Installation Guidelines for Spark-Ignited Stationary Emergency Generators 11
Section 3 Foundations & Mounting
3.1 — Generator Foundations
Install the generator set on a concrete pad or base slab able to support its weight and accessories. A proper foundation
is needed to resist dynamic loading and reduce transmitted noise and vibration. The exact composition of the mounting
pad must follow standard engineering practices for the required loading and application. Securely fasten the genera-
tor set to the foundation using suitable grade, size and style fasteners. Holes are provided in the base frame for
this purpose.
3.1.1— Concrete Pad
Follow all federal, state, and local codes when designing a concrete pad or base slab.
Seat the concrete pad on a prepared solid subsurface and use appropriate reinforcing bar or expanded wire mesh. A
common specification calls for 2500 psi concrete reinforced with 8 gauge wire mesh or number 6 reinforcing bars on six
(6) inch centers.
3.1.2— Dimensions
Extend the concrete pad beyond the frame of the unit at least six (6) inches. This provides a mounting surface for fuel
line support, as well as space for maintenance and repair.
The base pad must be:
• Capable of supporting 125% of the unit wet weight for single unit applications.
• Flat and level to within 1/2 inch.
• Capable of withstanding severe torque reactions.
To calculate the depth of the concrete pad, the following formula may be used:
W = Total wet weight of generator set in pounds (kg)
150 = Density of the concrete (pounds per cubic foot)
2400 = Density of concrete (kilograms per cubic foot)
B = Foundation width in feet (meters)
L = Foundation length in feet (meters)
Suggested mixture of concrete (by volume) is 1:2:3 of cement, sand, and aggregate with a maximum four inch
(100mm) slump with a 28 day compression strength of 3000 psi (200 MPa).
3.1.3— Unit Clearance
Verify that the site provides easy access to the generator set for maintenance, repair, and firefighting purposes. Keep a
minimum of 5 feet of clearance around each side of the generator set to facilitate service or maintenance.
3.1.4— Stub Up Area
For load conduit, auxiliary power conduit (high voltage), and control wiring conduit (low voltage), see the installation
drawings for the location and dimensions of the stub up areas. See Figure 3-1.
Depth of Base =
W
150 X B X L
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