Weather compensation on a Vaillant UFH & rad setup

17 Mar 2016
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United Kingdom
Am considering fitting the Vaillant weather compensator, the logic behind it makes sense to me but not sure if we have the right setup for it to work properly.

Existing system is:
637 Plus system boiler
UniStor cylinder
Zone 1 - Radiators (upstairs & downstairs) with Honeywell room stat
Zone 2 - Towel rails
Zone 3 - UFH, in a new open plan extension, split into three zones, each with temperature control; Polypipe controller/manifold etc

I know the Vaillant kit can do two zones, but don't know if it would work properly with the UFH given different warm up times etc.

Keen to reduce gas use (I bought a loop monitor and it's painful to look at the report!) plus give better control over temperature, which is currently quite hard to balance throughout the house. I think all these stats everywhere complicate things..

The boiler is set to 65 degrees and outside the early morning warmup period I don't see a huge drop on the return temperatures, so I wonder if we would benefit from WC.

Views welcomed
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If you want to reduce gas usage, WC will only make a small difference, circa 5% with the wind blowing in the right direction. Won't make much impact at all on the UFH load, because that all returns low water temp to the boiler.

Multi zoning the rads could make a big difference, far more than 5%.

Most peeps with VRC470 have no idea how to control it on a day to day basis, it frightens them and they leave it on the same setting. Counter productive.
Hmm, well I'm willing to put the time in to learn how to use it! :)

So multi zoning would be something like Honeywell Evohome? Being able to vary temperatures in different rooms does seem to make more sense than setting one temperature in a common location with TRV's.

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