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1
The 425 range of traditional electro-mechanical programmers offer a simple
yet effective way of controlling hot water and central heating with the twin
circuit Diadem and Tiara also allowing independent control of both.
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
Horstmann 425 range
Installation Instructions
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Once the backplate has been removed from the
packaging please ensure the programmer is re-sealed
to prevent damage from dust, debris etc.
The backplate should be fitted with the wiring terminals
located at the top and in a position which allows the
relevant clearances around the programmer
(see diagram)
DIRECT WALL MOUNTING
Offer the plate to the wall in the position where the programmer is to be mounted, remembering
that the backplate fits to the right hand end of the programmer.
Mark the fixing positions through the slots, (fixing centres 60.3mm), drill and plug the wall, then
secure the plate in position. The slots in the backplate will compensate for any misalignment of the
fixings.
WIRING BOX MOUNTING
The backplate may also be fitted directly on to a single gang steel flush wiring box complying
withBS4662, using two M3.5 screws.
425 electro mechanical programmers 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.
The recommended cable sizes are 1.0mm² or 1.5mm² for a Diadem/Tiara and 1.5mm² for a
Coronet.
425 Electro-Mechanical Programmers are double insulated and do not require an earth connection
but an earth terminal is provided on the backplate for terminating any cable earth conductors.
Earth continuity must be maintained and all bare earth conductors must be sleeved. Ensure that no
conductors are left protruding outside the central space enclosed by the backplate.
Fitting the backplate:
END VIEW OF 425 ELECTRO-MECHANICAL PROGRAMMER
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Diadem/Tiara:
When used to control MAINS VOLTAGE SYSTEMS
Terminals L, 2 and 5 should be electrically
linked by means of a suitable piece of sleeved
conductor. When used to control EXTRA LOW
VOLTAGE SYSTEMS these links MUST NOT be
fitted.
Coronet:
When used to control MAINS VOLTAGE SYSTEMS
Terminals L and 5 should be electrically linked
by means of a suitable piece of sleeved
conductor. When used to control EXTRA LOW
VOLTAGE SYSTEMS these links MUST NOT be
fitted.
Interlocking - Diadem and Tiara only
If a Diadem or Tiara is used on gravity hot water/pumped central heating systems the selector
slides must be interlocked for correct programme selection.
This is achieved by rotating the interlock located at the top of the HW programme slide. First select
‘Twice’ on the HW selector slide, then select the Off position on the CH selector slide; this will reveal
the screwdriver slot in the interlock.
Position the screwdriver in the slot and rotate anti-clockwise until the slot is almost horizontal (a
stop will prevent the interlock from being turned too far).
Check for correct operation of programme slides. This should result in the HW selector slide moving
up to match any CH selection (twice, all day and 24 hours).
When the CH slide switch is returned to any of the lower positions (all day, twice and off), the HW
slide switch will stay in the uppermost position reached and will have to be manually moved to the
desired new position.
N L 1 2 3 4 5 6
MAINS
SUPPLY
E N L ON
OFF
TIMED
OUTPUT
N L 1 2 3 4 5 6
MAINS
SUPPLY
E N L
ON ONOFF OFF
TIMED
OUTPUT
HW
TIMED
OUTPUT
CH
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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 the 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, e.g. Horstmann, 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
Typical wiring diagrams
N
L
1
2
3
4
5
6
E
E
N
L
N L
MAINS
SUPPLY
COMBINATION BOILER TERMINALS
FOR PRECISE TERMINAL
CONNECTION INFORMATION
PLEASE REFER TO BOILER
MANUFACTURER INSTRUCTIONS
TERMINALS L - 5
SHOULD NOT
BE LINKED
REMOVE
LINK IF
FITTED
ROOM
STAT
CALL S AT
N C
BOILER LIVE OUT
E
N
L
MAINS
SUPPLY
N
L
1
2
3
4
5
6
ROOM
STAT
CYL
STAT
CALL
CALL
N N
L L
BOILER PUMP
SAT
SAT
N C
C
E
N
L
MAINS
SUPPLY
N
L
1
2
3
4
5 6
ROOM
STAT
ZONE
VALVE
N C
CYL
STAT
CALL
CALL
SAT
SAT
C
N
L
PUMP &
BOILER
425 Coronet controlling typical combination boiler
installation via room thermostat.
