Server Closet Cooling (Supermicro Fan Reversal + Venting Room)

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svtkobra7

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Jan 2, 2017
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I will be placing my Supermicro CSE-836 (and other server / network gear) in a closet. I live in a condo and this is the best (and only) location available. As that closet is 98" tall x 25.5" deep x 41" wide (or 59.2 cubic feet), it will require some creativity to fit components and manage temperature. Some of my ideas include:
  • Component Fitment: Since a 25.5" deep closet won't allow for traditional rack mount, I intend to use a Rack Solutions "Open Frame Wall Mounted Rack" and drop the server in from the top such that the front of the server is facing the ceiling (other components can be mounted horizontally below the CSE-836).
  • Modification to Supermicro CSE-836: I expect this server to generate a bit of heat as it will have two E5-2670 v1 processors in it and 16 x 6 TB HGST Deskstar NAS (7200 RPM) drives once up and running. Of course, the server pulls airflow from the front over the drives and pushes it out the rear. In my case, the rear would be facing the floor, so I wonder if there is an optimization here.
    • I know the fans can be reversed such that air is pulled in from the rear (facing the floor) and pushed out over the drives (facing the ceiling), but would doing so be beneficial in this situation?
    • Also, I haven't started to research less noisy replacement fans for both those at the backplane, rear, and CPUs, so if you have suggestions, please chime in.
  • Modifications to Closet: I'm toying with the idea of installing a ceiling fan to pull hot air out of the closet (59.2 cubic feet) which would blow that air into an enclosed space between the drywall ceiling and concrete slab overhead (several hundred cubic feet in volume). Initially, I considered connecting the fan to the dryer exhaust, but apparently this is against code. This closet is adjacent to a utility closet with water heater, etc. so a sidewall register could be placed at the bottom of the closet to pull cooler air in from that adjoining space. I've tried to find examples of something similar being done, but I've been unsuccessful in my research.
    • What are your thoughts on the general idea of adding a ceiling fan? And any suggestions as to a specific unit?
    • Any thoughts on how to make this fan temperature controlled instead of operated simply by a switch?
Thanks in advance for your help and thoughts. I'll post back once completed with pictures, results, etc.

Supermicro Chassis Airflow Diagram
SM Chassis Reversed Airflow.jpg
Rack Solutions "Open Frame Wall Mounted Rack"
features-wall-rack.gif
 

herby

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Aug 18, 2013
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You can install a line voltage thermostat pretty cheap if you aren't afraid to change out the light switch for one, but I don't really understand where the hot air is going and the cool air is coming in from.

In an smallish enclosed space you'd really just be swishing warm air around.


Could you get cool air in one way and warm another, or maybe a full louvered door?

Edit: If you get a full louvered door and it's still too warm, maybe a simple box fan pulling into the closet on the floor on an outlet thermostat (like this: https://www.amazon.com/Lux-Heating-Cooling-Programmable-Thermostat/dp/B000E7NYY8/)
would pull in enough cool air, and the warm air could exit the louvers nearer the ceiling.
 
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svtkobra7

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Jan 2, 2017
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but I don't really understand where the hot air is going and the cool air is coming in from.
Allow me the opportunity to paint a better picture:
  • Cool air: My idea is to create a "conduit" ~6" above the floor in the server closet for cooler air to enter. There are three walls to the closet (the forth has the door) and the utility closet is great as the other side wouldn't be visible unless you opened the utility closet and looked at the floor. That "conduit" for cooler air would be covered by a register on each side and is essentially holes in two pieces of drywall separated by a metal stud.
  • Hot air: I can't think of a great way to describe the enclosed space above the closet. In my building, the ultimate vertical boundary on the floor and ceiling is the 6" concrete slab between floors. In some areas there is exposed concrete and in some areas there is horizontal drywall ~20 inches below that concrete. That area is enclosed space and contains the dryer duct, other vents, Ethernet cabling, etc. As it is several hundred cubic feet of space, I believe simply pushing hot air into that space without a defined exit would be okay.
  • Reference poor diagram of my idea and an image from a for sale listing (where I have called out that enclosed space with red markup, note there is a different layout in my condo, but this should illustrate it adequately).
2017-03-24_0-17-15.jpg

