Sequence of operation – tekmar 371 House Control User Manual
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Optimum Start / Stop with only Indoor Sensors
When only indoor temperature feedback is available, the control must base all Optimum Start / Stop
calculations on
only indoor temperature. If there are large variations in outdoor temperature, this method
cannot provide the same level of accuracy as when both indoor and outdoor sensors are used.
Optimum Start / Stop with only an Outdoor Sensor
Every building, and often each zone within the building, has a different response time. When only an outdoor
sensor is used, the control must assume a particular response time for the entire building. Therefore this
is generally the least accurate method of calculating Optimum Start / Stop times.
Sequence of Operation
POWERING UP THE CONTROL
After the House Control 371 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 zone relays are
turned off. When an external Zone Control input is used, the
WWSD light is only turned on
when all the zones connected to the 371 and all the zones connected to the Zone Control
are satisfied.
SETPOINT OPERATION
The 371 can be used to supply a fixed water temperature whenever a setpoint demand is
provided. If 120 V (ac) is applied to terminal
Setp Dem (24), the control registers a setpoint
demand and turns on the
Setpoint Demand light. The setpoint load can be connected to
either the boiler (hot water) loop or mixing (warm water) loop.
BOILER OPERATION
The 371 operates the boiler whenever there is a call for heat from boiler zones, mixing
zones, DHW, or a setpoint load. The boiler supply water temperature is controlled by turning
the boiler on and off. The 371 ensures sufficient heat is supplied to satisfy the demand for
the hottest water temperature. In order to prevent boiler short cycling, the
Boiler relay has
a minimum off time of 20 seconds, and the boiler differential is automatically calculated.
Boiler Zones (hot water)
A boiler zone is selected by setting the zone DIP switch to
Boiler. Once
heat is required, the 371 uses an outdoor reset strategy with indoor
temperature feedback from each of the boiler zones.
Mixing Zones (warm water)
A mixing zone is selected by setting the zone DIP switch to
Mixing.
When a mixing zone requires heat, the speed of the variable speed
injection pump increases or the mixing valve opens. The 371 may also
raise the boiler water temperature to satisfy the mixing heating load.
Setpoint Boiler Supply
If the
Setpnt DIP switch is set to Boiler and setpoint operation is
required, the 371 targets a boiler temperature of at least 180
°
F (82
°
C).
Boiler Maximum Supply
At no time does the 371 allow the target boiler supply water tempera-
ture to exceed 212
°
F (100
°
C).
Boiler Minimum Supply
The 371 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 371 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.
Room
Temperature
Units (RTU's)
130
°
F
Off
165
Min. Boiler
Supply
100
Minimum
Boiler
Outdoor
Sensor
Only in the first 15 minutes after power up, does
the control respond immediatley to settings
adjustments.
70
M
Test
M
M
WWSD
Setpnt
Boiler
1 2 3 4 5 Zo
Mixing
Mixing
Device
mixing zones
boiler zones
24
Setp
Dem
Setpoint
Demand
4
L