Hybrid system for heating and underfloor

[PJB Spain]

Hi All,
New here and first post.

Currently working with a client on a refurb in Spain and would appreciate your thoughts.
The client has a new 500L tank that is currently heated via a boiler and some (defunct) solar panels. He would like to change this method to ASHP and new solar which is no problem. However, he will be installing U/F heating and cooling and would like to integrate this.
Proposed ASHP unit is 14kW Viesmann Vitocal 100-A which is sufficient for the U/F heating/cooling. The existing tank (Sonnenkraft DHW500R2) has all required connections for the required DHW system and I think that this could be modified to include the U/F requirements.
I have attached a simple schematic showing the proposed basic layout (excluding expansions, safety/strainers/bleed points etc).
Operating philosophy is as follows:

Summer.
The hot water is heated primarily through the solar panels, any requirement for rapid top up would be through the heat pump.
The underfloor cooling would be provided by the heat pump. Solar panels would be disconnected via the 3 way valves.

Winter:
Underfloor heating would be provided by a combination of both solar gain and heat pump. Should the sun not shine, the heat pump is correctly sized to provide the total loading required.

Hot Water:
At all times this would be prioritised. Solar when available, heat pump when necessary.

The system has been designed to interface with the proposed heat pump and solar pumping station. I have attempted to ensure that it is not over complicated and that in the event of any problems the systems could be isolated in order to ensure that hot water would be available. Basically, all will be monitored through temperature sensors in the tanks and solar array and will be controlled by a small logic block which could be taken out of circuit if required. Not quite dual redundancy but a system that can be easily reconfigured in case of any emergency or breakdown.

I then sent this over to one of our suppliers and received their response, (see second attachment).

Seems rather OTT to me. What do you guys think?
Many Thanks
Patrick

 

[Brambles]

Without the required heat loads it is difficult to comment on system performance.

The wet under floor cooling system will require a 3 degree neutral zone and humidity sensors to control each loop. If you don’t, you will get issues with condensation forming on the slab.

Generally I would opt for fanned chiller units to provide cooling rather than the UFH slab.

Just be aware that with the Viessman ASHP, it is quite hard to integrate non Viessman control units, but I guess you are familiar with that. That includes the ASHP flow valves, which generally need to be fast acting to prevent ASHP unit trips. Also, why you have valves on the return too?

 

[SJB060685]

The wet under floor cooling system will require a 3 degree neutral zone and humidity sensors to control each loop. If you don’t, you will get issues with condensation forming on the slab.

Hi Brambles can you explain this a bit further to me.
Many thanks

 

[Brambles]

SJB

Think of a cold water inlet under the sink ( a warm humid environment) as cold water flows in the pipe condensation forms on the pipes surface.

If you use an uncontrolled UFH circuit to chill a concrete slab if the room is warm and humid, exactly the same happens when the slab temperature hits the dew point. The way round it is to use humidity stats in keep the cool water temperature and slab temp in a neutral zone to prevent the formation of condensation. Not too much of an issue in the UK (other than where the pipes enter the slab) but it is in warmer climates with a high relative humidity

If it does form, black mould across the screed can follow very quickly and is hard to get rid of.

 

[SJB060685]

Thanks Brambles. I will re read my UFH guide then