diff --git a/paramod.yaml b/paramod.yaml
index f243099..4708c23 100644
--- a/paramod.yaml
+++ b/paramod.yaml
@@ -7,7 +7,7 @@ mqtt:
   user: admin
   password: 97sm3pHNSMZ4M5qUj0x8
   path: heizung/paradigma
-  button_circulation: zigbee2mqtt/WirelessButton
+  leitsystem_path: heizung/leitsystem2
 influxdb:
   bucket: Paradigma
   org: skaville
@@ -22,7 +22,7 @@ modbus:
   max_input_addr: 45
   max_holding_addr: 61
 modbus_coils:
-  - MgtSystem: {addr: 0, write: false, mqtt: false, influxdb: false, comment: Leitsystem aktiv}
+  - MgtSystem: {addr: 0, write: false, mqtt: true,  influxdb: false, comment: Leitsystem aktiv}
   - HK1pres:   {addr: 1, write: false, mqtt: false, influxdb: false, comment: HK1 vorhanden}
   - HK2pres:   {addr: 2, write: false, mqtt: false, influxdb: false, comment: HK2 vorhanden}
   - HK3pres:   {addr: 3, write: false, mqtt: false, influxdb: false, comment: HK3 vorhanden}
@@ -78,9 +78,9 @@ modbus_input_register:
   - VKW:   {addr: 43, type: INT16, factor: 0.1, mqtt: false, influxdb: true}
   - VSPm:  {addr: 44, type: INT16, factor: 0.1, mqtt: false, influxdb: true}
 modbus_holding_register:
-  - nothing:   {addr: 0,  type: UINT16, factor: 1,   write: true,  mqtt: false, influxdb: false}
+  - nothing:   {addr: 0,  type: UINT16, factor: 1,   write: false, mqtt: false, influxdb: false}
   - ErrLS:     {addr: 1,  type: UINT16, factor: 1,   write: false, mqtt: false, influxdb: true}
-  - TVsoll:    {addr: 2,  type: INT16,  factor: 0.1, write: false, mqtt: false, influxdb: true}
+  - TVsoll:    {addr: 2,  type: INT16,  factor: 0.1, write: true,  mqtt: true,  influxdb: true}
   - TV2soll:   {addr: 3,  type: INT16,  factor: 0.1, write: false, mqtt: false, influxdb: false}
   - TV3soll:   {addr: 4,  type: INT16,  factor: 0.1, write: false, mqtt: false, influxdb: false}
   - HK1soll:   {addr: 5,  type: UINT16, factor: 1,   write: false, mqtt: false, influxdb: true}
diff --git a/src/config.rs b/src/config.rs
index 8b2725a..5d1040f 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -24,7 +24,8 @@ pub struct MqttConfig {
     pub user: Option<String>,
     pub password: Option<String>,
     pub path: Option<String>,
-    pub button_circulation: Option<String>,
+    pub leitsystem_path: Option<String>,
+    pub set_write_interval_ms: Option<u64>,
 }
 
 #[derive(Debug, Serialize, Deserialize, Clone)]
diff --git a/src/modbus.rs b/src/modbus.rs
index d363210..5f1d87e 100644
--- a/src/modbus.rs
+++ b/src/modbus.rs
@@ -1,5 +1,6 @@
 use crate::config::{ModbusValueMaps, ModbusConfig};
 use crate::modbus_types::{ModbusInputRegisterConfig, ModbusHoldingRegisterConfig, ModbusCoilsConfig};
+use crate::config::AppConfig;
 use std::collections::HashMap;
 use std::sync::{Arc, Mutex};
 use std::thread;
@@ -9,6 +10,112 @@ use tokio_modbus::prelude::*;
 use tokio_modbus::client::tcp;
 use std::net::SocketAddr;
 
+pub fn write_value_by_name(config: &AppConfig, name: &str, payload: &str) -> Result<(), String> {
+    let addr: SocketAddr = format!("{}:{}", config.modbus.host, config.modbus.port)
+        .parse()
+        .map_err(|e| format!("Ungültige Modbus-Adresse: {}", e))?;
+
+    if let Some(ref coils) = config.modbus_coils {
+        for map in coils {
+            if let Some(coil) = map.get(name) {
+                if !coil.write.unwrap_or(false) {
+                    return Err(format!("Schreiben für '{}' nicht erlaubt", name));
+                }
+                let bool_value = parse_bool_payload(payload)?;
+                let rt = tokio::runtime::Runtime::new()
+                    .map_err(|e| format!("Tokio Runtime Fehler: {}", e))?;
+                rt.block_on(async {
+                    let mut client = tcp::connect_slave(addr, 1u8.into())
+                        .await
+                        .map_err(|e| format!("Modbus Verbindung fehlgeschlagen: {}", e))?;
+                    client
+                        .write_single_coil(coil.addr, bool_value)
+                        .await
+                        .map_err(|e| format!("Coil schreiben fehlgeschlagen: {}", e))
+                })?;
+                return Ok(());
+            }
+        }
+    }
+
