Do I need a separate UFH pump for an ASHP?

[Morninglory]

Hi,

As ever, apologies if this has been covered before. Looking at getting an ASHP in the future and kitting the house out in preparation. Would an underfloor heating manifold need a pump, or is the pump within the ASHP adequate? Two ground floor UFH rooms, 15 metre square each ie under 100m of 16mm pipe in each, then two upper floors with radiators all 22mm plumbing. House approx 100metre square floor area. Can I get a manifold without a pump, then add one later? Currently, we only have the two upper floors heated by a gas combi boiler and the ground floor is not connected. Any help much appreciated.

 

[ericmark]

The main reason for two pumps is to keep the UFH cool enough. As the circulating water cools, more hot is added, but this is where one has a mixture of temperatures, radiators and DHW being hotter than the UFH which in the main is kept under 27ºC.

The whole idea of using UFH with ASHP is so the pump does not need to get the water too hot, we have two completely different ideas with CH one is only to heat rooms as and when required, the other is to never turn the heating off so only needs to maintain the heat, two opposite ideas really.

There are different ways to plumb, much depends on the design of the home. My house gets sun through the windows, so I want rapid reaction, when the sun comes out, want to stop heating room, and underfloor heating simply can't react fast enough. And the idea of UFH is so the heat pump does not have to work as hard, so it's all or nothing. If some water still needs to get hot for some rooms or for DHW then the whole gain from UFH is lost.

 

[Mister Banks]

Hi,

As ever, apologies if this has been covered before. Looking at getting an ASHP in the future and kitting the house out in preparation. Would an underfloor heating manifold need a pump, or is the pump within the ASHP adequate? Two ground floor UFH rooms, 15 metre square each ie under 100m of 16mm pipe in each, then two upper floors with radiators all 22mm plumbing. House approx 100metre square floor area. Can I get a manifold without a pump, then add one later? Currently, we only have the two upper floors heated by a gas combi boiler and the ground floor is not connected. Any help much appreciated.

Some systems have an additional pump and some rely on the pump in the ASHP, it depends on the overall system design, heat pump rating, flow temperatures, floor coverings, DHW requirement, etc.

 

[Madrab]

The ideal is to have a separate pump for anything but the smallest of UFH zones. This allows the UFH to be much more controlled, balanced, managed etc as a separate entity to the radiator system. The fine tuning of UFH is different to the radiators.

It allows the separate zones to be better controlled whereby the radiators would be controlled by it's own stat, which would control the main pump and in turn the ASHP - same is applicable to the UFH zones/circuits but as the UFH supply requirements will different then having it's own pump makes that setup and ongoing conrtol much easier.