OpenHydronic

Open source ESP32 firmware that replaces the proprietary zone controller of a hydronic heating system.

OpenHydronic turns a cheap ESP32 relay board into the zone controller of an underfloor heating or radiator installation, in place of a Uponor, Danfoss, Watts or Salus box. It drives the thermal actuators and the boiler's room-stat contact, enforces the hydraulic protections that keep the hardware alive, and speaks the encrypted ESPHome native API to Home Assistant. When the server or the network goes down it keeps heating the house on its own, with a standalone web UI on port 80.

The board deliberately knows nothing about temperatures or schedules. Thermostats, hysteresis, presets and the sensor watchdog live in the companion integration, OpenHydronic-HA.

Important

This installation involves 230 VAC and, in most cases, a fuel-burning appliance. If you are not qualified to work on fixed electrical wiring and on the boiler, hire someone who is. Never remove or bypass the existing safety devices. Use at your own risk.

Features

Safety engine at 1 Hz. Home Assistant and the web UI place requests; the board decides if and when it is safe to apply them. No bug or restart upstream can short-cycle the boiler.
Power-on safe state. Every relay boots closed. A power cut never leaves a valve open with the burner starting by itself.
Minimum cycle times. 10 min ON and 10 min OFF per relay by default, protecting the PTC heads. A blocked request stays pending instead of being dropped.
Master relay for the boiler or circulator, with a thermal start delay, a residual heat purge and a boiler anti-short-cycle timer. Either on a local channel or handled in Home Assistant.
Circulator protection. A channel can drive a bypass valve that opens whenever the pump would run against a closed circuit.
Weekly anti-seize routine, so valves do not calcify over the summer.
Manual air purge: every valve open with the pump running, to bleed the circuit.
Emergency stop that ignores the minimum timers.
Runs without the server. Encrypted native API, standalone web server on port 80, recovery access point, captive portal, OTA updates. No cloud, no internet needed.
Parameterised. Channel count, GPIO map, channel roles and every timer are set at the top of the YAML; the timers are also runtime entities, adjustable without a reflash.

Compatibility

Item	Supported
Board	ESP32-WROOM-32 relay boards, 4 or 8 channels
Framework	ESPHome 2025.5.0 or newer, ESP-IDF
Home Assistant	2024.10 or newer, via the ESPHome integration
Actuators	230 V thermal heads, normally closed
Boiler interface	Dry room-stat contact (TA) only
Zones above 8	Use a second board, see Scaling the channels

Hardware

Control board

A commodity ESP32 Relay X8 board (ESP32-WROOM-32 plus 8 relays), sold as "ESP32 8 Channel Relay Module DC 12V".

Item	Specification	Notes
MCU	ESP32-WROOM-32, 4 MB flash	2.4 GHz Wi-Fi
Relays	8 x SPDT, 12 V coil	Contacts typically 10 A / 250 VAC
Supply	12 V DC, 1 A or more	All relays energised is about 700 mA
Isolation	Optocoupled drivers	Confirm on your actual board

Bill of materials

Typical installation, 7 zones plus boiler:

Qty	Component
1	ESP32 Relay X8 board
1	12 V DC 1 A DIN-rail power supply
7	230 V thermal actuators, NC (normally closed), for the manifold
1	Two-core cable for the boiler room-stat contact
1	2 A breaker plus a DIN-rail enclosure
—	Terminals, ferrules, cable glands

Warning

NC actuators are mandatory. With NO (normally open) heads the whole safety logic is inverted: a power failure would open every valve. Switching relay_inverted is not enough to fix that.

