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Phil
Phil, Shop owner
Category: Appliance
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Experience:  Degree, Mech. engr. shop owner. 51 years experience
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Buying a portable AC unit to cool a small room w/ big server...

Customer Question

buying a portable AC unit to cool a small room w/ big server... questions about AC unit: sizing, efficiency, performance, noise, power
Submitted: 1 year ago.
Category: Appliance
Expert:  Whrlp Master Tech replied 1 year ago.
Hello from JA
My name is Woody.
I will be glad to assist you today.
I have been servicing ALL Major Brands of Appliances for 34 Years,
and have over 100,000 in home repairs and over 60,000 phone and internet repairs under my belt.
How big is the room 6x6, 10x10?.
and how big of a server ? how much heat does it produce?
Customer: replied 1 year ago.

This is in an apartment's 2nd bedroom.

My project is in transition from 2x old servers --> 2x new server

Currently: two old legacy servers have a combined calculated 4600btu theoretical maximum.

I plan to replace both old legacy servers with a newer more powerful one (single) server with a pair of 920w power supplies and a calculated 6300btu theoretical maximum.

>>these server btu #'s are calculated maximums is the power supplies are ran at 100% output. I will **not** be running anywhere close to maximum, I do not know what will be the actual operating btu of the new server. so these are worst case scenario numbers.<<

I do not have the precise dimensions of the room, but it is not larger than 12ft x 12 ft.

This is in an apartment:
-- window ac unit is not an option
-- noise is concern

I sleep in the room next to this 2nd bedroom. I would like to find a AC unit that will reduce the temp of the room while also being quiet enough to live with.

Here's a unit that is "quiet" at 50 db, cools 10000 BTU or up to 400 sq feet:

http://www.honeywellstore.com/store/products/portable-air-conditioner-10000-btu-cooling-single-hose-honeywell-mn10cesww.htm

My concern is AC unit cooling performance. If the room is too small, or the inside temp of the room is not high enough, etc. does that affect the resultant cooling of the portable unit?

For example: if I use an AC unit rated up to 400sq feet in a room not larger than 144sq feet. Will this "choke off" the cooling performance of the portable AC unit?

Expert:  Whrlp Master Tech replied 1 year ago.
I think the 10,000 BTU will be fine .
Because you have the capabilities of up to 12,000 BTU of the server /power supplies.
And yes if it was just the room it self and the room and it was too small it will effect the air conditioners operation ,but you also have that possible 12,000 BTU to look at also .
Depending upon how the servers are mounted make sure you can have good air flow over them to remove all that heat .
And these portable unit are very quiet ,you should have no noise issue at all.
Customer: replied 1 year ago.

You said:
-- portable air conditioners are limited by the size of the room
-- portable air conditioners of both 9k btu and 12k btu are options for my situation

I provided the following estimates:
-- Room size not larger than 12ft x 12ft (144sq ft)
-- Server worst case scenario heat theoretical max calculated at 6300btu (1835watts)

Selection of portable air contioner unit:
-- Honeywell 10k btu portable air conditioner unit
http://www.honeywellstore.com/store/products/portable-air-conditioner-10000-btu-cooling-single-hose-honeywell-mn10cesww.htm

Question #1) Are you saying that my room size will allow proper effective efficient cooling performance of portable air conditoner units no larger than 12k btu?

Question #2) Are you saying that my Server worst case scenario heat theoretical max calculated at 6300btu would be best matched with a portable air conditioner unit no smaller than 9k btu?

Question #3) Power.... I only have 15amp circuits in my apartment. I want air conditioner on separate circuit from my server. I plan to use professional grade extension cord from the family room [w/ lights + tv] to put the portable air conditioner unit on the circuit powering the family room. Is this a bad idea?

Question #4) "auto-evap"... I like the idea of "auto-evap" because I worry about any water near my server. Servers are electronic, electricity + water = bad. I don't have a drain handy near by, would need to bring water to the bathroom. Is "auto-evap" reliable? Would you rely on "auto-evap" to handle water drainage such that you would leave the portable air conditioner unit unattended for days or a week or more?

Question #5) "condensation"... mixing cold air + warm indoor air, possible large amounts of condensation?

Question #6) "humidity"... what do I need to know? Plan for?

Question #7) Choosing a model... noise, I eat/sleep/live within 14 ft of the unit. What do you think about the Honeywell model I suggested (see link above)? What portable air conditioner would you suggest? Why? What have you experienced?

Question #8) This is my first time buying any air conditioner... you have many many years of experience over me... please do not worry about giving me too much info. I want you to overload me with details. Are there things I should be asking? Did I miss anything?

Expert:  Phil replied 1 year ago.

Welcome! We keep going until you have all of the information you need.[b/]. Extensive training & coaching also available.

The formula for cooling electronic equipment is 3.4 btu's per watt.
920 watts of power for the new server translates to 920x3.4 = 3,128 btu needed to cool the serve alone... It is not a good idea to de-rate the servers because the load is not always at the peak.

If the room is 144 square feet with window and possibly older with bad insulation and in a humid environment such as the gulf coast or much of the east coast, 5,000 to 10,000 btu/hr to cool the room depending on how much outside air infiltration there is.

(with **stand alone, portable AC units** exhausting roughly 350 cfm per ton, and in a humid area for instance, the humidity load alone will consume more than the 10,000 btu stand alone AC unit can produce.)... that is a very important set of issues.

I can write you a book, and will if its needed.

However for this post that the largest 15 amp **window unit** (not a portable AC) you can get would be the best choice... it it happens to be rated for 12,000 btu's, it will only put out 9,000 or 10,000 btu's on a very hot day, say over 95F... and you might have a chance of squeezing by.

We always design for worst case conditions.

Let me know which region of the US your are in, the age of the home so that I can assess air infiltration and most probable insulation. and if the room has an attic above it or another room.

Please insert comma's as needed when we talk about thousands of btu's an hour, that helps to eliminate confusion.

We can go from there.

Customer: replied 1 year ago.

My background: I'm a network engineer and a technical writer. You will **NOT** drown me with specifications/details/etc. You will turn me off with overly-general statements... unless you legitimately have had "...20 years of good experience with brand x..." okay.

The server has dual 920w power supplies.

The apartment complex is near Madison, WI; Thankfully, the windows are pretty new and good about leaks.

FYI -- I double checked. All my circuits are 10amp only.

I want to keep my server on separate circuit from the portable AC unit.... my thought was running a professional grade extension cable from the living room. The living room (TV+lights) are also on 10amp circuit, separate from the bedrooms.

-->> any concerns about even professional large gauge extension cords?

Looking over the portable AC units online. Knowing limit is 10amp. I suspect I am going to be limited to below 10,000 btu portable AC unit.

-->> would a 5,000 btu low amp (5amp to 6.x amp) air conditioner be helpful?

When the manufacturer lists power specs for these portable AC units... is that peak (surge) compressor usage? I know turning on a compressor consumes the highest wattage.

-->> how about water issues of the AC unit?

-->> noise, looks like range of 45 to 54 db is the norm *shrug*

-->> I'm not looking for anyone to be responsible for what I decide to buy, but I am looking to "go shopping online" with someone (if you will). please send me links to portable AC units that you feel match. Tell me what specification(s) you liked.

Expert:  Phil replied 1 year ago.
Hello again, I will answer your most recent post in context... my remarks in [[....]]

My background: I'm a network engineer and a technical writer. You will **NOT** drown me with specifications/details/etc. You will turn me off with overly-general statements... unless you legitimately have had "...20 years of good experience with brand x..." okay.

[[ I have NO experience with the brand of portable you might want to buy, maybe a month at most depending on the brand]] [[I do have 51 years experience on larger systems including large scale cray computer rooms, into the 20 to 250 million dollar range, its on my verified resume posted on JA you can access it...


My first 30 years as a mechanical electrical contractor with a crew of 27 ending in Los Angeles, the last 20 years consulting nationally for fortune 500 companies such as IBM, US Dept of Energy Nuclear weapons, Boeing military air craft and a dozen others. ]]

[[ The physics and math however remain the same, in this case largely because the portables exhaust air from the room (causing outside air to be sucked in) that is a problem in all cases and an insurmountable problem in high humidity areas, in those cases only 5% outside air is allowed. There are countless exceptions, none relevant here however.]]



The server has dual 920w power supplies.

[[ it is the total wattage that I need, very specifically. this is the first I have seen from you indicating dual 920w power supplies...or I had gone blind for a moment... whatever....

if its dual supplies at 920 watts each then 1,840 watts x 3.4 to get btu's per hour taking that cooling requirement into the 6,000 btu/hr range]]



The apartment complex is near Madison, WI; Thankfully, the windows are pretty new and good about leaks.

[[ the room will be pretty well insulated in that case with relatively low air leakage, however the portables do exhaust air and in the winter cold air will be drawn into the room and heated by the electronics and that will result in humidity well below 35 rh and that is damaging to computers ( low humidity allows static electricity charges to damage the electronics ]]

[[ you should not use portable ac units in this case for that reason and others I have mentioned earlier ]]



FYI -- I double checked. All my circuits are 10amp only.

[[ The US electrical code requires minimum wire size #14 awg, those should be fit with 15 amp breakers. Many if not most modern residences have #12 wire to the receptacles and 20 amp breakers. You can put a 12 amp continuous load on a 15 amp breaker circuit and 16.5 amps on a 20 amp circuit. ]]

[[ http://ecmweb.com/basics/sizing-circuit-breaker ]]

I want to keep my server on separate circuit from the portable AC unit.... my thought was running a professional grade extension cable from the living room. The living room (TV+lights) are also on 10amp circuit, separate from the bedrooms.

[[ indeed the server needs to be on a separate breaker, and through a UPS unit to insulate it electrical spikes on the utility grid ]].

It will most likely be necessary to run at least one extra #12 awg copper circuit to the server room.

Let me know what you think, we can go from there.

.