Capstone Turbine Corporation • 16640 Stagg Street • Van Nuys • CA 91406 • USA
Installation Guide: Capstone C1000S/C800S/C600S with C1000 Series Controller
480064 Rev C (December 2018) Page 51 of 122
Capstone reserves the right to change or modify, without notice, the design, specifications, and/or contents of this document without
incurring any obligation either with respect to equipment previously sold or in the process of construction.
The exhaust flow published in the C1000S Product Specification (Table 1) is presented in
"standard" CFM, so must be corrected for temperature and pressure where applicable. Corrected
flow CFM must be used for duct sizing and backpressure calculations. Please contact your local
Capstone Turbine authorized distributor for assistance with an “actual” basis estimate for your
conditions.
5.4.4.1. Exhaust Backpressure
Too much exhaust backpressure can result in engine damage. The maximum
allowable exhaust backpressure is 1245 Pa (5 in WC) for the low emissions
model and 1990 Pa (8 in. WC) for all other models, when measured prior to
any exhaust ducting/devices, heat exchanger, or CO reduction catalyst.
The total backpressure generated by all connected equipment and exhaust ducting downstream
of the microturbine exhaust outlet cannot exceed the maximum allowable backpressure of
1245 Pa (5 in WC) for the low emissions model and 1990 Pa (8 in. WC) for all other models.
Backpressure will impact engine performance, which is detailed in the Performance chapter of
the C1000S/C800S/C600S Technical Reference (Table 1). The maximum allowable
backpressure may be reduced by configuration. Refer to the C1000S Product Specification
(Table 1) for specific backpressure limitations.
5.4.4.2. Exhaust Ducting Considerations
Duct diameter and length must be designed such that backpressure at the microturbine is less
than that specified in the C1000S Product Specification (Table 1). Ducting needs to be supported
and designed to allow for servicing of the microturbine. The duct cannot be welded to the engine
or upper stack.
Allow for condensation drainage. The combustion process generates water as a byproduct.
Additionally, it is possible for the exhaust to condense — or continue to condense — especially
after a heat exchanger. It may be necessary to install drain ports in long exhaust ducting runs to
remove condensate so that it does not collect and run back towards the microturbine. It may also
be necessary to slope the exhaust ducting.
At full power, microturbine nominal exhaust temperatures can exceed 316 °C (600 °F).
Temperatures can be higher due to fuel contamination. It is recommended that exhaust ducting
be rated for 371 °C (700 °F).
Make sure that thermal insulation is sufficient to avoid hazards to personnel or buildings due to
contact with high temperature exhaust ducting. Double-wall stainless steel ducting with two-to-
four (2-4) inch ceramic fiber insulation is a general purpose solution. Specifics of the application
must be considered when designing a proper installation.
Make sure that exhaust stack material and thickness meets local codes. As a “medium heat”
device, be aware of requirements regarding penetration through roofs and walls of combustible
and non-combustible material. If these penetrations are designed and stamped by an engineer,
building departments are usually satisfied, allowing wall penetrations in multistory buildings.
Double-walled chimneys may be required.
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