Power Factor Correction

[augie47]

A friend of mine is maintenances manager at a fairly large local manufacturing facility. Someone has sold the facility on "energy savings" and installed new lighting, etc. One of the steps they are taking is to install power factor correction capacitors on many of the machines (CNC, Mills, etc) and welders.
He is questioning the need for the capacitors as the plant currently has a 97% power factor.
When asked, the suppliers simply say it will "improve his amperage".

 

[cpal]

has he consulted the utility?

 

[zog]

A friend of mine is maintenances manager at a fairly large local manufacturing facility. Someone has sold the facility on "energy savings" and installed new lighting, etc. One of the steps they are taking is to install power factor correction capacitors on many of the machines (CNC, Mills, etc) and welders.
He is questioning the need for the capacitors as the plant currently has a 97% power factor.
When asked, the suppliers simply say it will "improve his amperage".

Snake oil, or just dumb EC's that don't know better. Is your plant paying a PF penalty? If not than it will do you no good.

 

[bob]

When asked, the suppliers simply say it will "improve his amperage".

Run don't walk. Sure sign they speak with forked tongue. If the PF is at 0.97, they can't add many capacitors for sure and he will see little advantage with additions.

 

[chris kennedy]

the plant currently has a 97% power factor.

Are you sure?

 

[augie47]

I have not seen the facts and I know that number seems almost impossible, but he assured me that was the case as he was also suprised it was that high.

 

[skeshesh]

He is questioning the need for the capacitors as the plant currently has a 97% power factor.

Really? seems implausible... In any case, it's like saying your kid has a 3.93GPA and you want to hire him a tutor...

When asked, the suppliers simply say it will "improve his amperage".

Great word choices by these guys (I smell fresh-out-the-oven crapcakes). And at the end of the day Zog is correct - even if they manage a small improvement it won't save them money unless they were paying a penalty which can't be the case if they already have a 0.97pf.

 

[ty]

Really? seems implausible... In any case, it's like saying your kid has a 3.93GPA and you want to hire him a tutor...


Great word choices by these guys (I smell fresh-out-the-oven crapcakes). And at the end of the day Zog is correct - even if they manage a small improvement it won't save them money unless they were paying a penalty which can't be the case if they already have a 0.97pf.

Not sure if it is needed in your case. PFC can be helpful in the right senario.

But, because of the 'Go Green' and 'Save Energy' swing of things, these companies are really going after the unwary homeowner market.

Just the other day I had another phone call from these clowns trying to get me to buy into their nonsense.

They got the CEO on the phone.
I asked him if I had a motor running at 120v and drawing 6 amps, and was able to change it to run at 240v and 3 amps which was costing me less to run?

Then he went on to explain that they aren't really trying to correct power factor and that they are storing energy in their capacitors. The CEO said that their caps. store energy so that when your washing machine starts, it draws power from the caps and not 'outside'.
So I asked him if the caps are charged and I turn off my main breaker, will my washer start. He said 'yes'.

He finally had enough and hung up.

Oh, I also asked him if his snake oil box is Energy Star approved. of course not.

 

[Jraef]

I have not seen the facts and I know that number seems almost impossible, but he assured me that was the case as he was also suprised it was that high.

Doesn't matter with regards to saving energy, even if the pf was .70 or .30!

Improving pf does reduce "current", but current is not "energy", it is a component of energy. That's the basis of the scam these guys are perpetrating. The show you a current meter and it drops when the caps are connected. But it's just a trick; they are not showing you the whole picture. The utility bills you for kWh, which is not affected by the pf. Just ask them. They DO charge penalties for having poor pf, because it costs them more $$ to deliver power to you. So they pass that on as fees, related to energy consumption, but the actual amount of billable energy will remain virtually unchanged with or without the capacitors connected. But every utility I know of asks only that you correct to .90 or .95 at worst, so if you are already at .97, they love you!

Yes, there is a small amount of losses from resistance in wires etc., but it is so puny as to be not worth measuring, unless someone has not followed code and seriously under sized conductors.

 

[mivey]

...even if they manage a small improvement it won't save them money unless they were paying a penalty which can't be the case if they already have a 0.97pf.

And over-correcting to a leading pf is bad as well. Also, it rarely makes sense to go much beyond the mid-90 range as the payback is so poor.

 

[mivey]

...Yes, there is a small amount of losses from resistance in wires etc., but it is so puny as to be not worth measuring, unless someone has not followed code and seriously under sized conductors.

For large loads that run a lot and are located a ways from the meter, that may not be true. Crunch the numbers for 293 kW load, 4380 run hours/yr, 400 ft of 900 kcmil copper to meter point, 480 volts at meter, 3 phase. See if you get close to the following:

At 60% pf:
488 kVA, 608 amps at meter, 463 volts at load, 4.18 kW loss, 390 kvar.

At 95% pf:
308 kVA, 376 amps at meter, 473 volts at load, 1.60 kW loss (2.58 kW reduction), 96 kvar.

Loss reduction = 1 - 1.6/4.18 => 61.7% reduction. As a check use the formula:
% Loss reduction = 100 - 100 * (uncorrected pf / corrected pf)^2 = 100 - 100*(0.6/0.95)^2 = 60.11%

Annual loss reduction = 4380_hrs/yr * 2.58_kW = 11,300.4 kWh/yr. At 10 cents/kWh this is $1,130/yr in loss reduction savings. That should pay for the 300 kvar of correction used in a few years or so, not including the impact of the reduction in billing demand.

Add:
I forgot to adjust for ambient temperature: $963/yr savings.

 

[Besoeker]

I have not seen the facts and I know that number seems almost impossible, but he assured me that was the case as he was also suprised it was that high.

Maybe the high power factor is a result of already existing PFC?

 

[drbond24]

A friend of mine is maintenances manager at a fairly large local manufacturing facility. Someone has sold the facility on "energy savings" and installed new lighting, etc. One of the steps they are taking is to install power factor correction capacitors on many of the machines (CNC, Mills, etc) and welders.
He is questioning the need for the capacitors as the plant currently has a 97% power factor.
When asked, the suppliers simply say it will "improve his amperage".

A power factor that high is very unlikely unless they are already correcting.

I toss my vote in with the others that say run, don't walk, in the opposite direction. Your friend's plant is getting ripped off.

 

[mivey]

Maybe the high power factor is a result of already existing PFC?

Almost has to be. Maybe they are selling it as mo-better than what they already have.

Existing PFC practically kills whatever small economic benefit there might have been unless the old PFC is due for the trash heap already. A central PFC system is already covering the best benefit: pf penalty reduction.

Removing a central unit and installing dispersed units would only make sense in some very extreme cases (calcs similar to those I have above). Dispersed PFC units are the best when they are installed with the load. I am routinely disappointed that some of the large motors I see were not spec'd with PFC at build because that is the cheapest install cost.

 

[zog]

Maybe the high power factor is a result of already existing PFC?

Or if most of the motors are running off VFD's.

 

[Besoeker]

Or if most of the motors are running off VFD's.

Better displacement pf.
Poorer distortion pf.

 

[zog]

Better displacement pf.
Poorer distortion pf.

True but irrevalant for this specific topic.

 

[Marc L]

If I make the assumption that all reactive load currents within the facility are inductive in nature (no capacitive reactive currents such as over-excited synchronous machines) then your salesman's claim is bogus beyond a doubt. At 97% PF, those energy wasting reactive currents would have to be negligible.

Sherlock

 

[augie47]

Thanks for the responses. You confirmed my suspicions. I have passed the info along.