Hi All
Vaillant ecotec 637 plus, S-plan external cylinder, eBus control.
When in DHW mode the boiler acts weirdly as in it goes full on for ~5 seconds then minimum output for ~5 seconds and this forever until it stops.
It's shooting for 75 degrees and with the behaviour of full on / full off will have the water between 72 (when at minimum output for 5 seconds) and 79 (when going on strongly for 5 seconds).
Sometimes it overshoots and will go in anti-cycling mode with S.28 code (I suspect it is when it hits 80 degrees which is 5 degrees above the setting of 75, but that is a guess). Also when it cycles it only stops for 1 minutes and starts again, whilst an overshoot in CH mode will keep it off for 5 minutes or more.
Settings:
- D.78 (DHW max flow temp): 75 degrees
- D.77 (DHW partial load): 37 kw (note it's not possible to select "auto" like for the CH version of this setting which is D.0)
- Return water is around 67 / 69 degrees.
- Pump is on a set setting I think it puts it at 70% when in DHW.
- Finally D.07 (Cylinder temperature target value) and D.06 (Outlet temperature target value) do not go about 40 degrees. I can control it from my app from 30 to 40 degree by degree and it will change on the boiler display, but anything above 40 will stay at 40 on the boiler display.
Why is it not simply keeping a constant output to stay around a DHW flow temp of ~75 degrees (just like the CH does, with a target of ~65)?
Thanks!
Vaillant ecotec 637 plus, S-plan external cylinder, eBus control.
When in DHW mode the boiler acts weirdly as in it goes full on for ~5 seconds then minimum output for ~5 seconds and this forever until it stops.
It's shooting for 75 degrees and with the behaviour of full on / full off will have the water between 72 (when at minimum output for 5 seconds) and 79 (when going on strongly for 5 seconds).
Sometimes it overshoots and will go in anti-cycling mode with S.28 code (I suspect it is when it hits 80 degrees which is 5 degrees above the setting of 75, but that is a guess). Also when it cycles it only stops for 1 minutes and starts again, whilst an overshoot in CH mode will keep it off for 5 minutes or more.
Settings:
- D.78 (DHW max flow temp): 75 degrees
- D.77 (DHW partial load): 37 kw (note it's not possible to select "auto" like for the CH version of this setting which is D.0)
- Return water is around 67 / 69 degrees.
- Pump is on a set setting I think it puts it at 70% when in DHW.
- Finally D.07 (Cylinder temperature target value) and D.06 (Outlet temperature target value) do not go about 40 degrees. I can control it from my app from 30 to 40 degree by degree and it will change on the boiler display, but anything above 40 will stay at 40 on the boiler display.
Why is it not simply keeping a constant output to stay around a DHW flow temp of ~75 degrees (just like the CH does, with a target of ~65)?
Thanks!
Last edited:
