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Thread: Pulleys and V-Belts

  1. #1
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    Pulleys and V-Belts

    I'm not too sure where to post this (commercial/residential). It was a 5ton RTU on a light commercial and had a pulley and v-belt. I had to replace the belt as it was worn fabric, hairline cracks, and flopping around like a fish inside the unit. I tried to find out how tight I should tension the belt, but couldn't find any information on it, and supervisor wasn't too much of help either. I just wanted to know if anyone had any information they could share on these types of units as I have done mostly residential for the past 2yrs I've been in the trade, but want to expand to commercial and get out of the attics. Does anyone have any information they could share on this topic or anything else that could help move toward this direction? I've found some good videos on YouTube, but those will only tell you so much as to protect themselves from idiots who think they can do it too.

    Thanks in advance!

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    https://hvac-talk.com/vbb/attachment...5&d=1593794019

    Usually you leave a little slack, the belt should have a bit of movement up and down when you push it. But shouldn’t squeal or slip. Roughly speaking around 1” up and down.
    Too tight and you’ll destroy the bearings from too much tension.
    “I haven’t failed. I’ve just found 10,000 ways that won’t work.” - Thomas Edison

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    “I haven’t failed. I’ve just found 10,000 ways that won’t work.” - Thomas Edison

    “It’s not whether you get knocked down, it’s whether you get up.” - Vince Lombardi

    "In this house we obey the laws of thermodynamics" - Homer Simpson

    Local 486 Instructor & Service Technician

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    Keep reading
    Attached Images Attached Images

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    Pulleys and V-Belts

    One kinda interesting rule of thumb that I learned from a mechanic one time is that when you’ve got the belt about right you will be able to grab it and twist it 90 degrees but no further. Hopefully I explained that well enough. On a 5 ton unit it’s not something to fret yourself over too much. Also on really small stuff like that you can almost always roll the belt off and put the new one on without even touching the adjustment. If the new belt feels right and the old one got plenty of life out of it then I’d leave the adjustment alone. Last week I replaced a 1000 lb motor that used three belts and had no vfd and yes those belts were tight and yes we had to adjust the motor to get them off
    "I think Quantum tunneling would work great... "

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    First thing an apprentice should be trained to do when changing filters.... should always use a tension gauge until you are used to the feel.

    Tension gauge, new & used settings.
    Correct pulleys & belts match. Depth in groove correct, number belts typically fractional hp only.
    Pulley less than 1/32" wear. Use a .032 wire and key stock as gauge.
    Parallel and angular alignment using straight edge or string.
    Amp and voltage check
    TES check, fan rpm check

    If not done correctly, belt failure, pulley wear, motor overheating, bearing failures, improper air flow...

    Sometimes we still have to read.

    file:///F:/Service%20info/browing%20belt%20size%20calculation.pdf
    file:///F:/Service%20info/Optibelt-v-belt%20Installation-and-Maintenance-Instructions.pdf

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  9. #7
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    If you're getting into commercial start using the correct terms. Pulleys are for rope and sheaves are for belts. That may not sound like a big deal but a lot of experienced HVAC guys take notice of such things to form a first opinion.
    No man can be both ignorant and free.
    Thomas Jefferson

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    Purchase the Browning tension checker and follow the included instructions, pulley....oops, sheave alignment is the key to long belt life.
    "He who knows the least, knows it the loudest"
    I'm not young enough, to know everything...

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  12. #9
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    One rule of thumb is to tighten the belt just until it doesn't squeal on start up. Any more, as mentioned, you'll take out the bearings too soon.

    The problem with that rule of thumb is more and more units are having VFD's for the blower. So with that 'slower' start up, you'll never get that squeal even on a system with the belt much too loose.


    Quote Originally Posted by HVAC_wanna_be View Post
    I'm not too sure where to post this (commercial/residential). It was a 5ton RTU on a light commercial and had a pulley and v-belt. I had to replace the belt as it was worn fabric, hairline cracks, and flopping around like a fish inside the unit. I tried to find out how tight I should tension the belt, but couldn't find any information on it, and supervisor wasn't too much of help either. I just wanted to know if anyone had any information they could share on these types of units as I have done mostly residential for the past 2yrs I've been in the trade, but want to expand to commercial and get out of the attics. Does anyone have any information they could share on this topic or anything else that could help move toward this direction? I've found some good videos on YouTube, but those will only tell you so much as to protect themselves from idiots who think they can do it too.

    Thanks in advance!
    I do a triple evac with nitro to remove non condensables.

  13. #10
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    Quote Originally Posted by WAYNE3298 View Post
    If you're getting into commercial start using the correct terms. Pulleys are for rope and sheaves are for belts. That may not sound like a big deal but a lot of experienced HVAC guys take notice of such things to form a first opinion.
    Name:  Screenshot_20201126-084942_Google.jpg
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    My fault if I gave the false impression that I knew what I was talking about. But I will keep that in mind Wayne. Maybe you could slide over some of the terminology over my way so I don't look like a fool when I ask questions. Thanks!

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    Wayne does make a good point. I've always used that as a gauge with techs also.

    If you're getting into commercial, its even more important to raise your level of professionalism. When you start talking to manufacturers for tech support, its very easy to get confused, or for the guy on the other end of rhe line to get confused by incorrect terms.

    Also, in the commercial world, you'll find yourself standing in front of owners, engineers, etc. "Sounding" like you know what you're doing can be more important than actually knowing what you're doing!

    Used to work with a stationary guy at a hospital. He would call me up and say, "man, I cut this thing on and nothing happened!" I always had to take 5 minutes to slow him down to figure out what exactly he was trying to say. Funny thing is, he's now some sort "engineer"!! LOL!!

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    Quote Originally Posted by HVAC_wanna_be View Post
    Name:  Screenshot_20201126-084942_Google.jpg
Views: 261
Size:  359.4 KB

    My fault if I gave the false impression that I knew what I was talking about. But I will keep that in mind Wayne. Maybe you could slide over some of the terminology over my way so I don't look like a fool when I ask questions. Thanks!
    One is as good as the other. Look at the mfg literature; Carrier may be worded either way, McQuay mostly uses sheave, Trane uses sheave, Aaon, York, Climate craft uses pulley.

    Far more important to know proper application & set-up than terminology. Proof is in performance not bs. Customers can see thru it after a while.

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    Pulley and Sheave: Difference
    Ever Power
    Ever Power
    Dec 6, 2019·3 min read

    Pulleys have been used by mankind from time immemorial. They are used to make lifting heavy objects easier. A pulley allows a person to lift a particular load with less effort than what would have been required without a pulley. They are typically made with ropes and wheels. The term pulley is interchangeably used with the word sheave. This is not correct as they are different things. Here are the differences between a sheave and a pulley:-
    The basic difference — A pulley is one of the six types of simple machines that have been used for humans for a long time. It is a basic mechanism. The sheave that is pronounced as shiv is part of the pulley. It is the wheel with grooves where the rope fits in to.
    Complimentary — Pulley without a sheave changes the direction of the pull to lift the load but it doesn’t change the force or energy required to lift the object. By adding multiple sheaves we get a mechanical benefit as it reduces the energy or force required to lift a particular object. The force required reduces in half with each sheave you add to the rope but this cannot be done indefinitely as the utility with each sheave decreases till its negative.
    Problem — Though adding multiple sheaves reduces efforts, but it can also cause fiction. You cannot add an unlimited amount of sheaves as after a few the force required will start increasing with each added sheave, due to the friction caused by them. This increase in sheaves and ropes will make your work harder rather than easier. The solution to this is a compound pulley where the sheaves are added above and below each other and supported by an axle. This will increase the efficiency of your pulley by adding more sheaves.
    Simplicity — Maximum work can be done by attaching a single sheave to a rope. There are certain things to keep in mind while doing this. Firstly, the surface area of the sheave should be at the possible minimum to the rope attached. Secondly, the sheave needs to be abrasion-free. Lastly, the sheave must not be prone to warping. If these three things are kept in mind while making a pulley, your device should do its job without glitches or additional problems related to the same.
    Expert opinion — according to engineers who have worked with pulleys for a long time, the differences can lie in context. Pulleys and sheaves can mean different things depending on the industry you ply your trade-in. Another common answer that we got from experts is a sheave is mostly used as the name for a drive pulley. It can also depend on the area of the world you are staying like in Some parts of the united states where sheave is used as a substitute for a pulley. Another response that we got while asking for differences is that Sheave Pulley is a heavier duty pulley. Most experts though agree that there is no difference between a sheave and a pulley. The difference arises when you go into further details and they are also few and far in the middle.
    Etymology — the word pulley has been in use in the English dictionary since the early 1000 A.D. Before that the word for pulley in greek was polos which were used as far back as 400A.D. Whereas, pulleys have been used from around 200 B.C. the history of the pulley is long and the story of its name is incomplete. Sheave is an even older name than a pulley and can be traced back to the proto-germanic language where a Scheibe means a disc or a bundle. The history of the sheave is unfortunately not clear except its maybe origins.
    Dictionary — It’s always good to check the dictionary to check the meaning and difference between two things. According to the dictionary, a pulley means “a wheel on an axle or shaft” and a sheave means “ a pulley with a grooved wheel”. Therefore, it means that pulley with grooved wheels is sheave and all others are pulleys.
    There is not much difference between a sheave and a pulley. You may say that a sheave is a particular type of heavy-duty pulley and it is a part of the pulley. The difference lie is details of use and location but for the amateur user, there is a negligible amount of difference. These sheave pulleys are available around the world and in different qualities and sizes for suiting your work. To know more about sheaves and pulleys, please visit https://www.ever-power.net/pulley.

