Sequence of operation, Maximum system supply, Unoccupied (night setback) – tekmar 352 House Control User Manual
Page 3: Powering up the control, Warm weather shut down (wwsd), Boiler operation, Maximum boiler supply, Minimum boiler supply, Mixing operation, Boiler control
Copyright © D 352 - 06/00
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Maximum System Supply
Some systems, such as hydronic radiant floor heating, usually operate at water temperatures that are below
the minimum boiler supply temperature. This is due to the large surface area of the floors which radiate a
significant amount of heat at low water temperatures. Floor heating systems and flat panel convectors also
have a maximum surface temperature limit for occupant health reasons. In such systems a mixing device
is normally required to limit the supply water temperature.
UNOCCUPIED (NIGHT SETBACK)
During the night, or at times when people are not within the building, energy can be saved by lowering the
building temperature for an UnOccupied (Night Setback) period.
Sequence of Operation
POWERING UP THE CONTROL
After the 352 is powered up a certain combination of red LEDs are turned on for 2 seconds
indicating the software version. All red LEDs are then held on for 4 seconds. When the
control is powered up, the green
Power light remains on continuously.
WARM WEATHER SHUT DOWN (WWSD)
When the outdoor temperature rises above the heating curve starting point, the 352 turns
the
WWSD light on and shuts down the system pump and the Heat relay.
If the control is in
Boiler mode and the jumper is cut, the control ignores the WWSD feature
and keeps the boiler warm.
BOILER OPERATION
If the DIP switch is set to
Boiler, the system supply water temperature is controlled by turning
the boiler on and off. The 352 calculates the target supply water temperature based on the
outdoor temperature and optionally the indoor air temperature. In order to prevent boiler
short cycling, the 352 has a minimum time delay of 30 seconds before turning the boiler on
or off. The 352 calculates the boiler differential automatically. The
Heat light turns on
whenever the boiler is on.
Maximum Boiler Supply
The 352 does not allow the target boiler supply water temperature to exceed 212
°F
(100
°C). If the supply water temperature approaches 212°F (100°C), the 352 turns off
the boiler.
Minimum Boiler Supply
The 352 has a
Min. Boiler dial which sets a minimum target boiler supply temperature in
order to prevent corrosion from flue gas condensation. This dial has an
Off position for
condensing and electric boilers. If an RTU or Indoor Sensor is connected to the 352 and
the required system supply temperature needs to be lower than the
Min. Boiler dial
setting, the 352 turns on the boiler until the minimum boiler temperature is reached
. It then
keeps the boiler off for a calculated off time in order to prevent overheating of the zone.
The
Heat Demand light turns on when operation of the boiler is required.
MIXING OPERATION
If the DIP switch is set to
Injection, the system supply water temperature
is controlled by turning an injection device, such as a zone valve, on and
off. The 352 calculates the target supply water temperature based on the
outdoor temperature and optionally the indoor air temperature. To
prevent short cycling of the valve, the 352 uses a minimum time delay of
30 seconds. The
Heat Demand light turns on when heat is required.
If the jumper beside the outdoor sensor terminal is cut, the control will
ensure the injection device and system pump are turned on for at least
17 minutes every 7 days. This flushing function prevents bacteria growth
in applications where a water heater is used for DHW and heating.
Boiler Control
During mixing operation the boiler can be enabled using the end switch of the zone valve.
The boiler aquastat should be set at least 20
°F (11°C) above the system design water
temperature.
Maximum System Supply
The 352 has a
Max. Supply dial that can be used to set an upper limit to the system supply
water temperature. If the system supply temperature approaches the
Max. Supply dial
setting, the 352 turns on the
Max. Supply light and closes the injection valve.
Mix
Outdoor air temperature
50
(10)
30
(-1)
10
(-12)
-10
(-23)
70
(21)
3.6 3.0
2.0
1.6
1.2
0.8
0.4
0.6
90
(32)
°F
(
°C)
Supply water temperature
110
(43)
70
(21)
90
(32)
210
(99)
170
(77)
150
(65)
130
(54)
190
(88)
2.4
1.0
WWSD
Point
70
°F
Minimum Boiler
Supply Setting
130
°F
0.2
230
(110)
Maximum Boiler
Temperature 212
°F
Outdoor air temperature
50
(10)
30
(-1)
10
(-12)
-10
(-23)
70
(21)
3.6 3.0
2.0
1.6
1.2
0.8
0.4
0.6
90
(32)
°F
(
°C)
Supply water temperature
110
(43)
70
(21)
90
(32)
210
(99)
170
(77)
150
(65)
130
(54)
190
(88)
2.4
1.0
WWSD
Point
70
°F
Maximum
Supply
Temperature
(set on dial)
0.2
M
Jumper
6
Sen
RTU
7
Sen
Com
8
Sen
Sup
9
Sen
Out
Do not apply power
WWSD
Power
Min. Boiler /
Max. Supply
House Control 352
One Zone, Boiler /
Injection
Pump
WWSD
UnOcc.
Heat
Demand
Heat
24 V (ac)