Raise the Temperature!

by Gary Hill, President of DVL, LLC on 1/29/14 9:17 AM

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What better time to talk about raising the temperature than this frigid and gloomy month of January!  I am not talking about your house or office temperature, but your server room temperature, and specifically the return temperature of the air entering your cooling system.

Much has been written on improving efficiency of server room cooling system by raising the return air temperature.  What is not so well written is how to do this in smaller rooms that may not have the picture-perfect layout of a hot-aisle/cold-aisle design.  Let’s face it, there are many rooms that are oddly shaped, some with partial ceilings and even some with an exterior window wall.  These layouts are never properly addressed in articles we’ve seen.  The short answer may be DON’T, but if your room meets the following criteria you CAN.

  1. Understand the only temperature that matters is the temperature of the air entering your servers.  The hot-aisle (exhaust air) will always be hot, that’s physics.  It is important that that air stream is returned to the cooling system as directly as possible. 
  1. Sufficient cooling capacity in your dedicated cooling system to support the existing cooling load. Redundant cooling systems – which is always recommended is ideal. 
    What you need to determine is the capacity of your system at the conditions you desire to operate, and then compare it to your applied load.  The applied load should not be guessed!  You can start by looking at the load on your UPS system and then add-in non UPS-connected devices, external heat sources (like floor-mounted transformers that may have ended up in your room) and other seasonal or cyclical loads.  This can be a big task where you should engage available resources to help.  Hint – DVL engineers are happy to assist.  Please contact us if you would like our help.
  1. The building system is not heating your server room while your dedicated cooling system is trying to cool it!  The heat introduced by the building heating system should actually be part of the equation in determining your cooling load; but since we’ve seen it too many times it deserves special attention.  It is worth checking any supply air grilles in your room that are not part of your cooling system.
  1. The supply air is delivered, ideally by ductwork, to the front of your servers.  This ensures the coldest air is introduced to the servers that need it.  If you have a non-ducted system with either a floor, wall or ceiling-mounted system, you are cooling the space not just the cold-aisle and likely seeing a more even temperature distribution throughout the room.  Raising the room temperature is still a good idea if you meet the first criteria.  Keep in mind the temperature guidelines for data processing equipment as published by ASHRAE extend above 70 degF.
  1. You have sufficient temperature monitoring in place that will provide immediate feedback on the temperature entering your most critical servers.  Rack-mounted power distribution strips with temperature sensing capability is a good investment.  The Liebert MPH and MPX family of products have multi-node temp sensor that will allow you to profile your rack from top to bottom.  If you have dual power strips (always a good idea) to power dual-corded devices, you can use one sensor for the front, and one for the back.  The ability to track the temperature difference over time will confirm what your temperature operating range can be.

There is on caveat to all of this, and this applies to the rooms with the perfect layout and design:  If you lose your dedicated cooling system for whatever reason, your temperature safety cushion is much shorter.  Server room temperatures will rise dramatically without cooling.  Maybe you’ve experienced it so you understand the time to get to unacceptable temperatures is shorter, maybe much shorter than before.  Hopefully you didn’t skip over the comment about redundant cooling in #1 above!

Our next posting will continue this conversation with a thermal model of a small server room.

Check back soon to the DVL website, we will be posting two useful tools in helping you understand and calculate temperature rates and efficiency ratings.  Please visit www.dvlnet.com under our TOOLS section. To reach a Data Center Engineer, call us at 215-785-5950.

 

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