Power factor Correction help ??

Normal Residential customers ARE NOT charged demand charges nor do power factor correction devices do anything for them but relieve some back pain by taking some weight out of their wallets,
Companies selling power factor correction devices to residential customers are scammers regardless of their claims. However if you open a shop or office at your home location, you may have a new meter installed if your peak demand goes over a certain amount. That depends on your utility. Here that is 26KW last time I checked.

There are claims that improving PF to meet energy star compliance in an appliance will lower a residential bill because it makes the appliance run more efficient. I have no idea what it actually saves in year. Probably not much if anything since PF is not part of a residential bill.

Ok but a shop at home is not a residential load and the electric company will charge you like a shop if you use energy like a shop...

Anyway, If you aren't charged for peak demand, normally residential are just charged KW/h.

Demand and Powerfactor doesn't affect in any mesurable means kw or kw#h used...
A purist can point out that it could reduce heating power loss in cabling but we talk about micro-watts. Reducing inductive load from a fridge can reduce the reactive power flowing back and forth in the wires by 1 or 2 amps but how much heat does 2amps fluctuating current makes on a maybe 14 awg cable....Probably the smallest reading of the better meter cannot measure it...
Maybe installing a kind drive in a home appliance can increase efficiency but not because of the power factor but because it would reduce the speed or the voltage to the load at some point of use instead of keeping it 100% voltage and speed.
But someone selling a black box to save kw/h at a power entry is a scammer.
 
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I was involved with a similar effort where I used a controls system to monitor the 3 phase for the main and each section of the plant (temporary stuff, they rented the equipment from an OEM friend that installs power monitoring on regenerative printing presses as a marketing thing). We found some really weird stuff when he turned on his shop lights; I'm talking 10 minutes of power factor going ape **** while they warmed up. Rather than investigate further, he installed a strip of skylight and LED bulbs. He also put an Altivar32 on a few blowers that were reading crappy pf and high energy use in general.

We asked about any savings afterwards and he said it was substantial enough he wish he did it sooner. I think the skylight was probably the biggest money saver since they don't even turn on the lights some days and it's still brighter than before. He just had the shop guys do it one weekend; a strip of translucent corrugated roof running the whole length of the shop (standard feature for many countries, weirdly uncommon in US). He also stopped getting nailed on the penalty but changed both things in the same month, so we aren't 100% sure if it's the VFDs or the LEDs that was getting him.
 
Well in our country we use compensation device that has logic to turn on off contactors which are connected to capacitors... There is formula which provide you the most efficient size of compensation you should install. And then when power factor get lower than set value, device is turning on stages of capacitors.

Because if u send to much reactive power to grid or take from it you will pay well for it.
 
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Others will correct me if I'm wrong, but if when you start things matters to your electric bill, that's the demand charge. Its usually based on the highest 15 minute KW demand. The PF is important too, and I think there's a penalty if its too low.

This is exactly what was described to me, that they take the highest 15 minutes and that determines the rate for the period. I did not understand what he meant until I read your post.
So in this case reducing the starting demand would benefit us in that we wouldn't have that heavy demand that seems to be dominating the bill cycle...
 
This is exactly what was described to me, that they take the highest 15 minutes and that determines the rate for the period. I did not understand what he meant until I read your post.
So in this case reducing the starting demand would benefit us in that we wouldn't have that heavy demand that seems to be dominating the bill cycle...

That is sort of right... In the case of a 15-minute thermal demand meter it has nothing to do with what you start.

It has to do with the maximum load in "any" 15 minute period during the billing cycle.

If you do load shedding all month to keep your bill down based on a peak you allow during the month, and you let that go higher for 15 minutes the last 15 minutes of the month, you are going to pay for that max peak demand for the whole month plus the rate per KWH for the 15 minutes and other fees they tack on.

A fifteen minute thermal demand meter takes 15 minutes to register what ever demand is currently on it.


Example- you have 100kw on the meter for 7.5 minutes and shut it off on day "one" of your billing cycle and close the doors for the rest of the month, you are going to pay 50 times (1/2 of the peak you had on it for half of the 15 minutes) the demand charge for the entire month minimum. Its the same if you do that the last 15 minutes of the billing cycle. The meter only reached 50 KW in the 7.5 minutes.

So, Demand charge of $3.50 Per KW--. $3.50,times 50 = $175.00 to have that load on for 7.5 minutes. (Half of 15 minutes)


You are going to pay for the peak demand registered on the meter for the entire month regardless when you reach it. Sequencing start up won't matter - if they are all on for 15 minutes you are going to pay for it. Older meters had a red pointer that was pushed up by the demand pointer and would get reset to zero by the person reading the meter.

