Sequence of operation – tekmar 370 House Control User Manual
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Copyright © D 370 -06/99
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Sequence of Operation
POWERING UP THE CONTROL
After the House Control 370 is powered up, a software version code is displayed for 2
seconds and then the red indicator lights are turned on for 4 seconds. When the control is
powered up, the green
Power light remains on continuously. For the first fifteen minutes
after power up, the
Test light flashes and the control responds immediately to changes of
settings. This allows the installer to test the operation of the system. After 15 minutes the
control enters its normal operating mode in which reactions to setting changes are
significantly slower. A slower reaction time to setting changes allows the control to provide
a stable room temperature.
WARM WEATHER SHUT DOWN (WWSD)
When the outdoor temperature rises above the highest Room Temperature Unit (RTU) dial
setting and all heating zones are satisfied, the
WWSD light is turned on and the variable
speed injection pump and all zone relays are turned off. If the system pump is not required
for a DHW operation, the system pump is also turned off. When an external Zone Control
input is used, the
WWSD light is only turned on when all the zones connected to the 370
and all the zones connected to the Zone Control are satisfied.
BOILER OPERATION
If the DIP switch is set to
Boiler, the system supply water temperature is controlled by turning
the boiler on and off. An outdoor reset strategy is used with indoor temperature feedback from
each of the 4 zones. The boiler differential is automatically calculated. When the 370 control
is used in the boiler mode (DIP switch set to
Boiler ), the boiler sensor must be installed on
the supply pipe of the boiler, and the boiler sensor DIP switch must be set to
Boiler Supply.
If the boiler sensor DIP switch is set to
Boiler Return, a combination of LEDs will flash, as
shown in the error message table, to indicate an illegal DIP switch setting. To eliminate the
error message, simply set the boiler sensor DIP switch to
Boiler Supply.
Maximum Boiler Supply
−−−−−−−−−−−−−−−−−−−−−−−−−−
−−−−−−−−−−−−−−−−−−−−−−−−−−
−−−−−−−−−−−−−−−−−−−−−−−−−−
−−−−−−−−−−−−−−−−−−−−−−−−−−
−−−−−−−−−−−−−−−−−−−−−−−−−−
The 370 has a
Max. System Supply dial that can be used to set a maximum boiler supply
water temperature. If the supply water temperature approaches the
Max. System Supply
dial setting, the
Maximum Supply light is turned on and the 370 operates the boiler at one
differential below the
Max. System Supply setting. At no time does the control allow the
target boiler supply temperature to exceed 212
°F (100°C).
Minimum Boiler Supply
The 370 has a
Min. Boiler Supply dial which sets a minimum target boiler
supply temperature. This dial has an
Off position for condensing and
electric boilers. If the boiler is fired and the boiler supply temperature is
near or below the
Min. Boiler Supply dial setting, the 370 turns on the
Minimum Boiler light and reduces the heating load on the boiler. During
this warm up period, some of the zones may be prevented
from operating until the boiler supply water is at the required
minimum temperature.
MIXING OPERATION
If the DIP switch is set to
Mixing, the system supply water temperature is
controlled by varying the speed of an injection pump. See Essay E 021 for
more information. An outdoor reset strategy is used with indoor temperature
feedback from each of the 4 zones.
Boiler Control
When both a Supply and Boiler Sensor are present and located on the
mixed supply and boiler supply piping, the DIP switches must be set to
Boiler Supply and Mixing. The 370 controls the boiler directly and
automatically calculates the required boiler differential. The boiler
aquastat (limit) should be set at least 20
°F (11°C) higher than
boiler design.
Boiler Load Reset
As the heating load on the mixed loop increases, the speed of the
variable speed injection pump increases. Over time, the 370 also raises
the boiler temperature to satisfy this increased heating load. The 370
also ensures the target boiler supply temperature is above the
Min.
Boiler Supply dial setting, but does not exceed 212
°F (100°C).
Only in the first 15 minutes after power up, does
the control respond immediatley to settings
adjustments.
70
M
Test
Max. System
Supply
120
170
°F
220
Maximum
Supply
M
M
WWSD
M
M
Sensor
Minimum
Boiler
130
°F
Off
165
Min. Boiler
Supply
100
M
M
Sensor
Boiler
Boiler
Mixing
Operation
Supply
Sensor
130
°F
Off
165
Min. Boiler
Supply
100
Boil
Sensor
Mixing
Boiler Supply