Another KW gimmic that apparently works

[StephenSDH]

Well this is a follow up to my first post on this forum. It is another money saving gizmo. It seems to be a Capacitor Back with a line reactor for a large industrial system.

http://forums.mikeholt.com/showthread.php?t=110653

After the helpful responses to reassure my beliefs, I advised the customer it was fishy an there wouldn't be a grandiose payback. He went ahead and installed the system, along with Squard D PowerLogic monitoring system with data collection. Long story short. The customer said the system has reduced his KW, and he has been given pats on the back from Upper Management. Only issue he mentioned is he permanently turned off one of the systems because when it is unloaded one of his boilers tripped out on overvoltage. I do believe him that they shaved off some KW, but I also believe they are going to have issues over the years from adding capacitors to their system(Drive Failures, Capacitor Failures). I tip toe on this subject, because I am not knowledgeable in harmonic power losses or System Resonance.

Can anyone point me in the direction of information to read about this subject? I have read alot about harmonics and power factor corrections, but I am unable to determine were the power savings is. The customer has primary Motor loads 50% drives, 50% across the line. My understanding is that he would likely predominately 5th and 7th harmonics. He told me the sales man said he would save by removing harmonics in the line which would reduce harmonic losses in motor windings.

I am thinking about volunteering a day of my time to go on site and get some experience with some of my toys by analyzing the harmonics, looking at what this company actually supplied, and try to find out why they are having overvoltage issues.

Thanks for any help. Sorry so long winded.

Steve

 

[mivey]

But was it reduced because of other factors like a drop in production, other conservation efforts, etc?

Comparing last year's bill to this year's bill means nothing other than the bills are different. It does not give you enough information to determine why they are different.

See what supporting data you can get if you feel froggy. However, it will not re-write the laws of nature.

While I did not check the actual math, I think your assessment method from the first post was spot on.

 

[StephenSDH]

I would like to spend a day out there just because I don't understand it. They have a fairly steady processes. They can switch the gizmo on and off and see the the immediate reduction in KW on the Square D powerlogic.

 

[mivey]

Then by all means get the data. Don't forget a sketch of install location, meter location, and feeder/disconnect setup.

If you do the leg work, I'm sure it will be entertaining and educational for us to help with the number crunching, speculation, and pure out-n-out guesswork. :grin:

 

[Jraef]

I once had a situation where I stepped into the end of a project started by someone else. He had sold a sawmill on the FACT that putting soft starters on every motor over 25HP was going to save him on his Peak Demand charges by lowering starting current. He went belly up (for other reasons) and I got hired to finish the job. I did not know the original intent when I started, I was just implementing the last 20 large soft starter installations. When we finished, the plant manager bragged to me how much his Peak Demand charges had dropped! I was shocked, because soft starers, regardless of their other numerous benefits, do NOT reduce Peak Demand charges when the utility uses a sliding demand window for assessing them (as this one did). Yet here was the evidence; a set of utility bills showing that his peak demand charges had in fact gone down!

The point of this story however is this. I don't know everything, but I KNOW what I know unless I prove beyond my own doubt that I was wrong. So I HAD TO investigate this fully. Turned out there was a REAL explanation.

In the past when the workers went on breaks, the plant electrician had told them (falsely) that because of starting current surges, it was cheaper to leave machines running for up to 1/2 hour rather than turn them off and re-start! So twice per shift, the whistle would blow, the workers would walk away and leave EVERY MACHINE in the plant running unloaded! Once they installed soft starters on the bigger machines, they felt is was "safe" to turn them off during 20 minute breaks. Of course, when you turn off the Band Saw, it automatically turns off the Dust Collector and infeed conveyor for it, and right on down the line, almost every motor, large and small, was getting turned off. So 4 times per day (2 shifts), the mill had an almost complete shutdown, and therefore a staggered re-start. THAT was why the Peak Demand charges went down. Now indirectly, that was a result of the soft starter installation, but it was NOT for the reason the original contractor told them it would.

I would highly suspect your situation has a similar ring to it. BECAUSE they implemented an expensive "gizmo" to reduce their power consumption, they unconsciously also implemented numerous smaller changes to their way of doing things, and THOSE added up to a drop in kW consumption.

 

[mivey]

So 4 times per day (2 shifts), the mill had an almost complete shutdown, and therefore a staggered re-start. THAT was why the Peak Demand charges went down.

I don't really see that when the meter probably had a 15 or 30 minute demand interval. If they did not peak in the intervals that included the break, they would have peaked at another. Each interval stands on its own. There must be more to the story.

If they were shut down from 1 PM to 3 PM (say during the heaviest A/C load), I could see that.

 

[StephenSDH]

Thanks guys. I will do a site survey someday when I have a free day, and put all the data on here. Deep down I know it is going to still be a wash in savings, but there will be something to learn from it. It is painful to watch the customer bask in his black magic, but I can't burst his bubble because it would only be bad for me and him.

Anyone else with comments please let me know.

 

[qcroanoke]

Thanks guys. I will do a site survey someday when I have a free day, and put all the data on here. Deep down I know it is going to still be a wash in savings, but there will be something to learn from it. It is painful to watch the customer bask in his black magic, but I can't burst his bubble because it would only be bad for me and him.

Anyone else with comments please let me know.

I believe that unless the customer has a good understanding of electricity trying to
convince him that he is not really saving money will not work and only convince him that you do not know what you are talking about. If it was me, like you, I'd leave it alone.....

 

[drbond24]

I believe that unless the customer has a good understanding of electricity trying to
convince him that he is not really saving money will not work and only convince him that you do not know what you are talking about. If it was me, like you, I'd leave it alone.....

I agree with this 100%. The only reason stuff like that sells is because the purchaser doesn't understand the concept. Because they don't understand it, they want to believe that it is working and you aren't going to convince them otherwise even if you're right. The place is running, the guy is getting pats on the back from his management, don't worry about it if you don't have a stake in it for some reason.

 

[philly]

I believe that unless the customer has a good understanding of electricity trying to
convince him that he is not really saving money will not work and only convince him that you do not know what you are talking about. If it was me, like you, I'd leave it alone.....

I agree with this as well. I continually struggle with upper management at our plant regarding power factor correction caps on our large motors. These caps are constantly blowing (due to other reasons most likely harmonics) and managment is constantly ratteling everyones cage to get them replaced due to the fact that they are saving money. We do not get charged a power factor penalty from the utility, and I try to explain that there is no real savings hear but everytime it falls upon deaf ears.

I agree that there is a small savings due to losses, however the issue with these caps constantly causing problems is not worth the small amount of savings they provide.

 

[mivey]

I agree with this as well. I continually struggle with upper management at our plant regarding power factor correction caps on our large motors. These caps are constantly blowing (due to other reasons most likely harmonics) and managment is constantly ratteling everyones cage to get them replaced due to the fact that they are saving money. We do not get charged a power factor penalty from the utility, and I try to explain that there is no real savings hear but everytime it falls upon deaf ears.

I agree that there is a small savings due to losses, however the issue with these caps constantly causing problems is not worth the small amount of savings they provide.

If the motor is big enough (100's of HP), and far enough from the meter (several hundred ft+), and runs enough hours (~50+% of the time), and the correction is installed near the motor, the loss reduction may give a favorable payback. Constantly blowing is another issue, however.