425 Coronet controlling gravity hot water with
pumped heating via room stat and cylinder stat.
425 Coronet controlling fully pumped system via room
stat,cylinder stat and using a 2 port spring return valve
with auxiliary switch on heating circuit.
N
L
1
2
3
4
5
6
E
E
N
L
N L
MAINS
SUPPLY
COMBINATION BOILER TERMINALS
FOR PRECISE TERMINAL
CONNECTION INFORMATION
PLEASE REFER TO BOILER
MANUFACTURER INSTRUCTIONS
TERMINALS L - 5
SHOULD NOT
BE LINKED
REMOVE
LINK IF
FITTED
ROOM
STAT
CALL SAT
N C
BOILER LIVE OUT
E
N
L
MAINS
SUPPLY
N
L
1
2
3
4
5
6
ROOM
STAT
CYL
STAT
CALL
CALL
N N
L L
BOILER PUMP
SAT
SAT
N C
C
E
N
L
MAINS
SUPPLY
N
L
1
2
3
4
5 6
ROOM
STAT
ZONE
VALVE
N C
CYL
STAT
CALL
CALL
SAT
SAT
C
N
L
PUMP &
BOILER
E
N
L
MAINS
SUPPLY
N
L
1
2
3
4
5 6
ROOM
STAT
N C
CALL
SAT
N N
L L
BOILER PUMP
E
N
L
MAINS
SUPPLY
N
L
1
2
3
4
5 6
ROOM
STAT
N C
CALL SAT
N N
L L
BOILER PUMP
CYL
STAT
CALL S AT
C
E
N
L
MAINS
SUPPLY
N
L
1
2
3
4
5 6
N C
CALL S AT
BR
BL
W
GR
0
CALL SAT
C
N N
L L
BOILER
PUMP
ROOM
STAT
CYL
STAT
ZONE VALVE
425 Coronet controlling typical combination boiler
installation via room thermostat.
425 Diadem/Tiara controlling gravity hot water with
pumped heating via room stat
425 Coronet controlling gravity hot water with
pumped heating via room stat and cylinder stat.
425 Diadem/Tiara controlling gravity hot water with
pumped heating via room stat and cylinder stat.
425 Coronet controlling fully pumped system via room
stat,cylinder stat and using a 2 port spring return valve
with auxiliary switch on heating circuit.
425 Diadem/Tiara controlling gravity hot water with
pumped heating using a 2 port spring return valve with
changeover auxiliary switch on the hot water circuit.
N
L
1
2
3
4
5
6
E
E
N
L
N L
MAINS
SUPPLY
COMBINATION BOILER TERMINALS
FOR PRECISE TERMINAL
CONNECTION INFORMATION
PLEASE REFER TO BOILER
MANUFACTURER INSTRUCTIONS
TERMINALS L - 5
SHOULD NOT
BE LINKED
REMOVE
LINK IF
FITTED
ROOM
STAT
CALL SAT
N C
BOILER LIVE OUT
E
N
L
MAINS
SUPPLY
N
L
1
2
3
4
5
6
ROOM
STAT
CYL
STAT
CALL
CALL
N N
L L
BOILER PUMP
SAT
SAT
N C
C
E
N
L
MAINS
SUPPLY
N
L
1
2
3
4
5 6
ROOM
STAT
ZONE
VALVE
N C
CYL
STAT
CALL
CALL
SAT
SAT
C
N
L
PUMP &
BOILER
E
N
L
MAINS
SUPPLY
N
L
1
2
3
4
5 6
ROOM
STAT
N C
CALL
SAT
N N
L L
BOILER PUMP
E
N
L
MAINS
SUPPLY
N
L
1
2
3
4
5 6
ROOM
STAT
N C
CALL SAT
N N
L L
BOILER PUMP
CYL
STAT
CALL S AT
C
E
N
L
MAINS
SUPPLY
N
L
1
2
3
4
5 6
ROOM
STAT
N C
CALL SAT
CYL
STAT
CALL SAT
C
N
L
PUMP &
BOILER
ZONE
VALVE
ZONE
VALVE
E
N
L
MAINS
SUPPLY
N
L
1
2
3
4
5 6
N C
CALL S AT
BR
BL
W
GR
0
CALL SAT
C
N N
L L
BOILER
PUMP
ROOM
STAT
CYL
STAT
ZONE VALVE
E
N
L
MAINS
SUPPLY
N
L
1
2
3
4
5 6
N C
CALL
SAT
CALL SAT
C
W
BL
0
GR
MID POSITION
VALVE
N
L
PUMP &
BOILER
FROST
STAT
IF
FITTED
C
CALL
ROOM
STAT
CYL
STAT
425 Coronet controlling typical combination boiler
installation via room thermostat.
