Vaillant combi with underfloor heating?

[ian_black]

Hi there,

Im trying to see if is possible to run a wet underfloor heating system and conventional rad circuit from a Vaillant 937 combi boiler, with a 430 weather compensator.

I have rung Vaillant and they recomend using the vr61, vr81, with other pipe sensors, a low loss header and a separate pump for the rad circuit along with the pumped manifold for the UFH.

Has anyone achieved running an underfloor heating system from a vaillant combi, and did you need a low loss header?

 

[tackleburger]

You will need the low loss header as the boiler will need to have it's own circuit for the weather comp to work. The weather comp would then go into the combi directly. You can the run the radiator circuits and the UFH as normal using pumps and zone valves (mixer valve for the UFH) the VR61 mixer module isn't needed on this as the weather comp is direct to the boiler. I am surprised they have advised you in this way as I would just use honeywell controls beyond the low loss header. You may find the heatcurve will need a bit of adjusting.

If you haven't already fitted the 937 don't bother get a system boiler & cylinder and use the VR61, VR10 cylinder sensor, VRC 430 & VR81 this is what it is designed for. The reason you need low loss headers etc is because the 937 is a combi and the VR61 won't work because of a incompatibility with the hot water system in particular the aqua comfort.

Or ditch the weather comp and set up a standard S Plan with an underfloor circuit.

 

[erj]

fitted the same set up 4 weeks ago, do as vailant say and it will work great.

 

[ian_black]

Thanks all,

Just to clarify what Vaillant recomend,

1. the low loss header from the boiler with the vr10 pipe sensor back to the boiler
2. Pump for rad circuit controlled by the vr61 and vrc430. Does this need a 2 port zone valve? Is this controlled by the vrc430 heating program or the pump circuit program?
3. 2 port zone valve for the underfloor heating, which gives signal to UFH manifold pump and zone control. Vr10 pipe sensor on flow to the UFH manifold, back to the vr61.

Cheers

 

[SimonJohns]

You would have to have the external mixer as you will need the higher temps for the UFH even if the outside temp is rising. Stick with vailants plans!



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