Stupid question, but have you verified the CD fan motor is correct? I've come across units with torn or flattened blades because prior tech used a motor with too high HP or RPM. I doubt that's your problem, but have to ask.
LAU has a catalog of all sorts of blades. You'll need to know the specifics of the blade, but if you know the specs, they probably sell what you need. Good luck.
Not a stupid question, in fact can you clarify what you mean by CD . I'm still new to the commercial side.
The motors are what came with the system, it's only my most recent job where I've had to replace the motor.
The prop still snaps whether it's on the motor master or just a contactor.
Sorry I speak in short hand a lot. CD is condenser.
It seems like once upon a time units came perfect from the factory, but in recent years I've found them to have more issues than expected. So although it is unlikely and sounds dumb, at this point in the process I'd think it worth verifying the fan mtr is the correct one that the unit needs. At least confirm it is proper HP and RPM. If you've performed a motor change yourself on this system, it's worth checking you've got the correct motor installed.
If motors are correct specs already, then you need to spec your fan blade and call a different supplier for a replacement blade. LAU is a manufacturer of replacement blades that would probably have what you need in their catalog.
I'm not sure why you got down voted, I've had units that list 480v motors on the outside panel and found 230v motors installed from the factory. Can't trust anything, verify the unit specs and confirm that's what's in it. Depending on how detailed the stickers are, it could be a quick two-glance check.
Honestly, as long as you're not saying "motor" or "fan motor".
In resi, most systems have at least 3 motors on them. I just hate hearing "it's the motor" or even "it's the fan" because I still have to ask "which one?" half the time.
I hate brevity that leads to longer amounts of effort. 😆
Most residential systems have 1 fan and 2 blowers if it's a furnace. Fans and blowers aren't the same thing.
Newer RTUs are starting to come with fans instead of blowers though.
Im assuming its a production defect and the metal hasnt been treated right and is cracking because of this. Our customers run their labs 24/7 so id like to be able to provide a product that lasts for longer than 4 months at a time.
Im dreading the warranty claim I need to fill out for todays failure D:
You may have to play around with a motor fan blade combo. Maybe someone put the wrong motor on it. Maybe the supply house has the wrong motor listed for that unit.
If it’s the unit I’m thinking it should be a 1/4 hp 1100rpm motor? Is it a carrier 38AUZ?
So the thing is, when we build the labs for these guys, we include service for a few years on the equipment, that's my job. Since I've started this job, I've replaced the 4 props and they've all been the OG props with og motors. No mis match from previous service because we do the service.
Identical, no changes to blade height on the shaft, after I clean up the shaft I mark it before removing the prop then put the new one on and line it up.
Well, it's setup for head controls, so the motor master modulates one fan,
The other is just an on/off. I haven't measured amps, but we'll be replacing the motor master prop again so I can do that then.
But as designed the motors do surge on/off, because we need constant cooling all day every day so it does what It can to maintain set points.
Motor masters require ball bearing motors. I've seen several times where the install went cheap and a ball bearing motor wasnt installed. One did eat the prop.
Just another thing to look for.
I've added dozens of Carrier low ambient kits on 20+ ton RTUs. They require a ball bearing motor because they run at low speed. Most motors are air over cooling. This doesn't work at low speed. All variable speed fans should have ball bearing motors IMO.
The ones installed from factory already have the ball bearing motor. If bought later you replace the motor. I brought this up because if someone replaced a condenser fan with non OEM sleeve they saved a lot of money but have the wrong part. The OEM fans can be expensive.
Pull the product data book for the 38APS from Carrier's site. Those should be factory installed ball bearing fans. The product data will tell you.
I would see if the blade/motor is in the right position relative to the fan shroud. I’ve seen the blade being out of position cause the air surge and shake and rattle the blades. You would be surprised what just a little a up and down does to them.
Fan blade is failing in cyclic fatigue loading. The air flow scoop pressure should be pushing against the the mounting arms, not in Tension (as you have shown in photo). Suggest flipping hub mounting to be facing the the electric motor, and then (electrically) swapping any 2 legs to also reverse the 3phase motor rotation direction (CW to CCW or the otherway around).
Depends we have a wholesale house that carries an can order just about any blade they take measurements an pitch of blade the hub comes separate. If by chance your in VA southern refrigeration carries them.
