Ecodan query

[stratplus]

Air source heat pump, unvented cylinder with underfloor heating.
When calling for hot water the flow pipe gets quite hot but when calling for heating thw temp drops considerably.
Is this normal? Why would this be apart from the cylinder will need to be heated quicker?

 

[Nostrum]

Depending on the outside air temperature, it could be the weather compensation reducing the flow temperature or it could just be designed with a lower flow temp to increase efficiency.

 

[stratplus]

No weather compensation. Heating works off room stats.

 

[Nostrum]

It will be built into the unit and still controlled by room stats. Heat pump has an external sensor in the unit. Controller will have heating curve built into software. Most decent heat pumps have weather compensation as standard.

 

[Worcester]

It is normal that the flow when heating the DHW should be considerably hotter than when heating the house.

When there's a call for DHW, the HP fault created by high flow temperatures is usually overridden in the ASHP controller so that it can get the DHW up to 50°C plus.

When DHW is satisfied it should revert to heating. If it's an S plan that the heating system 2 port valve would usually be a NO valve so that as soon as DHW satisified the HP can dissipate its heat via the heating circuit (means that in summer even if no call for heat when DHW satisified you'll get a minute or so of flow to the heating circuit), if it's a Y plan, it will do that automatically.

 

[stratplus]

Thanks gor that worcester, that explains why all the ones ive installed seemed to ramp up in hw mode.
This particular one was linked to underfloor and a heated towel rail circuit.
Had a 3 port valve to the hw and underfloor manifold and then a 2 port to the towel rail. Individual polypipe programable room stats to each room apart from the towel rail rooms which must have been linked to another stat somewhere. No towel rails fitted so unable to tell although the 2 port was open so calling for heat but no circuit to flow through.