diff --git a/src/handler/control.rs b/src/handler/control.rs
index 686abcc..46c9f6f 100644
--- a/src/handler/control.rs
+++ b/src/handler/control.rs
@@ -18,6 +18,23 @@ use crate::{
     AppState,
 };
 
+fn validate_unit_timing_order(
+    run_time_sec: i32,
+    acc_time_sec: i32,
+) -> Result<(), ApiErr> {
+    if acc_time_sec <= run_time_sec {
+        return Err(ApiErr::BadRequest(
+            "acc_time_sec must be greater than run_time_sec".to_string(),
+            Some(json!({
+                "run_time_sec": ["must be less than acc_time_sec"],
+                "acc_time_sec": ["must be greater than run_time_sec"]
+            })),
+        ));
+    }
+
+    Ok(())
+}
+
 #[derive(Debug, Deserialize, Validate)]
 pub struct GetUnitListQuery {
     #[validate(length(min = 1, max = 100))]
@@ -293,13 +310,13 @@ pub struct CreateUnitReq {
     pub name: String,
     pub description: Option<String>,
     pub enabled: Option<bool>,
-    #[validate(range(min = 0))]
+    #[validate(range(min = 1, message = "must be greater than 0"))]
     pub run_time_sec: Option<i32>,
-    #[validate(range(min = 0))]
+    #[validate(range(min = 1, message = "must be greater than 0"))]
     pub stop_time_sec: Option<i32>,
-    #[validate(range(min = 0))]
+    #[validate(range(min = 1, message = "must be greater than 0"))]
     pub acc_time_sec: Option<i32>,
-    #[validate(range(min = 0))]
+    #[validate(range(min = 1, message = "must be greater than 0"))]
     pub bl_time_sec: Option<i32>,
     pub require_manual_ack_after_fault: Option<bool>,
 }
@@ -310,6 +327,33 @@ pub async fn create_unit(
 ) -> Result<impl IntoResponse, ApiErr> {
     payload.validate()?;
 
+    let run_time_sec = payload.run_time_sec.ok_or_else(|| {
+        ApiErr::BadRequest(
+            "run_time_sec is required".to_string(),
+            Some(json!({ "run_time_sec": ["is required"] })),
+        )
+    })?;
+    let stop_time_sec = payload.stop_time_sec.ok_or_else(|| {
+        ApiErr::BadRequest(
+            "stop_time_sec is required".to_string(),
+            Some(json!({ "stop_time_sec": ["is required"] })),
+        )
+    })?;
+    let acc_time_sec = payload.acc_time_sec.ok_or_else(|| {
+        ApiErr::BadRequest(
+            "acc_time_sec is required".to_string(),
+            Some(json!({ "acc_time_sec": ["is required"] })),
+        )
+    })?;
+    let bl_time_sec = payload.bl_time_sec.ok_or_else(|| {
+        ApiErr::BadRequest(
+            "bl_time_sec is required".to_string(),
+            Some(json!({ "bl_time_sec": ["is required"] })),
+        )
+    })?;
+
+    validate_unit_timing_order(run_time_sec, acc_time_sec)?;
+
     if crate::service::get_unit_by_code(&state.pool, &payload.code)
         .await?
         .is_some()
@@ -327,10 +371,10 @@ pub async fn create_unit(
             name: &payload.name,
             description: payload.description.as_deref(),
             enabled: payload.enabled.unwrap_or(true),
-            run_time_sec: payload.run_time_sec.unwrap_or(0),
-            stop_time_sec: payload.stop_time_sec.unwrap_or(0),
-            acc_time_sec: payload.acc_time_sec.unwrap_or(0),
-            bl_time_sec: payload.bl_time_sec.unwrap_or(0),
+            run_time_sec,
+            stop_time_sec,
+            acc_time_sec,
+            bl_time_sec,
             require_manual_ack_after_fault: payload
                 .require_manual_ack_after_fault
                 .unwrap_or(true),
@@ -355,13 +399,13 @@ pub struct UpdateUnitReq {
     pub name: Option<String>,
     pub description: Option<String>,
     pub enabled: Option<bool>,
-    #[validate(range(min = 0))]
+    #[validate(range(min = 1, message = "must be greater than 0"))]
     pub run_time_sec: Option<i32>,
-    #[validate(range(min = 0))]
+    #[validate(range(min = 1, message = "must be greater than 0"))]
     pub stop_time_sec: Option<i32>,
-    #[validate(range(min = 0))]
+    #[validate(range(min = 1, message = "must be greater than 0"))]
     pub acc_time_sec: Option<i32>,
-    #[validate(range(min = 0))]
+    #[validate(range(min = 1, message = "must be greater than 0"))]
     pub bl_time_sec: Option<i32>,
     pub require_manual_ack_after_fault: Option<bool>,
 }
@@ -373,12 +417,14 @@ pub async fn update_unit(
 ) -> Result<impl IntoResponse, ApiErr> {
     payload.validate()?;
 
