Adding short UFH loops - Manifold/Mixer or direct?

[Jdwood38]

Hi all,

Can anyone please suggest solution to adding two small (c.18 and c.12m) loops to an existing heating setup that consists, in short, of:

UFH throughout downstairs, split across 2 manifolds each with a mixer and pump set but no temperature control other than mixer and flow rate
Large K2 rads upstairs
Currently gas boiler running weather comp and max flow temp of 40degrees, probably will move to ASHP soon
28mm primaries, down to 22mm for feeding each pair of rads (each rad 15mm)

Each loop is in an upstairs bathroom and ensuite respectively. Neither need huge amounts of heat and didn't actually have any last winter and were just about ok with heat from the rest of the house but definitely need something.

So the question is how to plumb these two loops in. Access to the existing manifolds isn't an option.

1. Install a two port manifold with mixer and pump set and feed with the existing 22mm feed for the pair of rads in these rooms (feels like overkill!)
2. Install a two port manifold with just mixer and fed from existing
3. Install a two port manifold and feed directly from existing
4. Plumb directly into the existing 22mm pipework for the existing pair of rads and treat just like a radiator (but not sure how I'd do heat control, if indeed needed)

Thanks in advance for thoughts

 

[Madrab]

The duty of an UFH manifold is normally to > allow a larger UFH system to be centralised as far as control/temps/heat input/zoning/pumping is concerned.

When it comes to smaller additions then the norm would be to increase the capacity of the current system manifold and then add the extra zones to it. If that's not an option then, each small loop could be run from the system if the boiler and system pump has the capacity, the only other requirement is temp control.

To perform this properly then there needs to be a temp control added to the loop, usually this would be done through the manifold but as that's not an option then it would be down to using something like an FHV, RTL or similar to locally control the loop temps.

 

[Jdwood38]

Thank you for the helpful response. Getting to the existing manifolds would increase the loop lengths by at least 20m (10m on each F/R leg) and would be quite destructive so trying to avoid!

Could you please clarify what FHV and RTL mean?

Thanks

 

[Madrab]

Could you please clarify what FHV and RTL mean?

FHV (A or R) (floor heating valve) and RTL (room temp limiting) are both temperature regulating/control valves - they sit on either the flow or return on an UFH loop and regulate flow temps by limiting flow through the circuit by limiting the water set temp and/or controlled by the room air temp.

They are really the simplest types of UFH loop/air temp control and can be used separately or together