diff --git a/CHANGELOG.md b/CHANGELOG.md
index b2ed4dc3d..9abc2314f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -18,6 +18,7 @@ All notable changes to this project will be documented in this file.
 - Refactored I2C drivers HTU21, BH1750, SHT3x, iAQ and HYT
 - Add command entered to command error and command unknown message
 - ESP32 platform update from 2024.08.11 to 2024.09.10 and Framework (Arduino Core) from v3.0.4 to v3.0.5 (#22163)
+- SCD30 Lowered I2C clock from 100k to 50k (#15438)
 
 ### Fixed
 - Shutter missing HOLD on shutterbutton (#22108)
diff --git a/RELEASENOTES.md b/RELEASENOTES.md
index 5da816b04..4511b678e 100644
--- a/RELEASENOTES.md
+++ b/RELEASENOTES.md
@@ -148,6 +148,7 @@ The latter links can be used for OTA upgrades too like ``OtaUrl https://ota.tasm
 - Energy BL09xx command ``CurrentSet`` input changed from Ampere to milliAmpere
 - Energy force Apparent Power equals Active Power when (Calculated) Apparent Power is less than Active Power [#20653](https://github.com/arendst/Tasmota/issues/20653)
 - Refactored I2C drivers HTU21, BH1750, SHT3x, iAQ and HYT
+- SCD30 Lowered I2C clock from 100k to 50k [#15438](https://github.com/arendst/Tasmota/issues/15438)
 
 ### Fixed
 - Crash when calling TasmotaSerial destructor when initialized with incorrect arguments [#22036](https://github.com/arendst/Tasmota/issues/22036)
diff --git a/tasmota/tasmota_support/support_a_i2c.ino b/tasmota/tasmota_support/support_a_i2c.ino
index 660ce2fd1..8adabdba1 100644
--- a/tasmota/tasmota_support/support_a_i2c.ino
+++ b/tasmota/tasmota_support/support_a_i2c.ino
@@ -20,8 +20,16 @@ uint32_t i2c_active[2][4] = { 0 };
 #endif
 uint32_t i2c_buffer = 0;
 
+struct I2Ct {
+  uint32_t frequency[2];
+  int8_t sda[2];
+  int8_t scl[2];
+  int8_t active_bus;
+} I2C;
+
 bool I2cBegin(int sda, int scl, uint32_t bus = 0, uint32_t frequency = 100000);
 bool I2cBegin(int sda, int scl, uint32_t bus, uint32_t frequency) {
+  I2C.frequency[bus] = frequency;
   bool result = true;
 #ifdef ESP8266
   Wire.begin(sda, scl);
@@ -51,6 +59,24 @@ TwoWire& I2cGetWire(uint8_t bus = 0) {
   }
 }
 
+bool I2cSetClock(uint32_t frequency = 0, uint32_t bus = 0);
+bool I2cSetClock(uint32_t frequency, uint32_t bus) {
+  TwoWire& myWire = I2cGetWire(bus);
+  if (&myWire == nullptr) { return false; }               // No valid I2c bus
+
+  if (0 == frequency) {
+    if (0 == I2C.frequency[bus]) {
+      I2C.frequency[bus] = 100000;                        // Tasmota default I2C bus speed
+    }
+  } else {
+    I2C.frequency[bus] = frequency;
+  }
+  if (frequency != I2C.frequency[bus]) {
+    myWire.setClock(I2C.frequency[bus]);
+  }
+  return true;
+}
+
 /*-------------------------------------------------------------------------------------------*\
  * Return code: 0 = Error, 1 = OK
 \*-------------------------------------------------------------------------------------------*/
diff --git a/tasmota/tasmota_xsns_sensor/xsns_42_scd30.ino b/tasmota/tasmota_xsns_sensor/xsns_42_scd30.ino
index f67416bd2..cd4bf9d2d 100644
--- a/tasmota/tasmota_xsns_sensor/xsns_42_scd30.ino
+++ b/tasmota/tasmota_xsns_sensor/xsns_42_scd30.ino
@@ -69,26 +69,31 @@ struct {
 } Scd30;
 
 void Scd30Detect(void) {
-  if (!I2cSetDevice(SCD30_ADDRESS)) { return; }
+  I2cSetClock(50000);
+  if (I2cSetDevice(SCD30_ADDRESS)) { 
+    scd30.begin();
 
-  scd30.begin();
+    uint8_t major = 0;
+    uint8_t minor = 0;
+    if (!scd30.getFirmwareVersion(&major, &minor)) { 
+      if (!scd30.getMeasurementInterval(&Scd30.interval)) { 
+        if (!scd30.beginMeasuring()) { 
+          I2cSetActiveFound(SCD30_ADDRESS, "SCD30");
+          Scd30.found = true;
 
