Do I need a pump on my manifold

[ricardo100671]

We will be having UFH in communal areas, 5 loops and 5 rads, in bedrooms.

UFH is ProWarm 16mm foile faced routed boards and I have used Heat Punk to calculate the exact rad sizing to run the lot at 45deg C. Will set loop flows to ensure each loop achieves its design output as well all preset lockshield on rads for the same. Our heat loss is about 49W/m2 and so will use a Vitodens 050-W combi. 

Was thinking I do not need a separate pump on the manifold as, from my calcs, the one on the Vitodens should be plenty good enough, given that it all ground floor, single zone and only 5 rads.

Am I mistaken ?

Thanks in advance for any help

[JohnMo]

Only thing to be careful of, if you run on thermostat and not weather compensation your set point for flow temp can get a quite big overshoot. 

 

I don't have rads but did run direct from the boiler on simulated WC (resistor to give set outside temp and fixed flow temperature)

[ricardo100671]

30 minutes ago, JohnMo said:

Only thing to be careful of, if you run on thermostat and not weather compensation your set point for flow temp can get a quite big overshoot. 

 

I don't have rads but did run direct from the boiler on simulated WC (resistor to give set outside temp and fixed flow temperature)

Thank you. Not quite sure I understand all that. I am planning to fit the weather compensate sensor, for sure and also have a single room stat. Are these thing mutually exclusive? Assumed the weather compensate would adjust flow temp so we don't overshoot and also be mre efficient

[JohnMo]

If you have the boiler manufacturer controller they can do weather compensation load compensation and mix of the two sometimes. But loads compensation doesn't work well with UFH.

 

Weather compensation outside temp only control, load compensation uses indoor temperature only.

 

I would put dumb limit stop TRVs on radiators to control bedroom temps. Then do the weather compensation curve to suit UFH. Upstairs will also use heat from downstairs so unlikely the rads upstairs will have much work to do. Run it all UFH and rads on or all off.

[Nickfromwales]

9 hours ago, ricardo100671 said:

We will be having UFH in communal areas, 5 loops and 5 rads, in bedrooms.

UFH is ProWarm 16mm foile faced routed boards and I have used Heat Punk to calculate the exact rad sizing to run the lot at 45deg C. Will set loop flows to ensure each loop achieves its design output as well all preset lockshield on rads for the same. Our heat loss is about 49W/m2 and so will use a Vitodens 050-W combi. 

Was thinking I do not need a separate pump on the manifold as, from my calcs, the one on the Vitodens should be plenty good enough, given that it all ground floor, single zone and only 5 rads.

Am I mistaken ?

Thanks in advance for any help

I think the UFH might struggle to get adequate flow when the rads are open path and flowing freely, as the pump potential will always choose the path of least resistance. The UFH loop smallest / shortest will get nice and warm, but the longest one will likely perform less admirably. If you can make all the UFH loops hydraulically similar then it may work, but any time the rads are all open, flow to the floor will take second place.

 

Are you very sure the design is sympathetic to one flow temp from source? If so, I think a pump on the manifold would be wise, but obvs minus the TMV. 
 

With the second manifold pump, it will circulate the loops, vs pump flow and return to the manifold, so there will be hydraulic separation. The flow and return from the boiler & its pump would tee into that via 2 close coupled T’s, so the 2 pumps never conflict with each other.