Fan on Outside Unit reverses direction when compressor kicks on

Reply

  #1  
Old 05-23-09, 03:26 PM
M
Member
Thread Starter
Join Date: May 2009
Location: Ohio
Posts: 8
Received 0 Votes on 0 Posts
Fan on Outside Unit reverses direction when compressor kicks on

I have a Lennox 12ACB30-4P Value Series manufactured in 1996. It came with the house I bought 3 years ago. The unit never gave me any problem until 1 week ago when it would not cool. The fan would run, but the compressor would not kick in. There was a buzz every 20 seconds or so.

A tech was called based on the sticker on the unit (original installing company, but the residential service was sold, the new company still have service records.)

First tech looked and the wire was disconnected from the capacitor. He replaced it and cleaned it. All was well for 3 days, and there was no cool air again. The buzz returned in an interval of about 1 minute.

Called the company back and argued about cost of having to fix the same problem twice. Second tech came out the same day. The wire was disconnected again. This time, he replaced the capacitor and said the fan is running is reverse and would cost $400 to replace.

I thought I was crazy as I remembered the fan running in the correct direction (counter clockwise with air blowing out the top) before the capacitor was replaced. He left when the air is cool again (60F at the vent). I then turned off the unit by kicking the thermostat high. then waited several minutes.

When I started it again with the thermostat, the fan was running counter-clockwise with air blowing out the top. As soon as I heard the buzz and the compressor properly kicked in, the fan REVERSED itself to run in clockwise direction, with air blowing out the sides. I called the tech back, he said he has no clue and has to research. AFAIK, I do not think either tech has touched the fan itself.

Here are a couple questions:

1) Is it safe to run the AC in this condition? Would the fan motor and/or the compressor be damaged? I do not know if it was always running like this before the capacitor change.

2) Could the wiring on the capacitor be causing this? That is, could the second tech have wired the capacitor wrong?

Thank you. I appreciate any input.
 
  #2  
Old 05-23-09, 08:22 PM
D
Member
Join Date: Aug 2007
Posts: 2,021
Received 0 Votes on 0 Posts
Wire disconnected from the capacitor?? Huh? Do you mean burned off maybe? reversing fan is usually a bad capacitor. Mis wired? -could be. The fan was running before the compressor came on? Carrier used to do that years ago, no one has used that setup for years. Buzz noise? where is that originating from?
 
  #3  
Old 05-24-09, 12:00 AM
M
Member
Thread Starter
Join Date: May 2009
Location: Ohio
Posts: 8
Received 0 Votes on 0 Posts
1) Wire disconnected from the capacitor?? Huh? Do you mean burned off maybe?

I am assuming it is burnt off, the tech did not elaborate.

2) reversing fan is usually a bad capacitor. Mis wired? -could be.

I just found out he did not put in an identical cap (in spec)
OEM: 45-5 MFD 440VAC
Replacement: 45-5 MFD 370VAC

Yes, it uses a dual run capacitor. Would this be the culprit to the strange issue I am having?

3) The fan was running before the compressor came on? Carrier used to do that years ago, no one has used that setup for years.

That's what it did. You are not the first guy puzzled by this. I am going to youtube this for all. Don't know how else to describe it.

4) Buzz noise? where is that originating from?

That was before the cap was replaced. It came from the panel. The contactor was trying to pass on the signal to start the compressor.
 
  #4  
Old 05-24-09, 06:18 AM
D
Member
Join Date: Aug 2007
Posts: 2,021
Received 0 Votes on 0 Posts
Here's the scoop on run capacitors. For replacements, the mfd wants to be the same and the vac the same or [B]greater[B} You never go down on vac but you could replace a 370 vac with a 440 vac, no problem [they only come in 2 flavors, 370 and 440, clarification- motor run caps for hvac units that is]. Why anyone would even stock 370 vac caps on the truck is beyond me. You stock 440's and have all the bases covered. Matter of fact, you stock a multiple capacitor- AmRad Engineering, Inc. - TurboŽ200 Family of Product Flyer They cost a little more but cut down on inventory.

It's possible that the new cap is bad. It's rare to see a fan motor wire burned off at the capacitor, fan motors don't draw enough current to burn wires. Compressor motors are another story. They draw a lot of current, especially when starting. A compressor that has trouble starting could easily burn a wire terminal. You need to take the terminal cover off the side of the compressor and see if the connections in there are ok. I think the compressor is having trouble getting going either due to worn/pitted contactor points or mechanical tightness/bearing wear due to age. Now the problem is compounded by wrong diagnosis. There are hard start kits available for compressors. Often a compressor just needs a boost to start, however there's no gaurantee that it will keep going.
 
