Central room temperature controller for ERR underfloor heating

The heat pump can only respond based on the supply or return temperature as well as the outside temperature; it has no idea what the temperature is in the rooms or whether valves are open or closed.

This means that as soon as the temperature in only one room decreases and the supply temperature falls below the required value, the heat pump runs.

The less heating water is circulating, the faster the supply temperature reaches the setpoint and the heat pump switches off.

However, since the small amount of water also cools down faster, the heat pump has to start up again more quickly.

The result is then many starts per day.

Since modern heating systems control the pumps independently of the heating, a higher water volume also means that the heat pump can run longer at low power and the times when it does not have to heat are also longer.

In a well-coordinated system, this leads to single-digit start numbers per day.

Therefore, it is better to use modulating heating systems with the lowest possible minimum output.

By switching off, the thermostats simultaneously prevent heat that is too much in the room from being absorbed and then released again in other rooms.

Most systems today are controlled by outside temperature with supply temperature regulation.

The heat pump begins to heat when the supply temperature falls below the set temperature (with a certain tolerance of a few degrees).

If the thermostats in some rooms now shut off the flow, the volume flow and mass decrease.

If the flow falls below the minimum amount, it may happen that the heat pump cannot dissipate its heat quickly enough and reports a fault.

In air-water heat pumps, this can lead to the defrosting process failing.

To prevent this, buffer tanks are often installed, which, however, are efficiency killers.

Well, without ERR no heat would be transferred to the underfloor heating, and the high return temperature would lead to the heat pump shutting down, and the expensive pointless heating of the storage tank would be eliminated.

...exactly...

but the pump would still run continuously and consume electricity. Pumps, however efficient they are, consume a relatively high amount of power during operation and are one of the most worn parts in the system.

...and how much electricity does your ERR consume?

Can this ERR/heat pump discussion actually be applied to modern gas boilers with solar support?

Yes, a condensing boiler also likes to operate for a long time at low temperature.

The self-regulating effect is actually amplified by an ERR, which also argues in favor of thermostats.

Here is an example of what a thermostat can be good for:

The heat pump is set so that no hot water is provided for the underfloor heating until the outdoor temperature reaches 18°C.

However, because it was warm for weeks beforehand, causing the masonry to heat up and this heat release still keeps the rooms at 22°C, the thermostats shut off the valves.

The self-regulating effect is prevented because by shutting off the rooms there is no movement in the circuit.

Self-regulating effect means that the underfloor heating always releases heat in relation to the ambient temperature.

Room/screed 15 degrees underfloor heating 25 degrees = large heat output due to high difference.

Room/screed 22 degrees underfloor heating 25 degrees = low heat output due to small difference.

Room/screed 28 degrees underfloor heating 25 degrees = the heating water starts to absorb heat from the room/screed and transport it away.

If you had the ERR off and only the pump running, the heat pump wouldn’t have to heat at all because the supply line would not fall below the set temperature due to the heated screed.

I consider 18°C outdoor temperature as heating limit far too high for a new building; it should be around 10 degrees.

Here in my old building from 1996, I only have 13 degrees as the heating limit.

Can this ERR/heat pump discussion actually be transferred to modern gas heating systems with solar support?

Yes, absolutely, because the same thermodynamic laws and processes apply. As long as it is the same heating systems (low-temperature underfloor heating).

The self-regulating effect is actually increased by an ERR, which again speaks in favor of thermostats.

It's actually the other way around, because the ERR works against the self-regulating effect. The approach of the thermostats in each room tries to regulate everything down to zero.

However, since it was so warm for weeks beforehand that the masonry heated up and this heat output still keeps the rooms at 22°C, the thermostats close the valves. Ergo, I have no heating demand and the heat pump only heats for the storage tank.

Since no heat output takes place in the rooms, as you yourself describe that the masonry has heated up. In this case, an ERR is as necessary as a third wheel. With or without ERR, no energy is transferred to the rooms, and thus you can safely do without the ERR in this case as well.

Sounds logical what you all say. I was just skeptical because I assumed that a constant heat distribution through all rooms, although only one room has a demand, requires unnecessary pump operation and longer heating time of the room --> so energy waste. So you mean that I should turn all thermostats permanently to the maximum temperature and set the target value for the individual rooms directly on the heat pump?