Coils - Carrier 39HXC Manual

3 - FEATURES

3.9 - Coils

The unit may contain two coils (hydraulic and/or electric).
These coils are configured using parameters P28, P29 and P32.
They may be a cooling coil, a heating coil or a mixed coil (heating or cooling according to the network temperature), or an electric heater.
If a coil is ducted, there is an internal supply air temperature sensor situated at the machine outlet, and an additional sensor situated
at the ducted coil outlet.
28
29
32
3.9.1 - Mixed coil scenario
In the case of a mixed coil, the changeover may be made either via an on/off input or via the CMS (settable via parameter P162).
The changeover thermostat must be fitted by the installer on the mixed coil inlet, at a point where water is in constant circulation.
The changeover status (heating or cooling mode) can be viewed via parameter P422.
162
3.9.2 - Frost protection
The hydraulic coil frost protection is provided by monitoring the unit's supply air temperature. If this is below the threshold P248, the
frost protection fault is tripped and the isolation damper is closed, ventilation stops and the coil valves are opened 100%.
A frost prevention function is available once the unit is off (via the HMI, the CMS or a danger fault), or during the ventilation start-up
phase. It consists in leaving the hydraulic coil valve slightly open (settable value) to maintain water circulation (P260). This opening is
maintained constantly (including when the machine is shut down but still energised).
248
260
261
3.9.3 - Pumps
It is possible to control pumps (not supplied). They are actuated as soon as the coil valve opening demand is greater than 0%. Their
presence is indicated by parameters P92 and P93, and their status can be viewed in parameters P424 to P427
92
93
3.9.4 - External generator
It is possible to control an external heater or cooler (selected via parameter P90), which is activated when the associated coil control
is greater than 0%
90
3.9.5 - Electrical heater scenario
The control system is used to control an electric heater comprising 1 on/off stage or 2 on/off stages (3-stage control (stage 1,
then stage 2, then stages 1 and 2)) or 1 on/off + triac stage.
A minimum air flow rate is required to use the electric heaters (P126). If the flow rate is below this parameter, the electric heater will not be
able to start up and the message "control limited" will appear. This flow rate depends on the size of the AHU.
If an on/off electric heater is installed, the temperature control must not be based on the supply air (P154).
22
Coil 1
Coil 2
Electric heater
Changeover selection
Hydraulic coil frost protection safety threshold
Opening percentage for the coil 1 valve when unit stopped
Opening percentage for the coil 2 valve when unit stopped
Coil no.1 pump
Coil no.2 pump
External generator
0%
33%
Electric heating requirement
100%
66%