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Chapter 7
Control modes
Regio Midi manual
As the electrical heater is connected to UO1, and since an electrical heater may become very
hot, a fan stop delay has been implemented into the system. The fan stop delay will only be
activated in heating mode, and then only if the fan has been running prior to the stop. When
the heat output has been set to 0 %, the fan will continue to run for an additional 120 s, at the
same speed it had prior to stopping.
It is very important to note that Regio does not have any built-in function for monitoring when
the fan is running or if the heat battery is overheating. This function must instead be provided
by a supervisory system.
Control mode 10: Change-over with VAV function
This control mode is used when room temperature is controlled via VAV and the same duct is
used for both warm and under-tempered air. Change-over takes place on UO1. Min/max
limitations are active. CO
2
control is also active and operates according to a linear function.
For the system to function properly, the change-over sensor must be used to measure duct air
temperature.
For more information see chapter 12: Change-over.
Min and max supply air limitation
Analogue input 1 (AI1) can be configured for use with a supply air temperature limitation
sensor. The controller will then automatically switch to cascade control. There are four values
for min and max limitation. The settable range is 10...50°C. The default setting is:
Control mode
Min limitation
Max limitation
Heating
24°C
35°C
Cooling
12°C
24°C
A room controller will then work together with a supply air temperature controller using
cascade control, resulting in a calculated supply air temperature maintaining the room
temperature setpoint.
The cascade factor consists of the supply air controller being faster than the room controller.
The cascade factor in Regio Midi acts as a divisor which affects both the P-band and I-time.
Example:
If the cascade factor is 3 and the room controller has a P-band of 10°C and an I-
time of 300 s, the supply air controller will receive a P-band of 3°C and an I-time of 100 s.
The supply air controller will therefore be 3 times as fast as the room controller.
Additional features
CO
2
sensor and VAV control (RC-C3DOC, RCC-
C3DOCS, RC-C3DFOC)
RC-C3DOC, RCC-C3DOCS and RC-C3DFOC can be set to all of the above control modes.
When RC-C3DOC, RCC-C3DOCS or RC-C3DFOC are set to VAV control, the control mode
is combined with a CO
2
control function.
In control mode Heating/Cooling with VAV-control, the CO
2
concentration in the room will
make the VAV damper, cooling output UO2, open. The function is linear and the damper
works between the configured min. flow (FS=20 %) and 100 %, depending on the CO
2
concentration in the room. If the CO
2
concentration drops below the configured min. limit, the
damper will stay on the minimum allowed air flow. When the CO
2
concentration rises, the
damper will open linearly until reaching the configured CO
2
max. value, at which point it will
be 100 % open.