Wiring

Pin map

Channel	Default GPIO	Suggested role
Relay 1	`GPIO32`	Zone 1
Relay 2	`GPIO33`	Zone 2
Relay 3	`GPIO25`	Zone 3
Relay 4	`GPIO26`	Zone 4
Relay 5	`GPIO27`	Zone 5
Relay 6	`GPIO14`	Zone 6
Relay 7	`GPIO12`	Zone 7 (see below)
Relay 8	`GPIO13`	Zone 8 or master relay
LED	`GPIO02`	Status LED

Caution

GPIO12 (MTDI) and GPIO02 are strapping pins, read by the ESP32 during boot. GPIO12 must be low at boot. If it is high the chip sets the flash regulator to 1.8 V and the board does not start. With the default relay_inverted: "false" the output is low at boot, which is correct.

On an active-low board (relay_inverted: "true") GPIO12 sits high at boot and the board stops starting. Remap channel 7 to a free pin:

substitutions:
  relay_inverted: "true"
  relay_7_pin: "GPIO23"   # remapped, GPIO12 unused

Commissioning explains how to tell which polarity your board uses.

Electrical safety

Non-negotiable rules:

Never switch mains directly into the boiler's burner. Use only the appliance's room-stat / dry contact (TA) input.
Do not remove the existing safety devices — the underfloor high-temperature limiter, the pressure switch, the safety valve. OpenHydronic works downstream of them, never instead of them.
The floor temperature limiter must cut the actuator supply in series, so that it still works if the ESP32 is locked up.
Physically separate the 12 V DC and signal wiring from the 230 VAC wiring inside the box.
Feed the whole assembly from a dedicated, labelled breaker.
Size the common conductor for the inrush: each thermal head draws about 2 W steady but roughly 250 mA while its PTC warms up. Eight heads on one common is about 2 A of inrush.

Mode A — 8 zones, master in Home Assistant

All eight relays drive actuators. The boiler is switched by a device that already exists in Home Assistant, which follows the integration's master state machine.

  230 VAC                                            UNDERFLOOR MANIFOLD
  ┌─ L ──┬──────────────────────────────────────────┐
  │      │                                          │
  │   ┌──┴──┐  high temperature limiter             │
  │   │ 55°C│  (safety thermostat, NC)              │
  │   └──┬──┘                                       │
  │      │  switched L                              │
  │      │                                          │
  │   ┌──┴────────────────────────────────────┐     │
  │   │        ESP32 RELAY X8  (COM 1..8)     │     │
  │   │                                        │     │
  │   │  NO1 ─────────────────────────────────┼─────┼──► Zone 1 actuator (NC) ──┐
  │   │  NO2 ─────────────────────────────────┼─────┼──► Zone 2 actuator (NC) ──┤
  │   │  NO3 ─────────────────────────────────┼─────┼──► Zone 3 actuator (NC) ──┤
  │   │  NO4 ─────────────────────────────────┼─────┼──► Zone 4 actuator (NC) ──┤
  │   │  NO5 ─────────────────────────────────┼─────┼──► Zone 5 actuator (NC) ──┤
  │   │  NO6 ─────────────────────────────────┼─────┼──► Zone 6 actuator (NC) ──┤
  │   │  NO7 ─────────────────────────────────┼─────┼──► Zone 7 actuator (NC) ──┤
  │   │  NO8 ─────────────────────────────────┼─────┼──► Zone 8 actuator (NC) ──┤
  │   │                                        │     │                          │
  │   │  VCC ◄── 12 V DC ── DIN supply         │     │                          │
  │   │  GND ◄── 0 V ──────────┐               │     │                          │
  │   └────────────────────────┼───────────────┘     │                          │
  │                            │                     │                          │
  └─ N ──────────────────────────────────────────────┴──────────────────────────┘
                               │                              (actuator common
     12 V supply: L/N from the dedicated breaker                    neutral)

zone_count: "8"
master_channel: "0"     # no relay reserved for the master
bypass_channel: "0"

In Home Assistant, set the master manager to External entity.

Mode B — 7 zones plus a local master relay (recommended)

Channel 8 stops being a zone and switches the boiler's dry room-stat contact. This keeps working with Home Assistant switched off.