2017-03-24_1-04-48.jpg

You can install a line voltage thermostat pretty cheap if you aren't afraid to change out the light switch for one
Could you get cool air in one way and warm another, or maybe a full louvered door?
If you get a full louvered door and it's still too warm, maybe a simple box fan pulling into the closet on the floor on an outlet thermostat (like this: https://www.amazon.com/Lux-Heating-Cooling-Programmable-Thermostat/dp/B000E7NYY8/)
would pull in enough cool air, and the warm air could exit the louvers nearer the ceiling.
  • I think my plan does get cool air in / warm out, but with a better understanding now, I'm curious as to your assessment of potential effectiveness? It will be fun to quantify the effectiveness of the solution I implement by measuring temp before / after.
  • That outlet thermostat is very cool. It looks like it is designed for a fan to plug into, but I had intended to go the route of fan install with direct wire.
Thank you for your reply - your feedback is greatly helpful.
 

marcoi

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Apr 6, 2013
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I'm more of a function over forms guy, so my ideas are based on that concept. ;)

My question to you is, are you required to keep the door on the closet? If that isn't a requirement, you could get a smaller rack on casters and roll it mostly into the closet space. Then you wouldn't need to deal with modifying your server fans, etc. As for heat, you can still put a small vent or fan in the ceiling to let the heat travel up and out of the closet space. If noise is a concern you can always build an alternative "door" maybe made out of Styrofoam with some sound damping panels glued on. The pseudo door could have a small entry in the bottom with low RPM fans blowing cold air from floor area into the closet area.

Again, my ideas might not be Wife approved, so proceed with caution haha.
 

4004

Member
Feb 8, 2016
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Calculating about 300W idle.

Bottom line is I doubt the ceiling fan is necessary. If you are convinced convection will not work, then use a quality exhaust fan.

https://www.amazon.com/quiet-exhaust-fan/s?ie=UTF8&page=1&rh=i:aps,k:quiet exhaust fan

Open the top of the closet for the heat to escape (convection), too warm, then crack open the door until you decide the next step (vent the door or install a louvered door).

If the door is off of the hardwood floor it will likely be enough space for convection/fan to do the work.
 

svtkobra7

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Jan 2, 2017
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I'm more of a function over forms guy, so my ideas are based on that concept. ;)
I can dig it ... form follows function ... in absence of other variables. But, given the situation I think a happy median between form and function can be found, without compromise to form.

My question to you is, are you required to keep the door on the closet?
No

If that isn't a requirement, you could get a smaller rack on casters and roll it mostly into the closet space. Then you wouldn't need to deal with modifying your server fans, etc.
Certainly an interesting idea that I had not considered. In addition to not needing to modify the fans it does have the advantage of being an easier install. But wouldn't it be kinda fun to reverse them and see the effect, especially quantitatively measured? The problems I see with this approach are that I could not seem to find a ~12U enclosure at a reasonable price and unfortunately since this is a condo and I'm space constrained, that closet opens to the "living area" (dining room + living room) where aesthetics and noise are of concern.

As for heat, you can still put a small vent or fan in the ceiling to let the heat travel up and out of the closet space. If noise is a concern you can always build an alternative "door" maybe made out of Styrofoam with some sound damping panels glued on. The pseudo door could have a small entry in the bottom with low RPM fans blowing cold air from floor area into the closet area.
I'm not an engineer, so this is just a supposition, but since that closet is so small (59.2 cubic feet) and ceiling fans like I proposed can move several times that volume per minute, with the door left as is, wouldn't some static pressure be created? Removing the door would reduce the effectiveness of that heat extraction I would think, no?

