Optimum temperature to run rack rooms at ?

Question

We've got a AC unit in a rack room and are concerned about running it too cold as the heat from unit in the racks may cause condensation when with the cold air, is there a best practice to run the rack room AC at ?

We've got 1 AC unit for the whole room which takes an average temperature, rather than any specific temperature probes attached to specific hardware.

I think the current answers already address most of this, but I just felt it important to re-emphasize and contribute: - More important (save for extremes) than ambient air temperature is *temperature delta*, as the latter is what causes more damage to the equipment - You can obtain an independent desiccant unit (aka dehydrator), or if cost is a concern, you can use chemical-based agents such as dehydrated magnesium sulfate (epsom's salt) or diatomaceous earth, etc, to control moisture. — Arctiic, Feb 17 '22 at 06:54
@Arctiic I think your point about temperature delta is spot on. I don't think that you need to worry too much about too much humidity when cooling a server room, as the process of cooling the air will extract excess moisture. (ie the air out of the aircon will be cooler then ambient, and thus have less water in it then humid air going in - so I expect it will always bring down a high relative humidity in the room) — davidgo, Feb 17 '22 at 09:38

score 4 · Accepted Answer · answered Feb 06 '18 at 19:33

There is no single correct answer to this question.

Historically, colder was considered better.
Computers are designed to work in an environment suitable for humans, so 20-23 degrees is typical - and 19-22 degrees is typical for a data center.
Some places (like Google) have found it cheaper to run DC's hotter because the hardware failure rate is lower then the additional cooling bills.

I would be more concerned about having a single air conditioning unit - when it fails, you create a big change in heat, and this can be stressful to computer components - I expect more-so then a constant, warmer temperature.

Air conditioning units can typically maintain a reasonable level of humidity (aim for 45-55% if you can control it) for a DC - enough that static is not too much of a problem, and neither is condensation.

With respect of condensation, you probably don't need to worry too much about it (except for your air conditioning freezing up if its overworked). The amount of water that can be held in air is relative to the temperature. Thus any condensation which is going to occur is likely to occur at the point the air is cooled down - this is at the air conditioner - not the computers. (Especially because computers generate heat, they will drive away condensation because the air surrounding them can absorb more water). In fact, when an air conditioner is installed, it includes an outlet for the condensed water from the aircon.

[ Another tangentially related thought / explanation - if you ever have had a hot shower in a cold room - particularly with an extractor fan running, you will notice mist forming. This mist forms when the warm, wet air from the shower is cooled by the cold air moving past it, and squeezes out to form water droplets in the air. This happens at the place of cooling - ie by the air conditioner. If your mirror fogs up and you then blow over it with a hair dryer it clears rapidly (same effect of heat on a computer if their is water in the air) ]

Thanks just to clarify although i said we have an AC unit, its infact a comfort cooling unit (dosnt have the option to change / monitor humidity) — sam, Feb 06 '18 at 19:56
That should not be a problem - whats the make/model number ? — davidgo, Feb 06 '18 at 21:07
Surprisingly I could find no information on humidity or drying mode. That said, I would not worry too much about it. If you live in a very dry climate, maybe leave a glass/bowl of water out ( but not near the computes obviously (and top it up periodically)) if you are worried about lack of humidity and static discharge. Also make sure you have good grounding on your rack and equipment. Again, if you are worried about lack of humidity - you may be able to rip out or replace (regular) carpetting with something which won't generate as much static when move over it. — davidgo, Feb 07 '18 at 20:26

score 1 · Answer 2 · answered Feb 06 '18 at 19:32

I found this article from The American Society of Heating, Refrigerating and Air-Conditioning Engineers

https://www.ashrae.org/File%20Library/docLib/eNewsletters/steinbrecher--122011--11282013feature.pdf

hopefully this may be of use to you.

It mentions that Dry-Bulb Temperature can be within 64.4°F to 80.6°F

Dry-Bulb Temperature is usually referred to as "air temperature".

Optimum temperature to run rack rooms at ?

2 Answers2