                                    ┌───────────────────────────────┐
                                    │  BOILER / HEAT PUMP           │
                                    │                               │
   ESP32 RELAY X8                   │   TA input (dry contact)      │
   ┌─────────────────┐              │        ┌──────┐               │
   │  COM8  ─────────┼──────────────┼────────┤  TA1 │               │
   │  NO8   ─────────┼──────────────┼────────┤  TA2 │               │
   │                 │              │        └──────┘               │
   │  (relay 8 =     │              │  NO external voltage on       │
   │   MASTER)       │              │  these terminals. Check the   │
   │                 │              │  manufacturer's manual.       │
   │  NO1..NO7 ──────┼──► Zones 1..7 (230 VAC, NC actuators)        │
   └─────────────────┘              └───────────────────────────────┘

   Automatic sequence:
     A zone calls for heat ─┐
                            ├── 3 min ──► MASTER ON   (heads already open)
     Last zone closes ──────┴── 2 min ──► MASTER OFF  (residual heat purge)

zone_count: "8"          # 8 channels populated
master_channel: "8"      # channel 8 is the master
zone_8_hidden: "true"    # hide the "Zone 8" entity

Then switch Master Local Mode on, from Home Assistant or from the web UI.

Mode C — 6 zones plus master and bypass valve

Installations with a fixed-speed circulator need a minimum flow. Channel 7 drives a bypass valve that opens automatically whenever the pump would run with no zone physically open.

        MANIFOLD                                   RETURN
           │                                          │
   Zones 1..6  ══╤══╤══╤══╤══╤══╤═══════════════════► │
                 │  │  │  │  │  │                     │
                 ▼  ▼  ▼  ▼  ▼  ▼   (NC actuators)    │
                                                      │
           ┌─────────────────────────┐                │
           │  BYPASS VALVE           │                │
   FLOW ───┤  (channel 7, NC)        ├────────────────┘
           │  guarantees minimum flow│
           └─────────────────────────┘

           Channel 8 ──► boiler TA contact (master)

zone_count: "8"
master_channel: "8"
bypass_channel: "7"
zone_7_hidden: "true"
zone_8_hidden: "true"

Note

If the manifold already has a mechanical differential bypass, leave bypass_channel: "0". The electronic bypass is for installations that do not have one.

Master state machine

                        ┌───────────────────────────────────────────┐
                        │                                           │
                        ▼                                           │
                 ┌────────────┐     a zone calls for heat     ┌──────────────┐
                 │   IDLE     │ ───────────────────────────►  │  START DELAY │
                 │ master OFF │                               │   (3 min)    │
                 └────────────┘  ◄──────────────────────────  └──────┬───────┘
                        ▲            demand disappears               │
                        │                                  delay elapsed and
                        │                                  master_min_off met
                        │                                            ▼
                 ┌──────┴───────┐    last zone closes         ┌──────────────┐
                 │ HEAT PURGE   │ ◄────────────────────────── │  MASTER ON   │
                 │   (2 min)    │                             │  pump / heat │
                 └──────────────┘ ──────────────────────────► └──────────────┘
                        expired            demand returns

Overrides applied at the end of every 1 Hz pass, in order:

Condition	Effect
`Summer Mode` on	Master forced off, valves still work
Anti-seize with `Anti-Seize Runs Pump` off	Master forced off
`Master Min Off Time` not met	Start postponed (boiler anti-short-cycle)

Installation

Requirements

ESPHome 2025.5.0 or newer (Home Assistant add-on or CLI)
A 3.3 V USB-TTL cable if the board has no USB on it

Create `secrets.yaml`

Copy the template next to openhydronic-8ch.yaml, or into /config/esphome/secrets.yaml:

cp secrets.yaml.example secrets.yaml

wifi_ssid: "MyNetwork"
wifi_password: "my-wifi-password"

# Recovery access point (OpenHydronic-AP), minimum 8 characters
ap_password: "openhydronic"

# 32 random bytes in base64. Generate at https://esphome.io/components/api.html
# or with: head -c 32 /dev/urandom | base64
api_encryption_key: "REPLACE_WITH_A_32_BYTE_BASE64_KEY="

ota_password: "my-ota-password"

web_username: "admin"
web_password: "my-web-password"

secrets.yaml is gitignored and must stay that way.

