Carel µC2SE User Manual page 55

- Enable freecooling/freeheating
r34: Sets the type of freecooling/heating with or without compressors
r34= 0: disabled
r34= 1: freecooling / without compressors / cooling only
r34= 2: freecooling / with compressors / cooling only
r34= 3: freeheating / without compressors / heating only
r34= 4: freeheating / with compressors / heating only
r34= 5: freecooling and freeheating / without compressors / freecooling in cooling only and freeheating in
heating only
r34= 6: freecooling and freeheating / with compressors / freecooling in cooling only and freeheating in
heating only
r34= 7: freecooling / without compressors / always
r34= 8: freecooling / with compressors / always
r34= 9: freeheating / without compressors / always
r34= 10: freeheating / with compressors / always
r34= 11: freecooling and freeheating / without compressors / always
r34= 12: freecooling and freeheating / with compressors / always
The purpose of the function is to exploit the outside climatic conditions when such can cool or heat the
controlled environment by modulating the inlet of outside air into the room.
Freecooling can be enabled when: room T - outside T > freecooling differential (r29).
Key Fig. 5.b.p:
1. room T (B1);
2. room T - f/cool diff;
3. out T (e.g. B3);
4. outlet T (A1);
5. freecooling OFF;
6. time.
Key to Fig. 5.b.q:
1. freecooling;
2. room T - out T;
3. FC diff-hysteresis;
4. freecooling diff.
Freeheating can be enabled when: outside T - room T > freeheating differential (r30).
Key to Fig. 5.b.r:
1. out T;
2. room T;
3. out T - f/heat diff;
4. freeheating ON;
5. freeheating OFF
6. time.
The compressors can be used to support freecooling/freeheating if the latter are insuffi cient to provide for
the thermal load. The proportional control band is respectively:
1. divided by the number of compressor steps, when freecooling/heating is disabled (Fig. 5.b.s);
2. managed with freecooling/heating operating and the compressors activated (Fig. 5.b.t).
Key to Fig. 5.b.s:
1. damper disabled;
2. set point;
3. utility temperature;
4. operation with 4 compressors;
5. proportional band.
Special cases:
1. If the compressors are on and freecooling is disabled, when the conditions for starting freecooling are
reached, the controller will behave as follows:
• the compressors are switched off, and can only be started again if the damper is 100% open,
according to the control diagram shown in fi g. 5.b.t
2. If control is performed with the compressors on and freecooling enabled, when the conditions for
stopping freecooling are reached, the controller will behave as follows:
• fi rst the damper is closed for 110% of r28
• then the control diagram is changed (from Fig. 5.b.t to Fig. 5.b.s)
3. When starting the controller, changing from cooling to heating and vice-versa, or switching from
standby to ON, and with favourable of freecooling or freeheating conditions, the compressors are not
started until the following conditions are satisfi
t • he time r35 has elapsed
• the sum of the opening times is equal to 2*r28.
4. When switching from On -> Standby, cooling/heating or vice-versa, the damper will be closed for
110% of r28.
5. When switching from On -> Stand by, cooling/heating or vice-versa, the control diagram changes back
to the one shown in Fig. 5.b.t.
- Compressor deactivation time
r35: Compressor deactivation time when waiting for freecooling/heating.
- Damper cycle time
r36: Time used to calculate the duty cycle for opening and closing the damper.
µC 2 SE - +030220426 - rel. 2.0 - 03.08.2009
ed::
Example of freecooling
1
2
3
4
5
6
Fig. 5.b.p
Activation/Desactivation freecooling
1
ON
OFF
3
Fig. 5.b.q
Example of freeheating
1
2
3
4
Fig. 5.b.r
Example of freeheating
1
100%
0%
2
Fig. 5.b.s
Example of freecooling with the compressors on
3
1
4
r07
r38 r37
2
Fig. 5.b.t
Key to Fig. 5.b.t:
1. damper movement cycle time;
2. working set point;
3. cycle;
4. dead zone r02/4.
55
7
ON OFF
4 2
6
5
4
5
3
r02