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- Data Brochure |
D 352 |
House Control 352 |
06/00 |
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UnOcc. |
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House Control 352 |
WWSD |
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One Zone, Boiler / |
Min. Boiler / |
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Injection |
Max. Supply |
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Heat |
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Demand |
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Power |
Pump |
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The House Control 352 is a microprocessor-based outdoor reset control designed to control the temperature of a single zone hydronic heating system. The 352 regulates the supply water temperature based on the outdoor air temperature and optionally the indoor air temperature. The 352 can either operate a boiler and a system pump, or an injection valve and a system pump. To avoid boiler short cycling and large temperature swings, the 352 has a built in function which continuously adjusts the boiler differential.
The 352 includes features such as Warm Weather Shut Down (WWSD), system pump exercising, Night Setback (UnOccupied period), minimum boiler supply temperature setting (Boiler mode) and maximum supply water temperature setting (Injection mode). A Room Temperature Unit (RTU) 054 or an Indoor Sensor 076 can be connected to the 352 to provide indoor temperature feedback.
Control Strategy . . . . . . . . . . . . |
pg. 1 |
Testing the Control . . . . . . . |
pg. 7 |
Sequence of Operation . . . . . . . |
pg. 3 |
Error Messages. . . . . . . . . . . |
pg. 7 |
Installation . . . . . . . . . . . . . . . . . |
pg. 4 |
Technical Data . . . . . . . . . . . |
pg. 8 |
Settings . . . . . . . . . . . . . . . . . . . |
pg. 6 |
Limited Warranty . . . . . . . . . |
pg. 8 |
Output
System Pump
(through back of control)
Input
24 V (ac)
Power Supply
M or
Output
Boiler or Valve
Input tekmar Timer
H11191 |
140°F |
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Made in Canada by |
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tekmar Control |
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Systems Ltd. |
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170 |
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Off |
0.2 |
3.6 |
Min. Boiler / |
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Heating Curve |
Max. Supply |
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UnOcc. |
House Control 352 |
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WWSD |
One Zone, Boiler / |
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Min. Boiler / |
Injection |
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Max. Supply |
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Heat |
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Demand |
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Power |
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Pump Heat |
Aug 95 |
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Test |
31000265 |
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NRTL/C |
70°F (21°C) |
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Power: |
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LR 58223 |
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24 V 50/60 Hz 3 VA |
UnOccupied |
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Relays: |
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Injection/ |
120 V (ac) 10 A 1/3 hp |
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Do not apply power |
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pilot duty 240 VA |
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Boiler |
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Relay |
must be rated |
UnO RTU Com Sup Out |
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Signal wiring |
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Heat Heat |
at least 300V |
Sw Sen Sen Sen Sen |
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Input
Outdoor Sensor
Included
Input
Supply Sensor
Included
Input
tekmar RTU or Indoor Sensor
Control Strategy
OUTDOOR RESET
In order to properly control a hot water heating system, the heat supplied to the building must equal the heat lost by the building.
• The heat supplied to a building is proportional to the temperature of the |
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water and the surface area of the heating element. A small surface area |
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such as baseboard radiators requires a higher water temperature than |
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a larger surface area such as radiant floors. |
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• The heat lost from a building is dependent on the outdoor temperature. |
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As the outdoor temperature drops, the building heat loss increases. |
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Heat |
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Room Temperature |
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Loss |
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Increase |
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1 of 8 |
Copyright © D 352 - 06/00 |
Heating Curve
A hot water heating system can be accurately controlled by modulating the supply water temperature as the outdoor temperature changes. Using this approach the heat lost from the building is exactly matched by the heat input to the building. A tekmar reset control utilizes a heating curve to set the relationship between outdoor temperature and supply water temperature. The heating curve determines the amount the supply water temperature is raised for every 1° drop in outdoor air temperature. The heating curve is sometimes called an outdoor reset ratio.
Heating Curve Parallel Shift
All heating curves begin at the heating curve starting point. If the heating curve starting point is adjusted, the heating curve will be parallel shifted. The heating curve starting point is either set manually through a dial, or it is determined automatically by the control through indoor temperature feedback.
Indoor Temperature Feedback
Most buildings have internal heat gains due to people, passive solar heating and mechanical or electrical equipment. If only the outdoor temperature is measured, the control cannot compensate for these internal heat gains and the building may overheat. In order to prevent overheating, indoor temperature feedback should be combined with the outdoor reset strategy. From this indoor temperature feedback, the control can change the heating curve starting point in order to match the supply water temperature to the heat loss of the building. If the indoor temperature is too warm, the control automatically shifts the starting point and the heating curve down. If the indoor temperature is too cold, the control shifts the starting point and heating curve up.