Flash the board

esphome run openhydronic-8ch.yaml

The first flash is over USB; everything after that is OTA over Wi-Fi.

Add it to Home Assistant

The board announces itself over mDNS as openhydronic-<mac>.local and shows up under Settings → Devices & Services → Discovered. Accept it and paste the api_encryption_key.

For zone mapping, thermostats and presets, install OpenHydronic-HA through HACS afterwards.

A note on flash space

web_server with local: true embeds the UI assets in flash so the page works with no internet at all. If the build runs out of space:

web_server:
  local: false      # loads assets from esphome.io, browser needs internet

…or define a larger partition table under esp32: partitions:.

Configuration

Everything structural is set through substitutions at the top of the YAML, with no changes to the logic below.

Identity

Substitution	Default	Description
`device_name`	`openhydronic`	Base name. The MAC suffix is appended automatically.
`friendly_name`	`OpenHydronic`	Entity prefix in Home Assistant.

Channels and pins

Substitution	Default	Description
`zone_count`	`"8"`	Channels populated on the board (4 or 8 in this file).
`relay_1_pin` … `relay_8_pin`	see Pin map	GPIO remapping.
`status_led_pin`	`GPIO02`	Diagnostic LED.
`relay_inverted`	`"false"`	`"true"` on active-low boards. Mind the `GPIO12` warning.
`master_channel`	`"8"`	Channel reserved for the local master. `"0"` = none.
`bypass_channel`	`"0"`	Bypass valve channel. `"0"` = disabled.
`zone_1_hidden` … `zone_8_hidden`	`"false"`	Hide that zone entity in Home Assistant.

Timers (initial values, adjustable later without a reflash)

Substitution	Default	Description
`default_master_start_delay`	`"3"` min	Thermal delay before starting the master.
`default_master_purge_delay`	`"2"` min	Residual heat purge after the last zone closes.
`default_master_min_off`	`"5"` min	Boiler anti-short-cycle.
`default_min_run_time`	`"10"` min	Minimum ON time per relay.
`default_min_off_time`	`"10"` min	Minimum OFF time per relay.
`default_air_purge_time`	`"30"` min	Manual air purge duration.

Anti-seize

Substitution	Default	Description
`antiseize_days`	`"SUN"`	Weekday(s).
`antiseize_hour` / `antiseize_minute`	`"10"` / `"0"`	Time of day.
`antiseize_minutes`	`"5"`	Exercise duration.

All six timers are also number entities in Home Assistant (config category) with persisted values. The substitutions only set the factory default.

Hydraulic protections

Power-on safe state

Every relay uses restore_mode: ALWAYS_OFF. After a power cut the board starts with everything closed and the boiler off. It never inherits a previous state.

Minimum cycle

Thermal actuators use a PTC element that melts a wax plug over 2 to 4 minutes to open the valve. Switching them in short cycles degrades the PTC and never actually opens the valve.

The engine enforces, per relay:

10 min ON before accepting a close request
10 min OFF before accepting an open request

The request is not dropped: it stays pending and runs as soon as the lock expires. That is what the Zone N Pending binary sensor reports, and what the Lovelace card shows as a blinking valve.

Exceptions that ignore the minimum cycle: Emergency Stop, anti-seize, air purge, and switching Cycle Protection off (bench use only).

Master thermal delay (3 min)

The boiler must not start against closed valves. On the first request the master waits Master Start Delay to give the heads time to open. If the demand disappears meanwhile, the timer is cancelled.

Residual heat purge (2 min)

When the last zone closes the master stays on for another Heat Purge Delay, dissipating the heat stored in the exchanger and avoiding kettling and overheat lockouts.

