Horstmann CentaurPlus C21 Operation instructions



The Horstmann C21 two channel programmer gives independent control

over hot water and heating with up to 3 ON/OFF settings per 24 hours.

It also has a 1 hour manual boost button for the hot water and an advance

button for the central heating.

There is also a programming switch allowing permanent selection of:

OFF/ON/AUTO/ALL DAY.







The simple instructions contained in this user guide are designed to help with the

programming and operation of the unit.

 SET indicator - RUN is the normal position

 Time of day

 Switch period symbol

 SET button

 Hot Water BOOST or adjust (-) button

 Central Heating ADVANCE or adjust (+) button

 Hot Water (HW) programme select button or ENTER button

 Central Heating (CH) programme select button

 Hot Water ON indicator

 Central Heating ON indicator

 SET positions

 PROGRAMME positions

 BOOST symbol

 ADVANCE symbol

 AM/PM symbol

 PROGRAMME indicators

 









    











 

The boost facility will allow the user to boost the hot water channel which is currently

‘OFF’ for 1 hour. To indicate the boost being activated BOOST will be shown on the display

for the duration of the boost period. The hot water channel ON indicator will also be

illuminated.

 



The advance facility will allow the user to switch the central heating channel ‘ON’ which

is currently ‘OFF’ or switch the central heating channel ‘OFF’ which is currently ‘ON’. To

indicate the advance feature being activated ADVANCE will be shown on the display

until the next programme switching time. The central heating ON indicator will also be

illuminated.



The installer will have set the programmer to suit the installed system. This is normally a

Fully Pumped system which will allow independent control of the central heating and hot

water, however on an old Gravity system the central heating and hot water are linked so

that it is not possible to use the central heating independently. This will allow only one

common time setting for both hot water and central heating, and will become apparent

when setting the ON and OFF times as both will be indicated together.















































AUTO

ALL DAY

24 HRS

OFF

HW CH

AUTO

ALL DAY

24 HRS

OFF

6:35

RUN

CLOCK

HW PROG

CH PROG

RUN

CLOCK

HW PROG

CH PROG

BOOST

ADVANCE

HW CH



With the CentaurPlus C21 programmer operating in the normal running mode it is possible

to alter the functionality of the programme on each individual channel by means of the

CH and HW buttons.

The options include;

  - Channel follows all programmed ‘ON’ and ‘OFF’ times.

  - Channel operates from 1st ‘ON’ time until 3rd ’OFF’, ignoring all

switching times in between.

  - Channel will be constantly ‘ON’.

  - Channel will be constantly ‘OFF’, there is the ability to turn off the

heating during the summer without altering the programme times.

On the hot water channel the boost is still available. As both channels

are totally independent it is possible to have them set differently if

necessary.

All of the settings above will be permanent, i.e. unaffected by programme times, until

alteration by the user.

The diagram below illustrates how to alter the setting, it assumes that the channel is in the

AUTO mode to begin with.



















































































 

AUTO

ALL DAY

24 HRS

OFF

6:35

HW CH HW CH HW CH HW CH

AUTO

ALL DAY

24 HRS

OFF

6:35

AUTO

ALL DAY

24 HRS

OFF

6:35

AUTO

ALL DAY

24 HRS

OFF

6:35



The default time settings shown above are preset at the factory



To alter these settings please proceed as follows:-

NB. The factory default settings for the 2nd ON/OFF times are both set at 12:00pm

(midday) which cancels this ‘ON’ period giving 2 ON/OFF periods for 24hrs. If a midday

‘ON’ period is required set the 2nd ON and OFF times accordingly. If not press ENTER twice.

It may not be possible to programme heating and hot water independently on certain

systems.

























































































 



12:00 6:35

6:35

PM PM

RUN

CLOCK

HW PROG

CH PROG

RUN

CLOCK

HW PROG

CH PROG

1st ON 1st OFF 2nd ON 2nd OFF 3rd ON 3rd OFF

6.30AM 8.30AM 12.00PM 12.00PM 4.30PM 10.30PM



RUN

CLOCK

HW PROG

CH PROG



Electronic equipment can in some circumstances be affected by electrical interference.

If the programmer’s display becomes frozen or scrambled; or if you wish to revert back

to the default time settings please reset by pressing the SET and CH buttons together as

shown below.

After initial installation it is advisable, before programming the CentaurPlus for the rst

time, to reset the unit. Resetting can only be achieved with the power ‘ON’ by pressing

the SET and CH buttons together. This will return the programmer to the factory set default

times.

SET













The programmer is tted with a non-rechargeable, long life battery, which will

maintain the programmed time settings for a minimum of ten months with the supply

disconnected.

THIS SHOULD BE SUFFICIENT TO COVER POWER INTERRUPTIONS DURING THE LIFE OF THE UNIT.

During power interruptions the display will be blank, after 3 days the current time of day

will be lost. These measures are to prolong the battery life.



This programmer is NOT user serviceable. Please do not dismantle the unit.

In the unlikely event of a fault developing please refer to the RESETTING THE PROGRAMMER

section of this user guide shown above. If this fails to resolve the problem please contact a

local heating engineer or a qualied electrician.



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.



Email: [email protected].uk

Website: www.horstmann.co.uk

Horstmann Controls Limited, Bristol BS4 1UP

Leaflet number P60497 – Issue 5

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