diff --git a/tcl/drivers/ccu4he.tcl b/tcl/drivers/ccu4he.tcl
index 287dfcf..f6119e7 100644
--- a/tcl/drivers/ccu4he.tcl
+++ b/tcl/drivers/ccu4he.tcl
@@ -20,6 +20,9 @@ proc stdConfig::ccu4he {} {
     node hefull alias /cc/hh
     node helow alias /cc/hl
     node smooth upd
+    node undershoot par 30
+    node minfillminutes par 3.0
+    node maxfillminutes par 30.0
   }
 }
 
@@ -69,7 +72,7 @@ proc ccu4he::readCmd {} {
     updateval [sct]/state manual_fill$stxt
     return idle
   }
-  set level [hval /cc/h]
+  set level [hvali /cc/h]
   if {[sctval [sct]] == 1} { # filling
     set full_level [hval /cc/hh]
     if {$level < $full_level} {  # else CCU4 will stop
@@ -77,18 +80,15 @@ proc ccu4he::readCmd {} {
       set delta [expr min(30, $now - [silent $now sct last_time])]
       sct last_time $now
       set smooth [silent $level sct smooth]
-      # minimum fill speed: 1 % / 36 sec = 100 % / 60 min
-      set smooth [expr $smooth + $delta / 36.0]
+      # minimum fill speed
+      set smooth [expr $smooth + $delta / 0.6 / [hval [sct]/maxfillminutes]]
       if {$level > $smooth} {
-        # maximum fill speed 1/18 %/sec + 1/9 %/sec = 100 % / 10 min
-        set smooth [expr $smooth + $delta / 9.0]
+        # maximum fill speed
+        set smooth [expr $smooth + $delta / 0.6 / [hval [sct]/minfillminutes]]
       }
       sct smooth $smooth
-      catch {
-        # test on running system: [sct]/smooth does not yet exist
-        hupdate [sct]/smooth $smooth
-      }
-      if {$smooth > min($full_level, $level + 30)} {
+      hupdate [sct]/smooth $smooth
+      if {$smooth > min($full_level, $level + [hval [sct]/undershoot])} {
         if {$smooth > $full_level} {
           sct update 0   # watching
           cc hcd 0
@@ -106,9 +106,13 @@ proc ccu4he::readCmd {} {
     }
   } elseif {[sctval [sct]] == 0} { # watching
     sct smooth $level
+    hupdate [sct]/smooth [sct smooth]
     if {[hval [sct]/status] ne ""} {
       hupdate [sct]/status ""
     }
+  } else {
+    sct smooth $level
+    hupdate [sct]/smooth [sct smooth]
   }
   switch -- [hvali /cc/hv] {
     0 {