My question is in the title. Do the fans need to be the same speed? If I have a 1850rpm pushing, can I have a 1000rpm fan pulling? Anyone know if this will harm the pulling fan?
Fans in push/pull need to be same speed?
dseg
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It will either (and probably some of both) slow down 1 fan, or speed up 1 fan, which will be harmful to the motors - i would recommend going with two of the exact same fan or at least ones that are as close as possible. Even if it didn't ruin the motors on the fans, it would definitely be a hinderance for cooling performance and would be much better optimized if you had two of the same kind
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Appleg is right.
Just due to physics (if we are assuming similar CFM per rpm on both) the pushing fan will speed up the pulling one past it's normal motors limit, quite possibly damaging it. I doubt it would do anything immediately but over time it will degrade. (Does this make sense? It's sort of forcing through extra air, so it would speed up the slower fan).
In this configuration it should not affect the pushing fan though.
If you do not want to purchase new fans, I think you should at least swap the two, so that the one pulling is the higher RPM. But that's just a hunch :/
Just due to physics (if we are assuming similar CFM per rpm on both) the pushing fan will speed up the pulling one past it's normal motors limit, quite possibly damaging it. I doubt it would do anything immediately but over time it will degrade. (Does this make sense? It's sort of forcing through extra air, so it would speed up the slower fan).
In this configuration it should not affect the pushing fan though.
If you do not want to purchase new fans, I think you should at least swap the two, so that the one pulling is the higher RPM. But that's just a hunch :/
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Both of you are wrong
here is why
When with 1 fan being faster than the other, the faster fan will be doing more work relatively, the slower fan will be doing less work, with a lesser load on the fan because the faster fan will be pushing air into it
thanks to air resistance and the fact that there is not equilibrium in pressure, the slower fan will still have work to do in terms of helping air flow
No, having two different fans will not cause the premature death of the other fan.... What will end up hamper is one fan will hamper the other... In a sense, if you're adding in a faster fan, you will benefit. If you add in a slower fan YOU STILL BENEFIT. Why? Because its adding more static pressure drive.
The only real downside or negave effect is you lower your efficiency.
tl;dr - from an engineer, no there is no problem with different speed fans.
here is why
When with 1 fan being faster than the other, the faster fan will be doing more work relatively, the slower fan will be doing less work, with a lesser load on the fan because the faster fan will be pushing air into it
thanks to air resistance and the fact that there is not equilibrium in pressure, the slower fan will still have work to do in terms of helping air flow
No, having two different fans will not cause the premature death of the other fan.... What will end up hamper is one fan will hamper the other... In a sense, if you're adding in a faster fan, you will benefit. If you add in a slower fan YOU STILL BENEFIT. Why? Because its adding more static pressure drive.
The only real downside or negave effect is you lower your efficiency.
tl;dr - from an engineer, no there is no problem with different speed fans.
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