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Old 04-19-2020, 08:20 PM   #1
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Proper fan blade ass'y height in shroud of an old package unit AC only.


"In many cases the blade/shroud are designed so that the middle/center of the blade matches up with the bottom of the fan shroud (cowling) and if it isn’t it can decrease airflow."
https://www.hvacrschool.com/fan-blade-shroud-depth/

Agree?

What causes air flow to go horizontal out of the grill, besides a plugged condenser coil? (not fan running backwards) Can one fan blade bent up a bit higher than the others cause this?

On this unit (pic), fan blade puller would not work, after sanding shaft, penetrating oil, and whatever else I might be forgetting. Hub was apparently too soft. Maybe because this is an old Lear Siegler package unit AC only, and the hub has gone soft from excessive oxidation? The holding screws at bottom of puller put dents in the hub.

Also watched video with tech drilling a hole in top of motor shaft to relieve pressure against hub at top of shaft. Tried that, but no help.

Heat, then ice (3 applications) worked for me previously on other units when puller wouldn't.
Tried knocking motor shaft out of hub with 3-lb. hammer. Watched a video where tech used knockout-type puller, similar puller, but with knockout bolt instead of threaded bolt. It knocked out the whole hub leaving a perfect hex-shape hole for a new steel fan hub mounted with three screws.

Better way?
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Last edited by justplumducky; 04-19-2020 at 08:38 PM.
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Old 04-19-2020, 10:47 PM   #2
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Re: Proper fan blade ass'y height in shroud of an old package unit AC only.


I’d say that looks about right.
Are you sure the coil isn’t plugged. Seen many a coil that’s looked ok but was plugged internally.
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Old 04-20-2020, 04:38 AM   #3
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Re: Proper fan blade ass'y height in shroud of an old package unit AC only.


Dirty coil, or a an motor with too high of an RPM along with the fan blade being too low, will cause excessive amount of air to come out the side.

So unless you see that the hub has slide down the motor shaft, or the motor has been changed out recently. You got a very dirty/plugged condenser coil.
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Old 04-21-2020, 06:25 PM   #4
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Re: Proper fan blade ass'y height in shroud of an old package unit AC only.


Quote:
Originally Posted by roughneck View Post
I’d say that looks about right.
Are you sure the coil isn’t plugged. Seen many a coil that’s looked ok but was plugged internally.
I'm familiar with what you're saying, cuz I had a condenser unit (split system) blow fuses couple times before I realized owner hadn't cleaned the condenser coil like he was supposed to. "Well, it looked OK" he said, and was supposed to have done the cleaning in early springtime before I came to visit. The coil was colored black (no wonder it looked OK). There were 1/2" long strings of gunk coming out of the coil/hanging on to the fins momentarily, before letting go. Then when I went back over it to double check, there were more black strings still hanging on in some places. No more problems after cleaning.
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Last edited by justplumducky; 04-21-2020 at 06:46 PM.
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Old 04-21-2020, 06:29 PM   #5
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Re: Proper fan blade ass'y height in shroud of an old package unit AC only.


Sometimes the coil will look clean from the outside but be totally plugged.
I had an Aaon RTU one time. Tech working on it replaced the condenser fan motor 3 times over a 1 year period. Couldn’t figure out what was wrong. I went to help and the coil looked great. Not one bit of visible dirt. We started washing and the water running out of the coil was jet black. We must have spent an hour washing this one coil.
No more fan failures after that.
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Old 04-21-2020, 06:45 PM   #6
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Re: Proper fan blade ass'y height in shroud of an old package unit AC only.


Quote:
Originally Posted by beenthere View Post
Dirty coil, or a an motor with too high of an RPM along with the fan blade being too low, will cause excessive amount of air to come out the side.

So unless you see that the hub has slide down the motor shaft, or the motor has been changed out recently. You got a very dirty/plugged condenser coil.
The condenser fan motor locked up (tightened up actually, wouldn't improve) after some initial bearing screeching last year (yep, I oiled it), and I don't remember what condition coil was in. Will be installing new condenser fan motor in not-too-distant future. Will check coil.

Plugged coil will over-amp/overheat the original motor and cook the bearing?
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Old 04-22-2020, 04:31 AM   #7
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Re: Proper fan blade ass'y height in shroud of an old package unit AC only.


Quote:
Originally Posted by justplumducky View Post
The condenser fan motor locked up (tightened up actually, wouldn't improve) after some initial bearing screeching last year (yep, I oiled it), and I don't remember what condition coil was in. Will be installing new condenser fan motor in not-too-distant future. Will check coil.

Plugged coil will over-amp/overheat the original motor and cook the bearing?



If its plugged/restricted enough to throw the air out side ways. The motor will run fine. Takes a while to cook it since its still moving air across it. Could run for a few years like that.
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