Vaillant VR65 / vSmart & zone valve on constantly

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I have a Vaillant ecoTEC 418 / VR65 / vSmart control and just noticed one of the Honeywell zone valves is on when there is no CH demand showing at the boiler (S.31) or scheduled.

When DHW is requested via vSmart, the CH zone valve closes and the DHW valve opens and the pump runs. When finished, the DHW valve closes and the CH valve opens… the pump stops but the valve is left operating (and getting hot as it’s on 23hrs per day)

What steps would you take to determine where the fault is? I presume it’s either the VR65 at fault but as it’s all on eBUS could it be the boiler or vSmart? (d.8 shows 1 (is this just 3&4 jumpered?) but no symbols are shown on the display for demand.

How would you identify which part is at fault?
 
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Sounds more likely to be the motorised valve end switch stuck. If you have electrical test equipment you could test for voltage between orange wire and neutral/earth.
 
It sounds as if it has been wrongly wired to me. Have you a diagram for the VR65, to check the connections there? You can download the diagram.
 
Sounds more likely to be the motorised valve end switch stuck. If you have electrical test equipment you could test for voltage between orange wire and neutral/earth.

The orange / grey wires are not connected when using the VR65, only live/neutral/earth (the signals for on/off are sent over eBUS)

It sounds as if it has been wrongly wired to me. Have you a diagram for the VR65, to check the connections there? You can download the diagram.

I installed it originally and I’m 100% sure it used to switch on/off as expected. I did change the original vrt390 thermostat to a vSmart in June ‘19 (just two 24v eBUS wires, no other changes) but don’t recall specifically checking afterwards if was switching off when no demand (as otherwise it all works as expected) i think I would have noticed before now but cannot be 100% sure on a compatibility issue with vSmart/VR65!? Anyone know for sure these work correctly together?

I will double check for any loose connections and wiring tomorrow but the zone valves are just LNE connected to the VR65 so I’m thinking the problem is eBUS / PCB or loose wire related but presume there could be other sensors which have failed somewhere too!?
 
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I installed it originally and I’m 100% sure it used to switch on/off as expected. I did change the original vrt390 thermostat to a vSmart in June ‘19 (just two 24v eBUS wires, no other changes) but don’t recall specifically checking afterwards if was switching off when no demand (as otherwise it all works as expected) i think I would have noticed before now but cannot be 100% sure.

OK, it cannot be the VR65 contact welded, otherwise it would be energised permanently. I cannot see it being an eBUS issue, or some glitch in the software, other than an error in the original program and that 'they all do that'.

If you are certain everything is correct, email Vaillant tech and ask them.

My Vaillant eBUS system has a similar weird 'built in feature' of changing it's set / programmed room temperatures on a whim.
 
The orange / grey wires are not connected when using the VR65, only live/neutral/earth (the signals for on/off are sent over eBUS)
Apologies, I didn’t know how they were wired up.
If you are certain everything is correct, email Vaillant tech and ask them.
Probably best with @ScottishGasMan - he works for them and knows this stuff a lot better than vast majority of pro’s on here.
 
All connections in the VR65 are okay and no signs of any burnt out components in the PCB, however, as a test, I powered down everything, removed the eBUS connection to the VR65 e.g. completely removing any signals from the boiler or vSmart - powered back up and the CH valve opened, which unless that’s the default action (seems unlikely), the fault must be on the VR65? Do you agree @ScottishGasMan ?

Anyone know which component on the PCB is likely to have failed?
 
A photo of the wiring in the VR65 would be handy just to double check.

It's an odd issue. I've not come accross that before. Although I've never seen a VSmart on a VR65 before since the VR65 was discontinued way before the VSmart was released. They may just not be compatible fully.
 
Also have you ever changed any of the D.Codes in the boiler display?
 
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A photo of the wiring in the VR65 would be handy just to double check.

It's an odd issue. I've not come accross that before. Although I've never seen a VSmart on a VR65 before since the VR65 was discontinued way before the VSmart was released. They may just not be compatible fully.

I originally had a VRT392 with the VR65, then a few years later swapped to the vSmart - I’ve attached a photo of the inside…. However, I have got a bit further with my diags and at the moment, seem to have fixed it.

How? I removed the PCB in the attached and was prodding all around with my multimeter, whilst doing so found the S14K275 varistor (see red arrow) appears to be faulty as there is zero resistance. Looking at the circuit (I’m no expert) I’m not sure that would cause the fault as it just loops a leg of the DHW relay back to live when not switched.

I suspect I may have disturbed/reattached something else whilst I was prodding around, or it may have been one of the plugs which I disconnected / reconnected, but at the moment, the CH relay doesn’t come on as it was doing before! not sure how long it’s going to last though but at least I seem to have traced it down to the VR65

Also have you ever changed any of the D.Codes in the boiler display?

Yes, everything is on defaults AFIAK apart from:

d.0 = 11 (max heating kw)
d.77 = 8 (max kw for DHW)
d.17 = 1 (I tried changing this one back and it didn’t fix the issue)
 

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