The valves are still physically open during the purge: a thermal head takes several minutes to cool down and close. The purge uses that window.

Circulator protection (bypass)

With bypass_channel set, the bypass valve opens whenever the master is on, or counting down to on, and no other zone is physically open — the classic dead-head situation that causes cavitation and noise.

Anti-seize routine

Every Sunday at 10:00 all actuators open for 5 minutes. Valves that sit still all summer calcify and seize.

The exercise goes through the normal request path, so the master starts after 3 minutes and purges at the end, exercising the pump too. To exercise only the valves, without burning fuel, switch Anti-Seize Runs Pump off or turn Summer Mode on.

The Anti-Seize (run now) button runs it on demand.

Manual air purge

Air Purge (start), or the Air Purge Mode switch, opens every valve for 30 minutes with the pump running, pushing trapped air to the air vent.

The pump still honours the 3 minute delay, so the heads are open before there is any flow. The duration is set by Air Purge Duration and the mode can be cancelled at any time.

Summer mode

Summer Mode closes every zone and blocks the master, while keeping the anti-seize routine working. It is the right mode for the months without heating.

Emergency stop

Emergency Stop cancels every mode, clears all requests and de-energises every relay immediately, ignoring the minimum timers.

Entities

Prefixed with ${friendly_name} in Home Assistant.

Control

Entity	Type	Purpose
`Zone 1` … `Zone 8`	`switch`	Open request. The state read back is the real relay.
`Air Purge Mode`	`switch`	Air purge, cancellable.
`Summer Mode`	`switch`	Blocks heat production.
`Air Purge (start)`	`button`	Starts the air purge.
`Anti-Seize (run now)`	`button`	Runs the anti-seize cycle.
`Emergency Stop`	`button`	Closes everything now.
`Restart`	`button`	Reboots the ESP32.

Configuration (config category)

Entity	Type	Default
`Master Local Mode`	`switch`	off
`Cycle Protection`	`switch`	on
`Bypass Protection`	`switch`	on
`Anti-Seize Runs Pump`	`switch`	on
`Master Start Delay`	`number` (min)	3
`Heat Purge Delay`	`number` (min)	2
`Master Min Off Time`	`number` (min)	5
`Zone Min Run Time`	`number` (min)	10
`Zone Min Off Time`	`number` (min)	10
`Air Purge Duration`	`number` (min)	30

State

Entity	Type	Meaning
`Master Demand`	`binary_sensor`	The board says the boiler or pump should be running.
`Heat Demand`	`binary_sensor`	At least one zone is asking for heat, before the delay.
`Zone 1..8 Pending`	`binary_sensor`	Request differs from reality: opening or closing.
`Anti-Seize Active`	`binary_sensor`	Exercise cycle in progress.
`Air Purge Active`	`binary_sensor`	Air purge in progress.
`Open Zones`	`sensor`	Number of zones physically open.
`API Status`, `Uptime`, `Wi-Fi Signal`, `IP Address`, `SSID`, `ESPHome Version`	diagnostic	—

In Mode A the integration runs its own master state machine, with the same delays, and switches the external entity. Master Demand reports what the board decided and is useful for automations and for debugging; it is not the signal the integration follows.

API actions

Callable as esphome.<node>_<action> once the board is adopted by the ESPHome integration.

Action	Parameters	Effect
`zone_set`	`zone` (int 1-8), `state` (bool)	Records a zone request.
`all_zones_off`	—	Clears every request, still honouring `Min Run Time`.
`start_air_purge`	—	Starts the air purge.
`stop_air_purge`	—	Cancels a running air purge.
`start_anti_seize`	—	Starts the anti-seize cycle.
`emergency_stop`	—	Closes everything immediately.

action: esphome.openhydronic_a1b2c3_zone_set
data:
  zone: 3
  state: true

OpenHydronic-HA calls the purge, anti-seize and emergency stop actions itself, so those routines run on the board and survive a Home Assistant restart. Zones are driven through the Zone N switches instead, which is equivalent and keeps the state readable.

