diff --git a/CHANGELOG_LATEST.md b/CHANGELOG_LATEST.md
index fffbdbcf8..183e01c9c 100644
--- a/CHANGELOG_LATEST.md
+++ b/CHANGELOG_LATEST.md
@@ -7,11 +7,13 @@ For more details go to [docs.emsesp.org](https://docs.emsesp.org/).
 ## Added
 
 - analogsensor types: NTC and RGB-Led
-- Flag for HMC310
+- Flag for HMC310 [#2465](https://github.com/emsesp/EMS-ESP32/issues/2465)
+- boiler auxheatersource [#2489](https://github.com/emsesp/EMS-ESP32/discussions/2489)
 
 ## Fixed
 
 - dhw/switchtime [#2490](https://github.com/emsesp/EMS-ESP32/issues/2490)
+- switch to secure mqtt [#2492](https://github.com/emsesp/EMS-ESP32/issues/2492)
 
 ## Changed
 
diff --git a/src/core/locale_common.h b/src/core/locale_common.h
index a3cca81ce..2718db83f 100644
--- a/src/core/locale_common.h
+++ b/src/core/locale_common.h
@@ -369,6 +369,7 @@ MAKE_ENUM(enum_lowNoiseMode, FL_(off), FL_(reduced_output), FL_(switchoff), FL_(
 MAKE_ENUM(enum_hpactivity, FL_(off), FL_(heating), FL_(cooling), FL_(hot_water), FL_(pool), FL_(pool_heating), FL_(defrost), FL_(compressor_alarm)) // BV name COMPRESSOR_E21_STATUS
 MAKE_ENUM(enum_silentMode, FL_(off), FL_(auto), FL_(on))
 MAKE_ENUM(enum_4way, FL_(cool_defrost), FL_(heat_ww))
+MAKE_ENUM(enum_auxHeaterSource, FL_(not_installed), FL_(el_heater), FL_(exclusive), FL_(parallel), FL_(hybrid))
 
 // solar
 MAKE_ENUM(enum_solarmode, FL_(constant), FL_(pwm), FL_(analog))
diff --git a/src/core/locale_translations.h b/src/core/locale_translations.h
index 87b45a9ad..0c4d896ea 100644
--- a/src/core/locale_translations.h
+++ b/src/core/locale_translations.h
@@ -231,6 +231,11 @@ MAKE_WORD_TRANSLATION(perm, "perm. reduced", "perm. reduziert", "permanent gered
 MAKE_WORD_TRANSLATION(heat_ww, "heating & dhw", "Heizen & Warmwasser", "", "Uppvärmning & Varmvatten", "ogrzewanie i c.w.u.", "", "", "", "", "kúrenie a TÚV", "topení a TUV")
 MAKE_WORD_TRANSLATION(cool_defrost, "cooling & defrost", "Kühlen & Abtauen", "", "Kyla & Avfrostning", "chłodzenie i odladzanie", "", "", "", "", "chladenie a rozmrazovanie", "chlazení a odmrazování")
 MAKE_WORD_TRANSLATION(compressor_alarm, "compressor alarm", "Alarm Kompressor", "", "", "", "", "", "", "", "alarm kompresora", "")
+MAKE_WORD_TRANSLATION(not_installed, "not installed", "Nicht installiert") // TODO translate
+MAKE_WORD_TRANSLATION(el_heater, "electric heater", "Elektroheizer") // TODO translate
+MAKE_WORD_TRANSLATION(exclusive, "exclusive", "Exklusiv") // TODO translate
+MAKE_WORD_TRANSLATION(parallel, "parallel", "Parallel") // TODO translate
+MAKE_WORD_TRANSLATION(hybrid, "hybrid", "Hybrid") // TODO translate
 
