At 07:45, a production line starts, ovens recover from standby and several heating zones call for full power at once. That short interval can set the site’s maximum import charge for the entire billing period. Manufacturers can reduce peak demand from electric heating without accepting slower warm-up, poor temperature stability or compromised product quality. The answer is to control when, how and where electrical power reaches each heater.
For process plants, peak demand is not simply an energy management issue. It can trigger breaker trips, overload transformers, constrain a planned line expansion and leave operations paying for capacity they only need for a few minutes. Effective power control turns a coincident electrical load into a managed production asset.
Peak demand is the highest level of electrical power imported during a defined measurement window, often 15 or 30 minutes. Electricity costs therefore depend on more than total kilowatt hours consumed. A plant may use a sensible amount of energy overall, yet still incur high charges when multiple electric heaters energise together.
Resistance heaters are a common cause because they can draw their full rated load immediately. Similarly, cold heater elements may have a lower resistance than at operating temperature, increasing the initial current demand. Infrared systems, cartridge heaters, ceramic elements and electric furnaces can all create substantial coincident loads.
Conventional on-off control makes the issue worse. When several temperature controllers see a process temperature below setpoint, each output may close simultaneously. Consequently, the panel experiences a large step change in current, even if each heating zone operates correctly in isolation.
The commercial effect extends beyond the utility bill. High peaks can require a larger incoming supply, switchgear rating and transformer capacity. Moreover, repeated current surges add thermal stress to contactors, fuses, cables and distribution equipment. Production continuity becomes vulnerable when electrical infrastructure is operating too close to its limit.
Reducing demand begins with measured evidence, not a generic controller setting. Record the site import profile alongside the status, current and temperature demand of major heating zones. A power network meter at the main incomer, supported by sub-metering at heating panels, will show whether the peak comes from start-up, batch changeover, temperature recovery or normal cycling.
First, establish the real load of every heater bank. Nameplate ratings are useful, but measured phase current, duty cycle and firing behaviour reveal the operational demand. In three phase systems, phase imbalance must also be checked because one overloaded phase can limit capacity before the total connected load does.
Next, identify coincident events. For example, an extrusion line may start barrel heaters, die heaters and hopper drying at the same time. Meanwhile, a ceramics kiln may recover several zones together after a door opening. Those events are the practical opportunities for intervention.
A useful review should include four figures: connected heating load in kW, maximum simultaneous heating load, site maximum import and the available electrical headroom. However, the target is not always the lowest possible peak. Plants need enough controlled capacity to meet heat-up times, process recovery requirements and production schedules.
A 500kW installed heating system does not necessarily need 500kW at any one moment. Conversely, a 250kW heater bank can create a disproportionate site peak if it switches on during an existing high load period. Distinguishing those two conditions prevents expensive, unnecessary supply upgrades.
Power data should also be assessed against the tariff measurement interval. A brief one minute surge may be less significant than a sustained 15 minute plateau. Therefore, control strategies must be designed around the demand calculation used by the electricity supplier, not merely around instantaneous current.
The fastest improvement is often to stop every heating zone starting together. Sequenced start-up applies power in defined groups, with a delay or available capacity check between each group. As a result, total load rises in controlled steps rather than one sharp inrush.
Priority should reflect the process, not convenience. Critical zones that determine safe operation, material flow or line readiness should heat first. Secondary zones can follow once the priority load has reduced or the site demand remains below its agreed limit.
For batch equipment, a start schedule can be matched to shift patterns and upstream preparation. For continuous processes, the schedule may need to account for realistic thermal lag, so that delayed zones still reach setpoint before production material arrives. This is why a simple timer is not always enough.
Load shedding provides a further layer of protection. When measured import approaches a defined threshold, the system temporarily reduces power to non critical zones or pauses discretionary loads. Once headroom returns, it restores those loads in a controlled order.
That approach requires sensible limits. Aggressive shedding can produce temperature drift, longer recovery and wasted material, particularly in tightly controlled chemical, pharmaceutical or food processes. Instead, use temperature deviation, process state and zone criticality to decide which load can safely be curtailed.
