Beginner’s Guide to Server Room Air Conditioning

Welcome to Redcentric’s guide to server room air conditioning and cooling in a data centre. Even if you’ve never looked into cooling options before, by the end of this guide, you’ll be able to join in on technical conversations and make informed decisions on which air conditioning options are best for your company.

Overheating can cause irreparable damage to your IT equipment and your reputation if your network experiences significant downtime. Understanding air conditioning options is a crucial part of avoiding these issues.

We’re going to teach you all about air conditioning and put it in context so you can see for yourself what’s best for your IT set-up.

Before we start: a quick explanation of Comms Rooms, Server Rooms, and Data Centres

Most companies will have a comms room or a server room to look after their in-house servers. A data centre effectively does the same thing but on a much larger scale. While some companies have their own data centres, (often referred to as ‘enterprise data centres’), smaller businesses may decide to outsource this function to multi-tenant data centres, otherwise known as ‘colocation data centres’.

What is CRAC?

CRAC stands for Computer Room Air Conditioning, and refers to the cooling systems deployed in comms rooms and data centres – they are used to cool servers, which generate a lot of heat. CRAC is a catch-all term to refer to any cooling system used to cool servers, and they can vary greatly in design and the technologies they use.

What types of CRAC are there?

Every server room and data centre will have a unique design and layout, as a result, every cooling system is also different.

One feature which varies is the substance with which air conditioning systems carry heat away, (such as water, air, or chemical refrigerant) which is often referred to as ‘the medium’. The basics of an air conditioning system is that a medium goes through two heat exchanges, one to remove heat from the servers, and then another to remove heat from the medium. However, in almost all systems air is the medium which comes into actual contact with the servers, as liquids can be damaging, so often a system will have a final step where the water or refrigerant cools the air around it, and that air cools the servers.

The exception to this is immersion cooling. This is still a relatively new technology which involves putting computer equipment in direct contact with a non-conductive cooling liquid. This is incredibly efficient, but due to current set-up and running costs, it is not widely used.

As well as the cooling mediums, the structure of a cooling system can vary greatly. The potential layouts of server racks have infinite possibilities, but generally they can fit into two categories:

  • Whole room cooling – the entire server room is cooled, typically used in smaller set-ups.
  • Contained cooling – a specific and contained area around the servers is cooled, and the rest of the room is left unaffected by the cooling system.

The most basic air conditioning system for a server room would use small air conditioning units, which typically use chemical refrigerants, to generate cool air in a whole room cooling system.

This kind of system can be increased in scale, and more complicated heat exchanges and contained cooling areas introduced to increase efficiency.

Why are air conditioning systems so critical?

Overheating has the potential to damage every piece of equipment within a computer, and this damage will often be irreparable. As well as interrupting your IT processes, overheated IT equipment will need to be replaced, which could be at considerable cost. When lots of servers are kept in close proximity, the heat they produce becomes more of an issue, meaning you need to have highly-efficient server room air conditioning to handle the increased heat.

What are the pros and cons of using a CRAC in a server room versus using one in a colocation data centre?

Keeping an in-house server room cool has its advantages. You have complete control over the specifications of the machines used to keep your server room cool, and you can keep a close eye on their performance and maintenance.

However, outsourcing to a colocation data centre also brings with it a lot of advantages.

The first advantage is reliability. Data centres are built with redundancies, and the best will have 24-hour on-site technical staff to ensure there are no issues with the cooling system, and to make quick repairs if any are found. To implement a similar level of diligence in your own server room would be very expensive.

Arguably, the most important advantage a data centre offers is that running a cooling system on a large scale allows for fantastic efficiency, which then brings a range of other benefits.

Since data centres are built to store hundreds of server racks, they have the space to introduce a contained cooling system, often in the form of cold aisles. Cold aisles will be put in alternatingly between server racks, meaning each row of racks is next to one cold aisle and one warm aisle. The cold aisles are sealed areas, meaning the cool air only goes over the servers, and energy isn’t wasted cooling the rest of the room. This is a similar idea to how it’s best to keep your fridge door closed.

Additionally, the larger scale allows for the installation of more advanced cooling systems, one example being cooling towers. While small air conditioning units that can be installed in an office use, exclusively, electricity to cause heat exchange in refrigerants, cooling towers can take advantage of natural cooling processes, like evaporation, which requires no additional energy input.

All of this efficiency reduces the energy costs of data centres, and this saving is passed on to you as it reduces the monthly costs of using a colocation data centre. On top of this you would also save money through the consistent cost of a data centre. Colocation costs don’t vary month to month, but running your servers in-house would mean increased energy costs during the warmer months while your CRAC has to work harder to keep your servers cool.

How much does CRAC cost?

As mentioned earlier, CRAC in a colocation data centre is already built out. That means costs like testing, maintenance and its energy consumption, are already factored into the monthly rental cost of the rack itself.

If you’re looking to keep your own server room cool a basic CRAC unit for a small server room will cost around £3,000-£4,000 to purchase. Additionally, you will have to cover the costs of installation if the unit requires new airflow inputs and outputs, as well as the significantly increased energy bill each month. A unit of this quality would then only be able to cool one to two lightly-loaded server racks and might struggle to do so in the peak of summer.

Which CRAC option is best for me?

In summary, if your IT systems require server racks to be set up, they will need to be kept cool. Doing this in-house has some advantages but incurs serious costs. If you’d like more information about how Redcentric can more effectively cool your servers and help keep your company online 24/7, then you can find out more here, or get in touch and ask one of our experts for advice.

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