CentaurPlus C21 & C27 Series 2
Installation Instructions
Horstmann CentaurPlus C21 and C27 two channel programmers offer up
to three on/off periods a day for hot water and heating with a hot water
boost and heating advance facility.
Installation and connection should only be carried out by
a suitably qualified person and in accordance with the current edition
of the IEE wiring regulations.
WARNING: Isolate mains supply before commencing installation.
1
Fitting the backplate
Once the backplate has been removed
from the packaging please ensure the
programmer is re-sealed to prevent damage
from dust and debris.
The backplate should be fitted with the
wiring terminals located at the top and in a
position that allows a total clearance at last
50mm around the unit.
Direct wall mounting
Offer the backplate to the wall in the position where the programmer is to be mounted,
remembering that the backplate fits to the left hand end of the control. Mark the fixing
positions through the slots on the backplate (fixing centres of 60.3mm), drill and plug the
wall, then secure the backplate in position. The slots in the backplate will compensate for
any misalignments of the fixings.
Wiring box mounting
The backplate may be fitted directly onto a single gang steel flush wiring box complying
with BS4662, using two M3.5 screws. CentaurPlus controls are suitable for mounting
on a flat surface only; they must not be positioned on a surface mounted wall box or on
unearthed metal surfaces.
Electrical connections
All necessary electrical connections should now be made. Flush wiring can enter from the
rear through the aperture in the backplate. Surface wiring can only enter from beneath the
programmer and must be securely clamped. The mains supply terminals are intended to
be connected to the supply by means of fixed wiring. Recommended cable sizes are 1.00
or 1.5mm
2
CentaurPlus programmers are double insulated and do not require an earth connection but
an earth connection is provided on the backplate for terminating cable earth connectors.
Earth continuity must be maintained and all bare earth connectors must be sleeved.
Ensure no earth conductors are left protruding outside the central space enclosed by the
backplate.
Internal wiring diagram -
C21 & C27 Series 2
2
New installations
Example circuit diagrams for some typical installations are shown below. These diagrams
are schematic and should be used as a guide only.
Please ensure that all installations comply with current IEE regulations.
For reasons of space and clarity not every system has been included and the diagrams
have been simplified - for example some Earth connections have been omitted.
Other control components shown in the diagrams, i.e. Valves, Room Stats etc are general
representations only. However the wiring detail can be applied to the corresponding
models of most manufacturers, for example Honeywell, Danfoss Randall, ACL Drayton etc.
Cylinder and Room Thermostat key;
C = Common; CALL = Call for heat or break on rise; SAT = satisfied on rise; N = neutral.
1. Gravity Hot Water with Pumped
Heating
4. Gravity Hot Water with Pumped Heating
via Room Stat, Cylinder Stat and Two Port
Zone Valve ( with Changeover Auxiliary
Switch) on Hot Water circuit
6. Fully Pumped System using Room Stat and
Two (2 Port) Spring Return Zone Valves with
Auxiliary Switches
2. Gravity Hot Water with Pumped
Heating via Room Stat and Cylinder Stat
5. Fully Pumped Heating System using
Room Stat, Cylinder Stat and Three Port Midposition Valve
7. Fully Pumped System using Room Stat and
Two (2 Port) Motorised Valves with Auxiliary
Switches
3. Gravity Hot Water with Pumped Heating
via Room Stat and Cylinder Stat including
Frost protection via double pole FrostStat
3
New installations
Example circuit diagrams for some typical installations are shown below. These diagrams
are schematic and should be used as a guide only.
Please ensure that all installations comply with current IEE regulations.
For reasons of space and clarity not every system has been included and the diagrams
have been simplified - for example some Earth connections have been omitted.
Other control components shown in the diagrams, i.e. Valves, Room Stats etc are general
representations only. However the wiring detail can be applied to the corresponding
models of most manufacturers, for example Honeywell, Danfoss Randall, ACL Drayton etc.
Cylinder and Room Thermostat key;
C = Common; CALL = Call for heat or break on rise; SAT = satisfied on rise; N = neutral.
1. Gravity Hot Water with Pumped
Heating
4. Gravity Hot Water with Pumped Heating
via Room Stat, Cylinder Stat and Two Port
Zone Valve ( with Changeover Auxiliary
Switch) on Hot Water circuit
6. Fully Pumped System using Room Stat and
Two (2 Port) Spring Return Zone Valves with
Auxiliary Switches
2. Gravity Hot Water with Pumped
Heating via Room Stat and Cylinder Stat
5. Fully Pumped Heating System using
Room Stat, Cylinder Stat and Three Port Midposition Valve
7. Fully Pumped System using Room Stat and
Two (2 Port) Motorised Valves with Auxiliary
Switches
3. Gravity Hot Water with Pumped Heating
via Room Stat and Cylinder Stat including
Frost protection via double pole FrostStat
3
Fitting the programmer
If surface wiring has been used, remove the knockout/insert from the
bottom of the programmer to accommodate it.
Loosen the two ‘captive’ retaining screws on the bottom of the backplate.
Now fit the programmer to the backplate, ensuring the lugs on the
backplate engage with the control.
Swing the bottom of the control into position ensuring that the
connection pins on the back of the unit locate into the terminal
slots in the backplate.
Tighten the two captive retaining screws to fix the unit securely.
Then switch on the mains supply.
On completion of the installation please reset the programmer
- detailed below
End view of CentaurPlus
programmer
Resetting the programmer
On the CentaurPlus press the SET and SELECT buttons together. Then release the
buttons and the programmer will return to preset factory settings.
The preset factory settings are illustrated on page 5 or 6 of the USER GUIDE.
SET
SELECT
The unit can now be programmed to suit the user’s requirements.
Please refer to the User Guide provided.
General information
Before handing over the installation to the user, always ensure that the system responds
correctly on all control programmes and that other electrically operated equipment and
controls are correctly adjusted.
Explain how to operate the controls and hand over the users operating instructions to the
user.
5
Specification
CentaurPlus C21 & C27
CONTACT RATING:
3 (1) Amps 230V AC
CONTACT TYPE:
Micro-disconnection
SUPPLY:
230V AC 50Hz only
Pollution Degree 2
CLASS A SOFTWARE:
Type 1 control
OPERATING TEMPERATURE RANGE:
0°C to +40°C
BATTERY LIFE:
10 months continuous operation
(minimum)
CASE MATERIAL:
Thermoplastic, flame retardant
DIMENSIONS:
84mm x 150mm x 29mm
CLOCK:
12 hour AM/PM
Auto BST/GMT changeover
DISPLAY
Back lit liquid crystal
DISPLAYED TIME ADJUSTMENTS:
1 minute steps
SWITCHED TIME ADJUSTMENTS:
10 minute steps
OPERATING PERIODS PER DAY
3 per day for CH and 3 per day for HW
OVERRIDE:
1 hour boost (HW only),
1 hour extension to On period (HW only),
instant advance (CH only)
MOUNTING:
Industry standard 6 terminal plug in wall
plate
Horstmann Controls
South Bristol Business Park, Roman Farm Road, Bristol BS4 1UP
E-mail: sales@horstmann.co.uk
Web site: www.horstmann.co.uk
6
Leaflet number P84370 Issue 2
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