York P*UR Installation Instructions Manual

Contents

York P*UR Installation Instructions Manual Manual pdf 33 page image

035-17477-001 Rev. A (801)Unitary Products Group 33APPLYING FILTER PRESSURE DROP TO DETERMINESYSTEM AIRFLOWTo determine the approximate airflow of the unit with a filter inplace, follow the steps below:1. Select the filter type.2. Select the number of return air openings or calculate thereturn opening size in square inches to determine theproper filter pressure drop.3. Determine the External System Static Pressure (ESP)without the filter.4. Select a filter pressure drop from the table based uponthe number of return air openings or return air openingsize and add to the ESP from Step 3 to determine thetotal system static.5. If total system static matches a ESP value in the airflowtable (i.e. 0.20, 0.60, etc,) the system airflow corre-sponds to the intersection of the ESP column and Model/Blower Speed row.6. If the total system static falls between ESP values in thetable (i.e. 0.58, 0.75, etc.), the static pressure may berounded to the nearest value in the table determining theairflow using Step 5 or calculate the airflow by using thefollowing example.Example: For a 130,000 Btuh furnace with 2 return openingsand operating on high speed blower, it is found that total sys-tem static is 0.58" w.c. To determine the system airflow, com-plete the following steps:1. Obtain the airflow values at 0.50" & 0.60" ESP.Airflow @ 0.50": 2125 CFMAirflow @ 0.60": 2035 CFM2. Subtract the airflow @ 0.50" from the airflow @ 0.60" toobtain airflow difference.2035 - 2125 = -90 CFM3. Subtract the total system static from 0.50" and divide thisdifference by the difference in ESP values in the table,0.60" - 0.50", to obtain a percentage.(0.58 - 0.50) / (0.60 - 0.50) = 0.84. Multiply percentage by airflow difference to obtain airflowreduction.(0.8) x (-90) = -725. Subract airflow reduction value to airflow @ 0.50" toobtain actual airflow @ 0.58" ESP.2125 - 72 = 2053OPERATION AND MAINTENANCESEQUENCE OF OPERATIONThe following describes the sequence of operation of the fur-nace. Refer to the schematic wiring diagrams in the back ofthis manual for component location.CONTINUOUS BLOWEROn cooling/heating thermostats with fan switch, when the fanswitch is set in the ON position, a circuit is completedbetween terminals R and G of the thermostat. The blowermotor is energized through the cool terminal and runs on theselected speed. This allows constant air circulation at lowerflow rate.INTERMITTENT BLOWER - COOLINGOn cooling/heating thermostats with fan switch, when the fanswitch is set in the auto position and the thermostat calls forcooling, a circuit is completed between the R, Y and G termi-nals.The motor is energized through the cool fan terminal andruns on the selected speed. The fan off setting is fixed at 60seconds for SEER enhancement.HEATING CYCLEWhen the system switch is set on HEAT and the fan is set onAUTO, and the room thermostat calls for heat, a circuit iscompleted between terminals R and W of the thermostat.When the proper amount of combustion air is being provided,a pressure switch activates the ignition control.The ignition control provides a 17-second warm-up period.The gas valve then opens for 10 seconds.As the gas starts to flow and ignition occurs, the flame sensorbegins its sensing function. If a flame is detected during the10 second flame stabilization period the circulating blower willenergize 30 seconds after the gas valve opens (20 secondsafter the flame stabilization period ends). Normal furnaceoperation will continue until the thermostat circuit between Rand W is opened. When the thermostat circuit opens, theignition control is de-energized. When the ignition control isde-energized, the gas flow stops, and the burner flames areextinguished. The ventor continues to operate for 15 secondsafter the gas flow stops.Label all wires prior to disconnecting when servic-ing controls. Wiring errors can cause improper anddangerous operation. Verify proper operation afterservicing.