Caspian
 
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1) Power factor has nothing to do with power based penalties. If your company is being penalized on power factor, that is real and solvable, but not related to how your facility is started up. Add PFC caps to the motors, starting with the largest ones, until your facility PF is .95 or better, after that, don't waste any more money. That's the typical penalty point.

2) Unless you can somehow stretch the starting time out to more than 30 minutes, adding soft starters will likely have zero effect (directly) on what are called "peak Demand" charges, if that's what he is thinking. It's one of those "alternative facts" that is repeated so many times by people marketing soft starters that it begins to sound true, but from a pure engineering fact based standpoint, it's bogus. 99.000% of power utilities bill for Peak Demand based on what is called a "demand window", a snapshot of a 15 to 30 minute window of time in which the average power for that period is highest. Your utility likely publishes their Peak Demand schedule that will lay out that demand window length. But bottom line, the 20-30 second surge you might see from starting motors across-the-line is actually insignificant, and don't be swayed by people who tell you otherwise. That myth is as old as the hills and many many people have a vested interest in maintaining it, but if you still doubt me, call the utility and ask them how much your bill will drop by adding soft starters. They will tell you zero.

There are plenty of other REAL benefits to using soft starters, I happen to really like them, but the reduction of Peak Demand charges is not one of them. The reason the marketing people get away with this alternative fact is that in maybe a small handful (as in less than a dozen across the US) small utilities, mostly that buy power from other larger utilities, they did at one time use what were called "ratcheting instantaneous demand meters". I have not seen one of those in over 20 years now, yet the myth persists.

If you want to help your company avoid penalties the best strategy, and this by the way DOES often involve a controls engineer, is to thoroughly and carefully evaluate the real need to run any and all machines, then adopt control strategies that eliminate wasteful practices. I'll give you an example.

I did work at a wood mill-works, where they make molded wood products for furniture, picture frames, mantles, trim etc. They had dozens of machines like molders, saws, routers, chippers etc., each once had it's own dust collection blower that ran whenever the machine ran, plus many used compressed air and hydraulics, so any running machine was in fact running MULTIPLE machines. The first thing I implemented was that in observing the 2 shift operations for a week, I found that each machine was turned on by the first shift and turned off at the end of the second shift; NEVER off during breaks, lunch, dinner etc. Even if the machine was not being used, it was left running. When I asked operators why, their response was that they were told that "it cost more to re-start a machine than it does to leave it running for an hour, let alone for a 15 minute break." This of course was based somewhat on that same myth about peak demand charges, but also on a real issue of larger machine start-up sometimes causing a voltage drop that made the HID lights re-strike, which meant it was dark for 10 minutes. So we implemented soft starters on every machine over 20HP, mostly just to change their behavior, but also to prevent that voltage drop. That ALONE dropped their demand charges, not because the peak starting current was reduced, but because the OVERALL load demand was reduced and less energy was wasted.

The second phase was that we tied all of the dust collectors together with one common air duct system, then evaluated how much suction was required at each machine. When any given combination of machines were running, the dust collection control system decided which of the multiple dust collectors to turn on in a combination that got the desired effect. This of course could have been easier with a few collectors and VFDs, but they already had all of these multiple smaller collectors installed, so we used them. Overall this then reduced the overall energy consumption another 18% per year. The modifications, PLC and software paid for itself in under 60 days.

The point is, your boss has given you a golden opportunity to be a hero here. Use it, just not in the way he thinks it needs to be done. So my last piece of advice; don't fight him, manipulate him slowly into thinking it was his idea. Ask first for an opportunity to do a thorough study of energy usage so that you can make optimum suggestions without wasting money, then use that information you gather to come up with solutions that, as I said, usually fall into the controls realm anyway.

Good luck!

That is a well thought out explanation, And really puts it into the proper perspective.

THANK YOU !!

I am somewhat confused by the statement below,
So we implemented soft starters on every machine over 20HP, mostly just to change their behavior, but also to prevent that voltage drop. That ALONE dropped their demand charges, not because the peak starting current was reduced, but because the OVERALL load demand was reduced and less energy was wasted.
With the demand causing the voltage drop, by adding the soft starters you reduced the instantaneous demand, Right ?
 