Again, my ideas might not be Wife approved, so proceed with caution haha.
Thankfully wife approval doesn't apply ... yet ... I would definitely catch some flak from the girlfriend and friends though.
 

marcoi

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Apr 6, 2013
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check on Craigslist for racks, you might be able to find a few smaller ones for cheaper then online.

ps - i totally get modifying servers to experiment :)
 

svtkobra7

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Jan 2, 2017
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check on Craigslist for racks, you might be able to find a few smaller ones for cheaper then online.
I definitely have, but I've been unsuccessful in finding either: (a) a vertical wall mount (which is so niche that I doubt I will ever find), or (b) a ~12U enclosure. Of course there are regular racks for sale. I live in Atlanta and while there are a number of datacenters in Alpharetta (suburb) and Atlanta, the supply isn't quite there as this isn't Silicon Valley East. ;)

ps - i totally get modifying servers to experiment :)
:)
 

svtkobra7

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Jan 2, 2017
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Calculating about 300W idle.
I don't doubt your correctness, but may I ask for my own education how you got there?

Bottom line is I doubt the ceiling fan is necessary.
Again, I don't doubt your correctness, but may I ask why you think so? Is it because creating an escape for the warm air at the top of the closet (with only a vent cover, no fan) will be sufficient (I'm following your reply correctly)? If so, I didn't consider that and think you are right in no need for a fan.

Perhaps, my idea is biased by simply wanting to take this project "too far" and I will be the first to admit that I don't have the education or experience to support my proposal (it is, at best, an uneducated proposal - thus the request for community feedback).

I will say that with the door closed (no fan, etc.) I had temperature issues with just a QNAP TVS-871, TVS-453A, and TS-231 running concurrently. I had to leave the door cracked to allow heat to escape. Comparing those QNAPs to the Supermicro CSE-836 is an apples to oranges comparison from both heat and noise perspectives, right? Due to the noise, I would think that if possible I would want to leave the door closed.

If the door is off of the hardwood floor it will likely be enough space for convection/fan to do the work.
There is 3/16" of an inch between the floor and bottom of the door. Do you think that is enough?
 

Dawg10

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Dec 24, 2016
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There are a couple parameters you need to keep in mind...

First; it's preferable to force cool air in rather than draw hot air out. The cooler the air the denser it is; this translates to the same fan being able to push more cool air than warm. If you want to get real fancy you could have both a forced air fan at the bottom and an induced air fan at the top and balance their loads so the closet maintains a slightly positive pressure.

Second; air needs someplace to go... You can't force air into a plenum if there's no exit; it will simply pressurize the space. The corollary to this is you can't extract air from a space if there's no inlet; it will simply create a lower pressure inside the closet than out.
 

4004

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Feb 8, 2016
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I don't doubt your correctness, but may I ask for my own education how you got there?



Again, I don't doubt your correctness, but may I ask why you think so? Is it because creating an escape for the warm air at the top of the closet (with only a vent cover, no fan) will be sufficient (I'm following your reply correctly)? If so, I didn't consider that and think you are right in no need for a fan.

Perhaps, my idea is biased by simply wanting to take this project "too far" and I will be the first to admit that I don't have the education or experience to support my proposal (it is, at best, an uneducated proposal - thus the request for community feedback).

I will say that with the door closed (no fan, etc.) I had temperature issues with just a QNAP TVS-871, TVS-453A, and TS-231 running concurrently. I had to leave the door cracked to allow heat to escape. Comparing those QNAPs to the Supermicro CSE-836 is an apples to oranges comparison from both heat and noise perspectives, right? Due to the noise, I would think that if possible I would want to leave the door closed.


There is 3/16" of an inch between the floor and bottom of the door. Do you think that is enough?
Saying no to the ceiling fan you pictured because better choices exist. Like a multi speed exhaust fan and maybe just an opened ceiling + your plan for the louvers 6" above your floor, more below.

3/16 is not much surface area. 3/16 x door width = area below door, estimating that comes out to 5 or 6 sq inches. Louvers would be in order, exhaust fan or convection.

Not sure of the power draw or noise of your previous equipment. Weatherstripping the door / sound absorption material is low cost fine-tuning you DIY project.

