As you can see from illustration on 3.3, 1.25 m racks are “unconditionally” stable, and 1.6 m racks are very
difficult to overload, as they extend only 1 U above the critical height.
For 1.6 m and 1.96 m racks, add the weights of the units which have centers of gravity above 32 U, then
compare the sum of the weights below 32 U. Always configure racks for the majority of the weight below
the critical height.
Assumptions/Disclaimers
The center of gravity for the racks is found in the geometric center. Centers of gravity of products is assumed
to be at their Front/Back, Left/Right centers. Grossly imbalanced equipment will void the calculations. If
doubt exists, stability should be verified by tip-over testing, per UL-1950, SECTION 4.1.
WARNING
The stability information/work sheets in this manual are for stationary racks. When moving
a rack, take additional precautions to prevent tipping, including the following.
• Confirm that equipment is installed according to the users guide.
• Be especially careful with fully loaded racks, which have more momentum when moving, or top loaded
racks, which have a higher center of gravity.
• Before any movement, check that any movable items mounted in the rack are fully pushed in and
mechanically secured.
• Loosen the bolts securing the anti-tip feet and raise both feet. Tighten the bolts in the raised position.
• Move SLOWLY over any obstructions such as power cords, elevator thresholds, cracks in sidewalk,
tile/carpet interfaces, etc., which can catch the front wheels and start tipping.
• STOP PUSHING IMMEDIATELY if any tipping occurs and allow the rack to right itself.
• Negotiate obstacles one wheel at a time, rather than two wheels at a time, to minimize the possibility of
tipping.
• Keep speed SLOW ‹ heavy racks are hard to start moving and hard to stop.
• Exercise common sense and caution when moving ANY equipment configuration.
Slide-Mounted Products
Slide-mounted products and work surface/keyboard products need weight and balance calculations per-
formed to determine the need for ballast to reduce the risk of cabinet instability. The worksheets for both
are provided on the following page. If both slide-mounted and work surface/keyboard products are being
used, calculate both and add the results.
To reduce the risk of rack instability when operator serviceable, slide-mounted products are installed, use
the following worksheet to determine the need for additional counterweight ballast. If there are no operator
serviceable, slide-mounted products in the rack, this worksheet can be ignored.
An operator serviceable, slide mounted product is defined as any product which can be extended from the
rack for servicing without requiring the use of any tool. A product requiring the use of a tool to facilitate
servicing or extending the product is the definition of trained service personnel serviceable only. When a
trained service personnel serviceable only product is extended, the use of the anti-tip feet is required, but
counterweight ballast is not. See Figure 3-5.
Also note that some HP products preclude the use of counter weight, due to their mounting depth. These
products are appropriately labeled, and require that the rack anti-tip feet are installed before the slider
product is pulled out. Also, it is recommended that no more than one slider product be pulled out at one
time, to ensure the greatest possible stability.
NOTE
No slide mounted products may be extended at the same time the work surface is in use.
14
Chapter 3
Installation Guidelines