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He has to mean the peak demand for the period dropped. Not instantaneous, think of peak demand for the month on a sliding scale for the billing cycle. Any time during the month you increase the peak on the meter you are getting charged the new peak. But it takes 15 minutes or whatever period the utility uses to register that peak. So if you currently have 15kw reading and you add another 15 kw but only have it on for 5 minutes it will not register the whole additional 15kw.

Is that clear ?
Caspian
 
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Thanks,
So if I'm understanding the demand charge correctly it could actually be better that they start up everything in the morning Before everything else in the plant is running ??
 
That is a well thought out explanation, And really puts it into the proper perspective.

THANK YOU !!

I am somewhat confused by the statement below,

With the demand causing the voltage drop, by adding the soft starters you reduced the instantaneous demand, Right ?
Their demand charges dropped because their overall energy use dropped, ergo their demand dropped too. Their overall energy use dropped partly because the operators were no longer afraid of turning machines off when not in use, because they perceived the softer starting as being not so hard and on the big machines, it no longer made the lights restrike. In their case the utility determined the previous demand based on the demand from the same period in the previous year, likely because there was a seasonal element to it (lumber mills in cold climates use more energy in winter, not just because of heating but because the wood is harder to mill when cold). Most likely the elimination of their peak demand penalties was only going to last that first year, because a year later they would be compared to new values. But overall their reduction in wasted energy was paying off big time anyway.
 
Thanks,
So if I'm understanding the demand charge correctly it could actually be better that they start up everything in the morning Before everything else in the plant is running ??

No, it does not matter when you start it up as far as what you will get charged for peak demand in the billing cycle.

It is how much load you have on for the time it takes the meter to register the load. The actual peak demand of your plant is everything on at the same time. You can keep your charge down by shedding loads you don't need. A 15 minute thermal demand meter takes 15 minutes to register the full load but once it gets there you get charged, If you shut stuff off before starting something else. the meter will only go as high as the new demand. Turn the other stuff back on without turning anything off and the Peak demand registered on the meter will rise.

Some small shops can benefit by load control, not having everything on at the same time.

Example -- Run all electric furnaces first two hours,
total demand - 100kw

Shut them off and then turn on all of everything else
Total demand 100 KW

Demand charge will be based on 100kw

Now turn it all on and have it on for 15 minutes on a 15 minute thermal demand meter and you will get charged for 200kw -the total load of your small plant

Large shops cannot usually take advantage of this type of load management because in a production environment everything needs to be running 24-7

If your shop is such that you don't need everything on all day and night, you can turn some equipment off before you turn other equipment on to keep your "PEAK" demand down. You will want to do a survey of your facility to see what you can turn off before you turn something else on.

If you ever have to keep those items on that you were shutting off, to keep the PEAK demand lower, when you turn another load on, your peak demand will rise and you will not have saved anything on the demand charge, only the KWH.

Remember- it is the total Peak Demand on the meter during any 15 minute period in the billing cycle that you will be billed for. The only way to lower the "PEAK" demand - is shed loads "before" energizing other loads.

In a Church I know of they had 3 electric furnaces. During mild weather, they used an electrical interlock to prevent more than one running at a time. These furnaces combined were 240kw so what they did cut their demand charge to 1/3 (80kw ) 240kw/3 In severe cold weather they had to let them all run at once,. In that case, regardless when in the month they had to let them all run at once, even if it was only the last 15 minutes of the billing cycle, they had to pay for a peak demand of 240kw. It actually happened more than once that they had to let all of the furnaces run at the same time for only the last day of the month so they ended up not saving anything on the demand charge for the whole month.

Remember regardless what you do as far as load shedding during the month, once you let it all on at the same time your peak demand will rise on the meter and you will get billed just as if you never shed any loads during the month.
Here, Demand charge is the largest part of a commercial establishments bill, so anytime you can lower your peak demand you can save a lot. Auto Switching in an industrial environment is possible for some equipment. but you will have to check your facility to see what you can shed at different times to keep the peak demand down.

I hope that helps.

Caspian
 
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OK, I think this is starting to sink in, It doesn't matter when the peak demand occurs only the level of that demand for a given period. If I do a basic survey of our power usage, listing the loads in order of power requirements. Then I can look at when these loads are active and when they are not. It is quite apparent that adding a few soft starters / VFD's isn't going to make any big difference in this demand. Although these could be part of an overall plan to reduce the simultaneous demands...

This says it all !!
A 15 minute thermal demand meter takes 15 minutes to register the full load but once it gets there you get charged, If you shut stuff off before starting something else. the meter will only go as high as the new demand. Turn the other stuff back on without turning anything off and the Peak demand registered on the meter will rise.