+    if let Some(ref holding_registers) = config.modbus_holding_register {
+        for map in holding_registers {
+            if let Some(reg) = map.get(name) {
+                if !reg.write.unwrap_or(false) {
+                    return Err(format!("Schreiben für '{}' nicht erlaubt", name));
+                }
+                let numeric_value = payload
+                    .trim()
+                    .parse::<f64>()
+                    .map_err(|e| format!("Ungültiger Zahlenwert '{}': {}", payload, e))?;
+                let factor = reg.factor.unwrap_or(1.0);
+                let raw = if factor == 0.0 {
+                    numeric_value
+                } else {
+                    numeric_value / factor
+                };
+
+                let rt = tokio::runtime::Runtime::new()
+                    .map_err(|e| format!("Tokio Runtime Fehler: {}", e))?;
+
+                return rt.block_on(async {
+                    let mut client = tcp::connect_slave(addr, 1u8.into())
+                        .await
+                        .map_err(|e| format!("Modbus Verbindung fehlgeschlagen: {}", e))?;
+
+                    match reg.r#type.as_deref().unwrap_or("UINT16") {
+                        "INT16" => {
+                            let int_value = raw.round();
+                            if int_value < i16::MIN as f64 || int_value > i16::MAX as f64 {
+                                return Err(format!("Wert außerhalb INT16-Bereich für '{}': {}", name, numeric_value));
+                            }
+                            let register = int_value as i16 as u16;
+                            client
+                                .write_multiple_registers(reg.addr, &[register])
+                                .await
+                                .map_err(|e| format!("Holding Register schreiben fehlgeschlagen: {}", e))?;
+                        }
+                        "UINT32" => {
+                            let int_value = raw.round();
+                            if int_value < 0.0 || int_value > u32::MAX as f64 {
+                                return Err(format!("Wert außerhalb UINT32-Bereich für '{}': {}", name, numeric_value));
+                            }
+                            let val = int_value as u32;
+                            let high = ((val >> 16) & 0xFFFF) as u16;
+                            let low = (val & 0xFFFF) as u16;
+                            client
+                                .write_multiple_registers(reg.addr, &[high, low])
+                                .await
+                                .map_err(|e| format!("Holding Register (UINT32) schreiben fehlgeschlagen: {}", e))?;
+                        }
+                        _ => {
+                            let int_value = raw.round();
+                            if int_value < 0.0 || int_value > u16::MAX as f64 {
+                                return Err(format!("Wert außerhalb UINT16-Bereich für '{}': {}", name, numeric_value));
+                            }
+                            client
+                                .write_multiple_registers(reg.addr, &[int_value as u16])
+                                .await
+                                .map_err(|e| format!("Holding Register schreiben fehlgeschlagen: {}", e))?;
+                        }
+                    }
+                    Ok(())
+                });
+            }
+        }
+    }
+
+    Err(format!("Kein schreibbares Modbus-Mapping für '{}' gefunden", name))
+}
+
+fn parse_bool_payload(payload: &str) -> Result<bool, String> {
+    match payload.trim().to_ascii_lowercase().as_str() {
+        "1" | "true" | "on" => Ok(true),
+        "0" | "false" | "off" => Ok(false),
+        _ => Err(format!("Ungültiger bool-Wert '{}', erwartet 0/1 oder true/false", payload)),
+    }
+}
+
 /// Startet einen Thread, der zyklisch Modbus-Register abfragt und ModbusValueMaps aktualisiert
 pub fn start_modbus_polling_thread(
     modbus_config: &ModbusConfig,
diff --git a/src/mqtt.rs b/src/mqtt.rs
index 0610dc4..61cf3f4 100644
--- a/src/mqtt.rs
+++ b/src/mqtt.rs
@@ -1,8 +1,11 @@
 use std::sync::{Arc, Mutex};
+use std::process;
