# Passive Power Factor correction

C

Jan 1, 1970
0
E

#### Eeyore

Jan 1, 1970
0
Martin said:
Has anyone have experience with something like this?

http://www.ndaenergy.com/power-factor-benefits.html

Load of old garbage. Individual consumers don't need power factor
correction as the power company doesn't bother charging it for them.

They should be prosecuted for FRAUD. Refer it to you local DA

Graham

E

#### Eeyore

Jan 1, 1970
0
Cydrome said:
In short, it's a scam.

there is some truth behind power factor correction saving power,

In industrial situations.

but it's not 10 to the totaly bogus 25% savings they claim.

But it doesn't affect the home consumer whose meters read only TRUE power and
PF won't affect that.

Graham

N

#### Neon John

Jan 1, 1970
0
Has anyone have experience with something like this?

http://www.ndaenergy.com/power-factor-benefits.html

That old fraud again.

In a very simplified nutshell, a load with a power factor less than 1 draws
both real power and "wattless" or reactive power. "wattless power" seems like
a contradiction but its the slang used in the power industry. Wattless amps
flow out of phase with the voltage waveform and are caused (usually) by loads
that have an inductive component (electric motors, primarily) or (rarely) by
loads with capacitive components (un-PF corrected switchmode power supplies,
some types of fluorescent lights, etc.) The real amps and the wattless amps

Here's the critical part. Revenue meters only measure REAL power (some of the
new electronic ones also measure VARs [reactive power] but do not bill for it)
and REAL power is what you're paying for. Large commercial customers can be
billed for low PF (excessive VARs) but never in a residential or small
commercial (200 amp) service. Reactive power simply flows through the lines
unmetered.

Most VARs are lagging - that is, the current lags the voltage by some phase
angle. What that box does is supply leading VARS to counteract the lagging
VARS. That reduces the amps flowing through the circuit upstream of the box
(which is what they show unsophisticated customers) but that reduction has
essentially NO effect on the REAL power metered by the revenue meter.

I say "almost" because the extra amps flowing through the wire's low but
finite resistance developers a little heat. This is real power and gets
metered. The amount is tiny, though, a few watts at most.

The box contains ordinary motor run capacitors. Problem is, these capacitors
are not perfect - none are - and so they dissipate a little heat themselves.
That again is REAL power that is metered and billed for. Again, it is a small
amount but it may very well exceed the amount of power saved by reducing the
current in the low power factor house wiring.

Worse, the box supplies a fixed amount of leading VARs. When those VARs
aren't needed by, say, a furnace fan motor, they flow back out the service
entrance and to the utility network. The current flow through the conductors
between the box and the meter causes another small voltage drop and therefore
some heat generation. The amount of REAL energy consumed is undoubtedly small
but it very well could exceed any "savings" caused by correcting low PF loads
in the house.

In other words, having this very expensive box in place could and probably
will cost you a few cents more a month on your power bill. I bet they charge
a kilobuck or more for this box so that's money just pissed away.

There is only one instance where PF correction makes sense for small
consumers. That is, when the wattless current is (on the verge of)
overloading the service entrance. Even then, this box is the WRONG way to go

Let's suppose you have a store with lots of low PF pre-energy efficient
fluorescent lights inside and lots of neon signage outside. Low PF
fluorescent fixtures typically have a PF of around 0.5. Low PF neon
transformers around 0.4. That means that the fluorescent lamps draw TWICE the
current necessary to provide the fixture's wattage. The neon draws a little
OVER TWICE the necessary current.

If lighting and signage makes up the bulk of your load and the total current
is near or exceeds 200 amps then you'd be experiencing tripped main breakers,
an overheating breaker panel and perhaps complaints from the utility.

The thing is, only half that 200 amp (assuming an average pf of 0.5 at the
service entrance) is necessary to operate the lights and signs. The rest is
lagging reactive amps that do nothing other than heat wires and trip breakers.

If someone like me comes in and corrects each low PF load by placing the
appropriate capacitor across the load's power terminals so that the overall PF
is now 1, only 100 amps is drawn from the utility. The other 100 amps are
supplied by the capacitors that are scattered around the facility. I normally
correct each neon transformer at its power terminals and each fluorescent lamp
string (not worth the cost to do each lamp individually).

This process saves very little money on the power bill but it DOES eliminate
the excess current draw, the overheating, the complaining from the power
company and it opens up those 100 amps for other loads in case the store
expands.