Running without Home Assistant

The firmware is configured never to depend on the server or on the internet:

Setting	Effect
`api: reboot_timeout: 0s`	Losing Home Assistant never reboots the board.
`wifi: reboot_timeout: 0s`	Losing Wi-Fi never reboots the board.
`wifi.ap` plus `ap_timeout: 60s`	After 60 s with no network, `OpenHydronic-AP` comes up.
`captive_portal`	Joining the AP opens the configuration page automatically.
`web_server` with `local: true`	Full UI on port 80, with no external CDN.

Manual heating procedure:

Join the local network, or OpenHydronic-AP if there is none (password in secrets.yaml).
Open http://openhydronic-<mac>.local, or http://192.168.4.1 in AP mode.
Log in with web_username / web_password.
Switch the Zone N entries you need on. With a local master, switch Master Local Mode on too.

Every hydraulic protection is still active: the web server uses exactly the same request path as Home Assistant.

Note

The anti-seize schedule uses Home Assistant's clock, with SNTP as a fallback. With neither Home Assistant nor internet the board has no time source and the routine does not fire. The Anti-Seize (run now) button still works.

Scaling the channels

Channels	How
4	`zone_count: "4"` plus `zone_5_hidden` … `zone_8_hidden: "true"`. Channels 5-8 are ignored.
8	Default configuration.
12 / 16	This file instantiates 8 channels. Use a second board (recommended) or extend the YAML.

Multiple boards. Flash the same YAML onto two boards with different device_name values. The integration handles several boards in one Home Assistant instance and the master manager coordinates them.

# board-1.yaml
substitutions:
  device_name: "openhydronic-floor0"
  friendly_name: "OpenHydronic Floor 0"
  master_channel: "8"

# board-2.yaml
substitutions:
  device_name: "openhydronic-floor1"
  friendly_name: "OpenHydronic Floor 1"
  master_channel: "0"    # the master lives on board 1

Extending to 16 channels. ESPHome does not generate blocks conditionally, so the file has to be edited. Four mechanical changes:

Add relay_9_pin … relay_16_pin and zone_9_hidden … zone_16_hidden to the substitutions.
Duplicate the switch: - platform: gpio blocks for relay_9 … relay_16.
Duplicate the switch: - platform: template blocks (Zone 9 … Zone 16) and the Zone N Pending binary sensors.
In globals, widen the arrays from [9] to [17]; in the engine and in emergency_stop_script, change the <= 8 bounds to <= 16 and widen the R[] array.

Save it as openhydronic-16ch.yaml. The safety engine needs no other change.

Commissioning

Do the polarity test with the board out of the enclosure and no 230 V connected.

Relay polarity, on the bench

Power only the 12 V DC. Connect nothing to the contacts.
Flash with the defaults (relay_inverted: "false").
In the web UI, toggle Zone 1 and watch relay 1's LED and listen for the click.
- Relay actuates with the switch on → active-high → relay_inverted: "false"
- Relay actuates with the switch off, or sticks at boot → active-low → relay_inverted: "true" and remap relay_7_pin.
Reboot the board and confirm every relay starts de-energised.

Timings, without hydraulics

With Master Local Mode on and the boiler still disconnected:

Step	Expected
Switch `Zone 1` on	`Heat Demand` on at once, `Master Demand` still off
Wait 3 min	`Master Demand` turns on
Switch `Zone 1` off	Blocked, `Zone 1 Pending` on (10 min minimum)
Wait until 10 min	Relay 1 opens, purge countdown starts
+2 min	`Master Demand` off

To speed the test up, drop Zone Min Run Time and Zone Min Off Time to 0 temporarily, or switch Cycle Protection off. Restore them before putting the system in service.