I'd plan on keeping it simple, and have contingency plans. Plan on the cool air conduit (you mentioned earlier). Strongly consider a quiet exhaust fan & then an exhaust louver for the above closet space. Convection may work, but I am not standing in your condo and have reread your description about the area above being closed off and am hesitant to say it will work.

It may be you can install a vent between the concrete and the enclosed area IE, there will be two openings in the dry wall. One in the top of the closet and one between the concrete uppermost drywall. Guessing it is drywall below the concrete (below the top red line in your photo). If so then convection is a probable course.

-It really comes down to how much time you have to fine tune your cooling project.

Lastly, keeping it room temperature is not necessary, but maintaining operating range is necessary.
 

nk215

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How about building a small platform on top of the wall on the left and put the server there?
 

herby

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Aug 18, 2013
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So I just looked at your picture and it looks like your idea might work but I have a few reservations.

That plenum above the kitchen has an opening running below the concrete ceiling, likely for return air so that's good if the area above the closet isn't separated. In fact if it's connected you might not need a fan as a pentration into that plenum will naturally draw air to your air handler.

However I don't think you'll get a lot of cool air with a vent from the utility closet unless it has it's own register.

I still think a louvered door would be best, or a vent in it or some wall leading to an air conditioned space. If the area above you server closet's ceiling is common to that plenum just adding a ceiling vent should take care of the warm air.
 

svtkobra7

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Jan 2, 2017
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My apologies for the delayed reply, let me reply to several comments in one post. Thank you all for weighing in, I've learned quite a bit already.

There are a couple parameters you need to keep in mind...

First; it's preferable to force cool air in rather than draw hot air out. The cooler the air the denser it is; this translates to the same fan being able to push more cool air than warm. If you want to get real fancy you could have both a forced air fan at the bottom and an induced air fan at the top and balance their loads so the closet maintains a slightly positive pressure.
I will be honest, and not that it is any excuse for a lack of knowledge, but none of my degrees are scientific in nature (rather economics, business, and finance) and I'm certainly lacking in knowledge here.

If a fan moves X cubic feet of air per minute, it will move X cubic feet regardless of whether that air is hot or cold, right? Are you suggesting that due to the differential in density, that a fan is able to move more cool air? Not questioning whether you are right, just seeking academic understanding.

Second; air needs someplace to go... You can't force air into a plenum if there's no exit; it will simply pressurize the space. The corollary to this is you can't extract air from a space if there's no inlet; it will simply create a lower pressure inside the closet than out.
You have a solid point here, but allow me to humbly and ignorantly point out that your statement assumes the plenum is hermetically sealed, and while it is certainly "sealed" from view, it is by no means air tight. I assume that air expelled into that cavity, is displaced by "fresh" warmer air, and that cooler air, being denser sinks due to gravity and finds a way to "escape" perhaps between along the studs, etc. Further, I assume that pressure would not actually build with the type of fan I would be using (or maybe it does increase marginally). Perhaps a poor analogy, but as an example to the converse, when you turn a bathroom vent fan on and the bathroom door is closed, that fan doesn't cause the bathroom to implode.

That being said, what would actually occur in this scenario where you have a fan extracting warm air from a 59 cubic foot space into one that is at least 453 cubic feet? Also, what happens if I simply leave convection to do its magic with no fan? I imagine the temperature of those two spaces would balance and the solution would lose effectiveness?

Saying no to the ceiling fan you pictured because better choices exist. Like a multi speed exhaust fan and maybe just an opened ceiling + your plan for the louvers 6" above your floor, more below.
Thanks for the clarification. The link you provided is a search on Amazon for "quiet exhaust fans" and the fan I referenced (only directionally) actually appears as the third result.

