System Response In Case Of Fault; Communication Problems; Probe Faults; Control Issues - Rehau NEA SMART 2.0 Service Manual

4.9

System response in case of fault

When the system detects a problem e.g. a communication failure or a
defective probe, a message is triggered, and the fail safe mode is
activated.
The fail safe mode is designed to avoid any damages to the building
and – if possible – ensure a minimum of comfort.
4.9.1

Communication problems

Communication loss with room unit
The communication failure may be caused by almost empty batteries
in case of wireless Room Units or Room probes or by a damaged
Zone Bus system.
After 1 hour of communication loss the NEA SMART 2.0 Base reports
this via a flashing LED corresponding to the channel experiencing the
issue. The room will be heated in emergency mode (80 % of last
heating power). Cooling is stopped.
Communication loss between system components (Sysbus)
The System Bus connects the NEA SMART 2.0 Base units and the
U-Modules.
In case of communication break the SYSBUS LED's are flashing.
The connected components enter a fail safe mode to avoid damages
and to ensure comfortable conditions as far as possible. But it is not
possible in this case to operate the complete system via App or
integrated web pages.
4.9.2

Probe faults

Room temperature probe defective
Same reaction as "Communication loss of room unit".
Room humidity probe defective
Cooling of this room is stopped to avoid condensation problems. In
heating mode there is no reaction except the error message.
Outside temperature probe defective or no signal
The system reacts as if outside temperature would be 0 °C.
Flow temperature probe defective
In heating mode, the mixing valve is set to 10 % open, the mixed
circuit keeps on running.
In Cooling mode the mixed circuit is closed.
36
4.9.3

Control issues

Heating mode: Flow temperature too high
As long as the flow temperature does not exceed the defined maximum
value for this circuit, the mixed circuit keeps on running. When the
flow temperature is above this value, the mixed circuit will be closed
down. The magnitude of deviation determines how fast this is done.
When flow temperature is above 60 °C, the mixed circuit is stopped
immediately.
Cooling mode: Flow temperature is below calculated dew point
of one or more rooms
Valves of these rooms are closed.
are supplied with water, which could cause condensation problems.
1)
It is possible that during commissioning the safety offset for the flow temperature in
relation to the dew point was set to zero or even a negative offset. In such a case the
valves would be closed every time the flow temperature drops below the set point.
Cooling mode: Flow temperature too low
As long as the flow temperature does not fall below the defined
minimum value for this circuit, the mixed circuit keeps on running.
If the flow temperature is below the minimum value defined for this
circuit, will be closed down. The magnitude of deviation determines
how fast this is done.
When flow temperature is below 10 °C, the mixed circuit is stopped
immediately.
4.9.4

Other issues

Open window detected
It has to differentiated between these cases:
1. Automatic detection by room unit
In heating and cooling mode, for 30 minutes heating and cooling
is stopped and then continued with previous energy level.
2. Window dry contact connected to room unit
In heating mode, for 30 minutes heating is stopped and then
continued with REDUCED energy level. In cooling mode, cooling is
stopped and not started again until the window is closed.
3. Window dry contact connected to base or R-Module
In this case the window contact is assigned to a room and
behaviour is the same as in case 2)
Condensation problem detected
It has to be differentiated between these cases:
1. Detection by room unit (high humidity) or by a dew point monitor
connected to room unit:
Cooling of this room is stopped. Assigned dehumidifier is started.
2. Detection by dew point monitor connected to base or to R-Module:
Cooling of all rooms connected to this base and R-Module is
stopped. Mixed circuits linked to this Base or R-Module are
stopped. Assigned dehumidifiers are started.
This prevents that one or more rooms
1)