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V3+ Extension Kit and Vaillant Boiler with VR33

randrade
randrade ✭
edited February 28 in General Questions & Topics

Got a V3+ EK working with as Vaillant Ecotec boiler via ebus. Works ok.

Tried to make the V3+ EK work via Opentherm using a VR33 board. The VR33 is connected using the X31 bus on the main board and the X31 on the VR33 and the EK connected via 2 wire with the OT/T connectors. The problem ? The EK seems to have no power supply. The ebus connector used to supply the power correctly. Can the OT/T on the VR33 supply the EK correctly ?

Comments

  • Kissarmy
    Kissarmy ✭✭✭
    edited February 25

    This is an AI generated summary

    No, OpenTherm does not provide power in the same way as eBUS; while both are communication protocols used in heating systems, OpenTherm primarily focuses on sending signals to modulate boiler power based on heating demand, whereas eBUS can also carry power to operate additional system components like room sensors or actuators, essentially acting as a "power bus" in addition to communication. 

    When I first wired my system.system.up I didn't realise the eBus could power the EK, I ran 240v from a seperate spur to power the EK so when I tried adding the VR33 and changing to OpenTherm I didn't have any problem. You should be able to tap 240v out of the boiler it just means running another cable to the EK.

  • randrade
    randrade ✭

    Update

    Picked up a multimeter to check what was going ON. With the EK connected to the EBUS, measured 24V in the connections. OK.

    Connected the VR33, and 24V were measured in the OT connections. OK. Plugged the EK in the OT on VR33, the voltage dropped to 3.5V. Seems the VR33 is not able to fully supply the EK. Seems odd.

    Tried the VR33+OT to the EK and a separate 230V supply to the EK. Working OK.

    Anyone else had this experience ?

  • Kissarmy
    Kissarmy ✭✭✭

    Yes I have. That's what I tried to explain in my previous post. OpenTherm is not like eBus. OpenTherm is only data communication. The 1's and 0's are sent by alternating the voltage between a high state 24v for a 1 and I think 9v for a 0. The voltage is thete for signalling only and not to provide power to other devices.

  • randrade
    randrade ✭
    Thanks. That makes sense. I thought that the signal was modulated. A bit like HART.
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