Vaillant and underfloor heating

[davecraig]

Hi all,

At the beginning of the year we replaced our old central heating and hot water system. We told the plumber we wanted a Vaillant ecotec boiler and tank, and he spec'd out a Vaillant ecoTec 630 boiler, a UniStor tank, a VR 65 control centre and a VRT 360 thermostat. This was to provide radiator central heating, hot water and drive wet underfloor heating which was to be added a few months later by the same plumber.
When he came to do the underfloor heating, he found that it didn't work because the stuff he'd installed couldn't control the underfloor heating as well as the radiators and hot water. Since this all began I've trusted the plumber less and less, so could someone tell me what Vaillant control parts are required to drive radiators, hot water and a single underfloor heating loop? I found the Vaillant control section on their website rather impenetrable...
The plumber tells me that one of the part we (he) needs is a VRC 430 weather compensator. This must be made from ground up diamonds by elves who only work on Sunday's before noon as they seem to be somewhat unobtainable... I want to understand why it is that the VRC 430 is required, as none of it's description seems particularly applicable to us.

Thanks!

Dave.

 

[Agile]

Is the underfloor already fitted?

If so does it have its own pump and blending valve?

Tony

 

[davecraig]

Is the underfloor already fitted?

Yes

If so does it have its own pump and blending valve?

Yes there's an uponor manifold with a pump, some valves and a thermostatic cutout of some kind. Couldn't find any pictures on the web, so can't be more specific at the moment.

Thanks

Dave.

 

[davecraig]

One more thing to add. The pump for the underfloor heating as installed has an external room thermostat connected to it, and when the temperature drops the pump starts going - though the boiler may or may not be going at that point. The pump will come on in the middle of the night when it's cold just cycling the water round and round without the boiler being on.

 

[ctp]

the underfloor circulator should be linked into the main boiler and system wiring ,it sounds like its only wired to its own zone stat

 

[simond]

I'm afraid it can't be done with your controls if you want the UFH to come on independently to the main radiators.

VRC 430 is readily available next day, but won't help you one jot.

You will need to ditch the VRT360, VR65 and fit a conventional two zone control system. The uniSTOR will have to be wired using the internal mains cylinder stat (lets hope this part, which is removed when fitting VR65, hasn't been thrown out.....)

 

[davecraig]

I'm afraid it can't be done with your controls if you want the UFH to come on independently to the main radiators.

To be honest, I'd be quite happy if it came on with the main radiators. Can that be done with the current controls - getting rid of the thermostat that's currently controlling the underfloor heating?

VRC 430 is readily available next day, but won't help you one jot.

The plumber seemed to suggest that he needed the VRC 430 because he had to have one to work with the other part he needed to use for the 2 zone. Like I said, my confidence in him is now very low...

Thanks

DaveC

 

[simond]

It isn't approved by Vaillant, but you could run a relay off the VR65 zone controller (using the live feed to the CH motorised valve) so that the UFH pump and thermostat was only energised if the boiler had got the heating on.

This would probably be more satisfactory than running the UFH 24/7. The UFH room stat would then still work in so far as it would act as a upper limit, but ould not turn the boiler on independently of when there was a radiator demand.

The VRC430 is a good upgrade, they are readily available next working day from most merchants and have a better user interface than the VRT360. It also makes your installation weather compensated, which is for the better good......

 

[Agile]

It would not be very difficult for anyone who understands control to use a three port valve on the heating circuit so that a seperate timer could run the UFH only at preset times or bath when the heating was required.

Or an even simpler two port valve on the heating circuit with a timer circuit to "hold off" the heating when just the UFH was required. The UHF would then be stopped by de-powering its own circulation pump.

Tony

 

[simond]

The VR65 wiring centre means that the boiler can only be 'called' by a proprietary data bus linked controller, in this case, the VRT360.

If you wanted to carry on with the equipment already purchased, a simple relay, or, just using the redundant pin switch on the CH valve will do even better, now I have given it some more consideration.

This way, whenever the heating is on, the UFH can be energised. The Vaillant installation remains per plan, because the VR65 does not use the orange and grey cables from the microswitch......