Horstmann 425 Tiara Operation instructions

The Horstmann 425 Tiara and Diadem programmers are 2 circuit central
heating and hot water programmers able to switch ON and OFF twice
every 24 hours. An advance switch is provided to make temporary
overrides to the ON or OFF periods and a selector switch gives a further
choice of programmes.
Horstmann 425 Tiara/Diadem
Electro-mechanical Programmers
User Operating Instructions
1

The simple instructions contained in this user guide are designed to help with the programming and
operation of these units.
2
The 425 Tiara/Diadem Programmer
DIAL
DIAL
INDICATORS
TIME POINTER
TIME POINTER
SWITCH STATE
INDICATOR
SWITCH STATE
INDICATOR
PROGRAMME
SELECTORS
PROGRAMME
SELECTORS
ADVANCE
CONTROL
ADVANCE
CONTROL
TAPPETS
TAPPETS
425 TIARA
425 DIADEM

SETTING THE TIME
OF DAY
The dial rotates clockwise and makes
one complete revolution every 24
hours. To set the correct time turn
the dial clockwise by hand (using the
levers on the clock face) until the
correct time of day is against the line
marked TIME. (See diagram opposite)
SETTING THE ON/OFF TIMES
The four setting tappets, coloured red and blue, are moved around the circumference of the dial to
set your required ON and OFF times.
These tappets work in pairs to switch the
system ON and OFF.
- No 1 (red) 1st ON and No 2 (blue) 1st OFF
- No 3 (red) 2nd ON and No 4 (blue) 2nd OFF
The tappets may be moved in either direction.
(See diagram)
Please ensure that you press and hold down
any tappet that is too be moved, release
tappet only once correct time position has
been reached.
Tappets cannot be moved across the Time line.
The position of the dial may have to be altered
to set the initial ON/OFF time.
Please ensure the clock is set to the correct current time after altering the ON/OFF settings.
3
LIGHTLY PRESS
DOWN ON
No 1 TAPPET.
MOVE TAPPET
UNTIL REACHING
THE DESIRED
ON TIME
LIGHTLY PRESS
DOWN ON
No 2 TAPPET.
MOVE TAPPET
UNTIL REACHING
THE DESIRED
OFF TIME
REPEAT PREVIOUS
INSTRUCTIONS
FOR 2nd
ON/OFF
SETTINGS.
USING TAPPETS
3 AND 4
MOVE THE
PROGRAMME
SELECTION SWITCH
TO THE REQUIRED
POSITION ON
EITHER HW
AND/OR CH
  

Manual Overrides
ADVANCE CONTROL
The advance control allows you to start an ON or OFF period early without altering the tappet, time
or programme selection settings. Moving the advance control to the extreme right brings forward
the operation of the next tappet. The switch state indicator then changes to the appropriate number.
When the next tappet passes the time line, normal operation returns.
When the programme selector is in the All Day position, tappets 2 and 3 do not operate. If you
require switching the system OFF for the day, after the morning switch ON, you will need to step
forward with the advance switch until the number 4 is shown in the switch state indicator.
If you wish to switch ON and OFF by hand or vice versa, before the next automatic switching
operation, the advance control must be operated until the switch state indicator is returned to the
correct automatic sequence.
EXAMPLE: If you turn the system ON
again after the preset night shut down
time, when you turn it OFF before retiring
make sure to operate the advance switch
again until the number 4 is displayed in
the switch state indicator so that the red
tappet number 1 will switch the system
ON in the morning.
DO NOT OPERATE THE ADVANCE
SWITCH WHEN A TAPPET IS AGAINST
THE TIME LINE.
SWITCH STATE INDICATOR
Located above the ADVANCE switch, the switch state indicator shows you the number of the tappet
which operated last.
Eg. If the system was switched ON by tappet 1 at 7:00am and it is now 9:00am, providing that no
further tappets operations have past, a number 1 should show in the aperture.
If the switch state indicator does not agree with the programme set on the dial, rotate the dial one
whole turn and reset to the correct time of day. This will ensure that the switch state corresponds to
the last tappet operation.
4
SWITCH
STATE
INDICATOR

PROGRAMME OVERRIDE FACILITIES
The hot water (HW) or central heating (CH) may be individually overridden as shown below:
(options are limited on gravity systems)
24 Hrs - The system will be permanently ON
All Day - The system will switch ON from tappet 1 (red) and OFF at tappet 4 (blue)
Tappets 2 and 3 are ignored
Twice - The system switches ON at tappet 1 (red), OFF at tappet 2 (blue), ON at tappet 3 (red)
and OFF at tappet 4 (blue)
Off - The timer continues to operate but the system will be permanently OFF
FULLY PUMPED OR GRAVITY SYSTEMS
Fully Pumped - On this type of
installation the selectors are not
interlocked, as illustrated on the right,
and hot water and central heating
programmes can be set independently
of each other.
Gravity - On this type of system it is
possible to have hot water without
central heating, but not central
heating without hot water. In this case
the installer would have interlocked
the select switches as illustrated on
the right.
INDICATORS - DIADEM ONLY
The indicators will illuminate when the appropriate hot water and/or central heating circuits of the
time control are ON, even if the circuit is switched OFF by the Thermostats. However, with certain
fully pumped systems, the neon indicator may remain lit when the time control is in the OFF
position. This does not affect the normal operation of the unit.
5
HW CH
24 hrs
all day
twice
off
HW CH
24 hrs
all day
twice
off

Service and Repair
This programmer is NOT user serviceable. Please do not dismantle the unit. In the event of a fault
developing please contact a local heating engineer or a qualified electrician
Horstmann Controls Limited
South Bristol Business Park, Roman Farm Road, Bristol BS4 1UP
E-mail: [email protected]o.uk
Web site: www.horstmann.co.uk
Leaflet number P27647 – Issue 10
6
... an explantion for householders.
Programmers allow you to set ‘On’ and ‘Off’ time periods. Some models switch the central
heating and domestic hot water on and off at the same time; while others allow the
domestic hot water and heating to come on and go off at different times.
Set the ‘On’ and ‘Off’ time periods to suit your own lifestyle. On some programmers you
must also set whether you want the heating and hot water to run continuously, run under
the chosen ‘On’ and ‘Off’ heating periods, or be permanently off.
The time on the programmer must be correct. Some types have to be adjusted in Spring
and Autumn at the changes between Greenwich Mean Time and British Summer Time.
You may be able to temporarily adjust the heating programme, for example, ‘Override’,
‘Advance’ or ‘Boost’. These are explained in the manufacturer’s instructions.
The heating will not work if the room thermostat has switched the heating off. And, if
you have a hot-water cylinder, the water heating will not work if the cylinder thermostat
detects that the hot water has reached the correct temperature.
What is a programmer?