I would NOT use a box like that company is peddling. I use motor run
capacitors which, bought wholesale, cost about $5 ea. Here's a photo of one http://www.johndearmond.com/wp-content/uploads/2008/10/fan-11.jpg I repeat, this procedure is NOT necessary and is NOT financially justified unless the service entrance and panel is being overloaded by low PF VARs OR your power company is threatening a low PF penalty charge. The latter is very very rare on 200 amp services. Here's another situation. Suppose a business has a sign out on the street, located several hundred feet from the breaker panel. The sign is mostly neon. It has a 30 amp branch circuit run to it through either underground conduit or direct-burial cable. The sign is pretty much fully loading the branch, drawing a little less than 30 amps. Since the neon transformers have low PF (around 0.4), over half that current is wattless. Now suppose the store operator wants to install a larger sign with more neon. The 30 amp branch is at capacity and running a larger one would require tearing up his parking lot, costing thousands of$ and leaving an ugly scar
on his pavement. What to do?

We go into the sign and PF-correct each neon transformer (or buy high PF
transformers that have the caps built in) in the new sign. With each
transformer having a PF near 1, we can draw twice the real power over the same
30 amp branch. IOW, the sign can be twice as large while drawing the same
current.

The sign will, of course, cost twice as much to operate so the cost savings is
strictly in not having to dig up his pavement and run a larger branch.
Presumably the larger sign will draw more customers and thus pay for the extra
power consumption.

Making neon signs myself, I've run into this situation MANY times. Few sign
shop operators understand the concept of PF so I've been able to "save the
day" a number of times for sign shops that bought wholesale neon from me.

The only other common situation where correcting a low PF load makes sense is
when you're trying to run the load from a generator that is being overloaded
by the wattless current. We touched on that yesterday in another thread. In
this instance, correcting the PF of the low PF furnace blower will allow the
generator to handle the load AND power some other loads. It will also save
fuel so if you're off-grid or experience frequent power outages, PF correction
might be worthwhile, depending on your existing PF and how often you run your
generator.

Pre-energy-efficient fluorescent lamps, some mercury vapor and HID lamps and
lightly loaded motors (typically HVAC blower motors) are typically the only
low PF loads in the house. Some microwave ovens are also low PF. Most
fully-loaded motors have high PFs. Typical is the measurement someone posted
recently of his refrigerator having a 0.95 PF. If you have one, a well pump
may or may not be low PF, depending on how it is sized. A deep well pump in a
shallow well is quite under-loaded and will have a low PF. The only way to
know is to measure.

Let me repeat again, unless you're running out of service entrance capacity or
are having to run the load using a generator, low PF simply doesn't matter
around the house or small business.

If there is a lot of interest in this then I'll do a web page on DIY PF
correction. However, unless you have a special circumstance such as those
listed above, it's simply not worth the effort. It would take years for the
tiny power savings to pay back the cost of even $100 worth of capacitors. John -- John De Armond See my website for my current email address http://www.neon-john.com http://www.johndearmond.com <-- best little blog on the net! Tellico Plains, Occupied TN You can't turn [MS] shovelware into reliable software by patching it a whole lot. -Marcus Ranum N #### [email protected] Jan 1, 1970 0 Has anyone have experience with something like this? http://www.ndaenergy.com/power-factor-benefits.html That old fraud again. In a very simplified nutshell, a load with a power factor less than 1 draws both real power and "wattless" or reactive power. "wattless power" seems like a contradiction but its the slang used in the power industry. Wattless amps flow out of phase with the voltage waveform and are caused (usually) by loads that have an inductive component (electric motors, primarily) or (rarely) by loads with capacitive components (un-PF corrected switchmode power supplies, some types of fluorescent lights, etc.) The real amps and the wattless amps add quadratically to produce the total amps. [snip] The only other common situation where correcting a low PF load makes sense is when you're trying to run the load from a generator that is being overloaded by the wattless current. We touched on that yesterday in another thread. In this instance, correcting the PF of the low PF furnace blower will allow the generator to handle the load AND power some other loads. It will also save fuel so if you're off-grid or experience frequent power outages, PF correction might be worthwhile, depending on your existing PF and how often you run your generator. [snip] If there is a lot of interest in this then I'll do a web page on DIY PF correction. However, unless you have a special circumstance such as those listed above, it's simply not worth the effort. It would take years for the tiny power savings to pay back the cost of even$100 worth of capacitors.

