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Generator Control Guide

This guide covers how to start, stop, and monitor your generator using the RPi Generator Control system.

Table of Contents

Overview

The generator control system uses a master-slave architecture where GenMaster coordinates all operations and GenSlave physically controls the relay connected to your generator's two-wire start input.

Key Principles

  1. GenMaster is the source of truth - The PostgreSQL database on GenMaster maintains the authoritative state of whether the generator should be running.

  2. Heartbeat synchronization - GenMaster sends heartbeats to GenSlave every 10 seconds. If GenSlave's relay state doesn't match GenMaster's intended state, the heartbeat corrects it.

  3. Safety first - The system defaults to a safe state:

  4. Relay is disarmed on every GenMaster boot under the default fail_safe policy (operator must re-arm — see Boot Arming Policy)
  5. Generator can always be stopped even when disarmed
  6. GenSlave has an independent failsafe that stops the generator if communication is lost

Understanding Generator States

The state machine tracks the generator through several states:

Generator Running States

State Description
idle Generator is off, system is waiting
running Generator is actively running

Trigger Types

When the generator starts, the system records what triggered it:

Trigger Description
victron Started automatically by Victron Cerbo GX signal (low battery)
manual Started manually via web UI or API
scheduled Started by a scheduled run
exercise Started by an exercise schedule for maintenance

Stop Reasons

When the generator stops, the system records why:

Reason Description
victron Victron signal went inactive (battery charged)
manual Stopped manually via web UI or API
scheduled_end Scheduled run duration completed
exercise_end Exercise run completed
comm_loss GenSlave lost communication with GenMaster
override Force-stop override activated
error An error occurred
max_runtime Maximum runtime limit exceeded

Arming the System

The arming system is a safety feature that prevents accidental generator starts.

Why Arming?

  • Prevents unintended starts during maintenance
  • Requires explicit operator action to enable automation
  • Disarmed by default on system boot under the fail_safe boot policy (see Boot Arming Policy below for the alternative preserve_state mode)

Arming Behavior

State Can Start (Auto) Can Start (Manual) Can Stop
Disarmed No No Yes
Armed Yes Yes Yes

Note: The generator can always be stopped for safety, regardless of arm state.

How to Arm

Via Web UI: 1. Navigate to the Generator dashboard 2. Click the Arm button in the control panel 3. The status indicator will change to show "Armed"

Via API: 

# Arm the relay
curl -X POST https://your-genmaster/api/generator/arm \
  -H "Authorization: Bearer YOUR_TOKEN"

# Disarm the relay
curl -X POST https://your-genmaster/api/generator/disarm \
  -H "Authorization: Bearer YOUR_TOKEN"

Boot Arming Policy

Operator-selectable behavior for what happens to the relay's armed state when GenMaster restarts. Configure in Generator → Boot Arming Policy in the UI. The setting is stored in the database and persists across reboots.

Policy Behavior on GenMaster boot When to use
fail_safe (default) If the relay was armed pre-boot, disarms it and sets manual_disarm_active = True. Fires the boot_disarmed_failsafe notification so the operator knows they need to re-arm. Default for safety. Required when unsupervised auto-restart after a power event would be unsafe or undesirable.
preserve_state Keeps the prior slave_relay_armed value across the reboot. The system can resume operation automatically after an outage. Only when your installation can safely auto-resume (proper ATS, weatherproofing, fuel/CO safety). Requires confirming a UI warning before enabling.

Mid-operation GenSlave drops (network blip, slave reboot, etc.) are handled automatically and are independent of this setting — GenSlave reads armed from every heartbeat and matches GenMaster's database, so it re-arms on its own when communication is restored.

Notification on disarm: When the fail_safe policy disarms the relay, GenMaster fires the boot_disarmed_failsafe notification event. Configure the channels/groups that receive it under Notifications → Configure → Generator Events. Default message text reads:

Generator Disarmed After Reboot — Action Required

GenMaster restarted with the fail-safe boot policy enabled. The generator relay has been automatically DISARMED for safety. The generator WILL NOT START automatically until you log in and re-arm it from the web interface.

