Siemens 125-1957 owner manual Application 2284 Heating and DX Cooling, Ashrae Cycles I

APOGEE Unit Vent Controller⎯0 to 10 V Output Owner’s Manual

Application 2284 – Heating and DX Cooling, ASHRAE Cycles I and II

In Application 2284, the Unit Vent Controller⎯0 to 10V output controls a unit ventilator equipped with a DX coil for cooling, and/or a heating coil, which may be hot water, steam, or electric, for ASHRAE Cycles I and II. A face-bypass damper can be controlled, replacing the modulating (0-10V) heating actuator, but will modulate only in heating mode. If a face-bypass damper is used, two-position valves on the coils may be controlled. Cooling only units can also be controlled with this application by overriding HEAT.COOL (Point 5) to COOL.

Other features available in this application include morning warm-up/cool-down, night mode override, free cooling and auxiliary radiation in heating mode.

NOTE: The use of a low temperature detection thermostat (LTDT) is strongly recommended for hot water and steam systems.

While in heating, this application controls room temperature by resetting the discharge air temperature. While in cooling, this application controls room temperature by cycling the DX unit. This application also controls an outdoor air damper according to the schedules as defined by ASHRAE Cycles l and II. The free-cooling/economizer function is turned on and off by the field panel using FREE CLG (Point 23). If free cooling is not available, the outdoor air damper will be kept at minimum position; otherwise, the outdoor air damper will modulate open in sequence with the heating actuator or the DX. The unit ventilator fan is also controlled in this application.

Figure 14. Application 2284 Control Drawing.

16 Siemens Building Technologies. Inc.