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PT21 is a Czech product that offers a wide range of application for tempera-
ture regulation in households, offices or workshops. It is designed in such
way, so that it meets high standard of required functions and simultaneously
easy handling is maintained. 

Setting the hysteresis in the range from 0.1°C to 2°C represents a great advantage.

By using the digital thermostat, you can significantly save the energy necessary for heating

and simultaneously to keep optimal thermal comfort. Thanks to rich programming features

(up to 6 time intervals and temperatures for each day) you can define program suiting to

your needs.

ROOM THERMOSTAT PT21

For example:

We get up at 6:00 in the morning, so we select the temperature of 19°C.
We leave the house for work at 8:00 so the temperature can be lower: 17°C.
Family members return home at 14:00, they need warmth, so we set the 
temperature to 20°C.  
We want to watch TV in the evening and have pleasant warmth, so we set next
interval for 19:00: 24°C.

We are ready to go to bed on 22:00, so the temperature of 18°C is sufficient.
It is dealing with a model of daily temperature regime using 5 time intervals.

OPERATING INSTRUCTIONS

Switch functions: (from left side)

1. AUT   

: the thermostat works according to program as set

in 

advance.

2. MAN

: serves for manual setting of temperature, the temperature

should be constant up to next change. Symbol "      " is 
showed on the display.

3. HOD

: setting of present day and time

When you set the switch into 

HOD

position, time is shown on 

the display and indication of clock is blinking.  
By means of "

+/-

" buttons set required data, confirm by 

pressing "

i

"(register). 

Use the same procedure for setting the minutes, seconds and 

day (the day is indicated by "      " symbol).

4. PROG

: position for programming

How to proceed during programming: 

PT21 enables to set 6 temperature intervals for one day and also the 

HYSTERESIS in the range from 0.1°C to 1.5°C.

1.

By successive pressing of " 

Den, +/-Hod, +/-min. and +/- °C

" buttons set the 

day, the first time and the temperature within the program. 

2.

By pressing of " 

i

" button you pass on the setting of the second time and 

temperature. 

3.

For further temperatures within the same day set different time and temperature by 
"

+/-Hod, +/-min.,+/- °C 

" buttons. After setting the last temperature for one day, 

PT21 passes automatically to the setting for next day. Display shows "    " symbol 
for next day. 

4.

After completion of the program for whole week, recheck the program again. 

By pressing " 

i

"  button we can successively verify whether the program complies 

with our requirements and we register it in the table contained in Operating
instructions (for the case of program deletion from memory). 

After switching to 

AUT

position, thermostat starts to work according to defined program.

Note:

If we do not need to use all six settings for one day, we can use a quick zeroing

- by successive pressing of " 

Off 

" button we can zero not used time intervals. 

Short-term change of temperature in AUT mode (PARTY): 

By simple pressing of  "

+/-°C

" button in 

AUT

mode, it is possible to make a

short-term change of required temperature. Symbol " 

P

" is displayed.

The thermostat will maintain this temperature up to next temperature change
as defined in the program. When the " 

i

" button is pressed in 

AUT

mode,

required program temperature is displayed for a while (indicated by " 

P

" on the

display).

Function of " K " button: 

By pressing the " 

K

" button in 

PROG

mode it is possible to set 

HYSTERESIS

( 0.1; 0.2; 0.3; 0.4; 0.5; 1.0; 1.5°C) and confirm it by "

i

" button.  

Function of " Kopi " button: 

This function facilitates programming of the thermostat. 
Program from one day can be copied by simple pressing of 

Kopi

" button to subsequent day. 

1. Day indicator has to mark the day that has to be copied to 

next day. 

2. Press " 

Kopi

" button and whole program copies itself to next day and day 

indicator moves. Symbol " 

C

" (Copy) displays for a short time.

Function (holiday): 

This function is very useful in the course of holidays, when the
house is empty and it is not necessary to change room temper-
ature.  After pressing "      " button, symbol "      " is displayed.
By means of "

+/-Hod and +/- °C

" buttons set the number of

days and required temperature. 

Example:

On Sunday, we leave for 7-day holiday (we should return on Sunday)

and we require constant temperature of 18°C. On Sunday, before we leave, we set
the PT1 thermostat to      mode, namely in following way:  

1.

Select 

AUT

or 

MAN

by function switch.  

2.

By pressing "      " button switch to holiday mode. 

3.

By pressing "

+/-Hod

" buttons set the number of days, e.g. 7, because 

we should return on Sunday and we want the thermostat to return to 

AUT

or 

MAN

mode and work according to the program as set.

4.

Finally, set the temperature with using of " 

+/- °C

" buttons according to 

season, for example 18°C in the summer.

From now on, the thermostat will maintain constant temperature of 18°C for the period of 7 days.

One day from total number of the days set is deducted at each midnight.

Function of " Suma " button: 

This is an informational button that displays the number of boiler
operating hours. Symbol  " 

H

" is shown on the display.  

These hours can be reset by pressing " 

Off

" button.

(

Example:

1206 hours 23 minutes)

Function of " Off " button: 

RESET button: 

By pressing of this button the boiler is switched off. This
condition is indicated on the display by " 

" symbol and

can be cancelled by the same button or by changing the
switch position. In 

AUT

mode, 

Off

function is cancelled by

next program temperature change. 

On the rear side of the microprocessor part, there is a button that should be used
in the case of indeterminable conditions - all saved changes will be lost. 

Replacement of batteries: 

Use only alkali pencil batteries 

2x1.5 V of AA/R6

type. The thermostat is

able to preserve all information in its memory for time interval of approx. 

25 s

. Low battery is indicated on the display by "      " symbol.

Note:

Longer pushing of all buttons speeds up their functions. Blinking of 

indicates a free part of the program. Last change of temperature 

is maintained as set.  

_

_

Function of " Test " button: 

This button serves for the testing of correct connection of thermostat and
boiler. Pressing " 

Test

" button causes several switching on/off of the boiler.

pt21_en.qxd  23.6.2006  16:39  Page 2

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