  #5  
Old 05-24-09, 07:00 AM
pflor's Avatar
Member
Join Date: Dec 2007
Location: U.S.A.
Posts: 1,127
Received 0 Votes on 0 Posts
Mounty:
The Service Manual from Lennox for the 12ACB line of condensing units calls for a 5-45MFD, 370V for your unit (030), which is a 2.5-ton unit.

I'm not sure where did you get the information for a 5-45MFD, 440V. As per Mfr. Manual, the Tech installed the right cap. Having said that, whether he installed it properly or not is a different story.

Quite ODD a situation here that the fan would spin without the compressor also being up and running. For this unit, the compressor contactor is in charge of turning both (fan and compressor) ON (or OFF) at the same time.

The fan motor is a standard (old fashion) PSC-type motor, so if the capacitor is defective (or miswired), what you report could very well happen, and in a random fashion.

If this unit was ever serviced (prior to you buying this property) and perhaps the original blower motor replaced (as you see, this is all speculation), the problem you are reporting (other than a miswiring) could happen if the fan-blade was removed and installed backwards.

Hope this helps a bit.
 
  #6  
Old 05-24-09, 08:18 PM
M
Member
Thread Starter
Join Date: May 2009
Location: Ohio
Posts: 8
Received 0 Votes on 0 Posts
daddyjohn & pflor the system works fine, that's the strange part. The compressor will start and run, no problem there. The two odd things that I now know are:

1) Fan starts before the compressor if I turn off the compressor and restart it. The thermostat does not have a delay. I don't think if my unit used the older Timed-Off Control (TOC) either. So in theory, the compressor and fan should start and stop together.

2) When the fan does start before the compressor comes on, it spins correctly. When the compressor kicks in, the direction reverses. Someone else suggested start winding, but wouldn't the motor just choose to spin in the correct directly? But this one chooses to reverse itself to run backward everytime.

I am beginning to think there is grounding problem. Maybe this thing was struck by lightning.

I can duplicate the problem, so it's not a one off thing. Also, the company did all the past servicing. This is the first time I have to call them up. But they only have records going back a few years, so I do not know if the fan motor is OEM or one of those universal motor.
 
  #7  
Old 05-25-09, 06:40 AM
D
Member
Join Date: Aug 2007
Posts: 2,021
Received 0 Votes on 0 Posts
You have changed the story a little. If you shut the unit off at the stat and then try for a restart, the compressor will not start until the system pressures have equalized. You had made it sound like the compressor was delaying on an initial start. When the fan and compressor initally start together, does the fan run in the proper direction? The fan motor and capacitor both need to be checked. Cap for proper mfd, motor for an open winding. If you had a grounded winding the circuit breaker should trip, assuming the unit is grounded properly. It doesn't matter if the replacement motor is a universal as long as the specs are right. Lennox is hard for non Lennox servicers to get parts for and Lennox OEM parts are outrageously priced. A motor replacement job that might sell for $350 to $400 with a universal motor could be $600+ using a Lennox OEM motor. Universal motors are used every day with no problems.
 
  #8  
Old 05-25-09, 06:51 AM
pflor's Avatar
Member
Join Date: Dec 2007
Location: U.S.A.
Posts: 1,127
Received 0 Votes on 0 Posts
Originally Posted by Mounty View Post
daddyjohn & pflor the system works fine, that's the strange part. The compressor will start and run, no problem there. The two odd things that I now know are:

1) Fan starts before the compressor if I turn off the compressor and restart it. The thermostat does not have a delay. I don't think if my unit used the older Timed-Off Control (TOC) either. So in theory, the compressor and fan should start and stop together.
That the compressor may have a delayed start if you turn it off and re-start it is not odd, it is normal. And by the way, you should not be doing that, is not good for the compressor motor windings. Compressors have internal components such as an Internal Thermal Overload switch that would prevent them from re-starting right away (to avoid overheating). This is to allow the motor windings to cool-off.

2) When the fan does start before the compressor comes on, it spins correctly....BUT...what is correctly??? you would need to look at the pitch of the fan blades to know what is the correct spinning direction. When the compressor kicks in, the direction reverses. Look for a defective (or miswired) capacitor Someone else suggested start winding, but wouldn't the motor just choose to spin in the correct directly? But this one chooses to reverse itself to run backward everytime.

I am beginning to think there is grounding problem. Possible of course, but not too likely. Maybe this thing was struck by lightning.

