Electric utility monthly demand charges are determined by the highest (peak) average kW demand over a 15 to 30 minute period, typically during a calendar month, as recorded on the utility’s demand meter. The theory behind both Rayteq’s new IDMS™ and the more conventional DMS is that unsynchronized electrical equipment, including electric melting furnaces, will randomly but inevitably draw maximum power simultaneously a number of times during the utility’s month-long demand metering cycle. Just one such incident will drive the utility demand charge up to the maximum possible cost for that month. Because most metalcasters do not operate their equipment including furnaces at maximum red-line output there will always be room to reduce the total fleet kW demand. Demand management systems work to reduce utility demand charges through synchronized restriction of the total kW demand of an electric equipment group, and the manner in which they accomplish this has a major impact on (a) demand reduction effectiveness and (b) production output and quality control.

Rayteq’s Fleet Commander™ IDMS™ custom programmed software is loaded into an industrial-grade computer that communicates with a fleet of electric resistance furnaces equipped with Rayteq’s Furnace Director™ PLCs via standard Ethernet cables or industrial-grade wi-fi radio bridges. A furnace participant may be a Rayteq designed and built furnace or it can be a compatible conventional furnace such as a Dynarad* or StrikoDynarad* electric melter equipped with the Rayteq IDMS™ retrofit control panel which contains the required Furnace Director™ PLC.

Regardless of fleet makeup, the IDMS™ mission is interactive kW demand management—to minimize the total kW electrical demand of the entire furnace fleet supplied from a single metered electrical service without compromising the user’s production and quality control requirements.

In operation, the Rayteq IDMS™ software gathers all relevant information about the fleet and periodically provides each Furnace Director™ PLC with recommended actions which may include kW reductions in the form of heating element “brownouts” for each furnace. Each Furnace Director™ PLC considers the impact of these recommendations on the user’s preset production and quality control requirements before deciding to what extent it will implement them. In addition, the Furnace Director™ PLC can elect to shed a previously accepted “brownout” recommendation that is still in effect should it later become incompatible with the user’s production requirements. Giving each Furnace Director™ PLC local decision-making authority ensures that the user’s production and quality control needs for each furnace are always properly maintained.

Fleet Commander™ continuously tracks kW demand of all electric furnaces in its fleet, making it an effective sub-metering system. It is also a comprehensive data logger, storing nearly all of the information it gathers for later examination. Should “strange things happen in the night,” they can be tracked down and examined at a later time, making Fleet Commander™ valuable as an analytical tool.

Fleet Commander‘s highly effective control method spreads a large demand reduction across the entire furnace fleet in an orderly and efficient manner instead of applying harsh rolling 100% blackouts to one or more furnaces, whether they are meeting production needs or not, as do conventional first-generation on/off, non-interactive demand management systems (DMS). Because these early systems have no awareness of the state of each furnace, they attempt to hold total plant demand to supervisor adjusted, arbitrary set-point limits with no special attention given to any individual furnaces which may be falling short of the user’s required melting rates. In many cases this set-point limit is set unnecessarily high due to the supervisor’s hesitancy, possibly because of previous bad experience with production disruptions, and setting a higher than needed maximum power limit results in lower cost savings. By contrast, Rayteq’s interactive approach considers the conditions in each furnace before taking action, thus maximizing overall demand reduction while maintaining quality control and full production without interruption.

Every night after the last production shift the Fleet Commander™ IDMS™ automatically begins recalculating the furnace fleet’s daily kW demand requirements based on adjustments to production rates as well as changes in furnace status (on-line, off-line, etc.) without requiring a supervisor to input any demand set-points or continually “tweak” the furnace fleet kW demand target. As a result, Rayteq’s IDMS™ continuously adapts and squeezes every last drop of demand out of its furnace fleet without any human interaction or guesswork. The results are impressive—net IDMS™ kW demand savings can exceed conventional demand management systems by 100% to 500%!

The above image shows an actual graphic, real-time daily readout of a four-furnace IDMS™ network when all four furnaces were in full production melting operation. The yellow line on the top graph represents the maximum possible rolling average demand of 414 kW which is the combined kW ratings of all four furnaces in the fleet. The green trace shows what the total kW rolling average demand would have been without IDMS™ control (it would have reached maximum peak demand of 414 kW just after 6 AM and again at 2 PM), while the blue trace shows that the IDMS™ actually held the peak rolling average demand to 194 kW, a significant demand reduction of 53%. The red line shows the actual peak rolling average demand of 194 kW for the day, and the difference between the red and yellow lines is the IDMS™ controlled demand reduction of 220 kW for the day. Real-time graphs like this one as well as historical demand control statistics can be viewed at any time on any computer on the office network using any standard web browser.

How much of a reduction can be anticipated with IDMS™? While we’ve seen reductions between one-third to more than one-half of the total connected kW, the answer in any given case will depend on how many production cells are idle due to die or pattern changes, how many energy intense production jobs might be running simultaneously, etc. In a job shop where short and medium run jobs quickly move in and out of production, the results will be hard to predict. However, it is important to note that even in such circumstances, Rayteq’s IDMS™ will restrict kW demand to just what is needed to meet actual production melting requirements. With Rayteq Fleet Commander™ IDMS™ now available, it should no longer be acceptable to allow uncontrolled, random kW demand peaks determine the metalcaster’s monthly demand charge when IDMS™ is fully capable of reducing it.

Fleet Commander™ IDMS™ includes the ability to sense multiple types of events at each furnace such as:

• Furnace temperature deviation outside a specified range
• Tripped ground fault interrupter alarm
• Heating element over-temperature alarm
• Emergency Stop pushbutton engaged alarm
• Network trouble

These events can also be logged with timestamps in a password-protected Twitter account that can be reviewed at any time from any computer or smart phone. In addition, email alerts can also be delivered automatically to the appropriate personnel allowing for immediate corrective action.

The introduction of Rayteq’s Fleet Commander™ interactive demand management systems (IDMS™) for electric resistance melting furnaces has created a unique opportunity for metalcasters everywhere to reduce their aggregate kW demand, and hence the total electric utility expense, of electric resistance furnace fleets without impairing production rates or quality control, making them highly competitive with fuel fired melting. This means that even in states like California and the eastern seaboard where electricity is expensive, they can once again enjoy all the positive benefits of electric melting while substantially reducing their electric utility costs, truly giving them the best of both worlds.