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  • Belts or bearings?

    I have a engineered air MUA unit and the HVAC technician is telling me that the bearings are going on it.

    I had another technician change the belts on it and soon after it started to makes a noise that sounds like a bearing or perhaps a belt that isn’t rolling on the double pulleys correctly.

    My question here is it’s a double pulley when changing belts on these aren’t the belts supposed to be cut from the same band of belting? If that makes sense.

    Meaning they are the exact same length. Its interesting how soon after changing the belts that this noise started.

    I would like to hear from someone if this is true with the belts having to be the exact same length or will any B 73's work?

    Thx in advance gentlemen!

  • #2
    Re: Belts or bearings?

    It would be nice to have a little more info, such as model number and age of the unit. Are the bearings servicable (i.e. zerk grease fittings), if so, have they ever been serviced?

    With that said, The belts installed should be ok. I have seen quite a few bearing failures after belt changes due to the technician adjusting the belts too tight causing premature failure. I am not saying thats your problem, but just something to consider.

    REgards,

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    • #3
      Re: Belts or bearings?
      1. Up until 5 or 6 years ago, I was always told that belts had to be purchased as a matched pair for this type of application. What I've heard more recently is that the manufacturing tolerance and quality control have improved to the point that this is no longer necessary. I don't even think matched pairs are available any more.
      2. I agree that the belts could be too tight or too loose. The belts on a larger unit like this sounds like it is, one with ball bearings, need to be very tight compared to what they would be on a residential furnace. Residential blowers and motors only have brass bushings instead of ball bearings. A tight belt will destroy the bearings in residential equipment quickly.

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      • #4
        Re: Belts or bearings?

        The unit is 7 years old and the bearing get greased regularly.

        I will find out today what the model # is.

        Thx for the advice guys.

        Comment


        • #5
          Re: Belts or bearings?

          Everything must be lined up just right. Put a good straight edge on the edges of the motor and belt sheaves and be sure they are all aligned perfectly. Both shafts much be parallel. Sometimes they get out of alignment because the belts are pulling the ends towards each other. If anything doesn't line up just right it causes belts to slip and make wild noise. It also can damage bearings, and due to wasting energy over load the motor.

          Yes, to the belts being matched. They should be from the same batch number. You might try running the blower with just the inner belt and leave the outer belt off during a quick test. Besides being a matched pair the use of the wrong type of belt can result in noise. The belts need to match the grooves of both sheaves and they (both sheaves and the belts) need to be the same. If you look at your setup are the top (outside with lettering) of the belts riding near the top of the sheaves or are they down near the bottom of the grooves? Sometimes people install the wrong type of belt(s) trying to save a little money. This never works out very well it at all.

          Do not over tighten the belts. Without more info it's hard to state how tight they need to be. If too loose there will be some screeching at startup. You should be able to flex the center about 1/2 or so using thumb pressure.

          Test: Remove all belts and spin the blower shaft by hand. Does it sound ruff or feel ruff. If yes, the bearings should be replaced. Also, run the motor with belts removed but be sure it is securely mounted first. It should coast to a stop and not make ruff bearing noises. This doesn't mean it will sound perfect. A bad bearing in a motor is pretty easy to tell with it running and then coasting to a stop.

          Gobby: If you can do so, please try to take some good closeup pictures showing any numbers-letters of the belts and also showing them installed. If people can see how they are running and also the numbers it should help. If you see any numbers on the sheaves (pulleys) please post them too. The more info the better.
          Last edited by Woussko; 01-17-2008, 06:04 PM.

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          • #6
            Re: Belts or bearings?

            Sorry it took so long I just got back into town. I tried another set of excat cut belts and it still maid the same sound?

            The inside belts appears to be a little looser. I also did try running it with the one belt and the same sound. Certainly doesn’t sound like a grinding noise like a bearing more like the sound of the squirrel cage of centre or something??

            Thoughts?





            Comment


            • #7
              Re: Belts or bearings?

              Is it a banging or scraping sound?

              Did you try running the motor with the belts removed?

              Also, please remove the belts and both spin the blower and also try pushing and pulling on the blower shaft. If there's any end play you can feel (assuming it's riding on ball bearings) there most likely will be a need to replace the blower bearings. It could be something has over time worked loose. Try the process of elimination and go after one thing at a time. Be sure the motor runs well and coasts down to a stop with no grinding or scraping noises. If it does, then I would look at the blower. Be sure to look for and tighten up any set screws. I wish I could hear what it sounds like.

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              • #8
                Re: Belts or bearings?

                Well I ran it with the belts off and still the same sound.No grinding etc.Had a second opionion today and he thinks that its a vain on the blower that might be loose lol.

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                • #9
                  Re: Belts or bearings?

                  Wait a min please

                  Was it making the noise with just the motor spinning and the blower still, or did you spin the blower by hand when it made the noise? If the blower was still then it has to be a motor problem. In that case, I would disconnect it and remove it. Then look up places that rebuild electric motor and take it to one of them. It may just be something stupid like the cooling fan just starting to scrape, but bad ball bearings can and do make some very strange noises.

                  Please post more info. Exactly when and what was moving when you heard the noise? Try your best to describe the noise. Maybe you can spell it like a wild word.


                  Part 2:
                  That's a good size blower. Take a good light and get it inside the blower. Then look at the veins carefully and give each a gentle wiggle. You'll soon know if one is loose.

                  If the belts are off and the motor is spinning but not the blower then it has got to be a motor problem.


                  Part 3:
                  With the belts off, grab the large pulley on the blower shaft. Push it in and then pull out. Try this several times. Does it have any end play/slop that you can feel? Next try to move it up and down but without rotating it. Finally if you have any small diameter rope around wrap a few turns in the pulley groove and give it a pull. This will spin the blower faster than you can just by hand. Do be careful not to pull too hard or get whipped by the rope.
                  Last edited by Woussko; 02-06-2008, 10:43 PM.

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                  • #10
                    Re: Belts or bearings?

                    I took the belts off and spun the blower by hand and it maid that noise. To me it sounds like the squirrel cage is rubbing vs something.

                    I also took the shaft and tried pulling and pushing it and I didn’t notice any play in it. When I put the belts back on and run it it doesn’t sound very noisy just when I close the door then you can really hear it outside the unit.

                    The hvac technician I had out last week really didn’t know what the problem was. His recommendation was to change the shaft and blower and at the same time just in case change the bearing as well.

                    I’m going to go back to the unit today and try your advise with the flashlight and check those veins. I will keep you posted.

                    Once again thx for your time and help Woussko

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                    • #11
                      Re: Belts or bearings?

                      the only way a belt can be properly installed is to read the max amps on the motor nameplate,then take a ampmeter around the high leg(or wire)to the motor,and adjust belt tension to desired amps.careful to let wheel stop spinning before adjustments.

                      Comment


                      • #12
                        Re: Belts or bearings?

                        Originally posted by k-doghvacspec. View Post
                        the only way a belt can be properly installed is to read the max amps on the motor nameplate,then take a ampmeter around the high leg(or wire)to the motor,and adjust belt tension to desired amps.careful to let wheel stop spinning before adjustments.
                        !

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