I can duplicate the problem, so it's not a one off thing. Also, the company did all the past servicing. This is the first time I have to call them up. But they only have records going back a few years, so I do not know if the fan motor is OEM or one of those universal motor.
How about posting some pictures of the various component, with a good camera, so we can see close-ups of the wiring
 
  #9  
Old 05-25-09, 03:12 PM
M
Member
Thread Starter
Join Date: May 2009
Location: Ohio
Posts: 8
Received 0 Votes on 0 Posts
Originally Posted by daddyjohn View Post
You have changed the story a little. If you shut the unit off at the stat and then try for a restart, the compressor will not start until the system pressures have equalized. You had made it sound like the compressor was delaying on an initial start. When the fan and compressor initally start together, does the fan run in the proper direction? The fan motor and capacitor both need to be checked. Cap for proper mfd, motor for an open winding. If you had a grounded winding the circuit breaker should trip, assuming the unit is grounded properly. It doesn't matter if the replacement motor is a universal as long as the specs are right. Lennox is hard for non Lennox servicers to get parts for and Lennox OEM parts are outrageously priced. A motor replacement job that might sell for $350 to $400 with a universal motor could be $600+ using a Lennox OEM motor. Universal motors are used every day with no problems.
Sorry for not being clear the first time. There was no delay in initial start up. There is a delay in Compressor start up the second time, but the fan will start immediately rotating in the correct counter-clockwise direction with authority (not reduced power).

When the compressor starts, the fan reverses itself. Here is a video:

YouTube - Lennox Fan Motor on Outside AC Unit Reverses Itself

Pay attention to 0:27 is when the fan comes on by itself after I shut the AC off and turn it back on. At 0:43, the compressor kicks on, reversing the fan to blow incorrectly. I apologize for no sound and the slow framerates.

pflor, I am not even going to call myself a DIYer when it comes to high voltage equipment. I don't think I want to take the AC apart. The only thing I verified is taking the side panel out and verify that the wiring from the cap to the contactor, the fan motor and the compressor is correct.

In any regards, I know now what this guy needs to be doing: taking measurements and checking connections and grounding. I don't think he did that.
 
  #10  
Old 05-25-09, 04:27 PM
pflor's Avatar
Member
Join Date: Dec 2007
Location: U.S.A.
Posts: 1,127
Received 0 Votes on 0 Posts
Kuddos, nice video! It got a smile on me from ear to ear.

BTW, I'm not quite sure the fan blade actually is reversing rotation as you suggest. It may just be an optical illusion. Almost like when one watches those old-time western movies and the wheels on the forward moving horse-drawn carriage appear to be spinning backwards, when they actually are not.

The litmus test is that you put your hands on top of the unit, right above the fan grid. If you at all times feel air blasting upwards, the fan is doing the right thing. Go give this a try. Don't let your eyes do the thing, let your hands feel (or not) the blast.
 
  #11  
Old 05-25-09, 05:19 PM
M
Member
Thread Starter
Join Date: May 2009
Location: Ohio
Posts: 8
Received 0 Votes on 0 Posts
Originally Posted by pflor View Post
Kuddos, nice video! It got a smile on me from ear to ear.

BTW, I'm not quite sure the fan blade actually is reversing rotation as you suggest. It may just be an optical illusion. Almost like when one watches those old-time western movies and the wheels on the forward moving horse-drawn carriage appear to be spinning backwards, when they actually are not.

The litmus test is that you put your hands on top of the unit, right above the fan grid. If you at all times feel air blasting upwards, the fan is doing the right thing. Go give this a try. Don't let your eyes do the thing, let your hands feel (or not) the blast.
Thanks. Well, it's a bit hard to tell from the video. It looks fine on my PC, but youtube did something weird to it. The fan in fact reverses direction at 0:27 and 0:43.

At 0:27, it was when the fan was running on its own while the compressor cools (Which, by the way, I only re-create the situation while filming, and maybe once or twice before.)

At 0:43, the compressor kicks in, completely reversing the fan motor.

Looking at the fan blade, they are slightly scalloped (Concave) on the top. So I think it should run counter-clockwise with air blower upward at all time. But it is doing the reverse thing with the compressor on.

Also, the fan runs with authority in both direction, but louder when in reverse.
 
  #12  
Old 05-25-09, 05:44 PM
D
Member
Join Date: Aug 2007
Posts: 2,021
Received 0 Votes on 0 Posts
Yes, looking down from the top rotation of the blade is CCW. Notice how the motor can't seem to make up it's mind which way it wants to go? Either the motor has an open winding or the capacitor is bad or miswired. Easy diagnosis. If a tech can't figure that out, he/she needs to change careers. I like the one who told you he had no clue and had to research. Jeez. My money says the disconnected [probably burnt off] wire was a compressor wire. The fan motor is probably overheating and shutting off which in turn overloads the compressor. When the compressor keeps cycling on it's internal overload, the wiring got HOT and burned off.
 