John

I would appreciate info on power correction to reduce load on the
emergency generator when powering the furnace blower - less load =
less gas = fewer trips outside in the cold to refill.

Thanks,
John

E

#### Eeyore

Jan 1, 1970
0
I would appreciate info on power correction to reduce load on the
emergency generator when powering the furnace blower - less load =
less gas = fewer trips outside in the cold to refill.

How often does it trip ?

You just need to PF correct the blower. That's all. No 'central' PF.

Graham

E

#### Eeyore

Jan 1, 1970
0
Jim said:
If you can plug it into a Kill-A-Watt it will show you true Watts, VA
(Volt-Amps) and PF (Power Factor). Power factor correction will raise
PF towards 1.0 and reduce the VA closer to the Watts.

It still won't affect your bill.

Oh, the furnace blower. He needs to measure that seperately but by the
sound of it would not know what to do with the data.

It could also be 'start-up current' that's causing the tripping. In which
case he needs more amps on the supply and a larger rated breaker. Or a
better designed blower.

Graham

E

#### Eeyore

Jan 1, 1970
0
Jim said:
A bad power factor is somewhat like bad shock absorbers when driving
down a bumpy road. The vehicle bounces up and down more than the road
does. With a poor power factor some of the electric current bounces
back from the motor.

That is truly one of the worst explanations I have ever seen.
http://en.wikipedia.org/wiki/Power_factor

The truth is, it's complex (in more ways than one). ;~)

Graham

S

#### stu

Jan 1, 1970
0
generator to handle the load AND power some other loads. It will also save
fuel so if you're off-grid or experience frequent power outages, PF correction
might be worthwhile,
I was following you until I got to this part.
I don't understand how PF correction would save much fuel. If the gererator
is loaded to maximum with a 0.50PF load, isn't still only generating the
REAL power?

N

#### [email protected]

Jan 1, 1970
0
It still won't affect your bill.

Oh, the furnace blower. He needs to measure that seperately but by the
sound of it would not know what to do with the data.

It could also be 'start-up current' that's causing the tripping. In which
case he needs more amps on the supply and a larger rated breaker. Or a
better designed blower.

Graham

Rather than willy-nilly placing caps acroos the motor windings,it
seems more reasonable to look for a rule-of-thumb based on motor
amperage/hp.

Other descriptions in the thread indicate that a smaller generator
could be used if PF is properly corrected. Being able to use a
smaller generator makes a difference in the fuel used.

I'm only looking for coverage of short-term outages - something
requiring less than 10 gallons of fuel (worst outage in 20 years was
36 hours). More than that and I'll be closing off most of the house
and burning wood. I've learned to build a fireplace load that lights
with one match, burns at least two hours without any intervention, and
heats two rooms even with a window partly opened for proper draft -
not too bad for a city kid who's always had gas heat.

If there was a need for long-tem power, I would probably consider some
combination of solar (inverter AC plus charge batteries) and a
Listeroid powered generator (direct AC plus charge batteries after a
few rainy/overcast days). At a typical haf gallon or less per hour
for a Listeroid providing 2-3KW, 50 gallons of diesel would last a
long time.

John

E

#### Eeyore

Jan 1, 1970
0
stu said:
I was following you until I got to this part.
I don't understand how PF correction would save much fuel. If the gererator
is loaded to maximum with a 0.50PF load, isn't still only generating the
REAL power?

Now that's more complicated. If you're generating your OWN power then apparent
power WILL be a factor.

But only IF. With gris power it mostly all gets lost in the wash.

Besides, were you planning on running any low PF loads ?

Graham

p.s. and learn to trim headers properly. I ihaven't a clue who said what.

E

#### Eeyore

Jan 1, 1970
0
Rather than willy-nilly placing caps acroos the motor windings,it
seems more reasonable to look for a rule-of-thumb based on motor
amperage/hp.

Other descriptions in the thread indicate that a smaller generator
could be used if PF is properly corrected. Being able to use a
smaller generator makes a difference in the fuel used.

Where the hell did (personal) generators come into this ? It's an entirely
different ball game.

Graham

N

#### Neon John

Jan 1, 1970
0
I was following you until I got to this part.
I don't understand how PF correction would save much fuel. If the gererator
is loaded to maximum with a 0.50PF load, isn't still only generating the
REAL power?

This is true. However, the torque required of the prime mover is roughly
proportional to the current flowing in the generator. With a low power
factor, the engine has to supply more torque and therefore more HP since the
speed is fixed. The excess HP ends up being dissipated as heat in the
generator windings.

