Demand control
Maximum Demand controller: hold the peak, and see which panel built it.
A Maximum Demand controller watches the running interval and holds back chosen loads before the peak crosses your limit. KONDUKTOR® EMS does that through Modbus I/O cards, and also shows which panel built the peak. Here is how automatic load control works and how to set it up without hurting production.
What a Maximum Demand controller does
Your DISCOM bills demand on the highest average of any 15- or 30-minute interval in the month. One bad interval can set the whole month’s demand charge, and crossing Contract Demand can add a penalty on top. See MD penalty.
A Maximum Demand controller, also called an MD controller or demand controller, acts inside the interval, while there is still time to change where it ends.
How automatic load control works
- Read. It reads demand at the incomer through the interval, in step with your billing interval.
- Project. It works out where the interval will end if the load stays as it is.
- Hold back. If that crosses your limit, Modbus I/O cards switch off or delay chosen loads, lowest priority first.
- Restore. When demand falls, or the new interval starts, loads come back one at a time, so the restart does not build a fresh peak.
- Record. Every action is logged with its time and load, so you can see what it cost and whether it was needed.
A worked example
Take a plant with a Contract Demand of 500 kVA, a 30-minute interval and a control limit of 490 kVA. These figures are illustrative.
| Point in the interval | Figure |
|---|---|
| Average for the first 18 minutes | 510 kVA |
| Load right now | 530 kVA |
| Interval ends at, if nothing changes | 518 kVA |
| Load needed for the last 12 minutes to end at 490 kVA | 460 kVA |
| Load to hold back for those 12 minutes | 70 kVA |
Acting early means holding back less, for less time. Wait until minute 25 and the same interval needs far more load off at once. See what one spike costs in the MD penalty calculator.
Which loads can wait
| Load | Why it can wait | Keep in mind |
|---|---|---|
| Chillers and air conditioning | The building or product holds its temperature for a while | Respect compressor restart delays |
| Water and transfer pumps | Tanks hold a buffer | Keep a low-level limit |
| Air compressors with a receiver | The receiver carries the plant for a short time | Set a minimum pressure |
| Heaters and furnaces with thermal mass | Temperature falls slowly | Set a process temperature limit |
| Batch mixers and grinders between batches | The next batch can start a few minutes later | Never stop one mid-batch if the product suffers |
Fire pumps, lifts, safety systems and any load that would damage product stay off the list. Your team decides the list, the order and how long each load may stay off.
See which panel built the peak
A controller on the incomer sees one number. KONDUKTOR® EMS reads every metered panel, so you see demand panel by panel at the peak interval. You choose loads from what really builds the peak, and you can often fix the cause, such as two big machines starting together, so control has less to do. See seven ways to reduce Maximum Demand.
Setting the limit
- Leave a margin. Set the control limit a little below Contract Demand, so a late surge in the interval does not cross it.
- Match your billing interval. A 15-minute and a 30-minute tariff need different settings. Check your tariff order.
- Plan for restarts. After a power cut everything tends to load together, so loads return in steps.
- Review the trips. If loads are held back often, the real fix may be the load schedule or your Contract Demand.
Built to fail safe
Control sits above your electrical protection, never in place of it. Each project is engineered so that a lost connection leaves the loads in the state agreed with your team, operators keep a manual override, and only authorised users can change limits. Protection relays and process interlocks stay as they are.
The same cards do more than demand
| Control | What it does |
|---|---|
| TOD load shifting | Moves chosen loads out of peak-rate hours. See TOD tariff |
| Solar export limit | Throttles inverter kW to hold export at your limit, down to zero export, where the inverter allows it. See zero export controller |
| DG limits | Holds solar back so a running DG keeps its minimum load and sees no reverse power. See PV-DG synchronization |
| Idle switch-off | Switches off idle machines outside shift hours. See machine monitoring |
| Schedules | Runs chosen loads to shift and holiday timings |
Power factor correction stays with your APFC panel. Improve power factor explains what to check.
If you already have an MD controller
Keep it working and add monitoring beside it. You will see how often it acts, what that costs in production, and whether Contract Demand needs revising. The full comparison is in MD controller vs energy monitoring.
Questions to ask before you buy
- Does it show which panel built the peak, or only the incomer figure?
- Does it follow our DISCOM’s billing interval?
- How are loads restored after they are held back?
- What happens to the loads if the controller loses connection?
- Is every action logged, and can we export the log?
- Can it also track power factor, TOD and the bill?
How KONDUKTOR® EMS handles demand
- The running Maximum Demand interval on every meter, live, against Contract Demand, with alerts as it nears the limit.
- Monthly Maximum Demand history with the date and time of each month’s peak.
- Demand per panel, so you see which load built the peak.
- Automatic load control through Modbus I/O cards, engineered for your plant as part of your project, with the loads, priorities and limits agreed with your team.
- History, dashboard and control all on site, with no cloud server, and no Internet needed to run.
Common questions
What is a Maximum Demand controller?+
A system on the incoming supply that projects where the running 15- or 30-minute interval will end, and switches chosen loads off or delays them when that crosses a set limit. It releases them once demand falls.
How does automatic load control work?+
As the interval runs, the system projects its final average. If that crosses your limit, Modbus I/O cards hold back chosen loads in priority order, and bring them back one at a time.
Will it stop production?+
Not if the load list is right. Only loads your team agrees can wait are included, each with its own limit on time off. If loads are held back often, the load schedule or Contract Demand needs a look.
Do we need a separate MD controller with KONDUKTOR® EMS?+
No. The same system that reads your meters holds back chosen loads through Modbus I/O cards, engineered for your plant as part of your project.
Does it work with our existing meters?+
Yes, if the incomer and panel meters have an RS-485 Modbus port, as most panel multifunction meters do. The DISCOM meter stays as it is.
What does a Maximum Demand controller cost?+
We quote per plant, based on your panels and the loads to control. Book a demo or send your bill for a free check, and we will tell you where the demand charge can come down.
Hold the peak, and see what built it.
Book a live demo and see the running Maximum Demand, panel by panel, against Contract Demand on meters like yours.