diff --git a/usecases/api/cem_ohpcf.go b/usecases/api/cem_ohpcf.go
index 2dbde8e0..1fd930ea 100644
--- a/usecases/api/cem_ohpcf.go
+++ b/usecases/api/cem_ohpcf.go
@@ -71,8 +71,8 @@ type CemOHPCFInterface interface {
 	// scheduled process has not startet yet.
 	//
 	// parameters:
-	//   - start: The start time of the power consumption
-	SchedulePowerConsumptionProcess(entity spineapi.EntityRemoteInterface, start time.Time, resultCB func(result model.ResultDataType)) (*model.MsgCounterType, error)
+	//   - startIn: Delay from now until the power consumption starts (0 = start immediately)
+	SchedulePowerConsumptionProcess(entity spineapi.EntityRemoteInterface, startIn time.Duration, resultCB func(result model.ResultDataType)) (*model.MsgCounterType, error)
 
 	// stop (abort) the process [OHPCF-022/1].
 	AbortPowerConsumptionProcess(entity spineapi.EntityRemoteInterface, resultCB func(result model.ResultDataType)) (*model.MsgCounterType, error)
diff --git a/usecases/cem/ohpcf/events.go b/usecases/cem/ohpcf/events.go
index ebc1656e..23a4ccf6 100644
--- a/usecases/cem/ohpcf/events.go
+++ b/usecases/cem/ohpcf/events.go
@@ -43,6 +43,11 @@ func (o *OHPCF) connected(entity spineapi.EntityRemoteInterface) {
 				logging.Log().Debug(err)
 			}
 		}
+
+		// read the current data as a subscription only delivers future updates
+		if _, err := semp.RequestData(); err != nil {
+			logging.Log().Debug(err)
+		}
 	}
 }
 
diff --git a/usecases/cem/ohpcf/public.go b/usecases/cem/ohpcf/public.go
index 781fcd40..88f8e4df 100644
--- a/usecases/cem/ohpcf/public.go
+++ b/usecases/cem/ohpcf/public.go
@@ -291,8 +291,8 @@ func (o *OHPCF) PowerConsumptionMinimalPauseDuration(entity spineapi.EntityRemot
 // scheduled process did not start.
 //
 // parameters:
-//   - start: The start time of the power consumption
-func (o *OHPCF) SchedulePowerConsumptionProcess(entity spineapi.EntityRemoteInterface, start time.Time, resultCB func(result model.ResultDataType)) (*model.MsgCounterType, error) {
+//   - startIn: Delay from now until the power consumption starts (0 = start immediately)
+func (o *OHPCF) SchedulePowerConsumptionProcess(entity spineapi.EntityRemoteInterface, startIn time.Duration, resultCB func(result model.ResultDataType)) (*model.MsgCounterType, error) {
 	info, err := o.OptionalPowerConsumption(entity)
 	if err != nil {
 		return nil, err
@@ -305,7 +305,9 @@ func (o *OHPCF) SchedulePowerConsumptionProcess(entity spineapi.EntityRemoteInte
 					SequenceId: &info.PowerSequenceId,
 				},
 				Schedule: &model.PowerSequenceScheduleDataType{
-					StartTime: model.NewAbsoluteOrRelativeTimeTypeFromTime(start),
+					// relative start time (ISO 8601 duration); heat pumps advertise their
+					// scheduling constraints relative as well, so keep the schedule relative
+					StartTime: model.NewAbsoluteOrRelativeTimeTypeFromDuration(startIn),
 				},
 			}},
 		}},
diff --git a/usecases/cem/ohpcf/public_test.go b/usecases/cem/ohpcf/public_test.go
index 2f988a9f..2ebef37f 100644
--- a/usecases/cem/ohpcf/public_test.go
+++ b/usecases/cem/ohpcf/public_test.go
@@ -265,11 +265,11 @@ func (s *CemOhPCFSuite) Test_PowerConsumptionMinimalPauseDuration() {
 // Scenario 2
 
 func (s *CemOhPCFSuite) Test_SchedulePowerConsumptionProcess() {
-	_, err := s.sut.SchedulePowerConsumptionProcess(s.mockRemoteEntity, time.Now(), nil)
+	_, err := s.sut.SchedulePowerConsumptionProcess(s.mockRemoteEntity, 0, nil)
 	assert.NotNil(s.T(), err)
 
 	// Without valid data, the call should fail
-	_, err = s.sut.SchedulePowerConsumptionProcess(s.monitoredEntity, time.Now(), nil)
+	_, err = s.sut.SchedulePowerConsumptionProcess(s.monitoredEntity, 0, nil)
 	assert.NotNil(s.T(), err)
 
 	// Set up valid SmartEnergyManagementPs data
@@ -302,8 +302,7 @@ func (s *CemOhPCFSuite) Test_SchedulePowerConsumptionProcess() {
 	_, fErr := rFeature.UpdateData(true, model.FunctionTypeSmartEnergyManagementPsData, data, nil, nil)
 	assert.Nil(s.T(), fErr)
 
-	startTime := time.Now().Add(time.Hour)
-	msgCounter, err := s.sut.SchedulePowerConsumptionProcess(s.monitoredEntity, startTime, nil)
+	msgCounter, err := s.sut.SchedulePowerConsumptionProcess(s.monitoredEntity, time.Hour, nil)
 	assert.NotNil(s.T(), msgCounter)
 	assert.Nil(s.T(), err)
 }
diff --git a/usecases/cem/ohpcf/usecase.go b/usecases/cem/ohpcf/usecase.go
index c40284b2..2a81ed56 100644
--- a/usecases/cem/ohpcf/usecase.go
+++ b/usecases/cem/ohpcf/usecase.go
@@ -49,6 +49,8 @@ func NewOHPCF(localEntity spineapi.EntityLocalInterface, eventCB api.EntityEvent
 		UseCaseBase: usecase,
 	}
 
+	_ = localEntity.Device().Events().Subscribe(uc)
+
 	return uc
 }