diff --git a/itho-wpu.py b/itho-wpu.py
index 59bd02f..79c7f94 100755
--- a/itho-wpu.py
+++ b/itho-wpu.py
@@ -26,6 +26,7 @@ actions = {
     "getsetting": [0xA4, 0x10],
     "setsetting": [0xA4, 0x10],
     "getmanual": [0x40, 0x30],
+    "setmanual": [0x40, 0x30],
 }
 
 
@@ -454,6 +455,46 @@ def process_manual(response, wpu):
     )
 
 
+def process_setmanual(wpu, args):
+    logger.info("Current manual operation:")
+    response = wpu.get("getmanual", int(args.id))
+    if response is None:
+        return
+    process_response("getmanual", response, args, wpu)
+    message = response[5:]
+    datatype = message[3]
+
+    # TODO: check if Max Handbedieningstijd > 0
+
+    if args.value is None:
+        value = input("Provide a new value: ")
+    else:
+        value = args.value
+
+    # TODO: add support for negative values
+    if float(value) < 0:
+        logger.error("Negative values are not supported yet.")
+        return
+
+    logger.debug(f"New manual operation datatype: {datatype}")
+    logger.debug(f"New manual operation (input): {value}")
+    normalized_value = int(value.replace(".", ""))
+    logger.debug(f"New manual operation (normalized): {normalized_value}")
+    hex_list_value = [hex(v) for v in list(normalized_value.to_bytes(2, byteorder="big"))]
+    logger.debug(f"New manual operation (hex): {hex_list_value}")
+    parsed_value = format_datatype(args.id, hex_list_value, datatype)
+    logger.debug(f"New manual operation (parsed): {parsed_value}")
+
+    sure = input(f"Manual `{args.id}` will be changed to `{parsed_value}`? [y/N] ")
+    if sure in ["y", "Y"]:
+        logger.info(f"Updating manual operation {args.id} to `{parsed_value}`")
+    else:
+        logger.error("Aborted")
+        return
+
+    response = wpu.get("setmanual", args.id, normalized_value)
+
+
 def format_datatype(name, m, dt):
     """
     Transform a list of bytes to a readable number based on the datatype.
@@ -534,7 +575,7 @@ def main():
             logging.Formatter("%(asctime)-15s %(levelname)s: %(message)s")
         )
 
-    if args.action in ["getsetting", "setsetting", "getmanual"] and args.id is None:
+    if args.action in ["getsetting", "setsetting", "getmanual", "setmanual"] and args.id is None:
         logger.error(f"`--id` is required with `--action {args.action}`")
         return
 
@@ -548,6 +589,10 @@ def main():
         process_setsetting(wpu, args)
         return
 
+    if args.action == "setmanual":
+        process_setmanual(wpu, args)
+        return
+
     response = wpu.get(args.action, args.id)
     if response is not None:
         process_response(args.action, response, args, wpu)
diff --git a/itho_i2c.py b/itho_i2c.py
index aa5986d..04db68c 100644
--- a/itho_i2c.py
+++ b/itho_i2c.py
@@ -20,6 +20,7 @@ actions = {
     "getsetting": [0xA4, 0x10],
     "setsetting": [0xA4, 0x10],
     "getmanual": [0x40, 0x30],
+    "setmanual": [0x40, 0x30],
 }
 
 
@@ -87,6 +88,19 @@ class I2CMaster:
                 + byte_identifier
                 + [0x01]  # 1 = manual
             )
+        elif action == "setmanual":
+            byte_identifier = list(identifier.to_bytes(2, byteorder="big"))
+            byte_list_value = list(value.to_bytes(2, byteorder="big"))
+            request = (
+                [0x80]
+                + actions[action]
+                + [0x06, 0x07]  # write, length
+                + [0x01]  # bank
+                + byte_identifier
+                + [0x00]  # datatype
+                + byte_list_value  # new
+                + [0x01]  # 1 = manual
+            )
         else:
             # 0x80 = source, 0x04 = msg_type, 0x00 = length
             request = [0x80] + actions[action] + [0x04, 0x00]
@@ -107,7 +121,7 @@ class I2CMaster:
         request_in_hex = [hex(c) for c in request]
         logger.debug(f"Request: {request_in_hex}")
         result = None
-        if action == "setsetting":
+        if action in ["setsetting", "setmanual"]:
             sure = input("Are you really sure? (Type uppercase yes): ")
             if sure != "YES":
                 logger.error("Aborted")
@@ -120,6 +134,8 @@ class I2CMaster:
             if self.queue.qsize() > 0:
                 result = self.queue.get()
                 break
+            elif action == "setmanual" and self.queue.qsize() == 0:
+                return None
 
         if result is None:
             logger.error("No valid result in 20 requests")