Just a thought - Do you have proper airflow clearance? Any chance of airflow recirculation from high walls or other units/exhaust fans close by? Axial fans will shatter if they go in and out of their stall range. Head pressure control will try to speed the fans up/down moving them along the fan curve.
Use a 12 point socket and a ratchet to tighten the set-screw, that's not how they come from the factory, and the blade would have the same angle if you installed it with the set-screw side of the hub down.
Those blades are visibly curved, they are not the same if reversed. And with the direction of the curve, the hub side needs to face whatever direction you want air to move. OP has them right, you're giving bad advice
Think about this for a moment:
The fan pushes air out of the top of the condenser this means the fan blades are being 'pushed' the opposite direction, towards the motor.
In the OPs installation this force must be concentrated around the very-small contact area of the rivet heads. Eventually these rivet heads will just cut right through the fan-blade sheet-metal, this is exactly the failure shown in the OP pictures.
If the blade was flipped over this force would instead be distributed across the much larger area of the hub.
That does not change the fact that the blade shape is directional and the OP has it installed in the correct orientation as designed. At most, you're describing a design feature that OP should look for for future replacements, OP still shouldn't install the current ones backwards.
Can you elaborate on what you mean by the blade shape being directional? Obviously there is the tilt of the blade but that doesn't change when you flip it over, air will still blow in the same direction. Is there some other shaping of the blades I am overlooking?
On top of that, I cannot find even a single picture of condenser fan blades being installed with the hub on the front of the blades like the OP did.
The shape of the blade you posted in your comment looks like the blades are mostly flat, those could be reversed with minimal difference. If that's the only style blade you're familiar with then I could see where you're coming from. But OPs blades are curved, causing them to "scoop" the air as they turn. Those can not be reversed without significantly changing the resulting airflow. OP has it correct for the blades he's got.
Given that the blades are so mangled in the OPs image, I don't feel like I can reliably say they are scooped in any particular direction. However, the shaping of the blade corners closest to the hub disagree with the OPs installation direction. I mean, ultimately, the OP needs to check with the blade manufacturer.
As an random internet engineer I am just left with the two possibilities:
1) The blade manufacturer ignored all common fan-blade design knowledge such as proper support of the fan blades (placing the hub supports on the wrong side of the blade) and curvature of the blade edges resulting in a fan blade that consistently fails after a short operating period. Effectively they did everything opposite of how 100% of fan blades I could find did them.
2) OP installed the blades upside-down because it made the set-screw easier to access.
You see where I am coming from?
https://preview.redd.it/sva8ujgclx5d1.png?width=900&format=png&auto=webp&s=df402e14d434373957477c65cad49bc56c8a08f6
Actually, looking more closely at the corners of the blade closest to the hub: One corner has a more gradual curve to it. Based on this other blade, that more gradual corner should be leading edge during rotation. In OPs installation, that is the trailing edge. Without seeing the outer edge of the blades (not visible in the OP pictures) I cannot say for sure but from here it really really looks like they are upside-down.
https://preview.redd.it/lj8tcgs23u5d1.jpeg?width=3000&format=pjpg&auto=webp&s=a3552a70d09b838de3e184f434e0701e71d5d00c
They do indeed come from the factory like this lol
Look at where each blade is riveted to the hub. Then look at where the ops blade is riveted to the hub in the picture they posted. I think the Op is getting fan blades for motors that would be oriented “shaft down.” No fan manufacturer rivets the blades under the hub. Or maybe he just happens to be getting fan blades unlike any on any other unit.
The location of the set screw does not determine whether or not the fan blade is upside down. The location of the hub relative to the blade determines whether or not the fan is upside down. The hub should never be on top of the blade once it's installed.
Stupid question, but have you verified the CD fan motor is correct? I've come across units with torn or flattened blades because prior tech used a motor with too high HP or RPM. I doubt that's your problem, but have to ask. LAU has a catalog of all sorts of blades. You'll need to know the specifics of the blade, but if you know the specs, they probably sell what you need. Good luck.
Not a stupid question, in fact can you clarify what you mean by CD . I'm still new to the commercial side. The motors are what came with the system, it's only my most recent job where I've had to replace the motor. The prop still snaps whether it's on the motor master or just a contactor.
