Metering question

[elecsup1]

We are thinking of installing occupancy sensors in an area of our shop which is vacant a good part of the week. This area has 35 flourescent fixtures controlled by relay operated by a single switch (and no, just flipping the switch is not an option). My boss has asked me to calculate the savings and figure the payback for this project.
So I have:
35 ballasts x 120 vac supply x .8 amp (from the ballast) x 32 hrs/wk = 107.5 kwh/wk
Now our shop is fed and metered thru a 230V 3 phase entrance. According to the electric bill we currently pay $.005515 / kwh.
My question - is it accurate to just multiply the 107.5 kwh x $.005515? Or do I have to make some sort of correction because of the 120V single phase load and the 230V 3 phase metering?
Thanks for the help, sometimes my mind is a little scrambled after my 85 mph motorcycle crash last August.

 

[rattus]

You sure?

You sure?

We are thinking of installing occupancy sensors in an area of our shop which is vacant a good part of the week. This area has 35 flourescent fixtures controlled by relay operated by a single switch (and no, just flipping the switch is not an option). My boss has asked me to calculate the savings and figure the payback for this project.
So I have:
35 ballasts x 120 vac supply x .8 amp (from the ballast) x 32 hrs/wk = 107.5 kwh/wk
Now our shop is fed and metered thru a 230V 3 phase entrance. According to the electric bill we currently pay $.005515 / kwh.
My question - is it accurate to just multiply the 107.5 kwh x $.005515? Or do I have to make some sort of correction because of the 120V single phase load and the 230V 3 phase metering?
Thanks for the help, sometimes my mind is a little scrambled after my 85 mph motorcycle crash last August.

First off, your cost per KWH is only a half cent. Maybe the decimal point is in the wrong place? Even if it is a nickel per, that is only about $5.00/week! Plus there is a PF to consider. Doesn't sound like a good idea to me.

 

[LarryFine]

My question - is it accurate to just multiply the 107.5 kwh x $.005515? Or do I have to make some sort of correction because of the 120V single phase load and the 230V 3 phase metering?

Watts is watts. No correction needed.


Welcome to the zoo, and glad you're okay.

 

[bhsrnd]

Just doing rough math based on what you provided and making very conservative guesstimates of equipment, etc., for the sensor install, it could realistically take up to two years or more to see an ROI. Again, that's not knowing anything about your situation and just making things up on my end . I assume the ROI is what Rattus meant by "bad idea", in regards to significant cost savings.

 

[gar]

090203-2213 EST

elecsup1:

Since the lights are relay controlled you should be able to use an inexpensive one or more sensors to control your relay.

It appears you may have plant electricians under you that could do the work. If so, then they almost certainly have free time to do the work. Thus, no real cost other than the sensor(s).

You will reduce electrical costs about $250/year. But you may even save more on lamp costs.

.

 

[wireguru]

take the dollar amount on the bill and divide by kwh used to get your 'real' cost per kwh. The price per kwh listed on the bill doesnt include all the taxes, surcharges, fuel cost recovery fees, etc which sometimes can exceed the cost per kwh.

 

[notobnoxious]

Power Savers

Power Savers

I have read with interest thye many comments ref Powersave etc gadgets.
What is the opinion of members to a bank of capoacitors which are smart switched in or out as power drawn increases or decreases, to increase power factor?

 

[elecsup1]

Thanks

Thanks

Thanks for the input, you guys are great.
Rattus, the decimal point is correct but after taking wireguru's advice and dividing the total bill by the kwh's used it is more like $.15/kwh. It looks to me like a savings of $16/wk or $800/yr.
I have the job pegged at $250 in mat'l (of which we have almost $200 on hand and uncommitted) and 10 man hours. Roughly $600 total. Gar you are correct, I have a couple of union electricians I need to keep busy. We're going to pay them one way or the other.
Anyway, I see a complete ROI in less than a year. I say it's a go but I have to run it by the Plant Manager.
LarryFine, thank you also for your input and the positive words. I feel like I'm the luckiest man still walking this earth.
Paul

 

[benaround]

I have read with interest thye many comments ref Powersave etc gadgets.
What is the opinion of members to a bank of capoacitors which are smart switched in or out as power drawn increases or decreases, to increase power factor?

IT'S A SCAM, what does power factor have to do with kwh used ? WATTS ARE WATTS.

 

[broadgage]

I have read with interest thye many comments ref Powersave etc gadgets.
What is the opinion of members to a bank of capoacitors which are smart switched in or out as power drawn increases or decreases, to increase power factor?

When applied to homes and most small busineses such devices are a scam, as posted above by others.
Watts are watts, and the bill is on the number of KWH consumed, adding capacitors wont decrease the watts used, indeed the very small losses in the capacitors will minutly increase the bill.

However the metering of larger services to large commerical premises generaly also measures the power factor, and imposes a financial penalty for poor power factor.
In such cases improving the power factor can be worthwhile, this may be done by connecting capacitors across loads with poor power factor.
Alternativly automatic power factor correction may be installed in a switchroom etc. Such equipment should be obtained from an established reputable supplier, and not from firms making improbable claims via direct mail etc.

 

[htroberts]

What does power factor have to do with kwh used ? WATTS ARE WATTS.

Watts are watts, and VAR are VAR. The power company has to provide both, and if you need too many VAR, they'll charge you for both. If they do, then you may be better off paying for power factor correction and getting rid of some of those VAR.

Only really worthwhile in commercial and industrial settings, though, and if you need PF correction, the power company will tell you so.