[3DDick]

I’m at my wits’ end here and would appreciate some help. I have a Master Flow Whole House Fan (30 BWHF) that I purchased at Home Depot 15-1/2 years ago and installed myself. It worked beautifully before it began squeaking and chirping a few years ago.

I recently got up there to check it out. I figured it was: 1) a belt, 2) the motor, or 3) the fan shaft bearings. I first removed the louver and ran it. Not the louver. I replaced the belt, with the recommended loose tension. Not the belt.

I took a guess that it was the motor, so I ordered an equivalent replacement. The old one is A.O. Smith F48G98B32 1/3 HP, 1100/800 RPM, 4.2 A. This is no longer made. Home Depot offered a Century DL 1036. I bought a new run cap also. The shaft on this one was about ½ too long and was in the path of the blades, so I got new bolts and nylon spacers and remounted it, no problem. Flipped the switch, and S.O.B., the squealing, chirping and squealing was still there (the louvers are not yet on at this point).

Fast forward a few hours, and aha! I found it. There are two bearings for the fan shaft- (here I’m at a loss for the correct terminology) on top of the upper bearing is a collar (thrust bearing? thrust bushing?) fastened to the shaft with two set screws, and it is loose. When I turn it by hand, I can replicate the sound, just more slowly. I tighten up both set screws, power up and hit the switch. GONE! So far so good, yeah? I remount the lovuers and hit the switch. The louvers open only about half of what they should. After 10-15 minutes of operation, I shut down and restart, and the louvers barley open. OK, well, I’m going to reinstall the old motor, since that wasn’t the problem, right? I reinstalled the old motor, flipped the switch, and everything seemed great, except that the RPMs didn’t seem what they should be (no strobe). I reinstalled the louvers, and started up. The louvers barely open. The last thing I could think of, but probably not it was to install the brand new run cap on the old motor. Not it.

The louvers aren’t damaged, so that’s not it. The same behavior has occurred with two different motors, so we come back to the fan assembly itself. I took the fan assembly down and it turns fine by hand. I cant see anything else to do to it.

I could drop $300 and buy an entire replacement and install that, but it seems to me there is something simple that I’m just not getting.

WTH is wrong?

 

[3DDick]

Yeah, I'm pretty sure the wiring is right - the old motor is back in and wired the way it was for 15 years. When the new DL1036 was up there, I'm pretty sure that was right too. There's a wiring diagram right on it.

Now for the pics:

You can see the 2 set screws that I tightened on the close up.

 

[3DDick]

...lost my first post, grr.

Is it just 1 set screw per bearing? The picture looks like it got a bit compressed so it's hard to see. I can't see the shaft in the upper bearing, is that set screw actually hitting it?

The amp draw will tell you if the bearing friction is too high for the motor. (seizing) Yes unusual for a set screw to work it's self loose, but I've seen it from time to time.

The belt however seems a tad loose. Hard to say from the picture. I normally test that with pressure from my hand. The old way of tensioning is to get a deflection of t/64, where t is the span. So a 16" length would be 1/4" of deflection. The actual span is described below. It won't matter so much in your case. You also don't have to be super precise, if you're within 1/8" of tolerance, your good. The articles below explain it better if you wish to read it, including some other methods and tools that I don't own...

http://www.ero-joint.com/sites/default/files/ero-joint/Belt-adjustment/belt-deflection-diagram.jpg

http://www.clark-transmission.com/images/pdf/techinfo/CARLISLE_VBELT_TENSIONING.PDF

http://www.greenheck.com/library/articles/83

Cheers!

Here's a couple more close ups. There are 2 set screws at 90 degrees.

The belt might be a little on the loose side, but the manual (and see the orange sticker?) in BOLD ALL CAPS tells you not to make it too tight. Pinching the belt should have 1-3/4" span. I might have a little less and it's easy enough to get it spot on, but I don't think that's it.

I don't have an ammeter (not sure how to use one anyway).

 

[3DDick]

I'll get one and check it. I won't really know what the numbers mean, so I will have to report back. The motor is 4.2 amps according to the boiler plate.

Thanks

 

[3DDick]

Yes- airlfow opens the louvers.

The pulleys are aligned. Was the very first thing I did along with replacing the belt. That aint it.

The motor is wired correctly. For sure. Wiring diagram is right on it, in the photo.

 

[3DDick]

Since I've been asked that question 3 times now, Ive gone back to check. It is wired according to the diagram, the way it was for 15 years before I temporarily swapped in a new motor. So, yes, I'm sure.

 

[3DDick]

Yes, you're right, after all that I did, the is the only thing that I know is different is I tightened the set screws.

But why would I loosen them? The spinning of the shaft inside the collar is what caused the squeaking and chirping. Looks to me like they are designed to be tight, and it's all or nothing.

 

[3DDick]

OK, I loosened the set screws. Nothing really changed. The RPMs aren't high enough it seems (and someone else is gonna ask me if the motor is wired correctly).

I'm baffled. I don't really want to bite the bullet and drop $300 for a new one, but the prospects of a fix seem a bit bleak.

Anyone else?

 

[3DDick]

After walking away from this for well over a week, I bit the bullet and was ready to replace the whole dang thing, so I went to HD and bought a new one. Before I removed the old one, I decided to check a couple more things.

I opened the new fan (identical model) and read the instruction book (*identical to the one I have from the year 2000). In the mix was an insert that said something like " DISREGARD THE INSTRUCTIONS IN STEP 7 ON PAGE 4. TENSION THE BELT SO THERE IS 1/2 INCH OF DEFECTION". Remember now, they made a big deal about this. Look at the photo and you see the sticker right there - "KEEP IT LOOSE!" When I started all this a couple weeks ago, I followed their instructions and made it loose. According to those instructions, I estimate well over 1 inch of deflection.

Supers05, you were onto this.

So then, nothing wrong with the motor (it is still wired for high speed :wink2: ), nothing wrong with the bearings. It was the damn belt tension. The new motor and the new fan go back to HD, and I can move on.

Thanks for your replies!

 

[3DDick]

My mother used to love that page that got copied and passed around years and years ago before email that went " “When you are up to your ass in alligators, it’s difficult to remember that your initial objective was to drain the swamp”.

I'm glad to be out of the swamp at this point. :smile: