Liebert belt squeal

[allstar08]

Hey guys,

I have a data center with 3, 30ton liebert dx units. One of them has belt squeal. New sheave and pulley, 3 months later, belt squeal. Liebert belts, and a few days later, and you guessed it, belt squeal. Amp draw on the motor at 16, and rla is 22. I have tightened these things to the max, and then turned it some more, the sheave and pulley look great. Does anyone have any ideas?

[amickracing]

Are you sure you have the right belts for the sheaves? Might have a belt that's too small or too big (width/height here, not length).

Double check the alignment too. If they are off a bit it could be heating the belt up and causing it to wear out a bit fast and squeal.

Maybe the belts are too tight and causing premature wear?

I must say I have a couple Lieberts I take care of and run the belts a bit tighter than a normal RTU's belts, but there's still a bit of "wiggle" in them... just not much.

[yorktek37]

for lieberts I always use the "grip notch" belts.

[Heavyevans]

I had the same problem about ten years ago with a remodel. We were hired to install the new unit the customer had got a deal on.

If I remember correctly it turn out to be a high static unit that didn't fit the application. Of course the floor was packed full of cabling and the static was way too high.

The customer didn't want to replace their new unit so my only recourse was to slow the fan down to the minimum and add more perf floor tiles.

[Domcort]

allstar08,

Does the unit have a adjustable sheaves, and what HP motor is in the unit??

I have experienced this in the past with the larger HP motors, and going from the factory setup of the two belt drive to a three belt drive on the larger motors which will transfer the drive energy and distribute the load better over three belts rather that two, Liebert is doing that now in the new DS units. On the units that I have done this on in the past, we found no return visits for squealing belts.

Fixed sheaves will reduce your belt wear, make the belts run cooler and with proper alignment will last a lot longer.

Domcort

[Liebert_Tech]

allstar08,

Does the unit have a adjustable sheaves, and what HP motor is in the unit??

I have experienced this in the past with the larger HP motors, and going from the factory setup of the two belt drive to a three belt drive on the larger motors which will transfer the drive energy and distribute the load better over three belts rather that two, Liebert is doing that now in the new DS units. On the units that I have done this on in the past, we found no return visits for squealing belts.

Fixed sheaves will reduce your belt wear, make the belts run cooler and with proper alignment will last a lot longer.

Domcort

Domcort said it,

I have seen this to many times. I see this more on Upflow units because the starting torque of the 15hp motor will flex the unit frame and loosen the belts to cause belt problems. Is this unit upflow? Sounds like you have 15hp motors with RLA of 22. If so, you have to do away with the adjustable sheave and go to a fixed pulley. With that size motor, you must make sure the pulley's are inline. If they are off any, you will heat those belts and start to get squeal. Even on a fixed pulley.

[allstar08]

I changed them to fixed already. I was wondering if the static might be the issue. If I had high static wouldn't my amp draw be higher? I will get some model and serial numbers so I can verify the correct sheave and pulley size.

[Domcort]

I changed them to fixed already. I was wondering if the static might be the issue. If I had high static wouldn't my amp draw be higher? I will get some model and serial numbers so I can verify the correct sheave and pulley size.

Some other questions:
Upflow or Downflow Unit?
How deep is the raised floor?
Any obstructions in front of the discharge air?
Motor HP?
Fixed Sheave sizes, Blower and Motor? Belt Size?

Domcort

[mathias]

I had the same problem and replaced with new sheave and belts, problem solved!

[greg r]

I've had this problem AND belt wear. What I did was go to a larger motor sheave, and fan sheave to keep the ratio the same; you have to know the ratio to start with. With more contact area on the motor sheave, the belt didn't flex as much and the tension was more forgiving. The squeals stopped and the belts lasted longer. Because the shafts, motor and fan, are somewhat close; alignment is pretty critical. I keep a plumb string handy in my service kit for checking alignment.

[allstar08]

Downflow
b-40 x2
13 floor
15 hp

[Randy S.]

Is the differential across the fan higher than spec due to restrictions?
I've noticed a lot of data rooms with either too many wires and pipes under the floor, or too few outlets, and often a combination.

[Domcort]

I changed them to fixed already. I was wondering if the static might be the issue. If I had high static wouldn't my amp draw be higher? I will get some model and serial numbers so I can verify the correct sheave and pulley size.

From what you have indicated a 30-ton system should have close to 20 to 25 2x2 perforated floor tiles per system. I doubt it would be a static as the entire floor is your plenum. How many systems are in this Data Center? If you provide a serial number I can check the RPM / CFM setup that the unit left the factory with. So that if was changed prior to you out in the field you can adjust as needed.

Domcort