-  uint8_t major = 0;
-  uint8_t minor = 0;
-  if (scd30.getFirmwareVersion(&major, &minor)) { return; }
-  if (scd30.getMeasurementInterval(&Scd30.interval)) { return; }
-  if (scd30.beginMeasuring()) { return; }
-
-  I2cSetActiveFound(SCD30_ADDRESS, "SCD30");
-  Scd30.found = true;
-
-//  AddLog(LOG_LEVEL_DEBUG, PSTR("SCD: FW v%d.%d"), major, minor);
+//          AddLog(LOG_LEVEL_DEBUG, PSTR("SCD: FW v%d.%d"), major, minor);
+        }
+      }
+    }
+  }
+  I2cSetClock();
 }
 
 // gets data from the sensor every 3 seconds or so to give the sensor time to gather new data
 void Scd30Update(void) {
   Scd30.loop_count++;
   if (Scd30.loop_count > (Scd30.interval - 1)) {
+    I2cSetClock(50000);
     uint32_t error = 0;
     switch (Scd30.error_state) {
       case SCD30_STATE_NO_ERROR: {
@@ -129,7 +134,8 @@ void Scd30Update(void) {
 #ifdef SCD30_DEBUG
             AddLog(LOG_LEVEL_ERROR, PSTR("SCD30: Update: ReadMeasurement error: 0x%lX, counter: %ld"), error, Scd30.loop_count);
 #endif
-             return;
+            I2cSetClock();
+            return;
           }
           break;
         }
@@ -200,6 +206,7 @@ void Scd30Update(void) {
         Scd30.error_state = SCD30_STATE_ERROR_SOFT_RESET; // try again
       }
     }
+    I2cSetClock();
 
     if (Scd30.loop_count > (SCD30_MAX_MISSED_READS * Scd30.interval)) {
       Scd30.data_valid = false;
@@ -213,41 +220,49 @@ void Scd30Update(void) {
 
 void CmndScd30Altitude(void) {
   uint16_t value = 0;
+  I2cSetClock(50000);
   if (XdrvMailbox.data_len > 0) {
     value = XdrvMailbox.payload;
     scd30.setAltitudeCompensation(value);
   } else {
     scd30.getAltitudeCompensation(&value);
   }
+  I2cSetClock();
   ResponseCmndNumber(value);
 };
 
 void CmndScd30AutoMode(void) {
   uint16_t value = 0;
+  I2cSetClock(50000);
   if (XdrvMailbox.data_len > 0) {
     value = XdrvMailbox.payload;
     scd30.setCalibrationType(value);
   } else {
     scd30.getCalibrationType(&value);
   }
+  I2cSetClock();
   ResponseCmndNumber(value);
 };
 
 void CmndScd30Calibrate(void) {
   uint16_t value = 0;
+  I2cSetClock(50000);
   if (XdrvMailbox.data_len > 0) {
     value = XdrvMailbox.payload;
     scd30.setForcedRecalibrationFactor(value);
   } else {
     scd30.getForcedRecalibrationFactor(&value);
   }
+  I2cSetClock();
   ResponseCmndNumber(value);
 };
 
 void CmndScd30Firmware(void) {
   uint8_t major = 0;
   uint8_t minor = 0;
+  I2cSetClock(50000);
   int error = scd30.getFirmwareVersion(&major, &minor);
+  I2cSetClock();
   if (!error) {
     float firmware = major + ((float)minor / 100);
     ResponseCmndFloat(firmware, 2);
@@ -256,6 +271,7 @@ void CmndScd30Firmware(void) {
 
 void CmndScd30Interval(void) {
   uint16_t value = 0;
+  I2cSetClock(50000);
   if (XdrvMailbox.data_len > 0) {
     value = XdrvMailbox.payload;
     int error = scd30.setMeasurementInterval(value);
@@ -264,28 +280,33 @@ void CmndScd30Interval(void) {
     }
   }
   scd30.getMeasurementInterval(&value);
+  I2cSetClock();
   ResponseCmndNumber(value);
 };
 
 void CmndScd30Pressure(void) {
   uint16_t value = 0;
+  I2cSetClock(50000);
   if (XdrvMailbox.data_len > 0) {
     value = XdrvMailbox.payload;
     scd30.setAmbientPressure(value);
   } else {
     scd30.getAmbientPressure(&value);
   }
+  I2cSetClock();
   ResponseCmndNumber(value);
 };
 
 void CmndScd30TempOffset(void) {
   uint16_t value = 0;
+  I2cSetClock(50000);
   if (XdrvMailbox.data_len > 0) {
     value = XdrvMailbox.payload;
     scd30.setTemperatureOffset(value);
   } else {
     scd30.getTemperatureOffset(&value);
   }
+  I2cSetClock();
   ResponseCmndNumber(value);
 };