Introduction
The REG System is specifically designed for radiant cooling system and provides some algorithms to prevent condensation from forming on the radiant surface during summer operation.
The system calculates the Dew Point Temperature (Dew Point) for each zone equipped with a temperature+humidity sensor, that is the critical temperature below which condensation forms under the zone’s current conditions.
The Dew Point Temperature, corrected by an offset that can be set differently from zone to zone (Dew Point Control parameter, indicated as Ctrl DP in the Configuration Zone/1 sub page), is compared with the Outlet temperature of the circuit serving the zone; if the water temperature is equal or below the calculated limit, there are the conditions for condensation formation.
If the circuit serving the zone is equipped with a mixed valve controlled by the REG System, the Outlet temperature of the circuit is increased if the water temperature is too close to the Dew Point Temperature, otherwise the zone will be blocked.
Note
For zones used as “Integration” to the dehumidifiers in Cooling system, the Dew Point Control (Ctrl DP) value must be set very high (in the order of 20°C), because the associated user does not act directly on the radiant surface, but it is a “Support” to the action of the dehumidifier.
Temperature Control and Zone Locking
The REG System is able to manage, in a smart and flexible way, the condensation in two main ways:
Circuit Water Outlet Temperature Control
Zone Block
Both controls require the installation of a water probe to control the water temperature of the circuits/manifolds, while the water outlet temperature Control required the presence of a mixing valve or the ability to send the set point directly to the cold-water source (via 0/10V, Modbus, or OpenTherm).
If there is no water outlet probe connected when the system needs to compare the result of the dew point calculation, it will use the value indicated in configuration/1 “Theoric Dew Point Limit”:
It is obviously not recommended to use this mode of dew point management.
1. Calculation of Surface Temperature
A condensation condition occurs when the floor surface temperature drops below the Dew Point. The water outlet temperature probe may be colder than the floor surface temperature, which depends on the materials used for the finish (wood, tiles, etc.). the REG System has a parameter, within the Zone section and different for each zone, which allows to considerate this factor.
For a correct operation of the system, it is recommended to correctly set the value of the Ctrl DP:
Radiant Surface Material | Dew Point Control |
|---|---|
Marble | 3,0 °C |
Ceramics | 3,0 °C |
Wood | 4,5 °C |
The values of the Dew Point Control (Ctrl DP) given above are indicative as it can vary depending on the materials used for the system construction. In fact, it cannot be excluded that two surfaces with the same material may have different values; this difference can depend on several factors:
Screed thickness
Materials used for floor construction
Radiant system pipes materials
Note
Within the Zone section (in the red frame), for each zone equipped with humidity and temperature sensor, the Dew Point (°C), indicated by the abbreviation DP in the green frame, is calculated:
PHOTO TBD
for the zones without humidity sensor, the DP is NC, not calculated.
The calculated DP must be compared with the floor surface temperature, which is the sum of the cold-water temperature and of a delta that take into consideration the type of covering. The parameter that allows the delta to be taken into account is the Dew Point Control (K, Kelvin degrees are used to indicate that the parameter is a temperature difference and not a temperature value), indicated by the abbreviation Ctrl DP in the green frame:
PHOTO TBD
Let us, for example, consider the zone 6, for which the calculated dew point is 15°C and the Dew Point control is equal to 3 K. The calculated dew point (15°C) will not be compared to the value read by the circuit water outlet temperature associated with the zone (C2), but with the value read by the probe of C2 + 3 K. The zone 6 will be blocked to prevent condensation if the water outlet temperature of the associated C2 circuit is less then 12°C (15°C - 3 K). While zone 7 will be blocked if the water outlet temperature of the associated C2 circuit drops below 10,3°C (13,3°C - 3 K).
To the right of Ctrl DP is another column marked 0. This column ensures that the calculation of the temperature to be compared with the calculated DP takes into account not only the water temperature, but also the room temperature. The value in the box can range from 0 to 100 (dimensionless):
If 0 is indicated, it means that the room temperature is not considered in the calculation and that simply the DP is compared with the water outlet temperature + delta K of the Ctrl DP box;
If 100 is indicated, it means that water temperature is not considered in the calculation and that the DP is compared with the room temperature of the zone;
If a value between 1 a 99 is indicated, then a weighted average of the two temperatures is calculated to find the reference temperature to compare with DP. For example: I use 50, this means that the temperature to be compared with DP is = [(room T * 50) + (Outlet T + delta K) * 50]/100
2. Water Outlet Temperature Control
Before blocking the zone, the REG System tries to increase the water temperature by closing the mixing valve or by increasing the set point at the chiller (via 0/10V, OpenTherm, or Modbus).
To do this, the REG System uses the parameter Offset DP/Water Outlet T, highlighted in yellow in the Configuration/1 page; it is an increase given to the water Outlet temperature of all circuits to avoid being too close to the calculated Dew Point. This logic avoids the repeated lockout and unlocking of the zones as it protects against condensation by raising the water outlet temperature, before the zone block intervenes.
Considerando ad esempio di usare 3 K come Offset PdR / Mandata e avendo una zona collegata al circuito 1 che è a rischio condensa se la temperatura di mandata < 6,8°C (PdR calcolato = 7,3°C e CtrlPdR = 0,5 k con 0 = non si considera la temperatura ambiente), si può notare che il limite inferiore di mandata è 6,8°C + 3 = 9,8 °C che corrisponde anche al set point (temperatura desiderata) > 5 °C che sarebbe il set point del circuito in freddo in modalità Comfort:
Ovviamente l’Offset / Mandata si applica a tutti i circuiti nel momento che una sola delle zone collegate è a rischio condensa. Potrebbe essere che altre zone non siano a rischio condensa è che l’aumento della temperatura di mandata per evitare il blocco di una sola zona impedisca di raffrescare le altre zone.
Nel caso in cui si voglia limitare l’effetto dell’Offset / Mandata su un circuito bisogna utilizzare il parametro “Limite Correzione Dew Point” che è un valore di temperatura (non un delta):
Se lasciato a zero è come se fosse disattivato. Se diverso da zero rappresenta l’aumento massimo consentito per quel circuito. Nell’esempio sotto 12°C rappresenta l’aumento massimo, oltre i 12°C il set point in raffrescamento non sarà alzato:
A questo punto interverrà il blocco della zona per la zona che rischia di condensare, ma il resto dell’impianto può continuare a raffrescare le zone non a rischio condensa.
3. Blocco della Zona
Nel momento in cui fallisce il controllo della temperatura di mandata, la zona verrà bloccata (Output OFF) chiudendo la relativa testina. Una volta che la zona si blocca ripartirà considerando l’isteresi del Punto di Rugiada impostata nella pagina Configurazione 1 (nel riquadro verde):
Quindi nell’esempio della zona 6 della secondo immagine, se si dovesse bloccare ripartirebbe con PdR calcolato = 14°C se l’isteresi fosse 1 K come indicato in immagine.
Inoltre nel momento in cui la zona viene bloccata, viene dato il consenso al deumidificatore associato se presente anche se l’umidità rilevata è inferiore al set point di umidità impostato.