INDUSTRIAL/COMMERCIAL GENSET POWER RATING
Emergency Standby Power (ESP)
PURPOSE : The purpose of this document is to clarify Generac Power Systems position regarding the rating definition of Emergency and Standby Power
Generators. This rating is in accordance with ISO 8528-1.
DEFINITION : The maximum power available during a variable electric power sequence, under the stated operating conditions, for which a generating set
is capable of delivering in the event of a utility power outage or under test conditions for up to 200 hours of operation per year with the maintenance intervals
and procedures being carried out as prescribed by the manufacturer.
a
P5
P
P2
P3
b
P1
c
P4
30%
t1
d
t2
t3
t4
t5
t
d
Key
t = Time
P = Power
a = Emergency/Standby Power (100%)
b = Permissible Average Power During a 24h Period (Pb)
c = Actual Average Power Over a 24h Period (Pc)
d = Stop
PRODUCT PAPER
NOTE: t1 + t2 + t3 +…………+ tn = 24h
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Part No. 0187500SSB WIP
Rev. D 11/03/19
INDUSTRIAL/COMMERCIAL GENSET POWER RATING
Emergency Standby Power (ESP)
The permissible average power output (Pb) over 24h of operation shall not exceed 70% of the Emergency/Standby Power Rating unless otherwise agreed by
the manufacturer.
The actual average power output (Pc) shall be below or equal to the permissible average power output (Pb) defined for Emergency/Standby Power.
When determining the actual average power (Pc) of a variable power sequence, powers of less than 30% of the Emergency/Standby Power rating shall be
taken at 30% and the time at standstill shall not be counted.
The actual average power (Pc) is calculated as follows :
P1t1 + P2 t2 + P3 t3 + ………+ Pn tn
t1 + t2 + t3 + ……..tn
Where P1, P2 ………Pn is the power at time t1, t2 ……..tn
REFERENCE:
PRODUCT PAPER
ISO 8528-1 : 2018 - Reciprocating internal combustion engine driven alternating current generating sets
- Part 1: Application, ratings and performance
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Generac Power Systems, Inc. | P.O. Box 8 | Waukesha, WI 53187
P: (262) 544-4811 © 2019 Generac Power Systems, Inc. All rights reserved. All specifications are subject to change without notice.
Part No. 0187500SSB
Rev. D 11/03/19