BTW, We are a relatively small shop of about 40 employees, we are an OEM of machinery. We have a machine shop running around 20 machines. Our air compressors are a major factor. A Mix of CNC and manual lathes, milling machines etc.
We have a large painting area that has a large exhaust fan pulling air through a painting booth filter that is about 10'H x 25' Long.
 
OK, I think this is starting to sink in, It doesn't matter when the peak demand occurs only the level of that demand for a given period. If I do a basic survey of our power usage, listing the loads in order of power requirements. Then I can look at when these loads are active and when they are not. It is quite apparent that adding a few soft starters / VFD's isn't going to make any big difference in this demand. Although these could be part of an overall plan to reduce the simultaneous demands...

This says it all !!


BTW, We are a relatively small shop of about 40 employees, we are an OEM of machinery. We have a machine shop running around 20 machines. Our air compressors are a major factor. A Mix of CNC and manual lathes, milling machines etc.
We have a large painting area that has a large exhaust fan pulling air through a painting booth filter that is about 10'H x 25' Long.

I think you have it. There is another possibility but for the size shop you are it may not pay off.

I heard about a project with a large manufacturer that was able to negotiate lower KWH rate with the utility. Actually cut from 4 cents to 2 cents or less per KWH

This plant is huge and uses a tremendous amount of power.

They installed a generator that was capable of providing power to the entire facility, office and mfg space. The diesel engine was a refurbished Rail Road engine.

To get the lower rate they have to be able to get off the grid with only a 15 minutes notice.

It is all controlled by AB PLCs. The system cost them a million dollars. Because of the lower rate it paid for itself the first year and they were not ordered off the grid once.

If your boss is so concerned, You might try researching an option similar to this with your utility. Your small operation may not contribute enough savings to the utility to take advantage of this but it is worth looking into, Further, if you are in an industrial park, you may be able to team up with other shops nearby and put one or more generators to power all of the plants close by. You can look like a genius to your boss if you can pull that off. Get a power consultant to look at it for you.

Don't forget your plant / office lighting also- Mercury vapor sucks a lot of juice and is very inefficient. New LED fixtures throughout are expensive initially but they will pay for themselves by reducing your demand and your boss will see the savings every month.

I would like to suggest you call a consultant soon to help you with this issue of correcting your PF and controlling your peak demand. If you want to look into that, send me a Private Message and I will give you some names and phone numbers of people at Group Schneider - ( Formerly Square D ) that are experts in this area. You can at least find out what can be done. I have another contact that can provide you some help and he will provide you with some initial free consultation no obligation. He can probably give you some things to do that will start saving you money right away.

In the mean time, just see what equipment you can shut off before you start other things. You might be able to lower your bill a lot if you can control what equipment runs simultaneously. --

-- I don't believe in luck so.. May your endeavors succeed and prosper.

- Caspian
 
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You first need to know exactly what is your billing regulations because it is different from place to place and according to the power level you have.

Is there KW and KVA marked for the peak demand or just 1 number on your bill? How that number is read from your meter ?
Is it real KW or like i often seen: a calcul from KVA * 0.90 (For powerfactor) but still named ''kw'' on paper.
Don't assume they don't check PF because you see a kw number on the bill. Grid company should be concerned for PF as much as they could be of your peak demand...

Some place like in Qc, they read and show kw and KVA*0.9, They bill the highess of the 2 as your peak demand. So as long as you are above 90% you don't pay any extra but as soon as you fall below 90, the KVA calcul rise above the KW reading and you get extra charge for it...

PF = KW/KVA so you can play with the numbers and figure it out.

For rate there is many for the same grid company. You should check if you have the best one...(Like for your phone bill, they probably don't call you to change it for better one)
When i was working on power factor system we had customers with low level fare where a demand below 40kva wasn't bothered and got charged above this at 3-4$/kw. So this rate was good for 8hr/day, small installation with bad consuming habits. On these, saving on the peak demand take more time to payback....

The next rate was for a more regular consumption where the peak rate was 11-12$/kva but where the KW/h was a lot lower. The best for 24/7 company with a better control of the peak demand. This was my best customers because the payback on energy saving was 3x faster...
Then there was another rate for 5000+kva for very large use and i don't remember exact rate but peak demand was expensive and kw/h at the cheapest. PF was needed higher than 95% too...Some of them was called by the grid company to lower there electricity use during very cold weather with some special savings...
 

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