PF correction capacitors

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mannyb

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Florida
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Electrician
I have never worked or experienced a PFCC being used. I thought it was a transformer at first glance but realized what it was at closer look. Its installed at the service entrance with all service disconnects at Gutter. I kinda understand what they are used for but why would it be at gutter with service equipment and not near equipment being served. Im just wanting to figure out what the pFCC was doing to help system for DUMMIES.
 

GoldDigger

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Placerville, CA, USA
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I have never worked or experienced a PFCC being used. I thought it was a transformer at first glance but realized what it was at closer look. Its installed at the service entrance with all service disconnects at Gutter. I kinda understand what they are used for but why would it be at gutter with service equipment and not near equipment being served. Im just wanting to figure out what the pFCC was doing to help system for DUMMIES.

Ideally PFCC will be installed after the switch or contactor for the specific equipment with a poor power factor. That way there is no overcorrection (a bad thing for both you and POCO). But that may mean lots of small PFCC banks near individual equipment. And there should be a charging circuit to keep them from appearing as a sudden inrush when equipment contacts close or the contactor for each phase of the PFCC would need to close at or near zero voltage.

If you have lots of smaller pieces of equipment and you the facility operates 24x7 it is often easier and cheaper to install a single PFCC bank near the service, sized somewhat below the value necessary to bring the facility to unity PF during typical operation. The advantage for maintenance is that all of your eggs are in one basket.
 

Jraef

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Cheaper and easier, yes, but also more dangerous in my opinion. Not danger in terms of someone getting hurt, but most likely to cause serious damage to sensitive electronic systems and to interact with modern power equipment that has VFDs, servos, UPS systems etc.

What PFC caps do is to correct a "lagging power factor", the difference between when voltage peaks and when current peaks in each sine wave. Inductive loads like AC motors cause a lag in that time frame that makes the utility equipment have to deliver more kVA per unit of kW, while not having it show up on the bill (because you PAY for kW) to help pay for the larger equipment they needed to use. So the utilities make you pay for it indirectly by assessing a "penalty" for having your Power Factor dip below some value, usually .95. The capacitors store and release reactive power to compensate for the inductive loads, raising the PF measurement to where the utility is happy again. Hopefully in your case. The trouble with having "bulk" capacitors at the service like this is, as GD pointed out, that you have no control of how MUCH capacitance you are adding. So if some induction motors turn off, but the caps were sized for when they were on, then there is too much capacitance and you can end up with a LEADING power factor, which from the utility standpoint is just as bad.
 

GoldDigger

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... then there is too much capacitance and you can end up with a LEADING power factor, which from the utility standpoint is just as bad.
It is my understanding that from the utility standpoint the effect on revenue (kVA required of the infrastructure versus kW paid for) is the same but the consequences of unexpected leading PF, in terms of ferroresonance and other operational issues, can be much worse.
Is this a reasonable analysis?
 

mannyb

Senior Member
Location
Florida
Occupation
Electrician
The PFCC is located at an apartment complex at service entrance. I was doing a site walk to see what I was getting into with new feeder. I cant imagine the hvac unit is causing all the issues for them to install the PFCC. Thanks for info
 

GoldDigger

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Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
The PFCC is located at an apartment complex at service entrance. I was doing a site walk to see what I was getting into with new feeder. I cant imagine the hvac unit is causing all the issues for them to install the PFCC. Thanks for info
They may have been talked into expensive PFCC by a snake oil salesman. Such gadgets are commonly marketed to homeowners, but may be hitting the apartment market too.

If the concern were HVAC, then even if heat pumps were in use the PFCC would be overcorrection about half of the year!

Is there a manufacturer, installer, or brand name on the unit?
 
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