Server Rack Cooling
How heat leaves the cabinet, from a single fan to a cooled data center row
Server rack cooling decides how long IT hardware lives. Every watt a server, switch or storage system draws ends up as heat inside the cabinet, and that heat has to leave before it shortens the life of the components. The right method depends on the heat load, the room and the noise you can accept.
For small loads, fans and PWM fan control are often enough. Higher loads need a cabinet with an integrated cooling unit, a top-mounted unit or a closed cabinet with its own climate system. For high densities, water cooling and hot and cold aisle containment keep whole rows stable. Cold or humid sites can also need heating.
Lehmann IT has built server cabinets in its own production in Salach, Germany, since 1983. The questions below explain each cooling method in detail. Pick the one that matches your situation.
Questions on server rack cooling
How does integrated cabinet cooling work? →Cooling built into the server cabinetHow do water-cooled cabinets work? →Chilled water for high heat loadsWhen is an all-in-one cooling cabinet enough? →Compact cabinets with active coolingHow does a top-mounted cooling unit work? →Air conditioning on the cabinet roofWhat is the CoolRack DX? →Air-conditioned server cabinetHow does hot and cold aisle containment work? →Separating warm and cold airWhich fan system fits your cabinet? →Standard, silent and controlled fansWhat does PWM fan control do? →Fan speed that follows the heatWhen do cabinets need heating or climate control? →Options for cold and humid sitesWhat does automatic door opening do? →For climate-controlled cabinets
Find the products in the Lehmann IT shop
Ready to choose? These shop categories show the matching products with prices and configuration options.
Air-conditioned server cabinets →Precision cooling →Hot / cold aisle containment →Advisor: cooling a server cabinet
The most important questions on cooling a server cabinet, server room and data center, answered briefly by Lehmann IT.
Why does IT need cooling?
Servers, routers and switches turn almost all the power they draw into heat, and that heat builds up inside the cabinet. High temperatures cut performance, damage electronics and cause outages. Downtime and lost data usually cost more than the cooling.
Passive or active cooling?
Passive ventilation through perforated doors is enough only for low heat loads in a clean room. From roughly 1,000 watts total load in the cabinet, we recommend an air-conditioned server cabinet with active cooling.
How much cooling capacity do I need?
It follows the heat load, which is roughly the combined power draw of every device in the cabinet. Choose a little more rather than a little less, as reserve for new servers and hot summers. We are glad to work it out with you: ask us, free of charge.
Refrigerant or chilled water?
DX cabinets work with refrigerant and an outdoor unit, up to 14 kW. Where the building already has chilled water, CW cabinets cool up to 35 kW, and the RearCool rack can even be retrofitted without downtime.
Which cooling for which heat load?
The heat load in the cabinet is roughly the power draw of all the devices in it. Hover over a bar or click it.
Passive ventilation1 kW
Compact all-in-one1 to 4 kWCoolRack Silent5 kWDX cabinets14 kWCW cabinets35 kWCoolRow / InRow55 kWPrecision cooling260 kW →Scale 0 to 60 kW. Our recommendation: pick a little more cooling capacity than you need today, as reserve for new servers and hot summers.
How cold aisle containment works
Two rows of cabinets stand front to front. The aisle between them is enclosed, so cold and warm air no longer mix and the cooling unit works far more efficiently.
More on containment: cold aisle and hot aisle containment.
Small server room
For 1 to 4 kW a compact unit on the cabinet is enough, with a side or roof cooling module, and no separate air conditioning in the room. More on air-conditioned server cabinets.
Cold aisle and hot aisle
Containment separates cold and warm air and raises efficiency in the data center. We plan it to match your racks: cold and hot aisle containment.
How to choose the right cooling
- Work out the heat load first: add up the power draw of every device in the cabinet, because almost all of it turns into heat that the cooling has to remove.
- Check the room: a cool, ventilated room lets fans do the job, while a warm office or a closed technical room needs a cabinet with active cooling.
- Match the method to the density: fans for light loads, integrated or top-mounted cooling units for medium loads, water cooling and aisle containment for high densities.
- Think about noise: cooling units and fast fans are audible, so in offices a controlled or acoustic solution is often the better choice.
- Plan for growth: hardware is added over the years, so leave headroom in cooling capacity rather than sizing it for today only.
Frequently asked questions
How much heat does a server cabinet produce?
Nearly all electrical power drawn by IT equipment becomes heat. A cabinet whose devices draw 3 kW produces about 3 kW of heat. That figure is the starting point for every cooling decision, so it pays to measure or add up the real power draw instead of guessing from the number of devices.
When are fans enough?
Fans are enough when the room itself stays cool and the heat load is moderate. They move room air through the cabinet but cannot cool below room temperature. If the room warms up in summer or the load grows, the cabinet needs active cooling such as an integrated cooling unit or a top-mounted unit.
What is the difference between integrated cooling and a top-mounted unit?
An integrated cooling unit sits in the side or door of the cabinet and cools the air in a closed circuit. A top-mounted unit sits on the cabinet roof and blows cooled air down into the cabinet. Both keep the equipment independent of the room temperature; the choice depends on space, access and heat load.
When does water cooling make sense?
Water carries heat far better than air. Water cooling makes sense for high heat densities, for rooms where the warm air must not stay in the room, and for data centers that already have a chilled water supply. It needs more planning but keeps dense installations stable.
Why do hot and cold aisles matter?
Without separation, warm exhaust air mixes with cool supply air and the cooling has to work harder. Hot and cold aisle containment keeps the two air streams apart, so the cooling reaches the equipment intakes directly and the whole room runs more efficiently.
Can a server cabinet be too cold?
Yes. In unheated rooms, outdoor sites or cold warehouses, temperatures can fall below what the equipment tolerates, and condensation can form when warm and cold air meet. Cabinet heaters and climate control keep the temperature and humidity in a safe range all year.
Does better cooling save energy?
Cooling that matches the load wastes less energy. Controlled fans run only as fast as needed, closed cabinets cool only the equipment instead of the whole room, and containment stops cold air from mixing with warm air. Together these measures lower running costs and help meet efficiency rules.
Planning with Lehmann IT
Lehmann IT has designed and built server cabinets in its own production in Salach, Germany, since 1983. Because development and manufacturing sit under one roof, standard cabinets can be adapted and special versions built when a project needs them. This knowledge site explains the technology in depth, so you can understand the options before you decide. When you know what you need, the Lehmann IT shop at lehmann-it.de shows the matching products with prices and configuration options, and the team in Salach helps with questions on cooling by phone or email.