Under floor heating

[Chameleonclaude]

hi there,

So my CH is an Vented system. I want to install UFH into a new extension. Rather than plumbing into existiting secondary flow and return for rads, I’m told the best way is to create new flow and return control with its own motorised valve.

To avoid the pumped return spilling into the header tank I believe there’s something about the positioning of where the new flow and return intercepts the primary flow and return that is crucial.

Any clarity on this would be much appreciated.

Secondly, if I wanted to replace my header tank with one of those with a diaphram making it sealed, how much pressure does the system work under. Seems to me that it would only be marginally more than a gravity fed system.

Thanks for Any help given

 

[Nozzle]

Yes, you need not just a new zone valve but also a manifold, a dedicated circulating pump for the UFH, a blending valve and an overtemp protection. UFH is low temperature, and to achieve that from a high temperature source such as the normal CH circuit takes quite some effort. You may already know this, but there's nothing in your passage which recognises it to be so.

I can't comment on the positions of your flow and return to avoid pumping over - pick a manufacturer of the above parts and start to trawl through their installation guides. My plumber chose "Emmetti" on my behalf, take a look at their range.

Nozzle

 

[Chameleonclaude]

Thanks, yeah the pump etc are supplied with the kit which is why I didn’t mention it.

 

[DP]

Thanks, yeah the pump etc are supplied with the kit which is why I didn’t mention it.

The pump that is included is for blended lower temperature water circulation in the UF coil, nothing to do with primary flow from the boiler. If you are going to fit a motorised valve on the UF heating circuit, you will need to do the same for other zones. No reason why the system will not work with open vented.

 

[Chameleonclaude]

Thanks DP, I have MV’s for the Ch and HW as usual.

So the pump that drives the water around the primary flow and return boiler and tank isn’t powerful enough to drive water around the UF circuit, so the second pump is a booster.

Have I understood it right?

 

[DP]

Thanks DP, I have MV’s for the Ch and HW as usual.

So the pump that drives the water around the primary flow and return boiler and tank isn’t powerful enough to drive water around the UF circuit, so the second pump is a booster.

Have I understood it right?

No,..... the UH pump circulates the water in the coil only. Primary pump sends the water to the UF manifold ( and other zones) which take a spot of heated water to maintain lower temperature water circulation in the coil. The blending valve decides how much hot water needs mixing with coil circulating water