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On/Off Electric Reheat
The Airflow Setpoint Minimum Local Heat is enforced during reheat.
•
•
•
When reheat is de-energized, the cooling Airflow Minimum Setpoint is enforced. Refer to
p. 45
Hot Water Heat
Two types of control of hydronic heat are supported:
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BAS-SVX084A-EN
Stage 1; energizes when the space temperature falls below the active heating setpoint and
minimum airflow requirements are met. When the zone temperature rises above the active
heating setpoint by 0.5°F (0.28°C), stage 1 is de-energized.
Stage 2; energizes when the space temperature is 1°F (0.56°C) or more below the active
heating setpoint, and is de-energized when the space temperature is 0.5°F (0.28°C) below the
active heating setpoint.
Stage 3; energizes when the zone temperature is 2°F (1.11°C) or more below the active heating
setpoint, and de-energizes when the space temperature is 1.5°F (0.83°C) below the active
heating setpoint.
and
Table 12, p.
46.
ON/OFF
Refer to on/off electric heat for operation. The main difference with ON/OFF hot water heating
is the control of a two position hot water valve instead of the contactor energizing an electric
heat strip. Refer to
Table 11, p. 45
Modulating
Proportional hot water reheat uses 3-wire, floating-point-actuator technology. It is enabled if
there is no valid supply air temperature and disabled if the supply air temperature is greater
than the configured reheat enable setpoint.
When the space requires cooling, the air valve modulates between Airflow Setpoint Maximum
and Airflow Setpoint Minimum, to maintain space temperature at the active cooling setpoint;
and the water valve is closed. When the cooling load has decreased to the point where the air
valve has reached Airflow Setpoint Minimum, space temperature is allowed to drift downward,
in the deadband between the active cooling setpoint and active heating setpoint.
When the space temperature drops below the active heating setpoint, the air valve opens to the
Airflow Setpoint Reset Minimum Local Heat and the reheat valve modulates to maintain space
temperature at the active heating setpoint. Control of the water valve uses a separate
proportional plus integral control loop, and its position is dependent on the degree that the
space temperature is below the active heating setpoint and the amount of time that the space
temperature has been below the active heating setpoint.
If the discharge air temperature reaches the Discharge Air Temperature Design Setpoint, the air
valve opens further and modulates between Airflow Setpoint Reset Minimum Local Heat and
Airflow Setpoint Reset Maximum Local Heat to maintain space temperature at the active
heating setpoint, while the water valve modulates to maintain discharge air temperature at the
Discharge Air Temperature Design Setpoint. (See
Airflow Setpoint Reset Maximum Local Heat, the water valve opens further and modulates to
maintain space temperature at the active heating setpoint, while the air valve remains at
Airflow Setpoint Reset Maximum Local Heat.
An additional ON/OFF remote heat output is available and energized when the water valve is
driven 100% open and de-energized when the water valve reaches 50% open.
When reheat is de-energized, the cooling Airflow Minimum Setpoint is enforced.
Note: Steam is not supported.
Calibration, Operation Modes, and Control
and
Table 12, p.
46.
Figure 12, p.
Table 11,
45.) If the air valve reaches
47
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