HVAC APPLICATIONS
HVAC APPLICATIONS
The floor radiant system is a widespread hydronic system for heating and cooling rooms.
The heat transfer fluid circulates inside circuits made up of plastic pipes placed under
the surface covering of the floor; in the most common version, the pipes are laid on
an insulating layer and embedded in the cement base. The system is invisible and uses
the whole surface of the floor as a large terminal for the heat exchange prevailing at
radiation. In both seasons the system works with a very limited temperature difference
between the heat transfer fluid and the room air; for this reason it is also defined as
a“low-temperature difference” heating and cooling system.
The system shown in the example is intended for a residential building. It is a combined
system, i.e. it combines the radiant floor panels with one or more fan-coil units, mainly
for the integration of sensible loads in cooling conduction mode.
Control with Ekinex
The EK-TM1-TP time / astronomical digital switch (A) ensures that the system is allowed
to operate according to predefined time scheduling and is constantly synchronised with
date and time by the (optional) GPS module EK-GPS-1 (B).
The need to produce heat transfer fluid at two different temperatures for the combined
system (consisting in floor radiant panels / fan-coil units) is solved by controlling a
mixing group with the EK-HH1-TP controller (I). The device controls a mixing valve and
a circulating pump; by means of the EK-STI-NTC-3435 sensors (M, N) it can measure
the flow and return temperatures of the heat transfer fluid. On the unmixed circuit it can
also control, as required, a circulating pump (7) or a zone valve.
The room air temperature is controlled by room thermostats EK-EQ2-TP (E), measuring
temperature and relative humidity, in combination with actuators-controllers for
electrothermal drives EK-HE1-TP (O) and actuators-controllers for fan-coils EK-HC1-
TP (C). The thermostats are able to calculate and send to the bus the dew temperature;
if the thermo-hygrometric conditions of the room are close to those critical for the
formation of condensation on the cooled surfaces, it is possible to implement one of
the several protection strategies provided by the Ekinex® thermoregulation system (see
table on the right); for example, recalibration of the flow temperature of the heat transfer
fluid through the EK-HH1-TP controller (I).
The optional supervision by means of the Delégo Server (G) allows you to monitor and
control the home automation system by means of an App for mobile devices (9) and/
or a Delégo touch-panel (H).
Two-stage system (main / auxiliary)
In the system configuration of the example, the room thermostat EK-EQ2-TP (E)
allows you to easily realise a two-stage heating / cooling system. When the main stage
consists of a radiant panel system, the high inertia (especially typical of the version
with cement base), makes it rather slow in the start-up phase to achieve comfort
conditions. In this case, it is possible to configure the fan-coils as an auxiliary stage;
thanks to their much lower inertia, they contribute in the initial phase to quickly heat or
cool the room and then stop their action when the difference between the measured
and setpoint temperatures can be satisfactorily addressed by the main stage alone. The
auxiliary stage works in automatic mode with a configurable offset with respect to the
temperature setpoint set for the radiant floor (main stage).
Prevention of condensation in cooling conduction mode
In summer cooling operation, the latent loads (due to the increase in the humidity level
in the room) are taken care of by the air handling integration.
If this is not done satisfactorily, or in the event of a sudden change in thermohygrometric
conditions (e.g. due to accidental stopping of the machines or opening of windows),
additional safety measures must be taken to prevent or limit the formation of
condensation on cold surfaces. The EK-EQ2-TP (E) room thermostats provide various
active and passive protection strategies depending on the system configuration and the
presence of home automation devices.
Active protection is always preferable, as the intervention tends to prevent the conditions
of formation of condensation, while passive protection intervenes when the formation of
condensation has already begun.
Surface temperature limitation
In some cases it is advisable to limit the surface temperature when the radiant floor
system is used as an auxiliary stage for heating; the dispersions to the outside of the
building are handled by the main heating system, while the auxiliary stage works only to
maintain the temperature of the floor at a pleasant level in the bathrooms of residential
buildings or in the rooms of sports centers, spas, etc. This limitation is also included in
the EN 1264 standard (Underfloor heating, Part 3) which defines the maximum allowed
temperature (TSmax) for the surface of the floor from a physiological point of view as
follows:
- TSmax ≤ 29°C for areas of normal occupancy of the rooms;
- TSmax ≤ 35°C for the peripheral areas of the rooms.
Floor radiant system in residential buildings
Main
heating system
(high inertia)
Auxiliary stage
(low inertia)
Thermal power supplied [W]
t
T
T
T
T
T
zone 2
zone 1
zona 1
zona 2
Boiler room
Low-temperature distribution
Mixing substation
Air integration
A
B
C
D
E
E
F
F
I
L
M
N
O
1
2
3
7
8
9
10
11
12
13
13
14
15
16
IP
Delégo supervision system
G
4
5
6
�
Example
Ekinex devices
A) Time / astronomical digital switch EK-TM1-TP
B) GPS module EK-GPS-1
C) Actuator-controller for fan-coils EK-HC1-TP
D) NTC temperature sensor (contact) EK-STC-NTC-3435
E) Room thermostat EK-EQ2-TP
F) NTC temperature sensor (air) EK-STL-NTC-3435
G) Delégo server EK-DEL-SRV-...
H) Touch panel Delégo EK-DEL-xpan...
I) Mixing group controller EK-HH1-TP
L) NTC temperature sensor (external) EK-STE-NTC-3435
M) NTC temperature sensor (immersion, flow) EK-STI-NTC-3435
N) NTC temperature sensor (immersion, return) EK-STI-NTC-3435
O) Actuator-controller for electrothermal drives EK-HE1-TP
Other system components
1) Window contact
2) Fan-coil unit
3) Valve with ON / OFF servomotor
4) Access point LAN Wi-Fi
5) Switch
6) Smartphone with App Delégo (Apple iOS or Android)
7) Circolating pump for unmixed circuit
8) Mixing group
9) Mixing valve with servomotor
10) Circolating pump for mixed circuit (floor radiant system)
11) Distribution manifold for low-temperature circuits
12) ON / OFF electrothermal actuators
13) Condensation sensor
14) Thermal generator (warm and cold fluids)
15) Boiler room manifold (flow)
16) Boiler room manifold (return)
Type
Mode
Action
Passive
With condensation sensor (13) connected
to an input of the room thermostat (E)
Closing of the circuit serving the involved room
by means of the actuator (O)
With condensation sensor communicating
with the thermostat (E) via KNX bus
Closing of the circuit serving the involved room
by means of the actuator (O)
Active
Comparison between fl ow temperature
(fi xed design value, ETS parameter) and
dew temperature calculated by the room
thermostat (E)
Closing of the circuit serving the involved room
by means of the actuator (O) when the fl ow
temperature is lower than the dew temperature
Comparison between fl ow temperature
(measured value received from the KNX
bus) and dew temperature calculated by
the room thermostat (E)
Closing of the circuit serving the involved room
by means of the actuator (O) when the fl ow
temperature is lower than the dew temperature
The dew temperature from the thermostat
(E) is sent via KNX bus to the mixing group
controller (I)
Calibration of the cold fl uid fl ow temperature
by the controller (I) and maintenance of the
opening of the circuit serving the involved
room by the actuator (O)
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