+use std::collections::HashMap;
 use std::thread;
-use std::time::Duration;
+use std::time::{Duration, Instant};
 use crate::config::{AppConfig, ModbusValueMaps};
-use rumqttc::{MqttOptions, Client, QoS};
+use crate::modbus;
+use rumqttc::{Event, MqttOptions, Packet, Client, QoS, RecvTimeoutError};
 
 pub fn start_mqtt_thread(config: Arc<Mutex<AppConfig>>, values: Arc<Mutex<ModbusValueMaps>>) {
     let mqtt_config = {
@@ -12,59 +15,182 @@ pub fn start_mqtt_thread(config: Arc<Mutex<AppConfig>>, values: Arc<Mutex<Modbus
     let broker = if mqtt_config.broker.is_empty() { "localhost".to_string() } else { mqtt_config.broker.clone() };
     let port = if mqtt_config.port == 0 { 1883 } else { mqtt_config.port };
     let path = if let Some(ref p) = mqtt_config.path { p.clone() } else { "paramod/values".to_string() };
+    let leitsystem_path = mqtt_config
+        .leitsystem_path
+        .clone()
+        .unwrap_or_else(|| format!("{}/leitsystem", path));
+    let set_write_interval = Duration::from_millis(mqtt_config.set_write_interval_ms.unwrap_or(2000).max(100));
     let user = mqtt_config.user.clone().unwrap_or_default();
     let password = mqtt_config.password.clone().unwrap_or_default();
     let user_is_empty = user.is_empty();
 
     thread::spawn(move || {
-        let mut mqttoptions = MqttOptions::new("paramod-client", broker, port);
+        let client_id = format!("paramod-client-{}", process::id());
+        let mut mqttoptions = MqttOptions::new(client_id, broker, port);
+        mqttoptions.set_keep_alive(Duration::from_secs(5));
         if !user_is_empty {
             mqttoptions.set_credentials(user, password);
         }
         let (mut client, mut connection) = Client::new(mqttoptions, 10);
+
+        let set_topic = format!("{}/+/set", path);
+        if let Err(e) = client.subscribe(set_topic, QoS::AtLeastOnce) {
+            eprintln!("MQTT Subscribe fehlgeschlagen: {}", e);
+        }
+        let leitsystem_state_topic = format!("{}/state", leitsystem_path.trim_end_matches('/'));
+        if let Err(e) = client.subscribe(leitsystem_state_topic.clone(), QoS::AtLeastOnce) {
+            eprintln!("MQTT Subscribe Leitsystem fehlgeschlagen: {}", e);
+        }
+
+        let publish_interval = Duration::from_secs(5);
+        let mut last_publish = Instant::now() - publish_interval;
+        let mut last_set_write = Instant::now() - set_write_interval;
+        let mut pending_set_values: HashMap<String, String> = HashMap::new();
+        let mut leitsystem_enabled = false;
+
         loop {
-            {
-                let values = values.lock().unwrap();
-                // Input Register
-                for (name, val) in &values.modbus_input_register_values {
-                    if let Some(v) = val {
-                        if should_publish(&config, name, "input_register") {
-                            let topic = format!("{}/{}/state", path, name);
-                            let payload = format!("{}", v);
-                            let _ = client.publish(topic, QoS::AtLeastOnce, false, payload);
+            if last_publish.elapsed() >= publish_interval {
+                {
+                    let values = values.lock().unwrap();
+                    // Input Register
+                    for (name, val) in &values.modbus_input_register_values {
+                        if let Some(v) = val {
+                            if should_publish(&config, name, "input_register") {
+                                let topic = format!("{}/{}/state", path, name);
+                                let payload = format!("{}", v);
+                                let _ = client.publish(topic, QoS::AtLeastOnce, false, payload);
+                            }
+                        }
+                    }
+                    // Holding Register
+                    for (name, val) in &values.modbus_holding_register_values {
+                        if let Some(v) = val {
+                            if should_publish(&config, name, "holding_register") {
+                                let topic = format!("{}/{}/state", path, name);
