This is a very difficult question to answer because obviously electric rates are different throughout the country, but also, the horse powers are different and the startup power required to get a grinder going varies greatly.
Just like at your home, you are charged at the peak usage that you incur per month. So, for example at your home, if both your air conditioner units and your clothes dryer and swimming pool pump, happen to be running at the same time, you are charged by your electric supplier as if those items were running 24/7 for the entire month. You know they are not, but you needed that much power at one time so you are charged accordingly. This example is known very well to me!
Although I cannot really answer this question, I can give you a few ideas, additional items to consider and places to go to collect the information you are looking for:
· The best idea is to get references from a potential grinder company and ask them for as much information as they can supply. Then actually call those references to confirm the numbers you were given by your potential vendor.
· Searching Google for “Electrical Calculators” will give you websites that have calculators that you can plug in your information from your potential system. You will need to figure out how many electric motors you will be using, and how many hp each of them uses. This includes all the conveyors, screens, hydraulic units, as well as the grinder.
· In almost all cases, you will need to install a transformer to supply your power. DO NOT undersize this, in fact, oversize the transformer by about 500kva. The startup power and potential unexpected heavy loads, equipment stalls, may send you back to the electric company purchasing a new transformer
· Variable-Frequency Drives (VFD) can be used to limit startup loads, but are very expensive for the large horsepowers. This can also be done by using the controller display at a much cheaper cost. Ask your vendor about this.
· The most important thing to do is contact your electric company and sound as if you are considering, potentially, may, thinking about, purchasing an electric grinder instead of a diesel model. If you call and say, bring me out a 2500kva transformer and install it, then the price is the price. If you call and say, I'm thinking about doing this, but I think it's too expensive? What is it going to take to do this? What would my rate be? Would you run power into my site and put in a transformer? You will have a lot more negotiating power. They want your business, especially with that much power being consumed, so play the game and see what you can get. Don't tell them your diesel fuel cost per year, but if you do, divide by two! Make sure you have your potential usage numbers from your grinder supplier, so they will know quickly about how much power you are talking about using.
· One question to ask the grinder company is if they use one motor or two to drive the hammer ill or rotor. Typically for smaller hp only one is used, but when you get into the 800-1000 range, two are used. This is a benefit because the electric motors can be setup with one working all the time, and the second just riding along. Then at certain amperage on the first motor, the second motor starts working, this can save on electric usage considerably. Also, one thing to consider, use standard size motors as much as possible. It's easier to get a 500hp motor off the shelf, then to find a 750hp motor just sitting somewhere.
· Keep this power separate from office, warehouse or other.
· Leave room for expansion. Have room to possibly increase horsepower in the future. Most likely you will need to get a different hammermill if you need more horsepower, but build your platform where it is possible to add on to it and be able to use 2 motors for example. Stability in the motor bases is essential.
Hope this helps. Good Luck.
Questions? Dave Whitelaw Grinderguy@askthegrinderguy.com