Some basics of VFD install

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Ingenieur said:
in my experience it is not prudent to count on electricty to supply water
gravity seldom fails
have a tank with 2 days supply
sometimes due to elev of some areas a booster pump may be required to maintain the legally required press of ~ 25 psi at a residence 2nd floor
elev head charges the system
OVERpress is usually the issue, hence prv's, no need for pumps

normal flow may be 100-200 gpm for an area
crack a fire hydrant or 2 and >1000
a pump is a bad application since way oversized and dependent on elec pwr
iirc a hydrant must supply min 500 gpm for 2 hrs at 50 psi
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Perhaps we should get back to the OP's topic.
 
Energy savings with a VFD is a variable torque load (pump or fan) can be significant due to pump laws. IE cut speed by 1/2 cuts power by cube function or 1/8.
My first experience was a 30 hp 480V motor for a pump pressure maintaining system extra pressure was recircirculated back to the supply tank. Power bill was $1500 a month dropped to $300 with the VFD. Got a $20,000 grant for that project, and the energy saving paid for the $40,000 cost pretty quickly.

That was 20 years ago and we are just now going to replace the VFD. Maintains pressure right on, flows vary from nothing to 600 GPM, (its a two pump system), but still works great.
 
tom baker said:
Energy savings with a VFD is a variable torque load (pump or fan) can be significant due to pump laws. IE cut speed by 1/2 cuts power by cube function or 1/8.
My first experience was a 30 hp 480V motor for a pump pressure maintaining system extra pressure was recircirculated back to the supply tank. Power bill was $1500 a month dropped to $300 with the VFD. Got a $20,000 grant for that project, and the energy saving paid for the $40,000 cost pretty quickly.

That was 20 years ago and we are just now going to replace the VFD. Maintains pressure right on, flows vary from nothing to 600 GPM, (its a two pump system), but still works great.
Click to expand...
Well done that man - the voice of common sense.
It's what justifies water companies installing them.
 
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