Vaillant VRT392 not calling for heat diags

[UpgradeME]

Hi All,

I have a Vaillant VRT392, VR65 and ecoTEC Plus 418 all connected via eBUS. All was working well until today where I found that the DHW works (i.e. it's calling for heat when asked via the VRT392 and is showing the symbol on the 418) however when changing the room temp to heat the radiators, nothing happens.

The call for heat radiator symbol doesn't appear on the 418, no matter what room temp is set on the 392. Is there a way to determine where the fault lies? I'm assuming it's the 392 but I guess it could be anywhere on the eBUS (418/65)

I set the system up a few years ago (search me on here for background) and am able to change any settings as necessary to diagnose if anyone can help?

Thanks!

UM

 

[undertrained]

So you have an open vent system? Have you checked the motorised valve?

 

[UpgradeME]

So you have an open vent system? Have you checked the motorised valve?

Yes, OV. I've just moved the valve manually but that didn't make any difference (the valve is connected to the VR65 so not sure that would call for heat if opened manually!)

EDIT: I've just looked at my wiring diagram and as I suspected, the value switches are not used/connected when using the VR65. (Although manually switching over the value and turning on the DHW does heat up the radiators so I have a temp workaround whilst diagnosing!

 

[undertrained]

So I’m guessing it’s a 3 port mid position valve? Any idea on the make/model? Any photo of valve? If it works manually then I’m guessing it’s not diverting over to heating, so possibly the motor?

 

[UpgradeME]

So I’m guessing it’s a 3 port mid position valve? Any idea on the make/model? Any photo of valve? If it works manually then I’m guessing it’s not diverting over to heating, so possibly the motor?

It's S-Plan with 2xHoneywell 2-port valves. The issue appears to be there is no call for heat (or symbol) at the boiler, which is triggered by the VRT392 thermostat.... (if it were the valve, I would assume there would still be a call for heat at the boiler, just not working....

As it's eBUS, suspect it could in theory also be an issue with the boiler or VR65 control centre. Is there a way to narrow it down? (I'm thinking to replace the 392 with a vSmart as I was looking to upgrade it at some point anyway... thoughts anyone? will the vSmart work with the VR65?)