When your rack installation equipment or components cannot be directly mounted to your EIA-310-D standard rack or cabinets , you need a shelf.
In this article, we will go over the common types and features from a high level. In upcoming blogs, we will look deeper into each type of shelf and the features' pros and cons along with an example or two regarding its common application.
2-Post vs 4-Post Rack-Mount Shelves
If you have a 2-Post rack or cabinet, only 2-Post shelves can be used. If you have a 4-Post rack or cabinet, you may use 2-Post shelves, 4-Post shelves, or a combination of them.
Similar to the differences between a 2-Post and a 4-Post racks , 4-Post shelves usually have a high weight capacity and are less susceptible to cantilever-type sag in the rear.
However, 2-Post shelves have the potential to be less expensive, are easier to install, allow better airflow, and can sometimes take up fewer rack units enabling the rack installation to be more compact.
Steel vs Aluminum Rack-Mount Shelves
Steel is by far the most common material for rack shelves in the market. Compared to Aluminum shelves, steel shelves are typically stronger, less expensive, and are more scratch resistant. However, Aluminum shelves are much lighter, which can play a significant role in certain applications we will discuss further in the future.
Vented vs Non-Vented Rack-Mount Shelves
Non-vented shelves have no holes giving the setup a cleaner look. Sometimes, non-vented shelves can be less expensive because there is less material to be removed. Vented (a.k.a. slotted) shelves can provide better airflow and the slots can be used to secure equipment’s location or for cable management.
Cantilever Rack-Mount Shelves
Cantilever shelves are the most common type of 2-Post shelf. When buying a cantilever shelf, it is important to review the shelf's rated weight capacity. Similar-looking shelves can have different weight capacities due to different structural designs, like ribs on the sides, lip in the rear, sheet metal gauge, and different rack units. Although overly simplified, center mount shelves are two cantilever shelves mounted facing each other.
It is important to know that not all similar-looking 2-Post racks are equal. In a future blog, we will discuss the importance of choosing the right mounting post by evaluating the post's structure and sheet metal gauge. Why do we bring this up?
We often get customer inquiries about the purchase of a NavePoint cantilever shelf with 110 pounds rated weight capacity sagging with a piece of equipment weighing only 50 pounds. Unfortunately, the sag is originated from the weak mounting posts, meaning no strong shelf can fix the issue.
4-Post Rack-Mount Shelves
There are four major types of 4-Post shelves, fixed, sliding, "cabinet", and server rack rails. 4-Post shelves are mounted to all four mounting rails in a rack or cabinet. While most fixed, sliding, and server rack rails have adjustable rack mounting depth, "cabinet" shelves have a fixed rack mounting depth. Furthermore, "cabinet" shelves are not compatible with all racks and cabinets.
Otherwise, server rack rails are most suitable for holding large and wide equipment, fixed 4-Post shelves are most used, and sliding 4-Post shelves are fixed 4-Post shelves with a slide in and out feature to add accessibility to the equipment while also adding to the shelf’s price.
Summary
To wrap things up, there are many types of rack shelves with different features and tradeoffs used for different applications.
