Basic Documentation

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Siemens Universal controllers RMU710B, RMU720B, RMU730B CE1P3150en
Building Technologies Aggregates 03.10.2011
10.4.3 Maximum Economy changeover (MECH)
The purpose of this function is to optimize control of heat recovery in air
conditioning systems with regard to operating costs.
To activate Maximum Economy Changeover (MECH) of the heat recovery
equipment, relevant inputs must be assigned.
Main menu > Commissioning > Extra configuration > Aggregates >
Heat recovery equipment >
Operating line Adjustable values / remarks
MECH input 1 ---, N.X1, N.X2, ..., Outside temperature,
[Logic 1] digital, [Logic 2] digital
(only °C, kJ/kg, 100, 1000, Digital)
MECH input 2 ---, N.X1, N.X2, ..., Room temperature, Extract air
temperature (only °C, kJ/kg, 100, 1000)
Main menu > Commissioning > Settings > .... or
Main menu > Settings > Aggregates > Heat recovery equipment >
Operating line Range Factory setting
MECH limit value
1)
3 K, 20 °C
3 kJ/kg, 40 kJ/kg
3, 40 ---
1) The MECH limit value operating line is used when changing over to a settable value as absolute
value, or when changing over based on a difference of two measured values as relative value. In this
case, it is used to consider heat sources in the extract air duct (e.g. dissipated heat fan).
There are three changeover options:
1. Changeover triggered externally via a digital signal:
Here, a digital input must be assigned to "MECH input 1".
The following applies:
Normally closed (low outside temperature) = No inversion
Operating position (high outside temperature) = Inversion
Control by heating sequences (S1, S2, S3)
w
Y
Q
S
Normal position
Operated position
3150S28en
Control by cooling sequences (S4, S5)
AO
T
Digital
X...
Y...
DI
12 1 2
Y
y1 y2

Q
S3 S2 S1 S4 S5
yp yp yp yp yp
a
d
Controller 1
(Ventilation)
With supply air limitation
Cascade
Constant (supply air)
Cascade/const (alternating)
Seq. limit. Casc/Const
3150S44en
MECH
HR
CC....................
w
Y
Q
S
Normal position
Operated position
3150S29en
Configuration
Setting values
Changeover options