diff --git a/src/emsdevice.cpp b/src/emsdevice.cpp
index a23efce2d..6851ed9e4 100644
--- a/src/emsdevice.cpp
+++ b/src/emsdevice.cpp
@@ -42,7 +42,7 @@ static const __FlashStringHelper * DeviceValueUOM_s[] __attribute__((__aligned__
 static const __FlashStringHelper * const DeviceValueTAG_s[] PROGMEM = {
 
     F_(tag_none),            // ""
-    F_(tag_system_data),     // ""
+    F_(tag_heartbeat),       // ""
     F_(tag_boiler_data),     // ""
     F_(tag_boiler_data_ww),  // "warm water"
     F_(tag_thermostat_data), // ""
@@ -61,7 +61,7 @@ static const __FlashStringHelper * const DeviceValueTAG_s[] PROGMEM = {
 static const __FlashStringHelper * const DeviceValueTAG_mqtt[] PROGMEM = {
 
     F_(tag_none),                // ""
-    F_(tag_system_data_mqtt),    // "heartbeat"
+    F_(tag_heartbeat_mqtt),      // "heartbeat"
     F_(tag_boiler_data_mqtt),    // ""
     F_(tag_boiler_data_ww_mqtt), // "ww"
     F_(tag_thermostat_data),     // ""
diff --git a/src/emsdevice.h b/src/emsdevice.h
index cd6b04b98..6d7cf71c7 100644
--- a/src/emsdevice.h
+++ b/src/emsdevice.h
@@ -71,7 +71,7 @@ enum DeviceValueUOM : uint8_t { NONE = 0, DEGREES, PERCENT, LMIN, KWH, WH, HOURS
 // TAG mapping - maps to DeviceValueTAG_s in emsdevice.cpp
 // use empty string if want to suppress showing tags
 MAKE_PSTR(tag_none, "")
-MAKE_PSTR(tag_system_data, "")
+MAKE_PSTR(tag_heartbeat, "")
 MAKE_PSTR(tag_boiler_data, "")
 MAKE_PSTR(tag_boiler_data_ww, "warm water")
 MAKE_PSTR(tag_thermostat_data, "")
@@ -85,13 +85,13 @@ MAKE_PSTR(tag_wwc3, "wwc3")
 MAKE_PSTR(tag_wwc4, "wwc4")
 
 // MQTT topic names
-MAKE_PSTR(tag_system_data_mqtt, "heartbeat")
+MAKE_PSTR(tag_heartbeat_mqtt, "heartbeat")
 MAKE_PSTR(tag_boiler_data_mqtt, "")
 MAKE_PSTR(tag_boiler_data_ww_mqtt, "ww")
 
 enum DeviceValueTAG : uint8_t {
     TAG_NONE = 0, // wild card
-    TAG_SYSTEM_DATA,
+    TAG_HEARTBEAT,
     TAG_BOILER_DATA,
     TAG_BOILER_DATA_WW,
     TAG_THERMOSTAT_DATA,
diff --git a/src/mqtt.cpp b/src/mqtt.cpp
index 53bec453d..4f97b4cb6 100644
--- a/src/mqtt.cpp
+++ b/src/mqtt.cpp
@@ -599,16 +599,16 @@ void Mqtt::ha_status() {
     Mqtt::publish_ha(topic, doc.as<JsonObject>()); // publish the config payload with retain flag
 