Not sure of the power draw or noise of your previous equipment. Weatherstripping the door / sound absorption material is low cost fine-tuning you DIY project.
Not that you asked the question, but I looked it up on qnap.com:
  • TVS-871: 82.51 watts (in operation) with 8 HDDs installed; 23.1 dB(A)*
  • TS-453A: 32.35 watts (in operation) with 4 HDDs installed; 19.7 dB(A)*
  • TS-231: 20.56 watts (in operation) with 2 HDDs installed, 15.4 dB(A)*
  • * "Testing environment: Refer to ISO 7779; Maximum HDD loaded; Bystander Position ; Average data from 1 meter in front of operating NAS"
Convection may work, but I am not standing in your condo and have reread your description about the area above being closed off and am hesitant to say it will work.
Perhaps additional description of the plenum and diagram provided at the end of this post assist in providing additional detail needed to make such a determination?

It may be you can install a vent between the concrete and the enclosed area IE, there will be two openings in the dry wall. One in the top of the closet and one between the concrete uppermost drywall. Guessing it is drywall below the concrete (below the top red line in your photo). If so then convection is a probable course.
I don't quite follow your suggestion (if you could explain further it would be appreciated), but let me add that all space in the plenum is common and there are no internal barriers* between the horizontal drywall (21.5" below the concrete slab) and the concrete slab ceiling.
* By this I mean, as an example, there is a wall between the laundry room and the bathroom, and the metal studs certainly extend the full length between the concrete floor and concrete ceiling, but above that plane of horizontal drywall, there is not additional vertical drywall above it, only below it, to create the partition between those rooms.

-It really comes down to how much time you have to fine tune your cooling project.
Plenty, I'd rather it take longer and do it right. To add support to that comment, I actually have removed the drywall from the rear of the closet and will be replacing it tomorrow.

How about building a small platform on top of the wall on the left and put the server there?
Thank you for the suggestion. My apologies for the confusion, but that actually is not my condo. As mine is too much of a mess at the moment, I pulled a picture from a for sale listing to visually illustrate the plenum I was referring to.

That being said, I believe there are two reasons why a shelf wouldn't be a tenable solution:
  • The "server closet" is where the Structured Media Enclosure is located and all of the Ethernet drops terminate, so my preference would be to keep everything consolidated in this space.
  • My condo has metal studs, which are not meant to be load bearing and extremely flimsy. I won't pretend to know the physics behind this statement, but: Assume you have a box 19" wide by 5.25" tall by 30" deep, it is much easier to securely fasten that box to the wall by the side which is 19" x 30" as opposed to the side that is 19" x 5.25".
So I just looked at your picture and it looks like your idea might work but I have a few reservations.

That plenum above the kitchen has an opening running below the concrete ceiling, likely for return air so that's good if the area above the closet isn't separated. In fact if it's connected you might not need a fan as a pentration into that plenum will naturally draw air to your air handler.

However I don't think you'll get a lot of cool air with a vent from the utility closet unless it has it's own register.

I still think a louvered door would be best, or a vent in it or some wall leading to an air conditioned space. If the area above you server closet's ceiling is common to that plenum just adding a ceiling vent should take care of the warm air.
Using a picture of another floorplan was a mistake, that is actually not my condo. To respond to your comments:
  • I actually have no clue what type of HVAC system is installed in my condo, but I can add that the utility closet contains an air handler (suspended above the water heater), the bottom of which is "open" and covered only by an air filter. Is it possible all of the vents are supply and that open air filter serves as the sole "return"?
  • Perhaps I should have added this earlier, but the door to the utility closet is louvered. My (unstated) thinking was such that adding a floor level vent (for cool air) to the utility closet was sufficient as: (a) it would allow for cooler air to flow into the server closet thanks to the louvers on the utility closet door and (b) since whoever designed the condo thought the utility closet to have sufficient circulation for the air handler, that it would serve my needs as well. Assumption: Air handler moves significantly more air than I'm looking to expel from the server closet.
  • The area included in that plenum is shaded grey in the attachment and includes space above the laundry room, bathroom, server closet, and entry to bathroom from bedroom. The aforementioned areas are connected to an area above the bedroom which leads to the exterior of the building and allows various vents to expel air to the outside world.
  • That plenum area excludes the utility closet, as all four sides of that closet extend fully to the concrete slab above.
Does providing that additional information add additional needed detail to what I'm working with here? If so, how does it impact your recommendation?

