diff --git a/storage-heater.yaml b/storage-heater.yaml
index b789f3a..0b817b1 100644
--- a/storage-heater.yaml
+++ b/storage-heater.yaml
@@ -8,22 +8,13 @@ esphome:
 packages:
   device_base: !include templates/mystrom.yaml
 
-globals:
-- id: heater_was_on_previous_interval
-  type: bool
-  restore_value: no
-  initial_value: "false"
-
-interval:
-- interval: 3hours
-  then:
-    # Turn off the heater if it's on for 3-6 hours in a row.
-    lambda: |-
-      if (id(mystrom_relay).state) {
-        if (id(heater_was_on_previous_interval)) {
-          id(mystrom_relay).turn_off();
-        }
-        id(heater_was_on_previous_interval) = true;
-      } else {
-        id(heater_was_on_previous_interval) = false;
-      }
+sensor:
+- platform: duty_time
+  id: row_heating_time
+  name: Row heating time
+  lambda: "return id(mystrom_relay).state;"
+  on_value_range:
+    above: 18000 # 5h
+    then:
+    - switch.turn_off: mystrom_relay
+    - sensor.duty_time.reset: row_heating_time