×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Maximum Demand - Standby and Duty Motors

Maximum Demand - Standby and Duty Motors

Maximum Demand - Standby and Duty Motors

(OP)
Hi Again All,

When doing maximum demand calcualations I assume one does not consider both the duty and standby motors where the duty/standby arrangement is provided. Both motors are the same size etc.

Functionally I am not sure how they operate and if they were to both run at the same time, i.e. when swapping from the standby pump to the duty pump, I would be in trouble as my TF would not handle the load

Any thoughts?

RE: Maximum Demand - Standby and Duty Motors

I respectfully submit that it would be prudent to learn more about the switching scheme between duty/standby units, and if in fact both will run simultaneously at any time.   

RE: Maximum Demand - Standby and Duty Motors

Because of the significant thermal time constant of transformers, there may not be a capacity problem if the motors only run at the same time for a short period.  There may be more of a voltage drop or motor starting concern.
 

RE: Maximum Demand - Standby and Duty Motors

(OP)
Yes I thought about it in a similar way.

There is nothing in the local codes over here (Australia) that says your point of supply has to be able to sustain all the appliances on your network.

RE: Maximum Demand - Standby and Duty Motors

123MB:

If you want to be a good engineer, you will have more success it you design a system that "works". Code are intended for safety and they do not care if a system works, but your client would who is paying the bills.

So the onus is on you to to design a sytstem that meets Owner's requirements. Codes are minimum statutary requirements that needs to be met and not a design criteria.

 

RE: Maximum Demand - Standby and Duty Motors

(OP)
Fair enough, Thanks.

RE: Maximum Demand - Standby and Duty Motors

The transformer current during the time that two pumps are running will be less than the starting current of one pump.  I wouldn't worry about transformer capacity.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources