# Ventilation fan automatic changeover

Canonical URL: https://eloragrid.ai/symbols/ventilation-fan-automatic-changeover
Publisher: Elora Grid
Updated: 2026-11-03
Lookup label: VFAC
Drawing use: Schematic
Reference families: Manufacturer

Representation: Functional block
Installation focus: switchrooms
Input: Duty-fan fault
Output: Standby-fan request

Transfers the documented ventilation duty when the active fan becomes unavailable.

## In plain English

### What this block does

Transfers the documented ventilation duty when the active fan becomes unavailable.

### A simple example

In a switchroom containing transformers and auxiliary panels, the room controller can supervise fan availability and send an alarm when the documented ventilation duty is not achieved. For this reference, the drawing identifies “Duty-fan fault” at the input and “Standby-fan request” at the output. Changeover conditions require the ventilation design.

### What the drawings help you do

Start at the named input: Duty-fan fault. Identify its source device or document and the state represented on the drawing. Follow the named output: Standby-fan request. Cross-reference its destination and separate the command from confirmation that the equipment responded.

### Terms

- Input: Duty-fan fault
- Output: Standby-fan request
- Application reference: An explanation of a named drawing function or circuit relationship; the project documents define the equipment and its connections.

Concept diagram: Duty-fan fault → VFAC → Standby-fan request
A reading guide. The entry's original illustration and input/output facts describe this application.

- [Ventilation in MV substations](https://www.electrical-installation.org/enwiki/Ventilation_in_MV_Substations)


## What it represents

Transfers the documented ventilation duty when the active fan becomes unavailable. Ventilation control coordinates the equipment that manages heat and air movement in an electrical room. A temperature request, a fan command and proof of airflow are separate signals, and the room design determines how they interact.
In a switchroom containing transformers and auxiliary panels, the room controller can supervise fan availability and send an alarm when the documented ventilation duty is not achieved. For this reference, the drawing identifies “Duty-fan fault” at the input and “Standby-fan request” at the output. Changeover conditions require the ventilation design.
Identify the monitored space, the selected ventilation mode and the equipment feedback. Avoid inferring airflow, temperature limits or a fire response from a generic fan symbol; these require the room-services design. The functional block is an independent explanation of this named application. Equipment-specific ratings, terminal connections and operating conditions must be established in the project documentation.

## How to read it

- Start at the named input: Duty-fan fault. Identify its source device or document and the state represented on the drawing.
- Follow the named output: Standby-fan request. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- Changeover conditions require the ventilation design.
- Identify the monitored space, the selected ventilation mode and the equipment feedback. Avoid inferring airflow, temperature limits or a fire response from a generic fan symbol; these require the room-services design.

## Information to show or reference

- Label the source and connection reference for duty-fan fault.
- Identify the destination and defined state of standby-fan request.
- Record the equipment or control-document revision supporting this functional block.
- Check this application limit in the project design: Changeover conditions require the ventilation design.

## Important distinction

Changeover conditions require the ventilation design. This reference describes the named application; it does not establish a new IEC graphical symbol, an ANSI device-function number or an exact manufacturer connection diagram.

## Facts

- Representation: Functional block
- Installation focus: Switchrooms
- Input / boundary: Duty-fan fault
- Output / connection: Standby-fan request
- Lookup label: VFAC is a library lookup label, not a standard device designation.

## Public references

- [Ventilation in MV substations](https://www.electrical-installation.org/enwiki/Ventilation_in_MV_Substations) — Schneider Electric. Public technical context for switchroom ventilation interfaces. Heat removal, condensation and environmental design context. The application text and educational graphic are independently authored; the publisher does not certify this representation.

## 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.