15#D (day)/20#N(night), 13#D/18#N,14#D/22#N, 16#D/25#N. The change-over is achieved normally by a time clock or the Building Automation System (BAS). If you replace a thermostat in an existing day/night system you must be sure that the change-over point on the new thermostat is adjusted to be suitable in the existing system. These thermostats must be calibrated using a calibration change-over board, allowing calibration of the change-over point as well as the day and night set points. (see calibration board page 3.22) The change-over point is calibrated by causing day side to have a 0# branch signal and the night side to have a full branch signal. Slowly raise and lower the main air pressure from the day main air setting to the night main air setting. The thermostat branch pressure will jump from 0# to full branch at the change-over set point of the thermostat as you raise the pressure. There is a means of adjusting this change-over function on every day/night thermostat. Adjust this point and check by raising and lowering the main air pressure until the change-over point is mid-range of the day main air pressure and the night main air pressure. Some day/night thermostats have only one dial and others have two dials. They all have an adjustment for calibrating the day mode and an adjustment for calibrating the night mode. -The two dial models are calibrated for day and night in the same manner at the single band thermostat illustrated on page 3.21. This is similar to calibrating two single band thermostats on one base. After calibration be sure to set the night dial to the desired night setting and the day dial to the desired day setting. The single dial models are a little more complicated to calibrate. The day bimetal is calibrated in the same manner as the single band thermostat illustrated on page 3.21. -For the night side you either have to cool the room down to the night set point, which is very impractical or cause the thermostat to “believe” that the room is 10F° cooler than actually exists. When calibrating the night side, turn the thermostat dial up 10F°, causing the thermostat to “believe” the room became 10F° cooler. Adjust the branch pressure to the desired control pressure reflecting the thermostat is satisfied. Breathe on the bimetal checking that the bimetal is correct and active. Turn the thermostat dial back down to the desired day set point for the thermostat. Some day/night thermostats are three pipe units, typically used on unitventilators (see page7.61), allowing one room day operation while the rest of the building is on night mode. The indexing switch on these thermostats must be manually pushed to re-establish day mode when the system is on nights. The next day, when the main system switches back to day mode, the indexing switch, which was pushed the night before, automatically resets to normal operation, cycling day/night with the rest of the building. SUMMER/WINTER THERMOSTATS These thermostats must be calibrated using a calibration change-over board, allowing calibration of the change-over point, the summer set point and winter set point. Calibrate during the season operating on the higher main air pressure, allowing calibration of the three functions at the thermostat locations. (calibration board page 3.22) Most are non-relay, low volume instruments; therefore, slow to drive the valve (s). ( Some are relay, high volume, instruments.) The normally closed pneumatic push button on the induction unit calibration 3.25
RkJQdWJsaXNoZXIy ODY1ODQy