Heat Pump Outdoor Fan Spin Backwards And The Unit Freezes In Extreme Cold Weather - HVAC - DIY Chatroom Home Improvement Forum
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Old 03-20-2017, 09:04 AM   #1
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Heat pump outdoor fan spin backwards and the unit freezes in extreme cold weather


usually below 30 degrees. once it gets, lets say above 40 degrees, the fan will start spinning correctly and the ice goes away.

the temp inside the house is fine - where it supposed to be; however, in this condition, the unit don't usually stops.

I checked the capacitor and it is fine.

besides the outdoor fan, what else could be causing this problem?

Lennox model #: 13HPP36AP-1A
serial #: 1613D18801

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Old 03-20-2017, 09:35 AM   #2
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Re: Heat pump outdoor fan spin backwards and the unit freezes in extreme cold weather


Does it go into defrost mode ?

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Old 03-20-2017, 12:51 PM   #3
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Re: Heat pump outdoor fan spin backwards and the unit freezes in extreme cold weather


The motor shouldn't be running at all during defrost mode. If it's always spinning backwards during this time, there's something wrong with it. If you're sure that the cap is good, then that only leaves the motor.

To be sure, you'd need a multimeter, and be comfortable working with electricity.

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Old 03-20-2017, 12:56 PM   #4
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Re: Heat pump outdoor fan spin backwards and the unit freezes in extreme cold weather


Does it go into defrost mode ? Yes i have seen it. i even changed the defrost cycle from 2 hours to 1 hour by moving the jumper on the defrost board.


I do not think that the fan spins while in defrost mode.
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Old 03-20-2017, 02:40 PM   #5
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Re: Heat pump outdoor fan spin backwards and the unit freezes in extreme cold weather


When the fan runs " backwards " is the coil frosted up ? How did you determine the fan was running backwards ?
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Old 03-20-2017, 03:57 PM   #6
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Re: Heat pump outdoor fan spin backwards and the unit freezes in extreme cold weather


- When the fan runs " backwards " is the coil frosted up? Yes

- How did you determine the fan was running backwards ? the fan sucks air instead of blowing.

at my house right now it went up to around 60 degrees. I just tested and everything is working as it should. the outside fan is blowing air instead of sucking air.
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Old 03-20-2017, 05:55 PM   #7
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Re: Heat pump outdoor fan spin backwards and the unit freezes in extreme cold weather


The motor is likely failing. (start windings are toast)

How did you test the cap?

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Old 03-20-2017, 06:33 PM   #8
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Re: Heat pump outdoor fan spin backwards and the unit freezes in extreme cold weather


- The motor is likely failing. (start windings are toast)
the fan motor? but how it only does it when is is around below 30 degrees?

- How did you test the cap?

with a meter.
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Old 03-20-2017, 11:09 PM   #9
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Re: Heat pump outdoor fan spin backwards and the unit freezes in extreme cold weather


Quote:
Originally Posted by form8829 View Post
- ... but how it only does it when is is around below 30 degrees?
...
Coincidence. Wind direction helps to get it started in either direction when the start windings aren't working.

Quote:
Originally Posted by form8829 View Post
...
with a meter.
A meter with a capacitance setting or only with resistance. (the latter is common with DIY's even if it's not particularly helpful.) What was the reading? What is the rating?

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Old 03-21-2017, 07:42 AM   #10
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Re: Heat pump outdoor fan spin backwards and the unit freezes in extreme cold weather


Lennox was having icing issues on heat pump fan blades. They have played with different logic in their defrost boards to address this. Some units will cycle the OD Fan if it sits idle for a period, to force it to shed water/ice.

They have a patent on reversing the airflow as well, US Patent 20080190131. Google it and read, shuts off fan like normal in defrost, but runs it in reverse sometimes too.
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Old 03-22-2017, 04:17 PM   #11
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Re: Heat pump outdoor fan spin backwards and the unit freezes in extreme cold weather


Done That, so you are saying that this is supposed to be normal operation of the machine in heat mode? running the outside fan backwards in heat mode?

but if that's the case, why is it that it get icy? it does not supposed to get icy right?
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Old 03-22-2017, 06:05 PM   #12
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Re: Heat pump outdoor fan spin backwards and the unit freezes in extreme cold weather


From: http://www.hannabery.com/faq1.shtml

Heat pumps can ice-up during the winter time. And it is normal for the entire coil to be covered in a white frost, even light ice, during certain weather conditions. But it is not normal for the entire unit to be encased in ice; including the top of the unit and the insides of the coil for an extended period of time.
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Old 03-22-2017, 07:57 PM   #13
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Re: Heat pump outdoor fan spin backwards and the unit freezes in extreme cold weather


supers05

so do you think that the motor start windings are messed up?

the capacitor ratings are 45+7.5 uF+10/-5%

i got exactly 45+7.5 uF readings of the capacitor.
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Old 03-22-2017, 08:04 PM   #14
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Re: Heat pump outdoor fan spin backwards and the unit freezes in extreme cold weather


i will say mine usually looks like the firs picture in the given link. again, only when it gets below around 30 degrees.
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Old 03-23-2017, 04:04 AM   #15
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Re: Heat pump outdoor fan spin backwards and the unit freezes in extreme cold weather


Quote:
Originally Posted by form8829 View Post
i will say mine usually looks like the firs picture in the given link. again, only when it gets below around 30 degrees.
Then it definitely has a problem.

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