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Publication Title | Backflow Damper Replacement

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Capstone Turbine Corporation • 21211 Nordhoff Street • Chatsworth • CA 91311 • USA Telephone: (818) 734-5300 • Facsimile: (818) 734-5320 • Website:

Service Notice SN0015

Date: From: Subject:


All Model C30 production systems installed with common ducting shipped from Capstone before May 11, 2005.


Some 5-inch backflow dampers installed on C30 MicroTurbines may occasionally “stick open”, which can cause exhaust to flow backwards into a non-operating turbine, when multiple MicroTurbines share a common exhaust duct. This exhaust backflow can cause damage to a non-operating turbine.

As a result, Capstone has redesigned the valve on the existing backflow damper and is offering a new backflow damper kit (516220-102), at no cost to existing sites. Travel costs and labor will not be reimbursed by Capstone, due to the variability of exhaust manifold designs. Installation at the customer’s site is recommended.

Service Providers should perform the following suggested test to determine if the existing 5- inch backflow valve is functioning as designed:

1. Power up all units and issue a Start command to all MicroTurbines except the unit under test. Allow all the other commonly manifolded engines to operate at full power.

2. Monitor the compressor inlet temperature of the MicroTurbine in Standby for 2 hours.

a. If the temperature exceeds 197° F at the end of two hours, the backflow valve leaks excessively and needs to be replaced.

Note: The compressor_inlet_temperature has an upper range of 198° F. At temperatures above 198° F, the controller still returns a value of 198° F.

b. If the compressor inlet_temperature is between 160° F, and 197° F, the service provider shall subtract the ambient temperature from the compressor_inlet_temperature. If the delta is less than 100°F, the backflow valve has an acceptable seal. For example, if the compressor_inlet_temperature is 190°F, and the ambient temperature is 80° F, then the delta is 110° F, and the valve leaks excessively.

c. If the compressor_inlet_temperature remains under 160° F at the end of two hours, the backflow valve has an acceptable seal.

Service Providers should refer to “Backflow Damper Installation Work Instruction,” (p/n 440066-001) to replace and install the new damper. If the customer does not install the new backflow damper, Capstone still requires a wiring interlock solution as described in Service Bulletin SB0073.

450062 Rev B (January 2006) Page 1 of 2

This information is proprietary to Capstone Turbine Corporation. Neither this document nor the information contained herein shall be copied, disclosed to others, or used for any purposes other than the specific purpose for which this document was delivered. Capstone reserves the right to change or modify without notice, the design, the product specifications, and/or the contents of this document without incurring any obligation either with respect to equipment previously sold or in the process of construction.

January 2006

Capstone Technical Support Backflow Damper Replacement

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