425 Tiara controlling fully pumped system using two
motorised 2 port valves with auxiliary switches via
room stat and cylinder stat.
425 Diadem/Tiara controlling gravity hot water with
pumped heating via room stat
425 Coronet controlling gravity hot water with
pumped heating via room stat and cylinder stat.
425 Tiara controlling fully pumped system using room
stat and two (2 port) spring return zone valve with
auxiliary switches
425 Diadem/Tiara controlling gravity hot water with
pumped heating via room stat and cylinder stat.
425 Coronet controlling fully pumped system via room
stat,cylinder stat and using a 2 port spring return valve
with auxiliary switch on heating circuit.
425 Tiara controlling fully pumped system using a mid
position valve via room stat and cylinder stat.
425 Diadem/Tiara controlling gravity hot water with
pumped heating using a 2 port spring return valve with
changeover auxiliary switch on the hot water circuit.
E
N
L
MAINS
SUPPLY
N
L
1
2
3
4
5 6
N C
CALL
SAT
CALL
SAT
C
FROST
STAT
IF
FITTED
C
CALL
ROOM
STAT
CYL
STAT
N
L
PUMP &
BOILER
ZONE
VALVE
ZONE
VALVE
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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 top of the unit.
Now fit the programmer to the backplate and line the lugs
on the programmer with the flanges on the backplate.
Swing the top of the programmer into position ensuring that the
connection blades 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.
The tappets can now be set to suit the user’s requirements.
Please refer to the user’s 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.
END VIEW OF 425 ELECTRO-MECHANICAL PROGRAMMER
End view of 425 electro
mechanical programmer
Page 6
Specification: Coronet, Diadem and Tiara
MODELS:
Coronet: Single Circuit 13(6)A 230V AC
Diadem: Double Circuit 6(2.5)A 230V AC
Tiara: Double Circuit 6(2.5)A 230V AC
Contact type: Micro disconnection
(Voltage free, Coronet and Tiara only)
Motor Supply: 230-240V AC 50Hz
Double Insulated:
Enclosure Protection: IP 20
Max. Operating Temperature: Coronet 35°C Diadem/Tiara 55°C
Dirt protection: Normal situations.
Independently mounted control for surface mounting.
Purpose of Control: Electronic Time Switch
Operating time limitation: Continuous
Type 1 Action
Case material: Thermoplastic, flame retardant
Dimensions: 153mm x 112mm x 33mm
Clock: 24 hour
Programme selection: 24 Hours, On all day, Twice, Off
Operating periods per day: Two
Override: Instant advance
Backplate: 9 Pin terminal connection
Leaflet number P27673 – Issue 17
6
Email: sales@horstmann.co.uk Website: www.horstmann.co.uk
Horstmann, Bristol BS4 1UP
Tel: 0117 978 8700 Fax: 0117 978 8701
Horstmann is a trading name of Secure Controls (UK) Ltd., a wholly owned subsidiary of Secure International Holdings PTE Ltd.
Registered office: Secure House, Moorside Road, Winnall Trading Estate, Winchester, Hampshire SO23 7RX.
Registered in England No. 457553
© MARCH 2012: Secure Controls (UK) Ltd: All rights reserved.
The company reserves the right to alter product specifications without notice.
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