Pressurized Tank vs. VFD Pump

[osakaz]

I have a project where we are doing some energy savings measures.
the site has a pump set at 90psi that supplies pressurized tank at 60psi which then delivers to the building. the pumps are originally constant speed.
we are thinking of adding VFD on the pumps but the facility people were frightened to death.
any support on that?

 

[pipehead]

before jumping to a vfd, get the pump curves. Analyize the savings, it the pumps are 5HP or less, it hard to justify the added cost. Look at the motors, can they be run a slower speeds (think cooling). After that kind of look, they are a great thing. Also, most people forget that a VFD has a Power factor of 1.0, so, you may get a huge cost savings in PF improvemnet.

 

[Artisi]

Have a look at this expansive posting - will give you some ideas and probably confuse you at the ame time

thread407-174752

 

[osakaz]

Thanks a lot pipehead.
the pumps are 60 HP each and currently they are constant speed/flow. savings from adding VFD on the speed/flow would bring in good savings.
i was asking about the booster pump system vs the prssurized tank systems in domestic water.

Thanks again

 

[thewellguy]

I don't understand your question then. Are you suggesting that you run the supply pumps into a large non-pressurized tank and the pull form it using a vfd pump? Also the pump is set at 90 and the tank 60?

In general a vfd will save you money IF the amount of water the pump produces varies. If the pump runs 24-7 at capacity, the only saving would be the increased power factor. To figure it out, I know yaskawa offerings a energy calculator on its website I think ABB to.

Also you need to consider local code. Is you pressurized storage part of you fire protection suppy?