Reference the diagram I have added to this message. The grey shading indicates the plenum area, inclusive to the area above the server closet, and there are no "internal" barriers.

Floorplan.jpg
 

herby

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Aug 18, 2013
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Wait, if the air handler is in the utility closet that's where you want your hot air to go.

All the air that comes out of vents in your apartment is sucked into that closet first. It goes through that filter in the air handler, passes over an evaporator coil to be cooled, and then is discharged through several drops to the registers in different rooms.

A vent connecting those closets near the ceiling and a vent down low in the server closet door would work pretty well. As an alternative you could always use a through wall fan and move more air from the server to utility closet.
 

svtkobra7

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Jan 2, 2017
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Wait, if the air handler is in the utility closet that's where you want your hot air to go
Correct, that is where it is. See below picture.

All the air that comes out of vents in your apartment is sucked into that closet first.
That is what I was thinking (so obviously, no return vents like would be typical in a single family home). I'm assuming this works as no return vents are needed when you are working with only 1200 square feet.

It goes through that filter in the air handler, passes over an evaporator coil to be cooled, and then is discharged through several drops to the registers in different rooms.
Tangential: That evaporator coil you mentioned isn't actually doing the cooling, right? As view able from Google Earth there are hundreds of these guys on the roof, and you can see dozens off to the side as you drive through the parking deck, etc. I'm assuming they are connected somehow. [Again, no clue on this stuff]

PC54560-d.jpg

A vent connecting those closets near the ceiling and a vent down low in the server closet door would work pretty well. As an alternative you could always use a through wall fan and move more air from the server to utility closet.
Let's assume:
  • Airflow to Server Closet: Vent, no fan @ 6" high allowing for passive movement of cool air from utility closet to server closet.
  • Airflow from Server Closet: Duct from fan @ 98" - 120" high actively moving warm air from ceiling of server closet to utility closet.
Is this solution predicated upon the (a) air handler being in operation by one of the following options or (b) are we just creating a loop (cool air moves from utility closet to server closet, warm air from server closet is expelled to utility closet, that warm air cools and descends toward floor, repeat):
  • A1. The air handler is consistently activated by the thermostat telling it to heat or cool and on the "AUTO" fan setting. I should note that I'm quite frugal and most people would find it far too cold in my condo during the winter and far too hot during the summer (I live in Atlanta). High temps just don't bother me for some reason.
  • A2. The air handler is activated by the thermostat being set to the "ON" fan setting.
I ask as I'm curious and also I'm not sure how the air handler comes into play, as currently with the fan set to "AUTO" it is active maybe 1% of the time.

So we are shooting for something like this?

IMAG1259_2.jpg

EDIT: Better illustration attached.
 

Dawg10

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Dec 24, 2016
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If a fan moves X cubic feet of air per minute, it will move X cubic feet regardless of whether that air is hot or cold, right? Are you suggesting that due to the differential in density, that a fan is able to move more cool air? Not questioning whether you are right, just seeking academic understanding.
The volume remains the same, but the static pressure generated by a fan moving warm air is less than the static pressure of the same fan moving cold air. The same fan at the outlet is moving less mass than it would at the inlet.

It's all about pressure differentials; the higher the differential the faster air moves.

You have a solid point here, but allow me to humbly and ignorantly point out that your statement assumes the plenum is hermetically sealed, and while it is certainly "sealed" from view, it is by no means air tight. I assume that air expelled into that cavity, is displaced by "fresh" warmer air, and that cooler air, being denser sinks due to gravity and finds a way to "escape" perhaps between along the studs, etc. Further, I assume that pressure would not actually build with the type of fan I would be using (or maybe it does increase marginally). Perhaps a poor analogy, but as an example to the converse, when you turn a bathroom vent fan on and the bathroom door is closed, that fan doesn't cause the bathroom to implode.

That being said, what would actually occur in this scenario where you have a fan extracting warm air from a 59 cubic foot space into one that is at least 453 cubic feet? Also, what happens if I simply leave convection to do its magic with no fan? I imagine the temperature of those two spaces would balance and the solution would lose effectiveness?
You are correct in your analysis of air finding escape routes. Again, it's about pressure differentials; with a large enough discharge opening from your overhead plenum there will be zero differential thus unrestricted flow out. While the overhead plenum may not be 100% sealed, it presents an area of pressure resistance to the movement of air: a large volume of static air that you are going to try and displace through cracks... This will be only marginally effective; a nice test but not a reasonable utilization of resources.

The same consideration needs to be applied to your source air: does your utility room have the ability to supply unrestricted air? (and the hot water heater must be electric, not gas).

/edit. Having reviewed the latest conversations, I must agree with Herbie on using the existing air handler as your primary solution. I would first create a single opening (12-16" square) between the top of the server closet and the utility room and install a louvered vent at the bottom of the server room door. Then, by using thin cardboard, adjust the size of the 3 openings to maintain operating temperature.

Adjustment points:
- inlet @ server room door louver
- connection between closets
- balanced with louver on utility room door.
 
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herby

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Aug 18, 2013
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That is what I was thinking (so obviously, no return vents like would be typical in a single family home). I'm assuming this works as no return vents are needed when you are working with only 1200 square feet.
With any air conditioning system (well any system with forced air) there is a return. The return to your air handler (AHU) is where the filter is located. The return to that utility closet is the existing louvered door. Warm air in your apartment is pulled into the utility closet, into the AHU, cooled by the evap coil, and discharged by the AHU's fan though ducts to other rooms, rinse and repeat.

Tangential: That evaporator coil you mentioned isn't actually doing the cooling, right? As view able from Google Earth there are hundreds of these guys on the roof, and you can see dozens off to the side as you drive through the parking deck, etc. I'm assuming they are connected somehow. [Again, no clue on this stuff]

View attachment 5003
That's a condensing unit, most A/C systems in residential are split systems with an evaporator coil inside and a condenser outside. Your AHU does several things, it moves air around your apartment with the fan, filters air with the filter (although the filter's mostly to keep the evaporator from clogging with dust), cools the air with the evaporator coil, and heats the air with either electric strip heaters, or a gas burner.


Let's assume:
  • Airflow to Server Closet: Vent, no fan @ 6" high allowing for passive movement of cool air from utility closet to server closet.
  • Airflow from Server Closet: Duct from fan @ 98" - 120" high actively moving warm air from ceiling of server closet to utility closet.
Is this solution predicated upon the (a) air handler being in operation by one of the following options or (b) are we just creating a loop (cool air moves from utility closet to server closet, warm air from server closet is expelled to utility closet, that warm air cools and descends toward floor, repeat):
You can't really get a loop there, all the air in the utility closet is getting sucked into that air handler, and all the air in your apartment is getting sucked into that utility closet.

  • A1. The air handler is consistently activated by the thermostat telling it to heat or cool and on the "AUTO" fan setting. I should note that I'm quite frugal and most people would find it far too cold in my condo during the winter and far too hot during the summer (I live in Atlanta). High temps just don't bother me for some reason.
  • A2. The air handler is activated by the thermostat being set to the "ON" fan setting.
I ask as I'm curious and also I'm not sure how the air handler comes into play, as currently with the fan set to "AUTO" it is active maybe 1% of the time.
You could leave the fan set to on, and the system on auto. The fan isn't using much power it's the compressor in your condensing unit, and to a lesser extent the strip heaters that are energy hogs.

With most thermostats the SYSTEM can be set to OFF/COOL/HEAT/AUTO and the FAN to ON/AUTO.

SYSTEM [OFF] FAN [ON] your AHU is just circulating the air in your apartment
SYSTEM [COOL] FAN [ON] your AHU is circulating the air in your apartment, and if the temperature is above the cooling set-point the compressor will run in your condensing unit and start the refrigeration cycle that cools.
SYSTEM [HEAT] FAN [ON] your AHU is circulating the air in your apartment, and if the temperature is below the heating set-point the heat strips in your AHU will be energized and heat.
SYSTEM [AUTO] FAN [ON] your AHU is circulating the air in your apartment, and if the temperature is above the cooling set-point the compressor will run in your condensing unit and start the refrigeration cycle that cools, or if the temperature is below the heating set-point the heat strips in your AHU will be energized and heat.

