Forums » Electrical Engineering

Sprinkler system motor

    • 156 posts
    January 3, 2020 9:16 AM PST

    Dear all,

    I need your help, I want to know what would be better to run a Sprinkler system by a electric motor connected to generator or diesel driven machine. 

    please share your experience.

    Thanks in advance.

     

    • 103 posts
    January 4, 2020 7:22 PM PST

    I would think the electric motor would be better for most customers. 

    1. Unless they already have diesel generators & have the expertise to maintain them.
    2. Diesel fuel storage & replenishing will be an ongoing cost, safety concern. 
    • 75 posts
    January 5, 2020 6:57 AM PST

    Whoops - fat fingered

     

    Working


    This post was edited by Carl Coulter at January 5, 2020 7:11 AM PST
    • 75 posts
    January 5, 2020 6:57 AM PST

    entered in error


    This post was edited by Carl Coulter at January 5, 2020 6:58 AM PST
    • 156 posts
    January 5, 2020 7:09 AM PST
    Carl Coulter said:

    Couple of questions on context:

    1.  I'm guessing this is a fire sprinkler?

    2.  What are the power requirements?

     

    1. Yes, exactly

    2. 250 kW for fire Sprinkler

    • 75 posts
    January 5, 2020 7:32 AM PST

    I fat fingered the previous posts - trying again

    Couple of questions on context:

    1.  I'm guessing this is a fire sprinkler?  Yes

    2.  What are the power requirements?   250KW

     

    3.  Non continuous run?  As is the pump driver (electric or recip diesel - doesn't matter) only starts up when the system is needed?

    4.  If you use a generator/electric motor, it is a dedicated genset used for no other purpose?

     

    If this is a dedicated gen that only starts when the sprinkler is needed, I would look at a direct drive recip diesel with the pump direct connected to the engine.

    It will take a lot smaller engine to direct run the pump as opposed to a gen big enough to start a 250kw electric motor. 

    This is pretty standard fire pump set up.  One can likely buy a package unit, complete with a control panel, already on a skid, ready to install.  Just need a tank.

     

    If a generator/electric driver is used, one is looking at a 500kw genset.  It has to be big enough to start the motor and keep the voltage drop with in spec.

    Either way there is maintenance on a recip diesel.  With the genset, one adds the maintenance on the generator/gen controls side.

    Now, if there are other uses for the gen, and it will run continuous, That would bring in other issues

     

     And, I'm thinking you already knew all this.  Tell us some more about the system.


    This post was edited by Carl Coulter at January 5, 2020 7:34 AM PST
    • 156 posts
    January 5, 2020 7:44 AM PST
    Carl Coulter said:

     

    If this is a dedicated gen that only starts when the sprinkler is needed, I would look at a direct drive recip diesel with the pump direct connected to the engine.

    It will take a lot smaller engine to direct run the pump as opposed to a gen big enough to start a 250kw electric motor. 

    This is pretty standard fire pump set up.  One can likely buy a package unit, complete with a control panel, already on a skid, ready to install.  Just need a tank.

     

    If a generator/electric driver is used, one is looking at a 500kw genset.  It has to be big enough to start the motor and keep the voltage drop with in spec.

     

    if   generator/electric driver equipped with VFD to limit the start up current of the motor. The purpose going with electric is to size this generator not only size dedicated for Sprinkler but also for other emergency. This save space. 

    What do you think?

    • 75 posts
    January 5, 2020 9:44 AM PST

    That would fall under the, "Now, if there are other uses for the gen, and it will run continuous, that would bring in other issues"

    But for "emergency" not necessarily "continuous".

    Are you looking at running the gen full time?

    Or is it only started in the event on an emergency?

    What capacity are you looking at for the other emergency loads?

    Do the other emergency loads have/require a normal power source?

    If so, what might that be?

    Fire pumps/sprinkler systems are not areas of my expertise. However, I am somewhat familiar with NEC fire pump provisions. So, treating this as a falling under NEC 695, Fire Pumps:

    On-site standby generation may require a second source

    Controllers are required to be listed for fire pump use

    And a whole bunch of other stuff - including voltage drops

    I have never seen a VFD used to run a fire pump motor. I suspect they are not listed for fire pumps.

    Generally space is not an issue, however, since it is, I would expect to spend money to solve all issues.

     

    I'm not much help once one gets out of the NEC realm.

     

    @carl: I am really Sorry, I was applying to points, and by mistake i edit your response. 

     

     

     


    This post was edited by Zone4 Engineer at January 5, 2020 10:34 AM PST
    • 156 posts
    January 5, 2020 10:32 AM PST
    Carl Coulter said:

    That would fall under the, "Now, if there are other uses for the gen, and it will run continuous, that would bring in other issues"

    But for "emergency" not necessarily "continuous". 

    1. Are you looking at running the gen full time? 
    2. Or is it only started in the event on an emergency?
    3. What capacity are you looking at for the other emergency loads?
    4. Do the other emergency loads have/require a normal power source?
    5. If so, what might that be?

     

     

    1. no, the generator will be as standby for back up only for emergency 

    2. Yes,

    3. The emergency load will be around 200kW and 250kW Sprinkler. 630 kW as a total and Gen size.

    4. Yes, in normal case all loads will be fed from Grid and transformer. Only in case Normal Grid fails, generator will feed the emergency loads

     

     

    • 75 posts
    January 5, 2020 11:17 AM PST

    The gen would be an 800KVA genset, maybe even 1000KVA

    And a VFD on the Sprinkler driver?


    This post was edited by Carl Coulter at January 5, 2020 11:19 AM PST
    • 156 posts
    January 5, 2020 11:48 AM PST
    Carl Coulter said:

    The gen would be an 800KVA genset, maybe even 1000KVA

    And a VFD on the Sprinkler driver?

    Yes, it only controls and decreases the start up of the motor for Sprinkler system. If the start up current is decreased, I do not think so that we need a big generator size. This is the purpose of VFD.


    This post was edited by Zone4 Engineer at January 5, 2020 11:49 AM PST
    • 75 posts
    January 5, 2020 12:18 PM PST
    Hameedullah Ekhlas said:
    Carl Coulter said:

    The gen would be an 800KVA genset, maybe even 1000KVA

    And a VFD on the Sprinkler driver?

    Yes, it only controls and decreases the start up of the motor for Sprinkler system. If the start up current is decreased, I do not think so that we need a big generator size. This is the purpose of VFD.

     

    Of course, absolutely true.

    Is there an issue with the VFD not being listed for use as a fire pump controller?


    This post was edited by Carl Coulter at January 5, 2020 12:21 PM PST
    • 156 posts
    January 5, 2020 1:01 PM PST

    I do not think so that there will be an issue using VFD with fire pump controller. 

    • 75 posts
    January 5, 2020 4:08 PM PST

    I agree, A VFD will easily drive the fire pump motor.  That is not a problem.

    The issue is the VFD will be considered the fire pump controller.  And, is the controller required to be listed?

    Under NEC, I believe the controller is required to be listed.

    If your regulatory authority does not require the controller to be listed, or would not consider the VFD as the controller, I agree, the system will be fine.

    • 156 posts
    January 6, 2020 1:47 PM PST

    The authority does not have problem with VFD. The Grid provider is only concern regarding back feed short circuit to the grid and they do not want. This can be solved with discrimination and control system study.