SCR or thyristor power controllers provide far more control than mechanical contactors for electric heating. They regulate power repeatedly without contact wear, supporting accurate temperature control and frequent switching. Crucially, the firing mode can influence both the electrical behaviour and the useful process response.
Time proportioned on/off (burst firing) is often well suited to resistance loads. The controller switches complete AC cycles on and off, allowing proportional power delivery with low switching stress. In addition, burst firing can be coordinated across zones so that their demand is distributed rather than concentrated.
Phase angle firing gives finer power control and can be appropriate for particular load types or fast thermal processes. Nevertheless, it may introduce harmonics and requires careful attention to EMC, supply impedance and power quality. The right choice depends on the heater characteristics, process sensitivity and network conditions.
Soft start functions can reduce the impact of energising cold elements and high-inrush loads. Current limiting may also protect the heater circuit and prevent a single zone from consuming disproportionate capacity during start up. Neither function should be applied blindly, because an overly restrictive limit can extend heat-up beyond the available production window.
Independent temperature loops can unintentionally compete for the same electrical capacity. A central demand limit signal, shared enable sequence or communications-based control scheme allows each controller to contribute to a site wide limit. Accordingly, the plant maintains thermal control while respecting an agreed maximum import level.
In practical terms, this can mean a controller receives a reduced power ceiling during a peak period, rather than being switched fully off. That distinction matters. Proportional limitation usually produces a smoother process response and avoids the repeated full-power recovery cycles associated with crude load shedding.
Demand reduction is only credible when the panel has been engineered as a system. Controller current rating, fuse coordination, cable sizing, thermal management and phase arrangement all affect whether the designed strategy will work reliably. Poor panel ventilation, for instance, can reduce semiconductor life even when the demand control logic is correct.
EMI power line filters and suitable installation practices are particularly relevant where phase angle control or sensitive instrumentation is present. Equally, harmonic assessment may be necessary on large installations or weaker supplies. Electrical compliance and production reliability should be considered together.
Maintenance teams also need clear visibility. Panel meters, alarm thresholds and recorded demand data make it easier to distinguish a planned power limitation from a heater fault or failing thermocouple. Consequently, operators can respond with confidence rather than bypassing controls during a busy shift.
Before commissioning, prove the strategy against realistic operating scenarios. Test cold start-up, full batch loading, door open recovery, loss of a heating zone and simultaneous starts after a power interruption. A demand limit that works only in steady state conditions will not protect the plant when it matters most.
The strongest results come when electrical demand is considered alongside the production plan. If a high temperature furnace, drying tunnel and extrusion line all need maximum power at 08:00, even the best controller has limited room to act. By contrast, moving one non critical warm up period by 20 minutes may remove a costly overlap with no effect on output.
CD Automation offers multiloop power control solutions for applications where several heating zones must share limited electrical capacity. Rather than allowing independent zones to switch at the same time, these systems synchronise power delivery and distribute the available load more evenly. The result is a steadier demand profile, fewer uncontrolled peaks and better use of the site’s existing electrical capacity, without simply switching critical heating zones off.
For compact systems, the REVO PB power optimisation controller combines three independent single phase channels in one unit and uses synchronised firing to manage demand across the connected zones. Where the application involves transformers, infrared lamps or variable resistance elements, REVO TH provides three independent channels with firing options including phase angle, soft start and current limiting.
For larger multizone installations, REVO PC works with REVO S power units to manage and synchronise up to 24 channels. A total power limit can be applied across the system while the controller distributes the available power between active zones. Per zone current, voltage, power and alarm information can also be made available to the PLC or plant network, helping engineering teams monitor demand, identify heater failures and refine the control strategy over time.
The right arrangement depends on the number of zones, heater type, phase configuration, current rating, production priorities and available site capacity. Contact CD Automation UK for help reviewing your load profile and specifying a practical multiloop solution. If possible, provide the supply voltage, current or kW of each zone, heater element type, phase configuration and any available demand data. Call 01323 811100 or email sales@cdautomation.co.uk to discuss your application.
Treat the maximum demand figure as an operational design constraint, not an unavoidable charge. With measured load data, prioritised heating zones and coordinated thyristor control, a manufacturing site can protect electrical capacity while keeping its process ready to produce.