+                                let payload = format!("{}", v);
+                                let _ = client.publish(topic, QoS::AtLeastOnce, false, payload);
+                            }
+                        }
+                    }
+                    // Coils
+                    for (name, val) in &values.modbus_coils_values {
+                        if let Some(v) = val {
+                            if should_publish(&config, name, "coils") {
+                                let topic = format!("{}/{}/state", path, name);
+                                let payload = format!("{}", v);
+                                let _ = client.publish(topic, QoS::AtLeastOnce, false, payload);
+                            }
                         }
                     }
                 }
-                // Holding Register
-                for (name, val) in &values.modbus_holding_register_values {
-                    if let Some(v) = val {
-                        if should_publish(&config, name, "holding_register") {
-                            let topic = format!("{}/{}/state", path, name);
-                            let payload = format!("{}", v);
-                            let _ = client.publish(topic, QoS::AtLeastOnce, false, payload);
+
+                let state_payload = if leitsystem_enabled { "ON" } else { "OFF" };
+                let _ = client.publish(
+                    leitsystem_state_topic.clone(),
+                    QoS::AtLeastOnce,
+                    true,
+                    state_payload,
+                );
+                last_publish = Instant::now();
+            }
+
+            if last_set_write.elapsed() >= set_write_interval {
+                let cfg = {
+                    let lock = config.lock().unwrap();
+                    lock.clone()
+                };
+
+                if leitsystem_enabled {
+                    for (name, payload) in &pending_set_values {
+                        if let Err(e) = modbus::write_value_by_name(&cfg, name, payload) {
+                            eprintln!("MQTT set -> Modbus Fehler ({}): {}", name, e);
+                        } else {
+                            mirror_set_value(&values, &cfg, name, payload);
                         }
                     }
                 }
-                // Coils
-                for (name, val) in &values.modbus_coils_values {
-                    if let Some(v) = val {
-                        if should_publish(&config, name, "coils") {
-                            let topic = format!("{}/{}/state", path, name);
-                            let payload = format!("{}", v);
-                            let _ = client.publish(topic, QoS::AtLeastOnce, false, payload);
+
+                last_set_write = Instant::now();
+            }
+
+            match connection.recv_timeout(Duration::from_millis(200)) {
+                Ok(Ok(Event::Incoming(Packet::Publish(publish)))) => {
+                    if publish.topic == leitsystem_state_topic {
+                        let payload = String::from_utf8_lossy(&publish.payload).trim().to_string();
+                        match parse_boolish(&payload) {
+                            Some(v) => leitsystem_enabled = v,
+                            None => eprintln!("Ungültiger Leitsystem state '{}', erwartet ON/OFF", payload),
                         }
+                        continue;
                     }
+
+                    if let Ok(name) = extract_name_from_set_topic(&path, &publish.topic) {
+                        let payload = String::from_utf8_lossy(&publish.payload).trim().to_string();
+                        pending_set_values.insert(name.clone(), payload.clone());
+                    }
+                }
+                Ok(Ok(_)) => {}
+                Ok(Err(e)) => {
+                    eprintln!("MQTT Connection Fehler: {}", e);
+                    eprintln!("Hinweis: Häufige Ursache ist eine zweite MQTT-Session mit derselben Client-ID.");
+                }
+                Err(RecvTimeoutError::Timeout) => {}
+                Err(RecvTimeoutError::Disconnected) => {
