UFH manifolds with larger downstream pipes

[Ommm]

I'm thinking of plumbing into my ASHP fan coils that have a 3/4" inlet, so I want to feed them with 22mm pipes, and a convenient way to do that is via an UFH manifold.   Some stupid plumbing questions:

 

• Is there a standard size of outlet pipe for UFH manifolds?  Many of them don't seem to specify it in the description
• If the thread is say 15mm, how much of a constriction is this going to be?  Going from 22mm throught the manfold outlet at 15mm back into a 22mm pipe. Obviously it'll offer some friction/turbulence, but will it completely constrain the flow (flow set by the smallest pipe diameter of the run, like drinking through a straw) or would it only offer a small reduction (eg for electricity resistance is proportional to length, so you can use a higher resistivity material if you keep it short)

 

[Temp]

Perhaps make a "manifold" from copper pipe and fittings. That's what our plumber did for our bathroom. It has a mixture of 22mm and 15mm isolation valves on it to suit pipes going to different places like the bath, shower, basin,  WC etc.

[Ommm]

There are also plumbing/sanitary manifolds, which are roughly what you describe.  However the reason for interest in UFH manifolds is the UFH actuators make it easy to electrically control the flow, rather than say a 2 port valve on each output, which would be quite costly and bulky.  I suppose I could solder up some pin valve seats in a row, but I'm not sure if actuators come in different sizes.

 

UFH manifolds typically have a flow limiter which I'd look to remove, or perhaps replace the flow side with a sanitary manifold with adjustable taps to allow balancing.

[JohnMo]

Standard UFH pipes is 16mm o/d.

Not sure why you need to run 22mm, unless the fan coil is rated over 3kW?

 

[JohnMo]

1 hour ago, Ommm said:

 UFH actuators make it easy to electrically control the flow

The actuators are on/off devises, so flow would be either on or off, so each fan coil would be in its own zone, which is not what you want with a heat pump.  Your generating a lot is small zones which will lead to the heat pump short cycling.

 

You would use the flow valve to control flow and ideally tune the flow to give the heat output required.

 

 

[Ommm]

This is for cooling.  The fan coil is >3kW for both heating and cooling (on paper anyway) - works out about 15000 BTU/hr for cooling, but I want a large FCU so I can run the fan as slow as possible.  I explicitly want the FCUs to be individually controllable so I'm not cooling places I don't need to.  There's a buffer tank to avoid short cycling, and generally the ASHP is good at ramping its output down in cooling mode when the return temperature isn't much different from the output (ie the emitters aren't emitting very much).