This is a fairly common question especially in a growing business. The need to add equipment to support growing demands is usually a welcomed problem. But, when it comes to electrical power capacity the decision to upgrade can be greatly confused by lots of opinions on how much is enough, how much you are using now and just how one goes about getting more power.
With all the opinions flying around, making an informed decision on which way to go can be virtually impossible. It’s like choosing between “what’s behind curtain #1, #2 or #3”. You might wind up choosing an option based on the presentation or the personality presenting it instead of the one that gives you the correct result.
There is really only one way to determine if you have enough power and how much more you need. It involves looking at the facility, measuring this and that and then doing the math. The calculations are not a mystery. In fact they are all covered clearly in the electrical code.
Without getting into all the technical aspects of performing a load calculation, there are basically two methods which give acceptable results. The first is performing a long-hand calculation by adding up all the loads and making standard adjustments for each type of load. The second is performing a demand-load-survey which involves connecting recording equipment to the electrical system for a period of thirty-days. The results are then evaluated and adjusted using code approved standards.
Long hand calculations will always come up with higher numbers than the actual or true loading on the system. This is because there is little, if any, consideration allowed for diversity of load (rarely, if ever, will all the equipment operate at full load at the same time). In the real world, it is not uncommon to have a new factory, calculated to require 1,125 amps, actually run at about 200 to 300 amps.
So, which method should you use?
Demand-load-surveys are the way to go when dealing with existing facilities that have been in operation for at least a year. As long as the operations have remained fairly consistent the results will be accurate. This method gives a good starting point when adding equipment. You can find out just how much power you are using now and know what you have left over.
Long-hand calculations are required when adding new loads. In the case of a new facility this is the only applicable option. Whether adding new machinery or relocating all of your machines to a new building, the long-hand calculation is the accepted method.
Southwest Industrial Electric