+                    eprintln!("MQTT Verbindung getrennt (request channel geschlossen)");
+                    thread::sleep(Duration::from_millis(500));
                 }
             }
-            // Handle MQTT connection events
-            for _event in connection.iter().take(1) {
-                // Optionally log or handle events
-            }
-            thread::sleep(Duration::from_secs(5));
         }
     });
 }
 
+fn parse_boolish(payload: &str) -> Option<bool> {
+    match payload.trim().to_ascii_lowercase().as_str() {
+        "1" | "true" | "on" => Some(true),
+        "0" | "false" | "off" => Some(false),
+        _ => None,
+    }
+}
+
+fn mirror_set_value(values: &Arc<Mutex<ModbusValueMaps>>, cfg: &AppConfig, name: &str, payload: &str) {
+    if let Ok(mut maps) = values.lock() {
+        if let Some(ref coils) = cfg.modbus_coils {
+            for map in coils {
+                if map.contains_key(name) {
+                    if let Some(v) = parse_boolish(payload) {
+                        maps.modbus_coils_values.insert(name.to_string(), Some(if v { 1.0 } else { 0.0 }));
+                    }
+                    return;
+                }
+            }
+        }
+
+        if let Some(ref holding) = cfg.modbus_holding_register {
+            for map in holding {
+                if map.contains_key(name) {
+                    if let Ok(v) = payload.parse::<f64>() {
+                        maps.modbus_holding_register_values.insert(name.to_string(), Some(v));
+                    }
+                    return;
+                }
+            }
+        }
+    }
+}
+
+fn extract_name_from_set_topic(base_path: &str, topic: &str) -> Result<String, String> {
+    let prefix = format!("{}/", base_path.trim_end_matches('/'));
+    if !topic.starts_with(&prefix) || !topic.ends_with("/set") {
+        return Err("Topic passt nicht zum /set-Schema".to_string());
+    }
+    let without_prefix = &topic[prefix.len()..];
+    let name = without_prefix.strip_suffix("/set").unwrap_or_default();
+    if name.is_empty() || name.contains('/') {
+        return Err("Ungültiger Variablenname im Topic".to_string());
+    }
+    Ok(name.to_string())
+}
+
 fn should_publish(config: &Arc<Mutex<AppConfig>>, name: &str, reg_type: &str) -> bool {
     let cfg = config.lock().unwrap();
     match reg_type {
diff --git a/static/settings.js b/static/settings.js
index 9e74e57..4d8f823 100644
--- a/static/settings.js
+++ b/static/settings.js
@@ -55,7 +55,8 @@ async function saveSettings() {
         user: document.getElementById('mqtt_user').value || null,
         password: document.getElementById('mqtt_password').value || null,
         path: document.getElementById('mqtt_path')?.value || null,
-        button_circulation: document.getElementById('mqtt_button_circulation').value || null
+        leitsystem_path: document.getElementById('mqtt_leitsystem_path')?.value || null,
+        set_write_interval_ms: parseInt(document.getElementById('mqtt_set_write_interval_ms')?.value, 10) || 2000
     };
 
     // InfluxDB
diff --git a/templates/settings.html b/templates/settings.html
index 0fa8b91..eba102e 100644
--- a/templates/settings.html
+++ b/templates/settings.html
@@ -98,8 +98,12 @@
                 <input type="text" id="mqtt_path" class="text-input" value="{{ mqtt.path | default(value="") }}" />
             </div>
             <div class="form-group">
-                <label for="mqtt_button_circulation">Button Circulation:</label>
-                <input type="text" id="mqtt_button_circulation" class="text-input" value="{{ mqtt.button_circulation | default(value="") }}" />
+                <label for="mqtt_leitsystem_path">Leitsystem Pfad:</label>
+                <input type="text" id="mqtt_leitsystem_path" class="text-input" value="{{ mqtt.leitsystem_path | default(value="") }}" />
+            </div>
+            <div class="form-group">
+                <label for="mqtt_set_write_interval_ms">Set-Sendeintervall (ms):</label>
+                <input type="number" min="100" id="mqtt_set_write_interval_ms" class="text-input" value="{{ mqtt.set_write_interval_ms | default(value="2000") }}" />
             </div>
         </div>