Product Information; Important Notices On Use; Function Definition; Basic Principle - Bosch MC 400 Manual De Instalación Para El Técnico

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Product Information

The module is designed to control cascade systems. A cascade system is
a heating system in which several heat sources are used to obtain greater
heat output.
• The module is used to activate the heat source.
• The module is used to record external, flow and return temperature.
• Configuration of the cascade system with a control unit with a BUS
interface EMS 2/EMS plus (not possible with all control units).
The combination options for the modules are shown in the connection
diagrams.
2.1

Important notices on use

The control unit is directly connected to the cascade module at the "BUS
" terminal (not BUS1...4) and the cascade system is configured in
MC 400.
▶ Do NOT reconnect the control unit directly into the devices for service
or operating purposes, but use the control unit as intended for
specific operations.
The settings for the cascade are no longer necessary due to the
reconnection and the control unit must be re-commissioned.
The module communicates via an EMS 2/EMS plus interface with other
EMS 2/EMS plus-enabled BUS nodes.
If the speed of heat sources with a speed-controlled pump is too low at
burner start, high temperatures and frequent burner cycles can arise.
▶ If needed, configure the pump to On/Off mode with 100% output,
otherwise set minimum pump output to the highest possible value.
• The module can be connected to control units with a EMS 2/EMS plus
(Energy Management System) BUS interface. Alternatively, an
external output demand or temperature demand can be connected
via the 0-10 V interface on the module.
• The module only communicates with heat sources with EMS, EMS 2,
EMS plus and 2-wire BUS (HTIII) (with the exception of heat sources
of the product series GB112,GB132, GB135, GB142, GB152).
• Only connect heat sources from Bosch Thermotechnology in the
system.
• Only use heat sources in a system with either gas or oil as the energy
source (heat pumps with a EMS 2 / EMS plus BUS interface are not
allowed).
• The installation room must be appropriate for the IP rating stated in
the technical data of the module.
• If a DHW cylinder is connected directly to a heat source:
– The system controller or 0-10 V controller does not display any
information about the DHW system and does not influence the
DHW heating.
– With direct DHW heating, it is recommended that a cylinder
smaller than 400 litres is used.
– The domestic hot water including thermal disinfection is
controlled directly by the heat source.
– Thermal disinfection may have to be monitored manually.
Observe the heat source instructions.
– If it is not possible to monitor thermal disinfection at the device,
do not connect a DHW cylinder directly to a heat source.
MC 400 – 6720890243 (2018/12)
2.2

Function definition

2.2.1

Basic principle

The module modulates the overall performance of the cascade
depending on the temperature difference between the flow temperature
(at the low loss header or at the heat exchanger for system separation)
and the system set temperature. For this purpose, the devices are
switched on or off one after the other. The devices are always modulated
via the performance specification and attain the maximum possible set
temperature as the set temperature. Before a device is switched on, the
module activates the heating pump for 2 minutes to bring the device up
to operating temperature.
Every device causes a significant performance boost when switched on
or off. The module uses the device previously switched on to reduce the
performance jump.
The module modulates the first device for maximum performance. Then,
if another device is switched on, it decreases the performance of the first
device at the same time. The second device therefore does not cause a
jump in overall performance. With further performance requirements,
the module then increases the performance of the first device again. The
second remains at minimum performance. Only if the first device
reaches maximum performance again, modulation is performed on the
second device. With the corresponding performance requirement, this
continues until all devices are running at maximum performance.
If the performance supplied is too great, the module reduces the
performance of the last device switched on to minimum. Then, the
previously started device (which is still running with maximum
performance) is modulated until the remaining performance of the last
device is reduced. Only then the last device is switched off, and the
penultimate is returned to maximum performance at the same time.
Thus, any abrupt reduction of overall performance is avoided. If the
operating temperature is too high, this will continue until all devices are
switched off. When the heat demand ends, all devices are switched off
simultaneously.
2.2.2

Time limits

If more performance is required than a heat source can provide or the
temperature falls below the set temperature
source is only available after a defined time
After the start of another heat source, the module waits 1½ minutes,
until a further performance increase takes effect. This prevents
overshooting of the temperature as far as possible.
This basic principle applies to the functions with codes 1 to 4 and 8 to 9.
With these functions, the module always controls the set temperature in
the system, and the tolerated lower/upper temperature and serves as a
switching differential for the heat source.
2.3

Control strategies

2.3.1

Serial standard cascade

The connected heat sources/modules are connected and disconnected
according to the wiring.
For example, the heat source connected to the BUS1 terminal is
switched on first, the heat source connected to the BUS2 terminal is
switched on second, etc.
If the heat source is switched off, the sequence is reversed. The heat
source which was switched on last is switched off first.
The controls take into account that performance increases or decreases
suddenly when a heat source is switched on or off.
1) Tolerated lower temperature, adjustment range 0-10 K, default setting 5 K (not
used for performance control)
2) Starting delay of the sequential device, adjustment range 0-15 minutes, default
setting 6 minutes
Product Information
1)
the next available heat
2)
switched on by the module.
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