KVAR - Power Correction - Your thought (lol!) and what we're using

[PaysonHVAC]

Yeah I'm sure this has come up before, ha ha!

On the radio they advertise these units for your home (which I'm not sold on) but last year my boss became interested in them for our large motors and motors that run 24/7.

I'm installing another one right now, so I thought I would start a thread and get the discussion going before I add some photos and videos of the "magic", Ha ha!

We've installed them on a few 50HP pump motors, some 15HP pump motors, one on a air handler, and today four more on air handlers.

Those who know me know I am shy of snake oil. :-p

Let's hear what you have to say and later I will update how we came to doing this ourself and how it works.

[PaysonHVAC]

Wow. Nobody's gonna bite?

[dijit]

http://www.nist.gov/pml/quantum/power_121509.cfm

http://www.nist.gov/customcf/get_pdf.cfm?pub_id=903669

The above links deal with residential use of these devices specifically. Don't know what the difference is in other than residential setups but I believe where I live they require power factor to be no less than .95

[PaysonHVAC]

Well they say it WILL work on single phase. Which they will.

However if the power factor isn't bad to begin with then it wont help.

Also, whatever load the motors are in when you calculate the caps to correct it, you will under correct or over correct when the load increases or decreases.

My boss took our new fangled $8,000 Fluke power factor analyser home to check his home unit and found that a KVAR would do little to no good. (power factor was over .9)

On our constant load blowers and pumps at work, however, we have found power factors as bad as .3 (1.0 being perfect).

[PaysonHVAC]

Here's what one of our smaller KVAR's looks like.
This was installed today on a make up air handler.


Using just my basic amp meter (will go back and recheck all of these with the analyser later)...


Got about 10 amps per leg without the KVAR. (480VAC 3 phase)






With the KVAR connected it's dropped to just about 3.2 amps.

Yes, dropped the LINE SIDE amp draw to just over 1/3





The "reactive" power is pretty high going through the capacitors.



It seems that if a motor is mismatched from it's load (low static, etc) that the power facotr goes way down.





We have some 50 or 60 HP pump motors that went from about 60 amps down to 40-ish if I remember right.

[PaysonHVAC]

Here's a bigger one on a 50HP motor.

[PaysonHVAC]

Made by G.E.

[billg]

I do something like this on the 3 phase converters i build.

Well they say it WILL work on single phase. Which they will.

However if the power factor isn't bad to begin with then it wont help.
Also, whatever load the motors are in when you calculate the caps to correct it, you will under correct or over correct when the load increases or decreases.


to account for changing loads i will change capacitance with relays connected to banks of capacitors triggered by current sensing relays. (as in when running idler motor only or idler and working motor.)



My boss took our new fangled $8,000 Fluke power factor analyser home to check his home unit and found that a KVAR would do little to no good. (power factor was over .9)

On our constant load blowers and pumps at work, however, we have found power factors as bad as .3 (1.0 being perfect).

[flange]

what does it do to current draw on the incoming power prior to the black box? I have seen the demo many times, but in no case would any of the salesman of these devices allow us to measure incoming current before and after box was installed.

[craig1]

what does it do to current draw on the incoming power prior to the black box? I have seen the demo many times, but in no case would any of the salesman of these devices allow us to measure incoming current before and after box was installed.

Current draw (amps) will drop with the correct correction capacitors installed. However the amount of energy used (watts) remains the same. This is why residential power correction is a scam. It will not reduce your bill because residential customers are billed only by kilowatt hours consumed. Power factor is not taken into account. commercial customers on the other hand are usually charged more if their load has bad power factor and installation of correction capacitors can reduce the electricity bill.

Utilities hate bad power factor since it puts additional load on their equipment but doesn't consume billable energy.

The charge for bad power factor is like a "restocking fee" to cover electricity that was transported but not consumed.

[flange]

I am fully aware of the charges for poor power factor, and also the benefit of correction done properly. My issue is this....about every five years or so some sales guy omes around pushing the magic black box. we know whats in there, and they sell based upon load side of box current draw reduction. when questioned, they wont let you check upstream side.

power factor, in effect is a measure of how much of the applied power actually gets used. poor power factor means your internal grid is inefficient, so the utility penalizes for that. they still bill on whats supplied, so to be usefull, you need to reduce kw at the meter by actual reduction in use, or proper correction to make your grid more efficient.

[hvacvegas]

...wtf is power factor?

So this box dropped your amp draw from 10 to 3? On 120 thats like a 840 watt reduction in consumption.

So payson, shoot me an e-mail with a power factor reducer cost for my 2 ton AC, please.

[PaysonHVAC]

...wtf is power factor?

So this box dropped your amp draw from 10 to 3? On 120 thats like a 840 watt reduction in consumption.

So payson, shoot me an e-mail with a power factor reducer cost for my 2 ton AC, please.

As I said, I'm not sold on using them on residential A/C.
For one the power factor is pretty good to begin with.
For another, I'm not sure how the residential power is charged.


Here is the basic online definition of what is going on:
"In an electric power system, a load with a low power factor draws more current than a load with a high power factor for the same amount of useful power transferred. The higher currents increase the energy lost in the distribution system, and require larger wires and other equipment. Because of the costs of larger equipment and wasted energy, electrical utilities will usually charge a higher cost to industrial or commercial customers where there is a low power factor."


I know there are several ways that power companies charge. So cost savings depend on several things.

With a low power factor what is happening is when the magnetic field collapses, and depending when per the phase of the power, current goes BACK into the grid (reactive power). Then on the next cycle it is drawn back in to charge the magnetic field + the power to do the word. Overall power pulled through the electrical system is the apperant power.
Theoretically, if you are not credited for the power going back and then you pull that power every cycle, you are being charged for it.

My standard clamp amp meter just shows overall amp draw through the LINE SIDE. It was indeed 10 amps before and just over 3 amps after.

The capacitor banks are wired in PARALLEL with each inductor winding.
When the magnetic field collapses it charges the cap. On the next cycle (I'm speaking of 60 cycles a SECOND, not START/STOP CYCLES) the field is charged but draws it from the capacitor primarily.

As it's running you are then only drawing the power form the ulitlity company that is being used to do the work.

Whether you get a cost savings fomr the utility company or not. On motors with bad power factors like these, you can reduce the overall current drawing throught your electrical distribution system. Even as much as freeing up enough capacity to double the amount of equipment on the existing electrical panels, wiring, etc.


On some other motors I saw 60 amps drop to 40 amps. @480 volts. So you're talking some pretty good amount of killowatts.

[PaysonHVAC]

I got busy today so I didin't get a chance to put the scope on it.
Hopefully tomorrow I will. We charted the volts, amps, power factor, everything.
And then we chart it again after we install these.

I will try to shoot a video of it using the scope analyser which gives all the phasing, power factor, etc.

I made a recording once but have to find the video.
It's pretty cool.


At first I was skeptical. I searched for a while. The thing is companies are trying to sell these to residential customers.
Well, what induction motors do we have? A compressor in our central A/C and a tiny comp in a fridge.
My boss tested his A/C and it was like .93 power factor. Not much benefit at trying to install a cap on that.

AND I'd have to wonder about installing these on motors that don't have one set load. A compressor load varies. So now you may be under correcting at one point and then over correcting at another point.

My boss was thinking of using one of these (it would be massive) on our centrifugal chiller. But I wonder about the varying load issue. I'd rather see a VFD be added.
Our other chiller (tri screw) already has a VFD.

BTW, these can not be used with a VFD.

[tjcsf07]

http://en.wikipedia.org/wiki/Synchronous_condenser

We talked about these in my e-machines class a few semesters ago...its in the same vein as the capacitor banks you guys are talking about.

Large facilities (especially industrial) go to great lengths to improve their power factor because the utility not only charges them for energy demand and usage (usually a few cents per KWH), they get wacked much harder in transmission demand charges (several dollars per KVA)

[PaysonHVAC]

Well I can't find my videos of checking one of our motors while using the $8,000 analyser / meter but here's a layman check on a 60HP motor using my amprobe.
Dropped from 60 amps to 40 amps on the line side.
Note that it's still near 60 amps at the motor side.


CLICK ON THE PICTURE TO PLAY THE VIDEO


I'll get some good pix/videos later using the good meter. Maybe tomorrow.

[Dr.phil]

Payson, I see you are using the Amprobe meter. Thats my favorite meter.

[PaysonHVAC]

Payson, I see you are using the Amprobe meter. Thats my favorite meter.

Indeed!
I have one for personal use and when I started the last job I asked to get one for work.

I had to ORDER the thing. They didn't stock it at my favorite parts house.

It's the same exact size and shape as the amprobe made 30 years ago. :-)

[PaysonHVAC]

Testing a KVAR unit today with the power analyser / scope.






Before connecting the KVAR.




After connecting the KVAR.

Line power amps dropped from 10+ to 4~5




Click this photo to play the video demonstrating the KVAR.

[madhat]

Utilities charge by the kWh, not by Amps. So you need a Watt meter. Also you need to check upstream "line side" from the box. Not downstream "load side" of the box.