Epic Engineering designs a PLC to automatically shut down parts of a customers process when power usage goes above a certain threshold.
A local brick and block manufacturer uses a lot of electric energy to produce bricks and concrete blocks. The manufacturer used to be on a A19 plan with PG&E where the demand was calculated by Kilowatts used and penalties for going into peak usage. They found that they rarely went over 500KW throughout the day. It was determined that if the process could be kept below the 500kw demand throughout the day, they would be able to move to a less expensive rate plan, A6.
Epic used a PLC connected to the P,G,&E power meter to accumulate kilowatt hours used. P,G,&E uses a 15 minute average to calculate real time demand so we replicated that average in the PLC. A warning and fault threshold are operator adjustable on one of the HMI touchscreen screens. A yellow light will flash when the 15 minute KWH exceeds the warning threshold. If the 15 minute average exceeds the fault threshold, a relay will open and stop a predetermined process line. This will reduce the KWH load to get the 15 minute average down below the fault threshold.
It is estimated that the manufacturer is saving about $70,000 per year. The project paid for itself in less then one year.