Storage heaters are primarily wired to utilize two distinct electrical circuits from your home's main consumer unit: one dedicated to drawing cheaper, off-peak electricity for charging, and another for on-peak electricity, often powering auxiliary functions like internal fans, controls, or boost elements. This dual-circuit setup is fundamental to their operation, enabling them to store heat during periods of lower electricity cost and distribute it throughout the day.
This intelligent wiring allows your electricity meter to accurately record how much electricity is consumed during different times of the day, ensuring you are billed correctly for both your discounted off-peak usage and standard rate on-peak usage. This distinction is crucial for maximizing energy savings with a time-of-use electricity tariff.
The Dual Circuit System Explained
The efficiency and cost-effectiveness of storage heaters hinge on their ability to differentiate between electricity tariffs. This is achieved through their unique wiring configuration:
-
Off-Peak Charging Circuit:
- This is the primary circuit that powers the heater's main heating elements.
- It's connected directly to the mains via the consumer unit but is controlled by a time switch or a signal from your electricity supplier.
- Electricity flows through this circuit only during pre-defined off-peak hours (typically overnight or during specific daytime periods, depending on your tariff).
- During these hours, the heating elements absorb and store thermal energy within high-density ceramic bricks inside the heater.
-
On-Peak Auxiliary Circuit:
- This is a separate circuit that provides continuous power to components that need to operate outside of the off-peak charging window.
- It ensures that essential functions are available whenever required without drawing power through the off-peak meter.
- Components typically powered by this circuit include:
- Thermostatic controls (both for charge input and heat output).
- Output fans in fan-assisted models, which help distribute stored heat more effectively.
- Any boost heating elements that can provide instant heat during on-peak hours (though using these can be more expensive).
Key Components and Their Connection
Understanding the individual components and how they connect provides a clearer picture of the wiring process:
- Consumer Unit (Fuse Box): This is the central hub where the main electricity supply enters your property. Both the off-peak and on-peak circuits for your storage heaters originate here, each protected by its own circuit breaker or fuse.
- Dedicated Circuits: Each storage heater circuit (off-peak and on-peak) will have its own individual Miniature Circuit Breaker (MCB) or Residual Current Breaker with Overcurrent protection (RCBO) within the consumer unit, rated appropriately for the heater's power consumption (e.g., 20A, 30A).
- Time Switch / Controller: Essential for the off-peak circuit, this device (often integrated into the electricity meter or a separate unit) dictates when the storage heater can draw power for charging.
- Fusing / Isolation: Every storage heater unit should have a dedicated fused spur or an isolator switch mounted on the wall near the appliance. This allows for safe and complete electrical disconnection of the heater for maintenance or emergencies.
- Thermostats:
- Charge Thermostat: An internal thermostat that monitors the core temperature of the storage bricks, preventing overcharging and regulating the amount of heat stored.
- Output Thermostat: Controls the release of stored heat into the room, either by opening a damper or activating a fan.
- Wiring Cables: Appropriately sized electrical cables (e.g., 2.5mm² or 4mm² twin and earth, depending on current draw) connect the consumer unit to the isolator switch, and from there to the heater's internal terminal block.
- Earthing: A robust earthing connection is vital for safety, protecting against electrical faults.
Wiring Schematic Overview (Conceptual)
While specific wiring diagrams vary by manufacturer and model, the general flow is as follows:
- Main incoming electricity supply routes to the consumer unit.
- A dedicated off-peak circuit (e.g., 30A MCB) runs from the consumer unit, through a time switch or external controller, and then to the storage heater's main heating elements via an isolator switch.
- A separate dedicated on-peak circuit (e.g., 6A or 10A MCB for controls) runs from the consumer unit directly to the heater's control circuitry, fan, or boost elements via a separate isolator switch.
- All circuits include robust earthing connections for safety, terminating at the heater's designated earth point.
Why Professional Installation is Crucial
Given the complexity of the dual-circuit system and the high power demands of storage heaters, professional installation by a qualified electrician is paramount. This ensures:
- Safety: Correct wiring prevents electrical hazards such as short circuits, overloading, and electrical fires.
- Compliance: Installation adheres to local electrical wiring regulations, such as BS 7671 (IET Wiring Regulations), ensuring the system is safe and legal.
- Efficiency: Proper wiring guarantees that the heater operates optimally, maximizing the benefits of off-peak tariffs and reducing running costs.
- Reliability: Professional installation minimizes the risk of system failures and extends the lifespan of the appliance.
- Warranty: Most manufacturers require professional installation to validate product warranties.
Circuit Functions at a Glance
This table summarizes the primary roles of each electrical circuit in a typical storage heater setup:
| Circuit Type | Purpose | Power Source Timing | Typical Components Powered |
|---|---|---|---|
| Off-Peak Charging | Powers the main heating elements to store thermal energy | Pre-set off-peak hours (e.g., overnight) | Main heating elements, internal charge thermostat |
| On-Peak Auxiliary | Supplies continuous power for controls and heat release | Available 24/7 | Output fan, boost elements, external controls |
Practical Tips for Storage Heater Management
To get the most out of your wired storage heaters:
- Understand Your Tariff: Familiarize yourself with your specific off-peak electricity times to ensure your heater is set to charge during the cheapest periods.
- Check Time Settings: Periodically verify that your heater's time switch or controller settings align with your energy provider's off-peak schedule, especially after power outages or clock changes.
- Maintain Clear Vents: For fan-assisted models, ensure the air inlets and outlets are clear of obstructions to allow efficient heat distribution.
- Consider Smart Controls: Upgrading to smart controls or a modern energy management system can offer greater flexibility in scheduling and optimizing your charging cycles, further enhancing energy savings.
