Economizer Damper Adjustment

Exhaust Air Dampers

Verify that the exhaust dampers (if equipped) close tightly when the unit is off. Adjust the damper linkage as necessary to ensure proper closure. An access panel is provided un- der each damper assembly.

Fresh Air & Return Air Damper Operation

The fresh air and return air damper linkage is accessible from the filter section of the unit. The damper linkage con- necting the fresh air dampers to the return air dampers is preset from the factory in the number 1 position. Refer to Table 4-5 for the appropriate linkage position for the unit and operating airflow (CFM).

WARNING

No Step Surface!

Do not walk on the sheet metal drain pan. Walking on the drain pan could cause the supporting metal to col- lapse. Failure of the drain pan could result in death or serious injury.

Note: Bridging between the unit's main supports may consist of multiple 2 by 12 boards or sheet metal grating.

Arbitrarily adjusting the fresh air dampers to open fully when the return air dampers are closed or; failing to main- tain the return air pressure drop with the fresh air dampers when the return air dampers are closed, can overload the supply fan motor and cause building pressurization control problems due to improper CFM being delivered to the space.

The fresh air/return air damper linkage is connected to a crank arm with a series of holes that allows the installer or operator to modify the amount of fresh air damper travel in order to match the return static pressure. Refer to

Table 4-5 for the equivalent return air duct losses that corre- spond to each of the holes illustrated in Figure 4-5.

To Adjust the Fresh Air Damper Travel:

1.Drill a 1/4" hole through the unit casing up stream of the return air dampers. Use a location that will produce an accurate reading with the least amount of turbulence.

Several locations may be necessary, and average the reading.

WARNING

Hazardous Voltage!

Disconnect all electric power, including remote discon- nects before servicing. Follow proper lockout/tagout procedures to ensure the power can not be inadvert- ently energized. Failure to disconnect power before ser- vicing could result in death or serious injury.

HIGH VOLTAGE IS PRESENT AT TERMINAL BLOCK 1TB1 OR UNIT DISCONNECT SWITCH 1S14.

Unit Start-Up (Continued)

2.Close the disconnect switch or circuit protector switch that provides the supply power to the unit's terminal block 1TB1 or the unit mounted disconnect switch 1S14.

3.Turn the 115 volt control circuit switch 1S1 and the 24 volt control circuit switch 1S70 to the "On" position.

4.Open the Human Interface access door, located in the unit control panel, and press the SERVICE MODE key to display the first service screen. Refer to the latest edition of the applicable SAHF-PTG manual for CV or VAV applications for the SERVICE TEST screens and programming instructions.

5.Use Table 4-1 to program the following system components for operation by scrolling through the displays;

Supply Fan (On)

Inlet Guide Vanes (100% Open, if applicable) Variable Frequency Drive (100% Output, if applicable) RTM Occ/Unocc Output (Unoccupied)

Fresh Air Dampers (Closed)

6.Once the configuration for the components is complete, press the NEXT key until the LCD displays the “Start test in __Sec.” screen. Press the + key to designate the delay before the test is to start. This service test will begin after the TEST START key is pressed and the delay desig- nated in this step has elapsed. Press the ENTER key to confirm this choice.

WARNING

Rotating Components!

7.Press the TEST START key to start the test. Remember that the delay designated in step 6 must elapse before the fan will begin to operate.

8.With the fresh air dampers fully closed and the supply fan operating at 100% airflow requirements, measure the return static pressure at the location determined in step 1.

9.Press the STOP key at the Human Interface Module in the unit control panel to stop the fan operation.

10.Open the field supplied main power disconnect switch upstream of the rooftop unit. Lock the disconnect switch in the "Open" position while working on the dampers.

11.Compare the static pressure reading to the static pres- sure ranges and linkage positions in Table 4-5 for the unit size and operating CFM.