# Dump load controller

Canonical URL: https://eloragrid.ai/symbols/dump-load-controller
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: DLC
Drawing use: SLD, Schematic
Reference families: IEC, IEEE / ANSI

A controller that diverts surplus generation into a resistive dump load to hold frequency or voltage in a small isolated system.

## In plain English

### What does Dump load controller mean?

A dump load controller keeps a small isolated system in balance by diverting surplus power into a resistive load, usually water or air heaters. In micro hydro systems it holds frequency constant by keeping total generator load fixed, and in small wind or battery systems it protects the battery from overcharge by dumping excess energy.

### A simple example

Drawings show a controller block, often with a thyristor or transistor switch symbol, connected between the bus and a resistor bank labelled dump or ballast load. A frequency or voltage sensing connection to the bus is included.

### What the drawings help you do

The dump load must be rated to absorb the full generator output if all consumer loads disconnect. The symbol does not show that rating or the heat rejection arrangement, both important for safety.

### This particular reference

A controller that diverts surplus generation into a resistive dump load to hold frequency or voltage in a small isolated system. A dump load controller diverts surplus energy continuously; a load bank is a test load used temporarily.

### Terms

- Terminal: An identified point where a conductor connects.
- Signal: Electrical information passed between devices, rather than necessarily the main power supply.
- Rating: A value stating the conditions for which equipment is specified.

Concept diagram: Identify the device and form → Read the connections and state → Check the equipment reference
A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram.

- [Resistors and heater-element symbols](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-1D071951-D38E-4B15-8B9E-C30ECBD55C19.htm)
- [AutoCAD Electrical: Semiconductor components](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-AC954072-7314-4682-88AF-38160D61E9A2.htm)


## What it represents

A dump load controller keeps a small isolated system in balance by diverting surplus power into a resistive load, usually water or air heaters. In micro hydro systems it holds frequency constant by keeping total generator load fixed, and in small wind or battery systems it protects the battery from overcharge by dumping excess energy.
Drawings show a controller block, often with a thyristor or transistor switch symbol, connected between the bus and a resistor bank labelled dump or ballast load. A frequency or voltage sensing connection to the bus is included.
The dump load must be rated to absorb the full generator output if all consumer loads disconnect. The symbol does not show that rating or the heat rejection arrangement, both important for safety.

## How to read it

- The resistor bank is a control element, not a consumer load.
- Check the sensing quantity: frequency for hydro, voltage for battery systems.

## Information to show or reference

- State dump load rating against generator rating.
- Show sensing and switching element.
- Reference heat rejection.

## Important distinction

A dump load controller diverts surplus energy continuously; a load bank is a test load used temporarily.

## Facts

- Control quantity: Frequency or DC voltage
- Load element: Resistive heaters
- Typical use: Micro hydro, small wind, off-grid systems
- Preview: Independent educational illustration; consult the applicable standard and project legend for the exact graphic

## Public references

- [Resistors and heater-element symbols](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-1D071951-D38E-4B15-8B9E-C30ECBD55C19.htm) — Autodesk. Public resistor and heater-element symbol context.
- [AutoCAD Electrical: Semiconductor components](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-AC954072-7314-4682-88AF-38160D61E9A2.htm) — Autodesk. Public semiconductor switch symbol context.

## Graphic scope

Independent original educational concept illustration by Elora Grid. Not a certified standards graphic or manufacturer footprint. Unitless; not to scale. Original artwork licence: https://creativecommons.org/licenses/by/4.0/. Publisher material is linked only.