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Discuss Vaillant VR33 (with Nest) and VR66 in the Central Heating Forum area at PlumbersForums.net

asoffe

Messages
9
Does anyone have experience of using a VR33 (for Heating OpenTherm control with Nest) and a VR66 for Hot Water Priority with Vaillant system boilers? I'm specifically using an EcoTec plus 624
I've got a system working with a Nest and VR66 to provide hot water priority and it works well with separate cylinder charge and heating flow temperatures. Currently this is all connected to the Nest using the switched CH and HW controls. I'd like to use the OpenTherm capability of the Nest for the heating but have questions about how the VR33 and VR66 coexist if they can at all. There is no timer or thermostat connected to the VR66. The only control input to the VR66 is the cylinder stat & nest HW switched line.
I'm hoping that the VR33 just behaves like an ebus thermostat and would work alongside the existing setup (with removing the switched CH controls on the boiler) but would love to know if anyone has experience of going into this level of detail.
 

ChrisB1982

Plumber
Gas Engineer
Messages
1,848
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2
I don’t believe Vaillant supports opentherm, only ebus which I believe is their equivalent.
 

asoffe

Messages
9
The VR33 Vaillant module converts OpenTherm to eBus in the boiler (unsupported in the UK but should work) but I'm trying to understand if plays nice with a VR66 when fitted and connected to a Nest 3rd Gen
 

theozaurus

Messages
3
I'm looking to do exactly the same thing. I'd like to use OpenTherm controls, but my house has a Vaillant boiler and is plumbed in an S-Plan configuration. I cannot find any controls that will use the OpenTherm protocol and manage the valves directly. My understanding is that the VR66 will allow the boiler itself to control the valves for DHW and CH so that the controls are not directly involved.
From the reading that I've done the VR33 acts as a bridge between eBUS and Opentherm so in theory the boiler will not know the difference between an eBUS controller connected directly, or an Opentherm controller connected via the bridge. There's a fair bit of discussion on the VR33 on the Automated Home forum. On this thread OpenTherm VR33 and Vaillant ecoTEC plus 428 - https://www.automatedhome.co.uk/vbulletin/showthread.php?6396-OpenTherm-VR33-and-Vaillant-ecoTEC-plus-428 someone suggests that the VR33 is 'low priority' and will not work with other eBus controls.
Looking at the specs: https://ebus-wiki.org/lib/exe/fetch.php/ebus/spec_prot_12_v1_3_1_e.pdf and https://ebus-wiki.org/lib/exe/fetch.php/ebus/spec_prot_7_v1_6_1_e.pdf eBus clearly supports multiple devices on the same bus (I guess the clues in the name), so it seems like it 'should' work.
 

asoffe

Messages
9
So I went ahead and tried it all anyway and it works perfectly. The vr66 provides hot water priority for the boiler and can control the valves for ch and hw. The vr33 allows the nest to control heating and hot water using opentherm! The only other thing I added (which you don't need) was the vr10 ntc sensor for my hot water cylinder so that nest can control the cylinder temp instead of the mechanical thermostat.
Now to fix the one radiator which seems to have sludged up!
 

ShaunCorbs

Staff member
S. Mod
Plumber
Gas Engineer
Messages
31,780
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2
Where are you connecting the ot off the nest to ?
 

asoffe

Messages
9
If you change from switch 230v to ot you need to put the link back into the 24v connection on the main board too
 

theozaurus

Messages
3
Oh, that's great. You've given me the confidence to do the same setup on my boiler. I've got an Opentherm gateway that I'm hoping to use between the controller and vr33 so that I can log the boiler metrics. Armed with that I'm hoping I can get it tweaked to eek out the most efficiency.
 

asoffe

Messages
9
I've been considering ebusd and associated interface board for boiler metric monitoring but haven't done it yet.
 

theozaurus

Messages
3
Incidentally, are you able to schedule your hot water using the Nest when it's connected on Opentherm or does it work solely on the VR66 switching the system to hot water priority (upping the temp, and controlling the valves) when the nest says there is demand.
 

asoffe

Messages
9
Yes. I originally set up heating with OT and HW with switched live (HW cylinder stat and switch in Nest linked in series to VR66 cyl stat connection) but then changed the HW to OT when I received my VR10 NTC as well and it controls the schedule. I don't know how it would behave with OT HW control and cyl switched stat.
 

asoffe

Messages
9
With the NTC and Nest HW set to OT, the nest also controls the cylinder target temp as well as schedule.
 

asoffe

Messages
9
You also get better feedback with the HW via OT. The two images below both show the HW set to on in the schedule but one shows that there is no demand from the cylinder.

Cylinder temp demand
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Cylinder no temp demand
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