Pagina
13 di 30
The P control is normally used in:
i. plants where temperature doesn’t change frequently and rapidly.
ii. plants where a constant deviation between the temperature and the
setpoint is acceptable (within a certain limited range)
iii. plants with great volumes (accumulators) or with constant flow rate.
Option “
Integral Band”:
the integral action acts on the actuator with a speed
proportional to the deviation between the temperature and the setpoint. Here
doesn’t exist a direct relationship between the valve position and the deviation
(error) as in case of a pure proportional regulation. The integral rate and time are
fixed and handled by the thermostat internally.
A pure integral regulation can be used in case of HVAC plants with a fast
reaction, without or with a small thermal inertia and with slow load variations.
Option “
Proportional/Integral Band”:
the PI regulation provides both features of
a pure proportional and integral controls, i.e. a fast response due to the
proportional regulation at the start up and a quite “load independence” of the
integral action at the end. Normally the proportional control acts immediately as
the thermostat is activated in order to reduce the quite big deviation at first, than
the integral regulation acts as the temperature move towards near the setpoint
reducing completely the permanent deviation remained after the proportional
control.
The PI control allows reaching immediately the setpoint reducing the permanent
deviation left by the proportional action especially in wide environments and
rooms with a big thermal inertia.
Type Plant
This parameter allow the selection of HVAC plant type installed inside the
premises.
In case a 2 or 4 tubes ON/OFF is selected the thermostat sends a switching
ON/OFF command via 1 bit object to the valves when the temperature cross the
range of actual setpoint ± temperature coefficient regulation (hysteresis)
∆
T in a
two steps algorithm. It’s therefore possible, for example, for electro thermal
control valves to be addressed via switch actuators. In case a 2 or 4 tubes circuit
proportional is used the control value is determined internally always according
to a two-step algorithm with an adjustable hysteresis and output via 1 byte
communication object. In this case the room thermostat sends only values 0
(=0%=valve closed) or 255 (=100%=valve fully opened).
The toggling between heating (winter) and cooling (summer) is not carried out
neither manually nor automatically but the two control are completely
independent.
Options:
2
Tubes Circuit ON/OFF
4
Tubes Circuit ON/OFF
2
Tubes Circuit Proportional
4 Tubes Circuit Proportional
Option “2
Tubes Circuit ON/OFF:”
with this option the HVAC plan is composed
of 2 circuits with ON/OFF switching valves. The thermostat provides only 1 bit
