4
WINTER TIME / SUMMER TIME CLOCK
When the clocks are changed from Summer Time to Winter Time (or
vica versa) there is no need to alter the clock by entering programming
mode (i.e. pressing the
PROG
button). Instead just press and hold
down the - button to change from Summer Time to Winter Time or the
+ button to change from Winter Time to Summer Time. The first time
this is done (after a RESET) the clock is set and can only be changed
by one hour as appropriate.
If a mistake is made, e.g. pressing the + button in the autumn when
the - button should have been pressed, rectify the problem by pressing
the correct button and then re-setting the clock by one hour as
appropriate. (Refer to SETTING THE CLOCK on the previous page).
TIME OR TEMPERATURE DISPLAY
The default display in RUN mode shows the time of day. This may be
changed to display the actual temperature being sensed by pressing
both
COPY
and
NEXT
buttons together. Return to time display by
pressing them together again.
THERMOSTAT MODE
The HC75 can be converted to control either heating or cooling, (not
both), at a constant user selected temperature by selecting "Thermostat
mode". To do this, press and hold down both
s t
buttons until the
display changes to that shown in fig. 6. When entering thermostat
mode the default setting is heating only, with a default temperature of
8°C (46°F), this can be changed as required by pressing either
s
or
t
until the require temperature is displayed.
To control at a constant cooling temperature (heat off), press the 'SEL'
button to select 'COOL', the temperature will be shown as 28°C (82°F)
(fig. 6a) use the
s
and
t
buttons to select the required temperature.
When in thermostat mode if "OFF" is selected by means of the
button, both heating and cooling are turned off.
To return to normal programmed operation, press and hold both
s
and
t
.
FROST THERMOSTAT MODE
While in thermostat mode the HC75 may be set to guard against
possible freeze damage in areas where the unit (or its remote sensor)
is installed. The heating control temperature may be set to a suitable
level using the
s
and
t
are pressed simultaneously.
HOLIDAY MODE - Heating only or Cooling only
While in thermostat mode with either HEAT or COOL selected,
pressing the
DAY
button will activate the vacation mode. The display
will change to that shown in Fig. 7 or Fig. 7a with a number indicating
the default vacation period of 00 days. Use the + or - buttons to set
the number of days required, in the range 1-99 days. If the number of
days is left at 00 then the unit will return to normal at event 1 the
following day. When the selected number of days have elapsed the
unit will automatically return to normal, controlling temperatures to the
set program.
Control may also be restored to normal before all days have
elapsed by pressing the
s
and
t
buttons simultaneously.
USER OVERRIDES
Whilst the unit is operating normally in RUN mode the following
overrides are available:
Fig. 5. Temperature Display.
(Space temperature is below
the set temperature, so the
heating plant and fan are
operating).
AUTO
HEAT
COOL
OFF
AUTO
ON
Fig. 8. Temperature raised -
heating plant & fan running.
AUTO
HEAT
COOL
OFF
AUTO
ON
Fig. 9. Temperature lowered -
cooling plant & fan running.
AUTO
HEAT
COOL
OFF
AUTO
ON
AUTO
HEAT
COOL
OFF
AUTO
ON
Fig. 6. Thermostat mode (Heating) Fig. 6a Thermostat mode (Cooling)
AUTO
HEAT
COOL
OFF
AUTO
ON
AUTO
HEAT
COOL
OFF
AUTO
ON
AUTO
HEAT
COOL
OFF
AUTO
ON
TEMPERATURE SETTING OVERRIDE
Press
s
to increase or
t
to decrease the current set temperatures.
Each press will change the temperature settings by 0.5°C (or 1°F). To
make larger changes press the button and hold it down. The
temperatures can be raised until the cooling temperature reaches
32°C(90°F) or lowered until the heating temperature reaches 5°C(41°F).
Note that the programmed dead band between the heating and
cooling temperatures is maintained whilst the override is being used.
PROGRAMME OVERRIDE
Whilst running in
AUTO
mode both the heating plant and cooling plant
will be switched on and off to maintain the selected temperatures.
The
SEL
(select) button can be used to select one of three other
modes.
AUTO
HEAT
COOL
OFF
AUTO
ON
AUTO
HEAT
COOL
OFF
AUTO
ON
AUTO
HEAT
COOL
OFF
AUTO
ON
AUTO
HEAT
COOL
OFF
AUTO
ON
With
HEAT
selected only the heating
plant will be controlled, the cooling
plant being switched off.
With
COOL
selected only the cooling
plant will be controlled, the heating
plant being switched off.
With
OFF
selected both heating and
cooling will be switched off. In this
mode there is no frost protection.
FAN OVERRIDE
Pressing the button marked
FAN
will
switch the fan between
AUTO
,
ON
and SMART
.
AUTO: Thermostat starts fan when
there is a demand for either heating
or cooling.
ON: Fan runs continuously.
SMART: Fan runs continuously
during events 1-6 unless a programmed 'OFF' is encountered, but
reverts to Auto mode during event 6-1. When in 'Smart' mode, the bar
on the display adjacent to FAN ON will flash.
BATTERY MAINTENANCE
It is recommended that high quality alkaline batteries are used.
New batteries will provide the power for switching the outputs on and
off for approximately 2 years. When the batteries volts fall to the
minimum level needed to maintain operation a battery symbol will blink
in the display. When this symbol appears both batteries should be
replaced with high quality alkaline cells. Operation will continue
normally until the 15th midnight after the symbol started blinking and
then the unit will switch off all outputs, and shut down with just the
time and the blinking battery displayed. Whilst the battery symbol is still
blinking, the old batteries may be removed and new batteries placed
in the sleeve provided and inserted
within one minute.
Internal
circuitry will maintain the user set programme memory during this
period.
28.0°c
8.0°c
Fig. 11.
Blinking battery symbol, change
batteries.
AUTO
HEAT
COOL
OFF
AUTO
ON
Danfoss Randall Ltd. continually strives to improve its products and
reserves the right to change designs and specifications without notice.
28.0°c
8.0°c
Fig. 7 - Heating
Fig. 7A - Cooling
Danfoss Randall Ltd.
Ampthill Road,
Bedford MK42 9ER
Tel: 01234 364621 Fax: 01234 219705
email: danfossrandall@danfoss.com
Website: www.danfoss-randall.co.uk
Part No: 8950 Iss. 9 12/01
