Features and technical data
8
1
▶
modulating premix burner with 1:9 ratio;
▶
automatic air purging valve;
▶
high efficiency modulating water pump;
▶
system drain cock;
▶
heat circuit temperature probe;
▶
condensate drain siphon.
Control and safety devices
▶
flue safety thermal fuse;
▶
3 bar safety valve;
▶
gas solenoid valve;
▶
safety thermostat;
▶
expansion tank;
▶
water differential pressure switch.
1.1.4
Control of the two heat generators
A control system has been designed for the K18 Hybrigas unit,
called Armonia, which allows integration between the heat
pump module and the condensing boiler module (auxiliary
boiler) that compose the K18 Hybrigas unit, to be managed as
optimally as possible in order to provide the best performance
in terms of comfort and energy efficiency.
Specifically, as shown in Figure 1.2
p. 8 below, various cases
are possible:
A. very low load: active auxiliary boiler in modulation and
heat pump off (replacement at a particularly mild outdoor
temperature)
B. low load: active heat pump in modulation and auxiliary boil-
er off
C. average/high load: active heat pump at full power and active
auxiliary boiler in modulation (integration)
D. high load: maximum power for the operating condition to
be reached quicker (integration)
E. very high load: heat pump out of the operating limits and
auxiliary boiler that autonomously covers the design load
(replacement at low ambient temperature)
Figure 1.2
Armonia control system diagram
Tj [°C]
outdoor temperature
PLRh(Tj) [%] plant partial load ratio at outdoor temperature Tj
A
Heat pump off. Active auxiliary boiler in modulation.
B
Active heat pump in modulation. Auxiliary boiler off.
C
Active heat pump at full power. Active auxiliary boiler in modulation.
D
Active heat pump at full power. Active auxiliary boiler at full power.
E
Heat pump off. Active auxiliary boiler at full power.
100%
0%
T j
20°C
A
B
C
D
E
PLRh(Tj) [%]
In the presence of a minimal thermal demand (scenario A), the
minimum power of the heat pump could still be excessive in
comparison to the demand. In this case it may be advantageous
to use only the auxiliary boiler (replacement mode).
In the presence of low thermal demand (scenario B), only the
heat pump will be active in modulation mode, whereas the aux-
iliary boiler will be off.
As the thermal demand increases (scenario C), the heat pump
reaches full power and, if the thermal load still cannot be ful-
filled, it will activate the auxiliary boiler, which will run in mod-
ulation mode. The heat pump will still remain active and at full
power, and therefore the power of the auxiliary boiler will be
added to that of the heat pump (integration mode).
When the thermal demand is high (scenario D), for example
while the system reaches operating conditions, the heat pump
and auxiliary boiler will run at maximum power, reducing the
necessary time for the operating conditions to be reached and
ensuring the optimal comfort even in harsher environmental
conditions.
If the heating system design require the water tem-
perature to be higher than the maximum that can be
dispensed by the heat pump, in high thermal demand
conditions (scenario E), the auxiliary boiler can be acti-
vated as its replacement. In this type of application the
maximum thermal load of the building must be at most
equal to the power of the auxiliary boiler and not to the
sum of the power of the two appliances (replacement
mode).
The auxiliary boiler can therefore be operated in four ways (see
also Paragraph 5.5.5
p. 43):
▶
inactive (the auxiliary boiler does not intervene in any way);
▶
emergency (the auxiliary boiler is only activated when there
is an alarm on the heat pump module);
▶
integration (active auxiliary boiler as necessary for