Willis heater advice

[andygo]

Hi

Could someone please walk me through adding a Willis heater to my UFH system (meant to do this last year, but only just getting around to it......) 

 

My UFH is a pretty basic system (see pics below). There are two loops for around 28m2 of UFH and no manifold - just two flow and returns - pump, filter, mixing valve (yellow knob) and end feed air cap. 

 

The UFH is currently connected to our Thermal Store - which at the moment isn't being heated (still working on replacing a solid fuel Rayburn).

 

Presumably separating the UFH from the Thermal Store is the most efficient way of doing it - so the Willis isn't trying to heat the entire 270 litres of water in the TS.

 

But I'd also like to keep the Willis in the system to use as a standby in the future once the TS is up and running again (and supplying the UFH).

 

I'm guessing the Willis could go between the filter and the pump?

 

If I'm separating the UFH (and creating an unvented system) I've read in the thread below about needing a small expansion vessel and cold water feed for it.

 

Where's the best place to put the expansion vessel and where would I get the cold feed from? Could I use the current UFH feed from the TS?

 

I've got an electrician friend to wire it up once it's plumbed in.

 

Any help appreciated. Obviously if there's a better way of doing it, let me know.

 

Thanks in advance

Andy 

 

 

 

I put vent but I meant end feed air cap.