 // thermostat
 MAKE_WORD_TRANSLATION(seltemp, "selTemp", "Solltemperatur", "doeltemperatuur", "Börtemperatur", "temperatura zadana", "innstilt temperatur", "consigne température", "ayarlanmış sıcaklık", "temperatura di consegna", "zadaná teplota", "zvolená teplota")
@@ -483,7 +488,7 @@ MAKE_TRANSLATION(wwEcoPlusStopTemp, "ecoplusstop", "eco+ stop temp", "ECO+ Stopp
 MAKE_TRANSLATION(auxHeatMode, "auxheatrmode", "aux heater mode", "Zusatzheizungsmodus", "Modus bijverwarmer", "Eltillskott Läge", "tryb pracy dogrzewacza po blokadzie z Zakładu Energetycznego", "tilleggsvarmer modus", "", "ilave ısıtıcı modu", "modalità riscaldatore addizionale", "režim pomocného ohrievača", "režim pomocného topení") // TODO translate
 MAKE_TRANSLATION(auxMaxLimit, "auxmaxlimit", "aux heater max limit", "Zusatzheizer max. Grenze", "Bijverwarmer grensinstelling maximaal", "Eltillskott max begränsning", "dogrzewacz, maksymalny limit", "tillegsvarme maksgrense", "ilave ısıtıcı maks limit", "limite massimo riscaldatore addizionale", "maximálny limit pomocného ohrievača", "maximální limit pomocného topení")
 MAKE_TRANSLATION(auxLimitStart, "auxlimitstart", "aux heater limit start", "Zusatzheizer Grenze Start", "Bijverwarmer grens voor start", "Eltillskott begränsningsstart", "dogrzewacz, początek ograniczenia", "tillegsvarme startgrense", "ilave ısıtıcı limir başlangıcı", "avvio limite massimo riscaldatore addizionale", "spustenie limitu pomocného ohrievača", "startovací limit pomocného topení")
-MAKE_TRANSLATION(manDefrost, "mandefrost", "manual defrost", "Manuelle Enteisung", "Handmatige ontdooicyclus", "Manuell avfrostning", "ręczne odladzanie", "manuell avisning", "", "manuel buz çözme", "sbrinamento manuale", "manuálne odmrazovanie", "ruční odmrazování") // TODO translate
+MAKE_TRANSLATION(auxHeaterSource, "auxheatersource", "aux heater source", "Quelle Zusatzheizer") // TODO translate
 MAKE_TRANSLATION(pvCooling, "pvcooling", "cooling only with PV", "Kühlen nur mit PV", "Koelen alleen met solar PV", "Kyla endast med solpanel", "chłodzenie tylko z PV", "kjøling med solpanel", "", "sadece PV ile soğutma", "solo raffrescamento con solare", "Chladenie len s FV", "chlazení pouze s FV") // TODO translate
 MAKE_TRANSLATION(hpCircPumpWw, "hpcircpump", "circulation pump available during dhw", "Zirkulation möglich bei WW-Bereitung", "Circulatiepomp WP beschikbaar tijdens ww", "Värmebärarpump på vid varmvattenberedning", "pompa cyrkulacji dostępna w trakcie c.w.u.", "sirkulasjonspumpe tilgjengelig under varmtvann", "", "SKS esnasında sirkülasyon pompasu uygun", "pompa di circolazione disponibile durante ACS", "obehové čerpadlo k dispozícii počas TÚV", "oběhové čerpadlo dostupné během TUV") // TODO translate
 MAKE_TRANSLATION(vp_cooling, "vpcooling", "valve/pump cooling", "Ventil/Pumpe für Kühlen", "Klep koeling", "Ventil/Pump kyla", "zawór/pompa chłodzenia", "varmepumpe kjøling", "", "vana/pompa soğuyor", "valvola/pompa raffrescamento", "chladenie ventilu/čerpadla", "ventil/čerpadlo chlazení") // TODO translate
diff --git a/src/core/modbus_entity_parameters.hpp b/src/core/modbus_entity_parameters.hpp
index ca33612ac..3b1e5e2d1 100644
--- a/src/core/modbus_entity_parameters.hpp
+++ b/src/core/modbus_entity_parameters.hpp
@@ -127,7 +127,7 @@ const std::initializer_list<Modbus::EntityModbusInfo> Modbus::modbus_register_ma
     REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpIn4Opt), 198, 8), // hpin4opt
     REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(maxHeatComp), 206, 1), // maxheatcomp
     REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(maxHeatHeat), 207, 1), // maxheatheat
-    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(manDefrost), 208, 1), // mandefrost
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(auxHeaterSource), 208, 1), // auxheatersource
     REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(pvCooling), 209, 1), // pvcooling
     REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(auxHeaterOnly), 210, 1), // auxheateronly
     REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(auxHeaterOff), 211, 1), // auxheateroff
diff --git a/src/devices/boiler.cpp b/src/devices/boiler.cpp
index 56421036e..956adfc25 100644
--- a/src/devices/boiler.cpp
+++ b/src/devices/boiler.cpp
@@ -675,7 +675,13 @@ Boiler::Boiler(uint8_t device_type, int8_t device_id, uint8_t product_id, const
                               FL_(maxHeatDhw),
                               DeviceValueUOM::NONE,
                               MAKE_CF_CB(set_maxHeatDhw));
-        register_device_value(DeviceValueTAG::TAG_DEVICE_DATA, &manDefrost_, DeviceValueType::BOOL, FL_(manDefrost), DeviceValueUOM::NONE, MAKE_CF_CB(set_manDefrost));
+        register_device_value(DeviceValueTAG::TAG_DEVICE_DATA,
+                              &auxHeaterSource_,
+                              DeviceValueType::ENUM,
+                              FL_(enum_auxHeaterSource),
+                              FL_(auxHeaterSource),
+                              DeviceValueUOM::NONE,
+                              MAKE_CF_CB(set_auxHeaterSource));
         register_device_value(DeviceValueTAG::TAG_DEVICE_DATA, &pvCooling_, DeviceValueType::BOOL, FL_(pvCooling), DeviceValueUOM::NONE, MAKE_CF_CB(set_pvCooling));
         register_device_value(DeviceValueTAG::TAG_DEVICE_DATA,
                               &auxHeaterOnly_,
@@ -2004,7 +2010,7 @@ void Boiler::process_HpPump2(std::shared_ptr<const Telegram> telegram) {
 