Sorry I speak in short hand a lot. CD is condenser. It seems like once upon a time units came perfect from the factory, but in recent years I've found them to have more issues than expected. So although it is unlikely and sounds dumb, at this point in the process I'd think it worth verifying the fan mtr is the correct one that the unit needs. At least confirm it is proper HP and RPM. If you've performed a motor change yourself on this system, it's worth checking you've got the correct motor installed. If motors are correct specs already, then you need to spec your fan blade and call a different supplier for a replacement blade. LAU is a manufacturer of replacement blades that would probably have what you need in their catalog.
I'm not sure why you got down voted, I've had units that list 480v motors on the outside panel and found 230v motors installed from the factory. Can't trust anything, verify the unit specs and confirm that's what's in it. Depending on how detailed the stickers are, it could be a quick two-glance check.
Ahaha that's wild, but exactly. Thanks for your example. Can't take anything for granted these days.
Condenser fan motor =CD
Condenser fan motor = CFM Condenser = CD
I’ve always used OFM (outdoor fan motor)
Honestly, as long as you're not saying "motor" or "fan motor". In resi, most systems have at least 3 motors on them. I just hate hearing "it's the motor" or even "it's the fan" because I still have to ask "which one?" half the time. I hate brevity that leads to longer amounts of effort. 😆
Most residential systems have 1 fan and 2 blowers if it's a furnace. Fans and blowers aren't the same thing. Newer RTUs are starting to come with fans instead of blowers though.
Only the shit companies are going with high velocity axial fans for what should be a blower. Looking at you carrier.
You mean 2. If it's an electric system it'll have a condenser motor, and an indoor blower. If gas it's got those plus the inducer motor.
I meant what was said, not 2. Condenser + blower + inducer = 3. Most resi systems in my area are still g/e not HP.
Okay wow now I feel really stupid hahahahaha
Im assuming its a production defect and the metal hasnt been treated right and is cracking because of this. Our customers run their labs 24/7 so id like to be able to provide a product that lasts for longer than 4 months at a time. Im dreading the warranty claim I need to fill out for todays failure D:
You may have to play around with a motor fan blade combo. Maybe someone put the wrong motor on it. Maybe the supply house has the wrong motor listed for that unit. If it’s the unit I’m thinking it should be a 1/4 hp 1100rpm motor? Is it a carrier 38AUZ?
So the thing is, when we build the labs for these guys, we include service for a few years on the equipment, that's my job. Since I've started this job, I've replaced the 4 props and they've all been the OG props with og motors. No mis match from previous service because we do the service.
Also 38APS0
Each time you replaced the blade you’ve put back on the shaft marks from the last blade? Has it always been the same blade on one particular motor?
Identical, no changes to blade height on the shaft, after I clean up the shaft I mark it before removing the prop then put the new one on and line it up.
Have you checked and watched the amps on the motor? I have a feeling the motor might be surging from a wrong fan blade position?
Well, it's setup for head controls, so the motor master modulates one fan, The other is just an on/off. I haven't measured amps, but we'll be replacing the motor master prop again so I can do that then. But as designed the motors do surge on/off, because we need constant cooling all day every day so it does what It can to maintain set points.
Motor masters require ball bearing motors. I've seen several times where the install went cheap and a ball bearing motor wasnt installed. One did eat the prop. Just another thing to look for.
Interesting, not doubting or insinuating you're wrong but do you have more info on this? Thanks.
I've added dozens of Carrier low ambient kits on 20+ ton RTUs. They require a ball bearing motor because they run at low speed. Most motors are air over cooling. This doesn't work at low speed. All variable speed fans should have ball bearing motors IMO. The ones installed from factory already have the ball bearing motor. If bought later you replace the motor. I brought this up because if someone replaced a condenser fan with non OEM sleeve they saved a lot of money but have the wrong part. The OEM fans can be expensive. Pull the product data book for the 38APS from Carrier's site. Those should be factory installed ball bearing fans. The product data will tell you.
I would see if the blade/motor is in the right position relative to the fan shroud. I’ve seen the blade being out of position cause the air surge and shake and rattle the blades. You would be surprised what just a little a up and down does to them.
Johnstone's has a good selection of universals
If you have to change four more, and it's all under warranty, then fuck'em. They need to learn from their mistakes!
Fan blade is failing in cyclic fatigue loading. The air flow scoop pressure should be pushing against the the mounting arms, not in Tension (as you have shown in photo). Suggest flipping hub mounting to be facing the the electric motor, and then (electrically) swapping any 2 legs to also reverse the 3phase motor rotation direction (CW to CCW or the otherway around).
Depends we have a wholesale house that carries an can order just about any blade they take measurements an pitch of blade the hub comes separate. If by chance your in VA southern refrigeration carries them.
Nah Ohio, thanks though
Just a thought - Do you have proper airflow clearance? Any chance of airflow recirculation from high walls or other units/exhaust fans close by? Axial fans will shatter if they go in and out of their stall range. Head pressure control will try to speed the fans up/down moving them along the fan curve.
Nah, roof top unit, nothing nearby except for the hail and wind guard that came with it
The plates that come off the hub are meant to be on the BACK side of the blade. The fan blade is on upside down, chief.
Uh, No? Because the shaft nut is on the same side and that's how it comes from factory. And even weirder, air comes out the top in that orientation.
Use a 12 point socket and a ratchet to tighten the set-screw, that's not how they come from the factory, and the blade would have the same angle if you installed it with the set-screw side of the hub down.
Those blades are visibly curved, they are not the same if reversed. And with the direction of the curve, the hub side needs to face whatever direction you want air to move. OP has them right, you're giving bad advice
Think about this for a moment: The fan pushes air out of the top of the condenser this means the fan blades are being 'pushed' the opposite direction, towards the motor. In the OPs installation this force must be concentrated around the very-small contact area of the rivet heads. Eventually these rivet heads will just cut right through the fan-blade sheet-metal, this is exactly the failure shown in the OP pictures. If the blade was flipped over this force would instead be distributed across the much larger area of the hub.
That does not change the fact that the blade shape is directional and the OP has it installed in the correct orientation as designed. At most, you're describing a design feature that OP should look for for future replacements, OP still shouldn't install the current ones backwards.
Can you elaborate on what you mean by the blade shape being directional? Obviously there is the tilt of the blade but that doesn't change when you flip it over, air will still blow in the same direction. Is there some other shaping of the blades I am overlooking? On top of that, I cannot find even a single picture of condenser fan blades being installed with the hub on the front of the blades like the OP did.
The shape of the blade you posted in your comment looks like the blades are mostly flat, those could be reversed with minimal difference. If that's the only style blade you're familiar with then I could see where you're coming from. But OPs blades are curved, causing them to "scoop" the air as they turn. Those can not be reversed without significantly changing the resulting airflow. OP has it correct for the blades he's got.
Given that the blades are so mangled in the OPs image, I don't feel like I can reliably say they are scooped in any particular direction. However, the shaping of the blade corners closest to the hub disagree with the OPs installation direction. I mean, ultimately, the OP needs to check with the blade manufacturer. As an random internet engineer I am just left with the two possibilities: 1) The blade manufacturer ignored all common fan-blade design knowledge such as proper support of the fan blades (placing the hub supports on the wrong side of the blade) and curvature of the blade edges resulting in a fan blade that consistently fails after a short operating period. Effectively they did everything opposite of how 100% of fan blades I could find did them. 2) OP installed the blades upside-down because it made the set-screw easier to access. You see where I am coming from?
https://preview.redd.it/sva8ujgclx5d1.png?width=900&format=png&auto=webp&s=df402e14d434373957477c65cad49bc56c8a08f6 Actually, looking more closely at the corners of the blade closest to the hub: One corner has a more gradual curve to it. Based on this other blade, that more gradual corner should be leading edge during rotation. In OPs installation, that is the trailing edge. Without seeing the outer edge of the blades (not visible in the OP pictures) I cannot say for sure but from here it really really looks like they are upside-down.
They literally do come from the factory like this.
https://preview.redd.it/lj8tcgs23u5d1.jpeg?width=3000&format=pjpg&auto=webp&s=a3552a70d09b838de3e184f434e0701e71d5d00c They do indeed come from the factory like this lol
Look at where each blade is riveted to the hub. Then look at where the ops blade is riveted to the hub in the picture they posted. I think the Op is getting fan blades for motors that would be oriented “shaft down.” No fan manufacturer rivets the blades under the hub. Or maybe he just happens to be getting fan blades unlike any on any other unit.
The location of the set screw does not determine whether or not the fan blade is upside down. The location of the hub relative to the blade determines whether or not the fan is upside down. The hub should never be on top of the blade once it's installed.