Trane VAV VV550 LonTalk, Руководство по установке и эксплуатации

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VAV-SVP01A-EN 75
Sequence of Operations
Staged Reheat Control (Electric and Hot Water)
The heat outputs of the controller are binary. Only discrete levels of discharge air temperature are
possible. Since discrete discharge air temperature levels do not always provide an instantaneous
temperature within the required band, staged reheat controls to a 30-minute average discharge air
temperature. The discharge air temperature setpoint is limited from 20°F to 70°F.
Staged Electric Reheat Control
Units that are equipped with electric reheat should be sized so that the maximum temperature rise
across the heating elements is 40°F to 48°F (22.22°C to 26.67°C); it should never exceed 50°F
(27.78°C) for safety reasons. These values were selected to allow the largest control range without
damage to the heater elements.
Figure 14, p. 75 shows the achievable control range for ventilation
flow control staged electric heat.
For staged electric ventilation flow control, the number of installed stages can range from one to
three. Three stages are recommended, since finer control is available with more stages. In cases
where the outdoor air temperature is more than 48°F (26.67°C) below the discharge air temperature
setpoint, the controller cannot provide the requested control performance.
The controller provides no cooling capacity. If the outdoor air temperature (OAT) is above the
discharge air temperature setpoint, the discharge air temperature cannot be controlled and the
discharge air temperature is equal to the OAT.
Staged Hot Water Reheat Control
Units equipped with hot water coils should be sized so the maximum temperature of air leaving
the coil does not exceed 140°F (60°C F). Since only one stage of hot water reheat is available, staged
hot water does not allow tight control of the discharge air temperature. Although the controller
operates in this configuration, it is not recommended.
Staged Reheat Control Algorithm (Integral Only)
An incremental form of the integral PID algorithm computes the desired level of reheat capacity.
The algorithm is run once every 10 seconds.
Modulating Reheat Control (Hot Water Only)
Units equipped with hot water coils should be sized so the maximum temperature of air leaving
the coil does not exceed 140°F (60°C). If hot water reheat is installed, the preferred method of
control is with a modulating valve. The modulating valve enables an instantaneous discharge air
temperature within the dead band of the discharge air temperature setpoint. The reheat capacity
algorithm for modulating hot water discharge air temperature control is the same algorithm used
to control modulating hot water valves for a space temperature controller.
Modulating Reheat Control Algorithm (Proportional-Integral)
An incremental form of the proportional integral algorithm runs once every 10 seconds and
calculates the reheat capacity required to meet the discharge air temperature setpoint. The
required capacity is equal to valve position.
Table 14. Ventilation flow control staged electric heat achievable control rang
Minimum OAT for control DAT Setpoint
Some tempering is possible Achievable control range No Control possible No cooling capacity
DAT setpoint cannot be achieved
Maximum
∆
T=50°F (27.78°C)
(Electric heat only)
DAT = OAT
Cold OAT temperature range Hot