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Thread: Anyone got a Vaillant eBUS timer/controller I could borrow

  1. #21
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    Just installed a VR66 and a VRT350F on a job today, first time i've installed one. Got DHW priority set up with the VR10 sensor. Does anyone know what the hot water differential temperature is on these? As usually the Vaillant books are least helpful. From what I can figure it's 5oc, however if possible i'd like to increase it due to a circulating return. However can't see any options in the controller or boiler settings to do this.

    EDIT: Just found it in one of the manuals, it is 5oc but looks like no option to change it.
    Last edited by mtmcgavock; 10th January 2018 at 09:33 PM.

  2. #22
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    Yes no option to change the 5C diff. Its fixed that way because if you wanted no time control, you could run the set up without the VRT350F. The boiler then kicks into HW heating mode everytime the 5C diff is sensed by the VR10.

  3. #23
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    Quote Originally Posted by bruce_miranda View Post
    Yes no option to change the 5C diff. Its fixed that way because if you wanted no time control, you could run the set up without the VRT350F. The boiler then kicks into HW heating mode everytime the 5C diff is sensed by the VR10.
    Surely you’d have to have some sort of Vaillant controller to control everything though? As there’s no S/L options on the VR66

  4. #24
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    You should use a Vaillant control, but you don't need to. You can run things with just the Vaillant wiring box. In that case CH will always be running until the return catches up with the flow max set on the boiler and HW will kick in whenever the diff drops below 5C below the HW set on the boiler.

  5. #25
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    Bruce I understand you have figured out the ebusctl write command to switch your vaillant boiler in and out of DHW mode and wondered if you might be able to shed some light on doing this.
    I spent some time grabbing data while the VR65 with NTC was clearly giving the boiler this command and so far haven't figured out what many of those grabbed exchanges are actually doing.

    I have managed to write to bai FlowsetHcMax and could use this for setting sensible flow temps for Heating and Hot Water but would really love to bring the DHW pot on the boiler into operation.

  6. #26
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    if you already have the VR65 and the VR10, then the boiler should already allow usage of both dials. What controller are you using?
    I don't use a VR65 or a VR10 because I have Evohome. What I was trying to do is to use the HW dial when Evohome was heating HW. And while I succeeded in working out the commands, the fact that the OT is sending/repeating a command every 5 seconds means my command is overridden in a matter of seconds.
    My new solution is to vary the FlowsetHcMax as required depending on what the Evohome is doing and that works well.
    Last edited by bruce_miranda; 27th January 2018 at 08:42 AM.

  7. #27
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    I guess you were sending Opentherm commands to the VR33 to switch the boiler to DHW while I’d like to find the raw Vaillant equivalent hex.
    I have the VR65 with ntc and the 350f attached at present, just for experimenting, along with ebusd on a raspberry pi.
    As you say, changing the FlowsetHcMax will probably do what I really need but would’ve liked to also have the option of directly controlling the boiler changes to/from DHW mode if possible, without the use of any other Vaillant controls.
    I’ll have another monitoring session or two and try to figure out exactly what’s being sent on the bus.

  8. #28
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    I wasn't sending any OT commands because currently I have no way of monitoring or controlling OT directly. I was sending raw eBUS commands.
    If you are using the 350F+VR65+VR10 then you should already have everything you need to use the two controls. Both your boiler controls need to be set to max. Turn all demand off from the controller. Then using the HW boost function on the controller turn just the HW heating on. You will notice the tap icon appear on the boiler and the flow temperature will ramp up all the way to 80C. Whereas if you use the CH demand only the radiator icon will show up on the boiler and flow temperatures will only ramp up to whatever the max is set to, normally 70-75C.

  9. #29
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    I've had another run and the Vaillant controls certainly do operate as you describe.

    The interesting unidentified commands such as

    unknown MS cmd: 1008b512020064 / 00 ,

    which seems to occur whether heating or DHW has just been switched on, are producing the same replies when issued from an ebusctl hex command but with no obvious change of state at the boiler.

  10. #30
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    Jackthom, what interface are you using from the Raspberry PI to the boiler?

    I've been looking at building a relay using an arduino to monitor my DHW motorised valve, using an opto-isolator to separate the 240V of the valve to the 5V of the arduino. This is doable, but my next step would be to then send the appropriate ebus command to boost the HW temperature to 80 degrees. Hence the question.

    I'd also need to have the device send an ebus command periodically to set the flow temp lower, otherwise the boiler will always fire at whatever is set on the dial on the front panel. All of this is more of a learning exercise for me, but if I can get some practical benefit, all the better. It'd be nice to be able to run the boiler at lower temps during the summer, whilst still ensuring the HW cylinder is heated appropriately to 65 degrees.

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