Starting the Generator

Automatic Start (Victron)

When Victron sends a "generator needed" signal (GPIO17 goes HIGH):

  1. System checks if relay is armed
  2. System checks for active override (force_stop blocks auto-start)
  3. System checks for runtime lockout or cooldown
  4. If all checks pass, generator starts

Manual Start

Via Web UI: 1. Ensure the system is armed 2. Click Start Generator 3. Optionally set a duration for auto-stop 4. Confirm the action

Via API: 

curl -X POST https://your-genmaster/api/generator/start \
  -H "Authorization: Bearer YOUR_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"duration_minutes": 60, "notes": "Testing"}'

What Happens on Start

  1. Database updated first - GenMaster sets generator_running = true
  2. Relay command sent - GenMaster tells GenSlave to turn relay ON
  3. Run record created - Start time, trigger type, and fuel info logged
  4. Webhooks fired - generator.started.{trigger} event sent
  5. Notifications sent - If configured, push notification goes out

Even if the relay command fails (network issue), the next heartbeat will synchronize GenSlave with GenMaster's state.

Stopping the Generator

Automatic Stop (Victron)

When the Victron signal goes LOW (battery charged): - System checks if the current run was triggered by Victron - If yes, generator stops automatically - If run was manual/scheduled, Victron signal is ignored

Manual Stop

Via Web UI: Click Stop Generator - works even when disarmed.

Via API: 

curl -X POST https://your-genmaster/api/generator/stop \
  -H "Authorization: Bearer YOUR_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"reason": "Maintenance needed"}'

What Happens on Stop

  1. Database updated first - GenMaster sets generator_running = false
  2. Relay command sent - GenMaster tells GenSlave to turn relay OFF
  3. Run record completed - Stop time, duration, fuel usage calculated
  4. Auto-stop jobs cancelled - Any scheduled auto-stop is removed
  5. Webhooks fired - generator.stopped.{reason} event sent
  6. Notifications sent - Runtime and fuel usage included in notification

Override System

Overrides let you force the generator into a specific state, ignoring normal triggers.

Override Types

Type Effect
force_run Keeps generator running, ignores Victron "stop" signal
force_stop Keeps generator stopped, blocks automatic Victron starts

Important Notes

  • force_stop only blocks automatic (Victron) starts
  • Manual and scheduled starts still work with force_stop active
  • Overrides persist until explicitly disabled

Using Overrides

Via Web UI: 1. Navigate to Generator dashboard 2. Toggle the Override switch 3. Select override type (Force Run or Force Stop)

Via API: 

# Enable force_run override
curl -X POST https://your-genmaster/api/override/enable \
  -H "Authorization: Bearer YOUR_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"override_type": "force_run"}'

# Disable override
curl -X POST https://your-genmaster/api/override/disable \
  -H "Authorization: Bearer YOUR_TOKEN"

Runtime Limits

Protect your generator from excessive runtime with configurable limits.

Configuration

Setting Description Default
runtime_limits_enabled Enable/disable the feature false
max_run_minutes Maximum continuous runtime 480 (8 hours)
cooldown_minutes Required rest after max runtime 60
lockout_on_max_runtime Require acknowledgment after max true

How It Works

  1. When generator reaches max_run_minutes, it automatically stops
  2. Stop reason is recorded as max_runtime
  3. If lockout_on_max_runtime is enabled:
  4. A lockout is activated
  5. Generator cannot restart until operator acknowledges the event
  6. If only cooldown is active:
  7. Generator waits cooldown_minutes before allowing restart
  8. Manual starts bypass cooldown

Clearing Lockout

Via Web UI: 1. A banner appears indicating max runtime was reached 2. Click Acknowledge & Clear Lockout

Via API: 

curl -X POST https://your-genmaster/api/generator/clear-lockout \
  -H "Authorization: Bearer YOUR_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"acknowledge": true}'

Fuel Tracking

The system tracks estimated fuel consumption for each run.

