CALIBRATION PROCEDURE -1- Calibrate all transmission gauges to be accurate at nine PSIG with a certified test gauge or one tested as accurate. -2- Calibrate the temperature and relative humidity transmitters to be accurate relative to their respective transmission gauges. -3- Temporarily install gradual switches allowing simulation of varying temperature and relative humidity values for both return and outdoor air. -4- For each of the two direct acting, reset receiver controllers, tube the temperature signal into the primary port and the relative humidity into the reset port with direct re-adjustment. (This means that an increase on either port signal will cause an increase in the receiver controllers’ out put signals.) -5- -a- Take one receiver controller and set the relative humidity value at 40% RH with your manual gradual switch and leave it at 40% RH, while you address the temperature side of the receiver controller. -b- Find the proportional band (sensitivity or gain) setting that causes an output signal change from 23.70 BTU/# of dry air to 29.10 BTU/#of dry air on your enthalpy indication gauge as you change the temperature from 70 ⁰F to 80 ⁰F. -c- Set the temperature gauge to 70 ⁰F and leave the proportional band at the setting determined in “b”. -d- Find the authority (reset) setting that causes an output signal change from 23.70 Btu/lb of dry air to 28.10 BTU/lb of dry air on your enthalpy indication gauge when you change the relative humidity from 40% RH to 60% RH. -e- Check the enthalpy values at the extremes on the chart and several points in the middle. You can use the psychrometric chart as well. -6- Remove your manual simulation gradual switches and re-connect the temperature and relative humidity transmitters as required. We did not expect the system values to be exactly the same as the psychrometric chart, as we are blending a linear signal (temperature) with a non-linear signal (relative humidity) into one signal. As you should see during checking the system values produced are plus or minus one BTU/lb of dry air. 8-109
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