 // Boiler(0x08) -> All(0x00), ?(0x0491), data: 03 01 00 00 00 02 64 00 00 14 01 2C 00 0A 00 1E 00 1E 00 00 1E 0A 1E 05 05
 void Boiler::process_HpAdditionalHeater(std::shared_ptr<const Telegram> telegram) {
-    has_update(telegram, manDefrost_, 0); // off/on
+    has_update(telegram, auxHeaterSource_, 0); // https://github.com/emsesp/EMS-ESP32/discussions/2489
     has_update(telegram, auxHeaterOnly_, 1);
     has_update(telegram, auxHeaterOff_, 2);
     has_update(telegram, auxHeatMode_, 4); // eco/comfort
@@ -3085,9 +3091,9 @@ bool Boiler::set_auxLimit(const char * value, const int8_t id) {
     return false;
 }
 
-bool Boiler::set_manDefrost(const char * value, const int8_t id) {
-    bool v;
-    if (Helpers::value2bool(value, v)) {
+bool Boiler::set_auxHeaterSource(const char * value, const int8_t id) {
+    uint8_t v;
+    if (Helpers::value2enum(value, v, FL_(enum_auxHeaterSource))) {
         write_command(0x491, 0, v ? 1 : 0, 0x491);
         return true;
     }
diff --git a/src/devices/boiler.h b/src/devices/boiler.h
index e8783aa0d..694374e32 100644
--- a/src/devices/boiler.h
+++ b/src/devices/boiler.h
@@ -259,10 +259,10 @@ class Boiler : public EMSdevice {
     uint8_t powerReduction_;
 
     uint8_t  pvCooling_;
-    uint8_t  manDefrost_;
     uint8_t  auxHeatMode_;
     uint8_t  auxMaxLimit_;
     uint8_t  auxLimitStart_;
+    uint8_t  auxHeaterSource_;
     uint8_t  auxHeaterOnly_;
     uint8_t  auxHeaterOff_;
     uint8_t  auxHeaterStatus_;
@@ -475,7 +475,7 @@ class Boiler : public EMSdevice {
     bool set_additionalHeaterDelay(const char * value, const int8_t id);
     bool set_tempParMode(const char * value, const int8_t id);
     bool set_auxHeatMode(const char * value, const int8_t id);
-    bool set_manDefrost(const char * value, const int8_t id);
+    bool set_auxHeaterSource(const char * value, const int8_t id);
     bool set_pvCooling(const char * value, const int8_t id);
     bool set_hpCircPumpWw(const char * value, const int8_t id);
     bool set_hpPumpMode(const char * value, const int8_t id);
diff --git a/src/version.h b/src/version.h
index 06be1ce7a..4cedd7c62 100644
--- a/src/version.h
+++ b/src/version.h
@@ -1 +1 @@
-#define EMSESP_APP_VERSION "3.7.3-dev.2"
+#define EMSESP_APP_VERSION "3.7.3-dev.3"