UFH near commisioning question

[Johnnyt]

We are almost ready to fire up our boiler with the final electrics being undertaken by the spark.

I am a tad confused, we have a viessmann system boiler piped up as a 2 pipe system.

The plumber has fitted 4 X 2 way diverters each for UFH, DHW, Towel Rads and 1st floor rads.

My question is, if I am to make use of a low flow temp from the boiler for the ufh to enable best condensing, how can this "low" temp adequately heat my 500l  indirect UVC and other circuits.

The rads are not oversized and the ufh is a John Guest system 12 way manifold but about  7 zones.

Am I missing something?

Pic attached if it helps

 

Thanks

 

 

 

 

 

 

 

[ProDave]

Don't worry about the boiler flow temperature, the UFH manifold should have a blending valve to mix the temperature down to a low temperature just for the UFH.  Upstairs rads and HW tank will operate at boiler temperature though of course the tank will have a thermostat to turn it off once it reaches it's set temperature.

[Johnnyt]

Got it, and thank you.

There is a mixing valve at the manifold and see how this lowers the temp for the ufh, so roughly what  range of flow temp would be best for the boiler to run at?

I thought the lower the flow temp the greater the boiler efficiency?

One of the reasons for a large uvc is to store DHW at relatively low temp to reduce losses (allowing for a legionella cycle) and have a large enough reservoir to blend in little cold water when using DHW for showering etc.