacitance in (mF) ratings. However, it is (not critical) to be of the [exact value].
4. You may get it from electrical stores or AC workshops. Motor rewinding workshops do not stock them.
Che Kuan Yau (Singapore)

 

[waross]

You need a motor running capacitor, not a motor starting capacitor.
A motor starting capacitor is not suitable for use on a Permanent Split Capacitor motor.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[wde0665]

As a complete aside, brought a chuckle remembering a similar issue with an oven damper system.

The OEM's recommendation was to monitor the damper position feedback against the commanded direction (e.g. open/close) through the SLC500. If going the wrong direction or not going at all, simply interrupt, pause a second or two, then re-engage the movement command. Of course, they didn't provide any code to back up their recommendation, and too expensive to bring their resources in from across the pond, so another opportunity to excel at the rubber-meets-the-road, gitter-dun-or-else plant level.

Well, it worked quite well, but not a solution I would expect from the OEM of the system...

 

[jraef]

The solution that gets you off the phone with them is a good solution from their viewpoint…


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[enigmapaul]

Checking the capacitor in question, yields no reading on a DMM capacitor meter. Also yields infinite resistance instantly and not changing over time, in both directions.

 

[itsmoked]

Sounds completely open failed or shorted failed you don't specify the resistance.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

I'm usually overlooking stuff like this. grin

Also yields infinite resistance instantly

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[itsmoked]

ugh.. I was having an optical migraine at the time.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[edison123]

Since the motor hums but runs once given a push, isn't it a starting cap issue?

Muthu

http://www.edison.co.in