     // create the sensors
-    publish_mqtt_ha_sensor(DeviceValueType::INT, DeviceValueTAG::TAG_SYSTEM_DATA, F("Wifi strength"), EMSdevice::DeviceType::SYSTEM, F("rssi"));
-    publish_mqtt_ha_sensor(DeviceValueType::INT, DeviceValueTAG::TAG_SYSTEM_DATA, F("Uptime"), EMSdevice::DeviceType::SYSTEM, F("uptime"));
-    publish_mqtt_ha_sensor(DeviceValueType::INT, DeviceValueTAG::TAG_SYSTEM_DATA, F("Uptime (sec)"), EMSdevice::DeviceType::SYSTEM, F("uptime_sec"));
-    publish_mqtt_ha_sensor(DeviceValueType::INT, DeviceValueTAG::TAG_SYSTEM_DATA, F("Free heap memory"), EMSdevice::DeviceType::SYSTEM, F("freemem"));
-    publish_mqtt_ha_sensor(DeviceValueType::INT, DeviceValueTAG::TAG_SYSTEM_DATA, F("# Failed MQTT publishes"), EMSdevice::DeviceType::SYSTEM, F("mqttfails"));
-    publish_mqtt_ha_sensor(DeviceValueType::INT, DeviceValueTAG::TAG_SYSTEM_DATA, F("# Rx Sent"), EMSdevice::DeviceType::SYSTEM, F("rxsent"));
-    publish_mqtt_ha_sensor(DeviceValueType::INT, DeviceValueTAG::TAG_SYSTEM_DATA, F("# Rx Fails"), EMSdevice::DeviceType::SYSTEM, F("rxfails"));
-    publish_mqtt_ha_sensor(DeviceValueType::INT, DeviceValueTAG::TAG_SYSTEM_DATA, F("# Tx Reads"), EMSdevice::DeviceType::SYSTEM, F("txread"));
-    publish_mqtt_ha_sensor(DeviceValueType::INT, DeviceValueTAG::TAG_SYSTEM_DATA, F("# Tx Writes"), EMSdevice::DeviceType::SYSTEM, F("txwrite"));
-    publish_mqtt_ha_sensor(DeviceValueType::INT, DeviceValueTAG::TAG_SYSTEM_DATA, F("# Tx Fails"), EMSdevice::DeviceType::SYSTEM, F("txfails"));
+    publish_mqtt_ha_sensor(DeviceValueType::INT, DeviceValueTAG::TAG_HEARTBEAT, F("Wifi strength"), EMSdevice::DeviceType::SYSTEM, F("rssi"));
+    publish_mqtt_ha_sensor(DeviceValueType::INT, DeviceValueTAG::TAG_HEARTBEAT, F("Uptime"), EMSdevice::DeviceType::SYSTEM, F("uptime"));
+    publish_mqtt_ha_sensor(DeviceValueType::INT, DeviceValueTAG::TAG_HEARTBEAT, F("Uptime (sec)"), EMSdevice::DeviceType::SYSTEM, F("uptime_sec"));
+    publish_mqtt_ha_sensor(DeviceValueType::INT, DeviceValueTAG::TAG_HEARTBEAT, F("Free heap memory"), EMSdevice::DeviceType::SYSTEM, F("freemem"));
+    publish_mqtt_ha_sensor(DeviceValueType::INT, DeviceValueTAG::TAG_HEARTBEAT, F("# Failed MQTT publishes"), EMSdevice::DeviceType::SYSTEM, F("mqttfails"));
+    publish_mqtt_ha_sensor(DeviceValueType::INT, DeviceValueTAG::TAG_HEARTBEAT, F("# Rx Sent"), EMSdevice::DeviceType::SYSTEM, F("rxsent"));
+    publish_mqtt_ha_sensor(DeviceValueType::INT, DeviceValueTAG::TAG_HEARTBEAT, F("# Rx Fails"), EMSdevice::DeviceType::SYSTEM, F("rxfails"));
+    publish_mqtt_ha_sensor(DeviceValueType::INT, DeviceValueTAG::TAG_HEARTBEAT, F("# Tx Reads"), EMSdevice::DeviceType::SYSTEM, F("txread"));
+    publish_mqtt_ha_sensor(DeviceValueType::INT, DeviceValueTAG::TAG_HEARTBEAT, F("# Tx Writes"), EMSdevice::DeviceType::SYSTEM, F("txwrite"));
+    publish_mqtt_ha_sensor(DeviceValueType::INT, DeviceValueTAG::TAG_HEARTBEAT, F("# Tx Fails"), EMSdevice::DeviceType::SYSTEM, F("txfails"));
 }
 
 // add sub or pub task to the queue.
@@ -916,6 +916,7 @@ void Mqtt::publish_mqtt_ha_sensor(uint8_t                     type, // EMSdevice
 // differs based on whether MQTT nested is enabled
 // tag = EMSdevice::DeviceValueTAG
 const std::string Mqtt::tag_to_topic(uint8_t device_type, uint8_t tag) {
+    // the system device is treated differently. The topic is 'heartbeat' and doesn't follow the usual convention
     if (device_type == EMSdevice::DeviceType::SYSTEM) {
         return EMSdevice::tag_to_mqtt(tag);
     }