Setting the FAN to AUTO will have the AHU fan wait until a call for heating or cooling happens to run.

So we are shooting for something like this?
View attachment 5005
EDIT: Better illustration attached.
The top vent yes, but the bottom vent would be pointless as the air isn't going to flow the way you want there.

Its all like a river the air flow, every thing is running towards that air handler. Some air will meet restrictions or have a longer path but it's all runing that way.

You are correct in your analysis of air finding escape routes. Again, it's about pressure differentials; with a large enough discharge opening from your overhead plenum there will be zero differential thus unrestricted flow out. While the overhead plenum may not be 100% sealed, it presents an area of pressure resistance to the movement of air: a large volume of static air that you are going to try and displace through cracks... This will be only marginally effective; a nice test but not a reasonable utilization of resources.

The same consideration needs to be applied to your source air: does your utility room have the ability to supply unrestricted air? (and the hot water heater must be electric, not gas).

/edit. Having reviewed the latest conversations, I must agree with Herbie on using the existing air handler as your primary solution. I would first create a single opening (12-16" square) between the top of the server closet and the utility room and install a louvered vent at the bottom of the server room door. Then, by using thin cardboard, adjust the size of the 3 openings to maintain operating temperature.

Adjustment points:
- inlet @ server room door louver
- connection between closets
- balanced with louver on utility room door.
Dawg raises a good point about air flow. with the utility closet’s louvered door way bigger than the new return you make from the server closet you might not get the pull you want. I think you can only try and see, and then make tweaks to direct the air flow as you need.
 

svtkobra7

Active Member
Jan 2, 2017
362
95
28
What about this, which is a slight play on Herbie and your recommendations:

1. Inflow to Server Closet: Vent, no fan @ 6" high allowing for passive movement of cool air from utility closet to server closet. I really want to stay way from a louvered door (I hate their appearance and there is already one on the utility closet).
2. Airflow from Server Closet:
  1. Install fan on ceiling of server closet. Route duct work horizontally from above the ceiling of the server closet to enter the utility closet.
  2. Further route duct work down and connect to the intake of the air handler by 3.25" x 10" transition* (or something similar which doesn't block too much of the air filter).
  3. Remove 3.25" x 10" portion of air filter (it would impede air flow) and seal filter to transition.
  4. Install filter media in ductwork so that air from this alternate air handler intake is filtered the same as air flowing in normally through the air filter.
* I went for the first image I could find (not recommending this actual transition, used for conceptual purposes).

I have some outstanding questions for Herby as to how this design (without the latest modifications proposed here) actually works, but moving on to this modification:
  • Does it work without the air handler fan off (which it would be most of the time)? I have no clue what goes on inside there, my concern is that if it isn't on, is there anything to prevent warm air traveling up through the air handler and then ultimately dispersing through the supply vents?
  • I'm nearly certain it works well when the air handler is active. Free heat during the winter to boot (well, not really).
IMAG1259_3.jpg

Now if we want to take it a step further, and take one out of the car tuner playbook, we add add a bottle of Nitrous Oxide and automate it spray when ever CPU utilization or temperature hits a certain threshold. That would add some cold, dense air to the equation! It would probably result in a 200% improvement on benchmarks as well. OK OK ... very bad joke (bad sense of humor generally) ... my head hurts from thinking about this and needed a laugh.
nos-14760_5.jpg
 

herby

Active Member
Aug 18, 2013
187
54
28
The utility closet is under negative pressure when the AHU fan is running, any vent to the utility closet is going to be pulling in air when the AHU runs.
No, air isn't really moving through your AHU or ducts unless the fan is running.

Personally I wouldn't make any modifications to your air handler unit or duct work, that seems overkill to me.

How about a set up like this, up top is a through wall fan, either always on, or on a thermostat. Lower in the wall is just a passive vent.