ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat Box
Recent Posts
Any Woodworkers here?
by gfretwell - 05/13/21 01:47 AM
Your favourite food?
by Bill Addiss - 05/12/21 05:23 PM
Lock-down Thread
by gfretwell - 05/11/21 12:30 PM
Do You Travel?
by gfretwell - 05/11/21 12:16 PM
Just be aware of this...
by gfretwell - 05/10/21 07:30 PM
New in the Gallery:
2020 - 2021 Winter Project
Garden 2021
Who's Online Now
1 registered members (HotLine1), 15 guests, and 13 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Generator sizing and fire pump motor starting #215813 07/21/15 03:38 PM
Joined: Jul 2012
Posts: 8
K
katwalatapan Offline OP
New Member
Hello,

I wanted to inquire about effects on generator sizing, if fire pump motor, soft-starting methods, and required manual electric/mechanical starting of the fire pump (as per NFPA 20) are taken into consideration.

A generator is required to be sized to back-up fire pump motor and controller loads in addition to regular building lighting, power, and motor loads. The fire pump motor is the largest load on the generator. The fire pump controller may have either a manual electric or manual mechanical starting (as required by NFPA 20), in addition to automatic starting. The fire pump controller also is configured for soft-starting the fire pump motor.

I've read that for fire pump application, the generator is permitted for a voltage drop upto 15%, but if the fire pump is operated manually by mechanical means, then the 15% voltage limit is not applicable. Even if the fire pump controller has a soft-starting method, if the fire pump is started mechanically, then it would be started across-the-line.

Considering the above scenario, I have the following queries:

1. What would be an acceptable voltage drop for the generator, when the fire pump is started via mechanical starting?

2. In a case, there the fire pump controller has a soft starting method, manual electric starting, and manual mechanical starting, would the generator be sized for fire pump motor locked rotor amperage calculated for soft-starting or the locked rotor amperage calculated for across-the-line starting. Would the generator size also be affected based on the increased threshold of voltage drop for manual mechanical starting?

Thank you.

Tools for Electricians:
Re: Generator sizing and fire pump motor starting [Re: katwalatapan] #215814 07/21/15 04:22 PM
Joined: May 2005
Posts: 984
G
ghost307 Offline
Member
15% based on the highest possible amperage draw.
You always design for worst case.


Ghost307

Featured:

2020 National Electrical Code
2020 National Electrical
Code (NEC)

* * * * * * *

2020 Master Electrician Exam Preparation Combos
2020 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
HotLine1
HotLine1
Brick, NJ USA
Posts: 7,261
Joined: April 2002
Show All Member Profiles 
Top Posters(30 Days)
Trumpy 19
Admin 11
Popular Topics(Views)
278,914 Are you busy
212,073 Re: Forum
199,103 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.3