With hydraulics

Open a single zone and confirm by touch that only that loop warms up.
Confirm the actuator opens in 2 to 4 minutes; most heads have a visual indicator.
With a bypass configured, force the case: run the master with no zone and confirm the bypass opens and the circulator does not cavitate.
Run a full air purge and check the automatic air vent.
Cut the mains and restore it: every relay must start off.

Troubleshooting

Symptom	Likely cause	Fix
Board does not start after flashing	`GPIO12` high at boot (active-low board)	Remap `relay_7_pin`, see Pin map.
A zone switch turns itself back off	`Zone Min Off Time` lock	Normal. `Zone N Pending` stays on and the request runs when it expires.
A zone never opens	Channel reserved for the master, or above `zone_count`	Review `master_channel` and `zone_count`.
The boiler never starts	`Summer Mode` on, or no master configured	Turn `Summer Mode` off; switch `Master Local Mode` on or configure the external entity.
`Master Demand` on but the boiler stays cold	Room-stat wiring	Check the dry contact and polarity in the boiler manual.
Noisy circulator with few zones open	No minimum flow	Set `bypass_channel` or fit a mechanical bypass.
Anti-seize never fires	No time source	See Running without Home Assistant. Use the manual button.
Build fails, out of flash	`web_server: local: true`	Set `local: false` or enlarge the partition.
Never appears in Home Assistant	mDNS blocked between VLANs	Add it by IP under Add Integration → ESPHome.

Live logs:

esphome logs openhydronic-8ch.yaml

Home Assistant

OpenHydronic-HA adds the thermal layer on top of this firmware: zone-to-sensor mapping, thermostats with hysteresis and presets, the global master manager, the sensor watchdog, runtime metrics and a Lovelace card. It installs through HACS and discovers the board over mDNS.

Changelog

See CHANGELOG.md.

Contributing

Pull requests are welcome. Read CONTRIBUTING.md first, especially the rule about never weakening a protection by default.

License

GNU General Public License v3.0. See LICENSE.

Disclaimer

This software is provided as is, without warranty of any kind, express or implied. It controls mains-powered equipment and a heating system that may involve combustion, pressure and high temperatures.

The authors and contributors accept no liability for property damage, personal injury or consequential loss arising from the use of this project. Installing, verifying and maintaining the safety devices of the hydraulic system is entirely the installer's responsibility, and the installer must hold whatever qualifications the law requires.

Never remove or bypass the original safety devices of the system.

Name		Name	Last commit message	Last commit date
.github/workflows		.github/workflows
.gitattributes		.gitattributes
.gitignore		.gitignore
CHANGELOG.md		CHANGELOG.md
CONTRIBUTING.md		CONTRIBUTING.md
LICENSE		LICENSE
README.md		README.md
openhydronic-8ch.yaml		openhydronic-8ch.yaml
secrets.yaml.example		secrets.yaml.example

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OpenHydronic

Features

Compatibility

Hardware

Control board

Bill of materials

Wiring

Pin map

Electrical safety

Mode A — 8 zones, master in Home Assistant

Mode B — 7 zones plus a local master relay (recommended)

Mode C — 6 zones plus master and bypass valve

Master state machine

Installation

Requirements

Create secrets.yaml

Flash the board

Add it to Home Assistant

A note on flash space

Configuration

Identity

Channels and pins

Timers (initial values, adjustable later without a reflash)

Anti-seize

Hydraulic protections

Power-on safe state

Minimum cycle

Master thermal delay (3 min)

Residual heat purge (2 min)

Circulator protection (bypass)

Anti-seize routine

Manual air purge

Summer mode

Emergency stop

Entities

Control

Configuration (config category)

State

API actions

Running without Home Assistant

Scaling the channels

Commissioning

Relay polarity, on the bench

Timings, without hydraulics

With hydraulics

Troubleshooting

Home Assistant

Changelog

Contributing

License

Disclaimer

About

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Create `secrets.yaml`