Small isolated generators (as opposed to large grid-connected generators) are
somewhat of a special case regarding PF.

John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
If the letters PhD appear after a person's name, that person will
remain outdoors even after it's started raining.

N

#### Neon John

Jan 1, 1970
0
I want to thank you for your replies on this subject. Having experienced
the PF problem on my little gen, I now understand (?) what is happening, and
why at a measured 300W, my little 850W generator sounded like it was running
flat out. I would like to put a vote in for a PF web page on your site.
But if not, at least now I can search to web to try to educate myself on how
to get the PF closer to 1.

As a side note, I just realized I have a poor copy of your cordless
battery charger as part of my emergency power arsenal. Found you on a search
for a 12v generator a few years ago.

You're most welcome.

OK, I'll do a page. It'll take a couple of weeks, as I need to drop by the
motor shop for some stuff and to take some pix. Ping me if I don't get it
done in a couple of weeks. My short-term memory isn't what it ought to be.

This is one of those things that is just begging for a video segment.
Unfortunately I'm stuck on dial-up so that's probably not practical. I'll do
the best I can with still pix.

John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
Save the whales, collect the whole set!

N

#### [email protected]

Jan 1, 1970
0
Where the hell did (personal) generators come into this ? It's an entirely
different ball game.

Graham

About two-thirds of the way down in Neon John's initial post in this

John

E

#### Eeyore

Jan 1, 1970
0
About two-thirds of the way down in Neon John's initial post in this

Ok, must have missed it. PF correction will most certainly affect them since
they don't have the power of the whole grid behind them.

Graham

C

Jan 1, 1970
0
Rob.....in Courtice said:
I want to thank you for your replies on this subject. Having experienced
the PF problem on my little gen, I now understand (?) what is happening, and
why at a measured 300W, my little 850W generator sounded like it was running
flat out. I would like to put a vote in for a PF web page on your site.
But if not, at least now I can search to web to try to educate myself on how
to get the PF closer to 1.

To approach unity power factor, you need to cancel out the extra current

You said your meter says the motor is using 300 watts. How many amps is it
drawing though?

The different between say 300watts/120 volts = 2.5 amps subtracted from
what the motor is really pulling will be what you want to cancel out.

So say the motor pulls 4 amps, and you want to get it down to 3.

you need a capacitor or bank of caps that pull 1 amp of reactive current.

At 120 volts as 60Hz, this is about 22uF per amp.

Keep in mind that just slapping caps across your generator with no
factor in the first place.

D

#### daestrom

Jan 1, 1970
0
Cydrome said:
To approach unity power factor, you need to cancel out the extra

You said your meter says the motor is using 300 watts. How many amps
is it drawing though?

The different between say 300watts/120 volts = 2.5 amps subtracted
from what the motor is really pulling will be what you want to cancel
out.

So say the motor pulls 4 amps, and you want to get it down to 3.

you need a capacitor or bank of caps that pull 1 amp of reactive
current.

Sorry, that's NQR (not quite right). The inductive current and the real
current are 90 degrees out of phase. So the reactive current and the real
current form the two legs of a right-triangle and the total current is the
hypotenuse. If you apply Pythagorean Theorem,

Total^2 = Real^2 + Reactive^2

4^2 = 3^2 + Ir^2
Ir^2 = 16-9
Ir = sqrt(5) = ~2.2 amps.

At 120 V, to draw that you need a capacitive reactance of about:
At 120 volts as 60Hz, this is about 22uF per amp.

So it works out to about 45uF total needed.

daestrom

J

#### Johnny B Good

Jan 1, 1970
0
The message <[email protected]>
from [email protected] contains these words:

====big snip====
I would appreciate info on power correction to reduce load on the
emergency generator when powering the furnace blower - less load =
less gas = fewer trips outside in the cold to refill.

It will make almost no difference to the mechanical loading on the PM
and therefore almost no difference to the fuel consumption. What it will
help is reduce the electrical losses, especially useful on a highly
reactive load from a high power motor with a wattage close to the
generator's limit.

The reactive VA is called 'wattless' because it draws power during
every other quarter cycle and returns that power every other quarter
cycle in between making for a net consumption of zero (neglecting I2R
losses in the wire and generator windings).

Provided the VA load from a low PF load doesn't exceed the VA rating
of the generator, PF correction will have almost no effect on fuel
consumption.

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