Thank you for the replies. I hardly ever deal with PF in my day to day duties. The problem is somehow these vendors get access to those near the top of the command chain and then we have to deal with it. Another issue as I see it is the devices in question are not switched out after the motor loads stop. Then the power factor goes the other way----now we are capacitive.
Since (as you stated) that this is vendor-supplied equipment, I would assume they would deal with
“TURN KEY “ contracts.
This is the usual procedure in dealing with government projects. The government would invite contractors to bid on projects from scratch. . . meaning the contractors would only be given the
criteria as to how and what purpose the project is going to be.
In essence,
turn-key contracts are: you build us something and you give us the key to turn the thing on when its done.. . . that is all the contractor needs to do.
This is why we "paeans" (engineers) are not privy to powers-that-be decisions.
Here are the plans . . . you do it.
And people would wonder why it cost so much. . . to build a toilet to operate in gravity-free environment. Water doesn't flush up there in space you know.
![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
]
Is that off topic?
Lockheed for example is invited to create a supersonic fighter jet. This is all what the engineers have to go by. This also applies to projects like building structures.
Now, back to power factor correction using PFC capacitor.
Your idea of shutting down the caps when the motor loads stop is good. Anything you don't need when things are supposed to remain idle is a plus. Anything that emits heat when not in use is just wasted energy. Resistors known as vampire loads do consume energy those--that are used for controls and sensors.
But there is an issue when you connect/disconnect a capacitive load. Capacitors store energy that needs to be drained (discharged) before the next command to turn on. Undesirable results would happen if not heeded.
There is this inherent current surge every time you engage a capacitor in the circuit.
Your application (HVAC) loads are meant to cycle on and off. For huge capacitors in industrial application, this “draining “ process takes time. Normally (theoretically) it takes 60 seconds.
If your project can live with one minute waiting period after you shut down, then, by all means more power to you.
NEC requires this draining time.
OK NEC hounds, I'm ready for the lynching.
Having said this, the equipment supplier must have included this feature in their design.