TrickleCharge
Member
- Location
- CA
Ok this may seem like a dumb question but the EE has me all confused now. I have a 100HP 208 fire pump that they originally were going to install a separate service (400A), but based on the LRC for a 208 motor it would be well over 1600A. So then they removed the OCPD and wanted to go direct connection. Now they had 300'+feet of service conductors that would have to be installed "outside the building" (which the conduit and feeders were already installed). Now the engineer is asking if the control module is set to no more than 300% of the FLA, then can they just size the OCPD at the new service to that number? Please see below from the manuf. of the fire pump:
Description?Firetrol? FTA1930 Digital Solid State Starting
Fire Pump Controllers feature soft start, soft stop and
system sensing capabilities that not only provide for reduced
current starting, but also offer an improved level of
hydromechanical performance. The controller monitors,
displays and records fi re pump system information.
When called to run, the motor will accelerate beginning
at 100% of motor FLA up to a maximum of 300% FLA while
rated torque is reduced to 15%. When stopping, the motor
will decelerate to a preset level and pause, allowing for
a restart if required, limiting stress in the piping system.
If no additional starting causes are present, the motor
will continue to decelerate to a full stop. This controller
helps to reduce water hammer in the system.
My understand is that the manufacturer rating of 300% is not in lieu of, or an exception to using the Locked Rotor Current (LRC). The reasoning behind the LRC is basically to withstand catastrophic failure prior to shutting down entirely. This means that the system cannot rely entirely on an electronic module to control whether or not the maximum current would not exceed 300% of the FLA. Thanks for the input!
Description?Firetrol? FTA1930 Digital Solid State Starting
Fire Pump Controllers feature soft start, soft stop and
system sensing capabilities that not only provide for reduced
current starting, but also offer an improved level of
hydromechanical performance. The controller monitors,
displays and records fi re pump system information.
When called to run, the motor will accelerate beginning
at 100% of motor FLA up to a maximum of 300% FLA while
rated torque is reduced to 15%. When stopping, the motor
will decelerate to a preset level and pause, allowing for
a restart if required, limiting stress in the piping system.
If no additional starting causes are present, the motor
will continue to decelerate to a full stop. This controller
helps to reduce water hammer in the system.
My understand is that the manufacturer rating of 300% is not in lieu of, or an exception to using the Locked Rotor Current (LRC). The reasoning behind the LRC is basically to withstand catastrophic failure prior to shutting down entirely. This means that the system cannot rely entirely on an electronic module to control whether or not the maximum current would not exceed 300% of the FLA. Thanks for the input!