Configuration

Set these in Settings > Generator Info:

Field Description
Fuel Type lpg (Propane), natural_gas, or diesel
Expected Load 50 or 100 percent
Consumption @ 50% Gallons per hour at 50% load
Consumption @ 100% Gallons per hour at 100% load

How It's Calculated

estimated_fuel_used = (runtime_seconds / 3600) × fuel_consumption_rate

The consumption rate used is based on the expected load setting at the time the run started.

Viewing Fuel Usage

Via Web UI: - Dashboard shows total fuel used since last reset - Each run in history shows individual fuel consumption

Via API: 

# Get fuel usage
curl https://your-genmaster/api/generator/fuel-usage \
  -H "Authorization: Bearer YOUR_TOKEN"

# Reset fuel tracking (e.g., after refueling)
curl -X POST https://your-genmaster/api/generator/fuel-usage/reset \
  -H "Authorization: Bearer YOUR_TOKEN"

Run History

Every generator run is logged with detailed information.

What's Recorded

Field Description
start_time Unix timestamp when started
stop_time Unix timestamp when stopped
duration_seconds Total runtime
trigger_type What started it (victron/manual/scheduled/exercise)
stop_reason Why it stopped
notes Optional user notes
fuel_type_at_run Fuel type when run started
load_at_run Load setting when run started
estimated_fuel_used Calculated fuel consumption

Viewing History

Via Web UI: Navigate to Generator > History to see all runs with filtering options.

Via API: 

# Get last 50 runs
curl "https://your-genmaster/api/generator/history?limit=50" \
  -H "Authorization: Bearer YOUR_TOKEN"

# Filter by trigger type
curl "https://your-genmaster/api/generator/history?trigger_type=victron" \
  -H "Authorization: Bearer YOUR_TOKEN"

Statistics

Get aggregate statistics for a time period:

# Last 30 days (default)
curl "https://your-genmaster/api/generator/stats" \
  -H "Authorization: Bearer YOUR_TOKEN"

# Last 90 days
curl "https://your-genmaster/api/generator/stats?days=90" \
  -H "Authorization: Bearer YOUR_TOKEN"

Returns: - Total runs - Total runtime (hours) - Average runtime per run - Breakdown by trigger type

API Reference

Endpoints Summary

Method Endpoint Description
GET /api/generator/state Get current generator status
POST /api/generator/start Start the generator
POST /api/generator/stop Stop the generator
POST /api/generator/arm Arm the relay
POST /api/generator/disarm Disarm the relay
GET /api/generator/history Get run history
GET /api/generator/stats Get runtime statistics
GET /api/generator/fuel-usage Get fuel usage since reset
POST /api/generator/fuel-usage/reset Reset fuel tracking
GET /api/generator/runtime-limits Get runtime limits status
POST /api/generator/clear-lockout Clear runtime lockout
POST /api/override/enable Enable override
POST /api/override/disable Disable override
GET /api/override/status Get override status

Response Examples

GET /api/generator/state 

{
  "running": true,
  "state": "running",
  "current_run_id": 42,
  "start_time": 1714567890,
  "runtime_seconds": 3600,
  "trigger": "victron",
  "armed": true,
  "slave_connected": true
}

GET /api/generator/stats 

{
  "period_days": 30,
  "total_runs": 15,
  "total_runtime_seconds": 54000,
  "total_runtime_hours": 15.0,
  "average_runtime_seconds": 3600,
  "runs_by_trigger": {
    "victron": 10,
    "manual": 3,
    "scheduled": 2
  },
  "runtime_by_trigger": {
    "victron": 36000,
    "manual": 10800,
    "scheduled": 7200
  }
}

Safety Features Summary

Feature Purpose
Arming Prevents accidental starts, requires explicit operator action
Heartbeat Sync Ensures GenSlave always matches GenMaster's intended state
GenSlave Failsafe Independent watchdog stops generator if communication lost
Runtime Limits Prevents generator damage from excessive continuous operation
Lockout System Requires human acknowledgment after max runtime events
Override Safety force_stop still allows manual intervention
Relay OFF Always Works Can always stop generator regardless of arm state

Next Steps