Reduce Start Time for Your Emergency Power Supply

by Visitor Power-Pop ‎03-25-2014 10:28 AM - edited ‎04-15-2014 01:23 PM

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We don’t always think about our emergency power supply setup until it’s needed. However, managers of critical power applications, like hospitals and data centers, need to be prepared for any duration of power loss. Not only is the reliability of the backup system crucial, quick start times are required before an electrical load can be accepted. The longer it takes for the system to start, the longer a critical application goes without power.    


The National Fire Protection Agency’s (NFPA) 110 standard requires a 10-minute start up time for life-safety systems. Managers of critical power applications should complete a system-level start time analysis (STA) to ensure power restoration time requirements are being met. The STA covers every aspect of the critical power path from component selection and performance (including settings, time delays, and inherent component processing delays) to site conditions that may impact system performance. It’s possible that the STA may reveal a start-up time that takes longer than 10 minutes for an emergency power supply system. In this case, the following considerations can help managers achieve a faster generator set start-up time.



  • Examine rotational inertia: Oversized and high voltage generators have a larger rotational inertia than the standard low voltage generator, which will increase start times.
  • Energize critical loads: Ensure the critical loads are less than the capacity of the smallest generator set for paralleled systems. Energizing all critical loads as soon as the first breaker closes to the bus can increase start times.
  • Test engine-driven fans: Remote radiators with electric-driven fans will decrease inertia during start-up, particularly when using an oversized or high-voltage generator.



  • Consider a software upgrade: The latest software version will provide the best start-up time for system controls.
  • Review the ramp rate: Match the ramp rate to the site and application needs, as adjustments from the default value will improve start time. You’ll notice that increasing the ramp rate will result in more black smoke on start-up.
  • Regulate DVR: Decreasing the soft start feature in the digital voltage regulator (DVR) will decrease the time it takes the generator to build rated voltage.


Electric Starters & Batteries

  • Test the battery charge: Use heavy-duty electric starters and back-up starters with fully charged batteries for faster start times.
  • Consider a second starter: Single-starter generator sets provide slower start-up times.
  • Check crank speed: Ensure the electric starter and battery set is able to crank the engine above 10 rpm for 10 seconds.


Air Starter

  • Examine engine model: Air starters may increase or decrease cranking speeds depending on engine model.
  • Maintain air pressure: Size the air tanks and related lines to crank the engine above 110 rpm for at least 10 seconds.


Temperature Control

  • Maintain water temperature: Use a water jacket heater to keep water temperature at 32°C (90°F) minimum.
  • Combustion air supply: This should be kept at 21°C (70°F) minimum.
  • Consider a battery heater:If ambient temperatures are below 0°C (32°F), use a battery heater to avoid longer start-up times.



  • Use clean fuel: Change fuel filters regularly and monitor fuel system tubing to avoid air intake and leaks.
  • Consider pre-lubrication: If available with the engine model, use continuous engine oil pre-lubrication to ensure smooth flow.


When every second counts in emergency backup system start times, managers can implement an STA report to determine whether or not the system meets the 10-second standard. Unfortunately, each system requires individual assessment, but the good news is that applying any combination of these options will likely improve start time.


For more information on reducing backup system start time and other Caterpillar Product Support services, visit us online.


We want to hear from you. Tell us about your experiences with emergency and backup power system start times.


  • Have you ever had problems with system start times?
  • Are you familiar with these tips for reducing start-up times?
  • Is there anything you would add to this list of system considerations?

by Visitor Power-Pop
on ‎05-06-2014 01:36 PM

"PlantPro, good call on the lube oil and jacket water heaters for improved emergency power supply start time.  Thanks for the feedback."


by Ivo Roberts jr
on ‎08-01-2014 02:36 PM

In natural gas systems flooding can occur when the start signal activates the fuel valve, ignition and governor at the same time. 

We have found that with natural gas the newer ignitions system needs to see rotation (at a min rpm) before it fires & performs a diagostic check which may take 2 or 3 seconds and with out a time delay the fuel gas flowing into the engine with out ignition. It also fills the exhaust system which can lead to exhaust explosions. Older Magnetos require a minimum crank speed which may take a couple of seconds also. The good thing is the fuel response is generally quick enough when the fuel valve opens that the 10 second to rated speed and breaker closure can be met. In draw thru carburation the timer is a must. 

You made good points on maintaining batteries, starters, jacket water heaters & lube oil heaters, fuel quality (Bio-diesel) and to exercise these standby units at least monthly with a startup.

by Contributor SPW
on ‎11-30-2014 11:04 PM

There seems to be some typos.

Isn't the starting time 10 seconds not 10 minutes?

Also the electric starter calls for " above 10 rpm for 10 seconds".


Otherwise good info

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