View Full Version : Two stage lift using UFH

27-12-2016, 12:07 AM
Some years ago I seen a new build home fitted with a GSHP which heated a large UFH area in a residential property.
The hot water was provided with an unvented cylinder that had a separate smaller heat pump integrated with the cylinder.

The collector for this heat pump was the UFH circuit.
Do systems like this require the main heat pump to operate in tandem with the hot water heat pump?
So that the system is providing a 2 stage temperature lift to the hot water cylinder?

Also could anyone name any companies using this method?
Many Thanks.

Rob White
27-12-2016, 01:44 AM

If i have understood you, the hot water cylinders collector (evap)
is piped into the floor where the Ground Sourced Heatpump, heats?

I have never seen that done but could think it would help with the
higher water temps required in the cylinder, trouble is, the critical temp??

What refrigerant was inside it? I think that would be a very big factor
in whether it would work efficiently or not.

As for the main heatpump working or not?? think what temp the floor would
be if it was not, low 20's maybe high teens? Could it be a form of cooling
when the main heating is off in the summer?

Condensation would be a hugh factor in this and dew point temps would have
to be closely controled for it to work.

I have never seen it so I can't coment on who would do it.




27-12-2016, 02:17 PM
I found the manufacturer...

27-12-2016, 02:59 PM
The layout is schematic 13.4 that I seen installed. Except without the buffer tank and radiators.

This system has been running now for 9 year now without issue.

What are the servicing procedures for both set ups?
Many Thanks.

24-02-2017, 04:59 PM
Both heat pumps need to be running.

The DHW cylinder heat pump is using the RETURN flow from the ufh to the heating HP as its heat source.

The UFH system isn't the collector for the DHW heat pump, it's the return flow to the main heat pump that is, so effectively the DHW heat pump has a 'warm source' making it more efficient.

It does mean that the main heating pump will be working harder / longer, and that both heat pumps are needed to be running when the DHW heat pump is. However the DHW heat pump should be highly efficient.

Having said that, in hot climates, with careful control, the DHW cylinder could effectively be acting deliberately to cool without any heat input from the heating heat pump. - Dew point and condensation are critical when using ufh to cool the house in the summer.