  19. #14
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    Quote Originally Posted by ehsx View Post
    One is as good as the other. Look at the mfg literature; Carrier may be worded either way, McQuay mostly uses sheave, Trane uses sheave, Aaon, York, Climate craft uses pulley.

    Far more important to know proper application & set-up than terminology. Proof is in performance not bs. Customers can see thru it after a while.
    Man that’s extremely well put and I couldn’t agree more! There’s no need to impress anybody. Talk about things you know with a little confidence and that’s all it takes. In my experience nobody cares about the word pulley or sheave they just want you to fix the problem and be competent. In fact, in my neck of the woods if you start calling things sheaves people will perceive you as a nerd trying to talk over them. Sorry but that’s just the way it is. The maintenance guys just want you to give a simple English explanation of things. Better to just keep things simple.
    "I think Quantum tunneling would work great... "

    "Call a technician for God's sake. Or we'll see you on the news or the Dark Side of the Moon."

  20. #15
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    I have read the articles about what the "experts" say however in the beginning there was a pulley and they were used for rope. When belt drives came along they were called sheaves because the grooves were different than a pulley. If you ordered a pulley you got the same basic thing as a sheave with the difference being the groove and years ago nobody at the supply house even thought about giving you a sheave when you ordered a pulley.
    My comment wasn't meant to belittle anyone. Call it whatever you wish but another thing I have heard "experts" say is in the beginning pulleys were used to change direction. That is also false they were mostly used for mechanical advantage.
    At any rate I wasn't trying to upset anyone. I'm sorry if that happened.
    No man can be both ignorant and free.
    Thomas Jefferson

  21. #16
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    I’m used to terminology difference verbal and written. Reviewed and written mfg literature. Edited out trade names and tried to use industry standards and often found there is no standard so just looked for most common used. Bolts & screws were terms most often misused. Tried to keep Sales, Installation, operation & maintenance, and parts literature consistent .
    Sometimes lots of opinions.
    Southern boys may know what a “pecker head” is, while someone from another part of the country think something different.
    Always recommended you have the vendor parts manual before ordering parts so you can confirm the correct component by name and pn.

  22. #17
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    I'm not here to impress, I'm here to learn. So I don't mean any disrespect to anyone that's trying to share their knowledge, but I'm not looking to be judged by my terminology either. I'm sure as time goes and I get more accustomed to commercial, I know the words will come. Being in the kitchen for 18yrs, it took me a few months just to get basic things down like terminals and spade connectors. But I really do appreciate all of you who share their knowledge and passion for the trade that I am looking to expand in.

  23. #18
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    A kid I grew up with came from down south and a bolt to him was a tap and a nut was a burr. After terms are used interchangeably for a while whether right or wrong they become acceptable.
    No man can be both ignorant and free.
    Thomas Jefferson

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    I've known worthless techs that can BS anyone, while really good techs that can't express themselves professionally, are thought of as being idiots.

    Regardless of your skill level, a high level of professionalism gives a service technician credibility.

    Maintainance men know what a pulley is....a service technician knows what a sheave is, how to apply it, why you use the sheave you are using, and how to properly install, align, and tension it.

  25. #20
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    Not sure how or when I picked up the terminology I use, anyway, it goes like this:

    Let's say I need to write up one of these, I call it a motor sheave or a blower pulley. It may have started if/when someone told me that is a sheave, pointing to the adjustable motor sheave. I may have thought that since it was adjustable, that made it a sheave.

    No matter, it seems everyone always knows what I'm talking about. All that really matters is the guys behind the counter give me the correct part.
    I do a triple evac with nitro to remove non condensables.

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