Vaillant VRT 430 - Heating Curves

[exocet]

Looking at retrofiting a VRT 430 + VR65 to my ecoTEC 428 boiler.

I've been reading through the setup instructions and whilst I understand the concept of linking internal house temperature / external temperature / boiler flow temp - I don't understand what assumptions have been factored in to the preset heating curves - other than heat loss / insulation?

Surely the ability to heat a room space adequately has to be related to radiator size, if my radiators are sized for standard 80 deg Flow / 69 Return operation, running the flow at 60 deg is going to result in a 'cool room'?

Can anyone share their experiences?

Realistically, what sort of heating curve / flow temps am I looking at if I want to try and save on fuel bills? Up until now I have been running flow at 70 deg mainly to allow the DHW to heat to 60 deg without short cycling everytime. As part of the system changes I am also changing some rads and will be effectively oversizing by 40% compared to the rads that are being replaced (new rads have additional convector fins where the old rads had none.)

 

[Agile]

Expressed simply the system has to provide the rad temp which keeps the house at 21°C while its say 8°C outside as an example.

Thats done by setting the curve. Gas4U has had lots of fun with these and I think he recommends setting the curve at 2.6 but see some of his posts.

I think there are different ways of using that controller and in the best it monitors interior temperature when located in the habitable area.

As always the lower the flow temp the more the boiler is condensing and so more efficient.

Tony

 

[islandman]

We upgraded last year to a Ecotec 831 combi and had all the rads replaced & new TRV's installed. We considerably oversized 2 'strategically' placed rads downstairs plus others slightly.

We run the heating flow at 65 and the VRT 50 room stat at 20. Once up to 20 the VRT 50 modulates the ecotec and will keep the temp stable with the rads only lukewarm ----- the flow temp is then usually only in the 40's/50's

Works very well in fact.

Hope this helps