KVA to KW Calculation - help please

[wade88]

Morning fellas,

Been getting some rather high meter readings lately so trying to compile a machinery list so i have a good idea of what is consuming what and where, and how much our bills should really be looking like each month etc. Pretty standard maintenance stuff.

However im having trouble with the calculations converting KVA to KW as the asset list i am tabulating is all in Kw's, but some machines only state their KVA not KW rating.

I know that this KVA = KW/PF is the equation, but im having a hard time working out the power factor? Anyone out there a bit of a wizz with such things?

Cheers, Ben

 

[Knobhead]

To be honest you’re on a hiding to nothing with out a recording power meter. PF is rarely constant on a machine, as it’s load changes so does it’s current and PF. Lightly loaded the PF drops. Even with a recorder you’ll have a hell of a time transposing the data in to real time unless you can record all the machines at the same time. The only realistic way is to monitor your incoming supply. Are you wanting to add PF correction?

Have a look at http://www.allaboutcircuits.com/vol_2/chpt_11/3.html

 

[wade88]

No i realise this and figured it would have been an incredibly ambigous result anyway, but just wanted to give myself a ball park figure, all be it a very vague one. Its not actually that important and i think im going to abandon efforts anyway as i have arranged for a company to install individual circuit monitoring, that will give me a real time data stream to my PC of each circuits useage, that updates automatically every 10 seconds and records the hourly, daily, weekly, monthly, and annual figures.

 

[Knobhead]

Sounds an interesting project. Will you be doing anything about PF correction?

 

[wade88]

By adding capacitors and inductors etc? I dont know a great deal about such things Tony mate, so simple answer is probably no...im sure everything is sitting nicely around 0.9 anyway.....if all else fails im sure i could get my hands on an automatic power factor correction unit.


Yea im actually quite excited about this install, should be a great system and will really highlight where this company is taking a hit on energy wastage, allowing us to make an accurate cost of manufacture figure for many products. The system will monitor about 6-8 DB boards covering approx 80-90 circuits and costing circa £3600, which will pay itself off in no time once i have reduced our monthly energy bill from £3k alone

 

[Knobhead]

Hehe the old conundrum, getting management to spend money to save money. I used to despair at times. There are times when you’re like Don Quixote tilting at windmills.

I spent 3 years arguing to make a one off investment of £900 to save £7000 PA in maintenance consumables. OK I’d got a bee in my bonnet about it, it was a totally off the wall idea and I wanted to try it just to see if it worked. There was hell to play at board level when they found out how long I’d been banging on about it and nothing had been done. There was a strong smell of s**t in the local management offices, I smelt of roses. I was playing about with 1700V at 1250A and loving every minute of it. If it hadn’t worked there would have been a smell of singed Tony!
The next mad idea got instant funding!

 

[wade88]

Well fortunately, the brass here are quite open to any ideas that could save the company some cash, so i just took it upon myself to build a good case for this company and this monitoring system, jumbled around some estimated annual savings and a repayment time against money saved and money spent and got the green light in about 15 minutes. Just waiting on some of our newly built highly bespoke, machinery to arrive from china and then be fine tuned in sheffield before we get delivery, then i need to wire the buggers in and these guys will come and install their bits and hand me over the software keys and im cooking.

I have a pretty good deal here, if i need tools, they get bought, if i need new PPE it gets bought, if i need a PAT tester to test workshop tools and office bits, £1500 gets spent on a Seawood "look at me with my bells and shiny bits" tester, which im allowed to use outside of work. So i cant grumble too much with my management i have to say.

 

[Engineer54]

Exactly what machinery and bit's are you talking about here?? Perhaps a link to the system you have purchased on behalf of your company would be of interest to all....

How is this bit of kit going to reduce your energy bills, ....Is this some sort of optimum Voltage gizmo??

 

[wade88]

Well the new machinery we are having brought in is still being built and its quite a fluid project it changes weekly, so im afraid i cant endulge you in such information as i am also perpeutally somewhat in the dark with it myself.
But the company doing this energy monitoring system are called Utilitywise and they work along side a comapny who has developed the Edd:e system as its called.

edd:e - Login

This link takes you to the demo page where you can play around and get the general jist of whats what.

 

[Engineer54]

Can only see monitoring functions, nothing in the way of energy reduction!!

 

[netblindpaul]

Ahh but E54, remember if you can't measure it you can't manage it as my old boss used to drum into me!

 

[Engineer54]

Ahh but E54, remember if you can't measure it you can't manage it as my old boss used to drum into me!

For sure!! just that measuring it, doesn't in itself manage it!! I was getting the impression from Wade that this ''machinery'' somehow or other was going to reduce energy consumption. Now we both know, that is a lot easier said than done. Which is why i was asking if it was one of these ''Optimum Voltage'' gizmo's??? lol!!!

 

[wade88]

Well of course it manages it guys, buy seeing where the main consumers are, and where they are drawing power when not necessarily needing it, highlighting wastage etc. By picking up on energy consumption in places where it is not necessary will save money. I can get an accurate idea of how much energy all our lighting banks are using and then make an educated decision around whether or not to change to different bulbs, same applies to office lighting, i can also grasp an idea of how much it costs in energy to manufacture certain products which can then be factored into their costing and a new more applicable price can be applied to the product based around accurate knowledge of their total manufacturing costs.

The idea of this equipment isnt a self supportive, singing and dancing do it all energy reducing system , its just a highlighter to consumption. Its effectively just a mini clamp meter on every circuit on a permenent basis sending me real time info. If i can see where the energy is being used and wasted, i can therefore effectively manage it. The energy reduction aspect therefore comes in based on my own initiative.

 

[geofff]

Back to the original question, converting KVA to KW, I knocked this up for you.

 

[wade88]

Geofff, is it really that straight forward using that equation?! If so, top stuff mate much appreciated. I am expecting a barrage of comments coming our way however.....