20 McQuay IM 987
Mechanical Installation
IBC Seismic Compliant Units
It is important to follow these installation instructions for all
IBC Seismic compliant McQuay Rooftop units.
IBC Seismic compliant McQuay Rooftop units can be
mounted to either a roof curb or a post and rail setup. If using a
roof curb, it must be specifically designed for seismic restraint
and be IBC seismic compliant (spring isolated or non-isolated
type seismic roof curbs are available). Typical construction of
a seismic rated roof curb is from structural steel framing and
contains seismic hold down brackets for attachment of the
rooftop unit (see Figure 21). Post and rail arrangements rated
for seismic applications are also available (spring isolated or
non-isolated).
IMPORTANT: An acceptable IBC seismic installation
provides a direct positive attachment to both the building
structure and the roof mounted equipment.
Refer to the roof curb manufacturer’s submittal drawings for
actual roof curb assembly, attachment details and rigging
instructions for both roof curb and post and rail arrangements.
Roof Curb Arrangement
1 Set the rooftop unit on the roof curb (McQuay Rooftop
units are designed to overhang from the roof curb).
2 Adjust the seismic hold down brackets so they come into
contact with the unit base per Figure 22 and Figure 23,
page 21.
a The seismic hold down brackets should be adjustable
and accommodate the overhang of the rooftop unit.
b If the hold down bracket cannot reach the unit base,
use a shim spacer. See Figure 23, page 21.
3 Weld each seismic hold down bracket (and shim spacer,
if required) to the unit base as shown in the acceptable
weld zone detail in Figure 22, page 21.
Note: High temperature insulation is installed at the factory to
allow for field welding along the lower front edge region
of the unit base.
Figure 21: Typical Seismic Roof Curb (Spring Isolated)
CAUTION
When welding unit to the curb, do not damage wiring (control
panel side). Weld ONLY in the specified zone in the acceptable
weld zone (see Figure 22, page 21). Welding must comply with
weld fillet size, etc. as indicated in Figure 22, page 21.
Seismic hold down brackets
Seismic hold down brackets
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