Vaillant VRC 400 without Vaillant Cylinder

[richiezander]

Thanks for all the help guys. The customer is happier now, still abit annoyed about hot water boost button not working.

I think I will have to travel down to Vaillant at Elland to have some training on these weather compensaters not only for installation purposes but so I know all the ins and outs of the device, so I look like I know what I'm talking about.

Also I think Vaillant need to make it a bit more clearer that all function will not work if a standard cylinder is used

 

[softlad1971]

Gas4you is right in saying the hot water boost will not work unless the vailiant thermistor is fitted and not a cylinder stat. I used a essex boss and a solar heating fitting to fit a valiant thermistor in a normal hot water tank.

You then get all the functions, including the temp of the stored hot water from the display on the boiler.

 

[simond]

We've used the VR10 in other unvented cylinders in the dry pocket, you can do it.

You need to wire the two port HW valve via the temp and OH stat supplied in the third party unvented cylinder package, then via the VR65.

Turn the thermostat in the unvented cylinder to max, so that the 2 port is normally under the control of the VR65 unless a serious overtemp occurs, in which case the two port closes and fails safe.

We also do this with weather compensated Viessmanns where an existing cylinder exists, adapted a Megaflo only the other day.

 

[gas4you]

I am sure that d70 is for internal divertor valves only will make no difference to external valves.

As said previously, d70 is telling the VR65 what to do in this case, not the boiler or any diverter valves.

 

[ashmont]

I am not a plumber, just another frustrated end user who can't understand why Vaillant doesn't put basic (and standard) functions like +1 hour DHW/CH on their programmers. Before purchasing the VRC470 I read the user guide and was lead to understnad that the Cylinder Boost recharged the hot water when it had run out. When my Vaillant 637 boiler and Gledhill cylinder were up and running, I was disappointed that cylinder boost didn't work.

I did some searching and found that others had used the VR10 to get it working. I managed to find the VR10 that came with my VR65 and my plumber was able to insert it into the standard thermostat pocket on my Gledhill cylinder. Since connecting the VR10 to the VR65 I can now read the cylinder water temperature and use the Cylinder Boost. The existing thermostat and wiring were literally left as is so the boiler will still switch off when the old thermostat temperature setting is reached. As another user suggested, you need to increase the temperature on the standard thermostat so that the VR10 can control the boiler while still having the other thermostat as a fall back. I increased mine to just over 65 degrees and it seems to work fine with VRC470 target temperature set to 60. So I am happy now.