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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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