-    if crate::service::get_unit_by_id(&state.pool, unit_id)
+    let existing_unit = crate::service::get_unit_by_id(&state.pool, unit_id)
         .await?
-        .is_none()
-    {
-        return Err(ApiErr::NotFound("Unit not found".to_string(), None));
-    }
+        .ok_or_else(|| ApiErr::NotFound("Unit not found".to_string(), None))?;
+
+    validate_unit_timing_order(
+        payload.run_time_sec.unwrap_or(existing_unit.run_time_sec),
+        payload.acc_time_sec.unwrap_or(existing_unit.acc_time_sec),
+    )?;
 
     if let Some(code) = payload.code.as_deref() {
         let duplicate = crate::service::get_unit_by_code(&state.pool, code).await?;
@@ -627,3 +673,52 @@ pub async fn get_unit_runtime(
     Ok(Json(runtime))
 }
 
+#[cfg(test)]
+mod tests {
+    use super::{validate_unit_timing_order, CreateUnitReq, UpdateUnitReq};
+    use validator::Validate;
+
+    #[test]
+    fn create_unit_req_rejects_zero_second_fields() {
+        let payload = CreateUnitReq {
+            code: "U-01".to_string(),
+            name: "Unit 01".to_string(),
+            description: None,
+            enabled: Some(true),
+            run_time_sec: Some(0),
+            stop_time_sec: Some(10),
+            acc_time_sec: Some(20),
+            bl_time_sec: Some(5),
+            require_manual_ack_after_fault: Some(true),
+        };
+
+        assert!(payload.validate().is_err());
+    }
+
+    #[test]
+    fn create_unit_req_rejects_acc_time_not_greater_than_run_time() {
+        assert!(validate_unit_timing_order(10, 10).is_err());
+    }
+
+    #[test]
+    fn update_unit_req_rejects_zero_second_fields() {
+        let payload = UpdateUnitReq {
+            code: None,
+            name: None,
+            description: None,
+            enabled: None,
+            run_time_sec: None,
+            stop_time_sec: Some(0),
+            acc_time_sec: Some(20),
+            bl_time_sec: Some(5),
+            require_manual_ack_after_fault: None,
+        };
+
+        assert!(payload.validate().is_err());
+    }
+
+    #[test]
+    fn update_unit_req_rejects_acc_time_not_greater_than_run_time_when_both_present() {
+        assert!(validate_unit_timing_order(20, 15).is_err());
+    }
+}
diff --git a/web/js/units.js b/web/js/units.js
index 38bf6f9..6c87bd0 100644
--- a/web/js/units.js
+++ b/web/js/units.js
@@ -34,10 +34,10 @@ export function resetUnitForm() {
   dom.unitId.value = "";
   dom.unitEnabled.checked = true;
   dom.unitManualAck.checked = true;
-  dom.unitRunTimeSec.value = "0";
-  dom.unitStopTimeSec.value = "0";
-  dom.unitAccTimeSec.value = "0";
-  dom.unitBlTimeSec.value = "0";
+  dom.unitRunTimeSec.value = "10";
+  dom.unitStopTimeSec.value = "10";
+  dom.unitAccTimeSec.value = "20";
+  dom.unitBlTimeSec.value = "10";
 }
 
 function openUnitModal() {