  #13  
Old 05-31-09, 12:26 PM
M
Member
Thread Starter
Join Date: May 2009
Location: Ohio
Posts: 8
Received 0 Votes on 0 Posts
Originally Posted by daddyjohn View Post
Yes, looking down from the top rotation of the blade is CCW. Notice how the motor can't seem to make up it's mind which way it wants to go? Either the motor has an open winding or the capacitor is bad or miswired. Easy diagnosis. If a tech can't figure that out, he/she needs to change careers. I like the one who told you he had no clue and had to research. Jeez. My money says the disconnected [probably burnt off] wire was a compressor wire. The fan motor is probably overheating and shutting off which in turn overloads the compressor. When the compressor keeps cycling on it's internal overload, the wiring got HOT and burned off.
Well, the thing is that the fan motor never shuts off and leave the compressor running on its own. It comes on and off with the compressor. I created the short cycling for video purpose, and under normal circumstances, there is no short cycling. Anyway, I am looking for a reputable tech in the Cincy area now, and will update if the source of the problem is found. Thank you all for the help and comments.
 
  #14  
Old 06-13-09, 02:11 PM
M
Member
Thread Starter
Join Date: May 2009
Location: Ohio
Posts: 8
Received 0 Votes on 0 Posts
It's fixed with a replacement fan motor. The old motor is OEM and is single direction, meaning it should not have run in reverse. Comparing to the new universal motor, the old motor seems to run very "loose."

No wiring was changed and the new fan runs fine, so the old motor was probably about to fail. I actually still have the old motor, and have no clue what to do with it now. LOL.
 
  #15  
Old 06-21-09, 12:01 AM
M
Member
Thread Starter
Join Date: May 2009
Location: Ohio
Posts: 8
Received 0 Votes on 0 Posts
Thank you so much!

One more post and it is the most important one! I want to thank daddyjohn and pflor in taking the time to help me out here. We have had 90 degree weather these past 2 days, and the AC is doing fine. It sure is good to have air (especially after a trip outside).

So once again, THANK YOU! Beer 4U2
 
  #16  
Old 06-21-09, 05:27 AM
D
Member
Join Date: Aug 2007
Posts: 2,021
Received 0 Votes on 0 Posts
You're welcome. We're happy you cool gain. Take the old motor apart for a look see. I used to teach my students how to specify a replacement motor when the nameplate is gone from the motor. Among other things, you need to know the motor speed which can be ascertained by counting the coils inside the motor. I would also bring failed motors to class and we would take them apart to see if we could figure out why they failed.
 
  #17  
Old 08-21-10, 10:08 PM
J
Member
Join Date: Aug 2010
Location: USA
Posts: 1
Received 0 Votes on 0 Posts
Similar Problem

My Heil A/C unit was running fine and then all of a sudden it quit cooling. The behavior was the following:

1) Turn on the unit.
2) Unit cools house for 30 minutes.
3) Fan on A/C stops turning.
4) Unit blowing warm air and compressor making loud noise.

I called the tech out and he said the motor wires were reversed on the fan motor because it was turning in the wrong direction. He said he fixed the problem, he took my money, and left. 30 minutes after he left, the same pattern as above occurred.

I called the tech back out and he replaced the motor. After after he left, the motor was turning in the correct direction. 24 hours after he replaced the motor, the motor reversed itself and overheated. Now, every time the unit starts, it's running in the reverse direction and will consistently follow the 4 step behavior outlined above.

I have left a call for the tech but I am curious if anyone has any ideas what this might be. It sound like Mounty's problem was fixed with a new motor. Would my tech or rather should my tech have put on a new capacitor with the motor? Is there something else that could be wrong?
 
  #18  
Old 08-25-10, 10:03 AM
Former Member's Avatar
Member
Join Date: May 2006
Location: US
Posts: 786
Received 0 Votes on 0 Posts
single phase motors can start and run backwards with the wrong capacitor. Check that first.
 
  #19  
Old 07-18-11, 10:48 AM
M
Member
Join Date: Apr 2011
Location: USA
Posts: 5
Received 0 Votes on 0 Posts
I have the exact problem. After 2 weeks without A/C, rooms were in 90+ deg, the problem was caused by the incorrecting wiring of the wires to the FAN and COMMON of a dual capacitor. Although, when I replaced the dual cap, I disconnected and reconnected one wire at a time, the fan reversed it rotation when the compressor kicked on. After the two wires swapped positions on the cap, the fan motor (which is an Emerson psc motor model 17435 or just 1743) pulls air from the side to the top. I suppect the wires were wired incorrectly since day one. Hope this helps some one as there are so many theories on the web to explain this.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: