Rack Cooling

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kevindd992002

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Oct 4, 2021
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My rack came with two 120mm fans (connected to a 220V outlet) on the top set as exhaust. They are no longer working now because of all the dust they accumulated over the years and I need to replace them. What are the best 120mm fans I can get for this purpose?
 

BlueFox

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Oct 26, 2015
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Best is relative? Higher CFM is going to mean more noise and higher power usage that isn't necessarily needed. Could just replace them with the same ones you have or a similar Delta or San Ace one?
 

kevindd992002

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Oct 4, 2021
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Yeah, well, but I'm not sure if higher CFM or higher pressure is what's needed for server rack cooling. The default fans are chinese knockoff ones so I wouldn't want those again. Do you have any specific Delta/San Ace in mind?
 

BlueFox

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Oct 26, 2015
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I'm in 110V land, so not too familiar with the 220V models, but I imagine something with similar current draw would be a good substitute. Also worth mentioning that I personally did not run separate fans in my racks. Just used blanking plates to ensure there was adequate airflow from front to back and minimal hot air recirculation.
 

kevindd992002

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Oct 4, 2021
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I don't have the model number now since the rack is in a remote site but I'm sure those are cheap fans that most of the time don't even have any datasheet available publicly.

These look like good rack fans from AC Infinity.

However, do you guys think a duct plus an inline duct fan will work better? I live in a tropical region and there are shelves above the rack so there is no direct path from the rack exhaust fans to the exhaust fan in the ceiling of the pantry (where the rack is) so a duct to direct the air outside seems to be a good idea.
 

jabuzzard

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Mar 22, 2021
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However, do you guys think a duct plus an inline duct fan will work better? I live in a tropical region and there are shelves above the rack so there is no direct path from the rack exhaust fans to the exhaust fan in the ceiling of the pantry (where the rack is) so a duct to direct the air outside seems to be a good idea.
Loosing the heat to the outside in hot climate will always be better.
 

jabuzzard

Member
Mar 22, 2021
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Yes ducting is better. In theory you could probably do a chimney with ducting but you probably don't want to be running ducting up the side of your property so I would just use an inline duct fan. However you need to make sure the ducting has backdraft protection so if it's windy outside it does not blow the air back into the property.
 

kevindd992002

Member
Oct 4, 2021
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Yes ducting is better. In theory you could probably do a chimney with ducting but you probably don't want to be running ducting up the side of your property so I would just use an inline duct fan. However you need to make sure the ducting has backdraft protection so if it's windy outside it does not blow the air back into the property.
Hmm, interesting. So no need to use additional rack top fans? My idea is to use shrouds on the top rack fan slots (w/ or w/o fans installed there) and use a duct with an inline duct fan up to the ceiling where the room exhaust fan is.
 

jabuzzard

Member
Mar 22, 2021
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Unless you carefully match the fans which is unlikely then having two lots of fans will make things worse as they will be fighting against one another. I would just fit an appropriately sized round fan vent to the top of the rack to attach the ducting to. Thought I would remove the grill, and that will give an easy way to attach the ducting. I would go for an aluminiumised flexible ducting at a minimum as these don't get a static charge build up, when then leads to a much faster fluff buildup which is then a fire hazard.
 

kevindd992002

Member
Oct 4, 2021
110
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Unless you carefully match the fans which is unlikely then having two lots of fans will make things worse as they will be fighting against one another. I would just fit an appropriately sized round fan vent to the top of the rack to attach the ducting to. Thought I would remove the grill, and that will give an easy way to attach the ducting. I would go for an aluminiumised flexible ducting at a minimum as these don't get a static charge build up, when then leads to a much faster fluff buildup which is then a fire hazard.
Which grill are you pertaining to?
 

kevindd992002

Member
Oct 4, 2021
110
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So I decided to go with duct cooling with these:

Dual 120mm to 4" diameter hole -> flexible 4" ducting tube -> AC Infinity Cloudline T4 (4" diameter hole) -> flexible 4" ducting tube routed to outside the building

Would you guys know if 4" is enough or should I go 6" diameter system? The 4" inline fan can do 205 CFM.