Warm Weather Shut Down (WWSD)
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water |
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Outdoor air temperature
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3.0 2.4 |
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Shift |
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temperature |
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UP |
of |
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water |
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Heating |
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DOWN |
Curve |
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Supply |
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0.4 |
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90 |
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70 |
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-10 |
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(32) |
(21) |
(10) |
(-1) |
(-12) |
(-23) |
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Outdoor air temperature
When the outdoor temperature is equal to the heating curve starting point, no additional heat is required in the building and therefore the heating system can be shut down. The WWSD point is normally the same as the heating curve starting point.
BOILER OPERATION
The supply water temperature from a boiler can be controlled by cycling the boiler on and off. Modulation of the boiler’s operating temperature in hot water heating systems not only provides more comfort but also offers significant energy savings. The cooler the boiler runs, the more efficient it is due to less heat losses up the flue and reduced boiler jacket losses.
Minimum Boiler Supply
Most boilers require a minimum supply water temperature in order to prevent corrosion from flue gas condensation. The control should therefore only modulate the boiler supply water temperature down to the boiler manufacturer’s minimum recommended operating temperature. Some boilers are designed to condense and should be operated at low water temperatures as much as possible for maximum efficiency.
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210 |
3.6 |
3.0 |
2.4 |
2.0 |
1.6 |
(99) |
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Minimum Boiler |
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Supply Setting |
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150 |
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130°F |
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0.8 |
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0.6 |
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Outdoor air temperature
Supply water temperature
Boiler Differential
An on / off boiler must be operated with a differential in order to prevent short cycling. When the supply water temperature drops below the bottom rail of the differential, the boiler is turned on. The boiler is then kept on until the supply water temperature rises above the top rail of the differential. If the differential is too wide, there can be large supply water temperature swings; however, if the differential is too narrow, the boiler short cycles and operates inefficiently. Some controls automatically calculate the boiler differential in order to achieve an appropriate balance between temperature swings and boiler efficiency. This also permits the control to adapt to changing loads and conditions.
Supply Water Temperature
165°F(74°C)
160°F (71°C)
155°F (68°C)
on ler Boi
B
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e r
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f f
Time
Differential = 10°F (5°C)
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MIXING OPERATION
The full range of water temperatures required through a heating season can be provided with a standard (non-condensing) boiler by incorporating a mixing device into the system. An On / Off Injection Valve or Pump can be used to modulate the system supply water temperature to improve comfort in the building and provide a maximum target supply water temperature limit. For more detailed information on mixing methods consult Essay E 021.
System |
Mixing |
Boiler |
Loop |
Device |
Loop |
Copyright © D 352 - 06/00 |
2 of 8 |
Maximum System Supply
Some systems, such as hydronic radiant floor heating, usually operate at water temperatures that are below |
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the minimum boiler supply temperature. This is due to the large surface area of the floors which radiate a |
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significant amount of heat at low water temperatures. Floor heating systems and flat panel convectors also |
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Mix |
have a maximum surface temperature limit for occupant health reasons. In such systems a mixing device |
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is normally required to limit the supply water temperature. |
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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.
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UnOcc. |
House Control 352 |
WWSD |
One Zone, Boiler / |
Min. Boiler / |
Injection |
Max. Supply |
Heat |
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Demand |
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Power |
Pump Heat |
24 V (ac) |
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power |
WWSD |
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Sup |
Out |
Jumper |
Sen |
Sen |
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 |
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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 |
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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 |
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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.
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Maximum Boiler |
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Temperature 212°F |
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3.6 |
3.0 2.4 |
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Minimum Boiler |
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1.2 |
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temperature |
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Supply Setting |
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130°F |
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0.8 |
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water |
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110 |
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WWSD |
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Outdoor air temperature
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210 |
3.6 |
3.0 2.4 |
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temperature |
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Temperature |
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0.8 |
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0.2 |
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(32) |
|
|||
|
|
|
|
|
|
|
|
|
|
70 |
|
||
|
|
|
|
|
|
|
|
|
(21) |
|
|||
90 |
70 |
50 |
30 |
10 |
-10 |
°F |
(32) |
(21) |
(10) |
(-1) |
(-12) |
(-23) |
(°C) |
Outdoor air temperature
3 of 8 |
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