HP 422690 I manual Measuring AIR Temperature Rise, Checking Controls

5.Make sure that blower speed taps are set for proper heating and cooling. Refer to Section 18, "Adjusting Blower Speed." Heating speed should be set according to Table 9. Cooling speed should be set to meet cooling equipment requirements. See Table 10 for cooling airflow capacities at 0.5 inch W.C.

6.Place slope gauge near furnace, level and adjust scale to read 0.00 inches W.C.

7.Insert one static pressure tap into supply-air duct between furnace and cooling coil or in supply air plenum for heating only systems. Connect this pressure tap to positive pressure side of slope gauge.

8.Insert other static pressure tap in return air plenum. Connect this pressure tap to negative pressure side of slope gauge.

9.Start blower.

??Blower heating speed can be run by jumping terminals "R" and "G" on 24-volt terminal block located on Fan Timer.

??Blower cooling speed can be run by jumping terminals "R" and "Y" on 24-volt terminal block located on Fan Timer.

NOTE: On cooling speed, there is a short on-delay before blower starts and a 60-second off-delay before blower

stops.

10. Read duct system static pressure from slope gauge.

NOTE: If air filter location is upstream of return-air pressure tap, static pressure must be adjusted to exclude filter pressure drop. Do this by subtracting 0.08 inches W.C. from the measured static pressure.

11.Remove jumper wire from 24-volt terminal strip. Remove pressure taps and seal holes in ductwork.

SECTION 20. MEASURING AIR TEMPERATURE RISE

You will need 2 thermometers with 1-degree resolution capable of reading up to 175 degrees F.

Air temperature rise (supply air temperature minus return air temperature) must be within allowable air-temperature

rise range specified on furnace rating plate and in Table 9.

Follow this procedure:

1.Open supply air registers and return air grilles. Make sure registers and grilles are free of obstruction from rugs, carpets, drapes or furniture.

2.Set balancing dampers in supply duct system.

3.Check ductwork for obstructions or leaks.

4.Make sure filters are clean and in place.

5.Make sure that blower speed taps are set for proper heating and cooling. Refer to Section 18, "Adjusting Blower Speed." Heating speed should be set according to Table 9. Cooling speed should be set to

meet cooling equipment requirements. See Table 10 for cooling airflow capacities at 0.5 inch W.C.

6.Place one thermometer in supply air plenum

approximately 2 feet from furnace. Locate thermometer tip in center of plenum to ensure proper temperature measurement.

7.Place second thermometer in return-air duct

approximately 2 feet from furnace. Locate thermometer tip in center of duct to ensure proper temperature measurement.

8.Set room thermostat on highest temperature setting. Operate furnace 6 minutes . Record supply air and return air temperatures.

9.Calculate air temperature rise by subtracting return air temperature from supply air temperature.

??If air temperature rise is above temperature rise range specified in Table 9, furnace is overfired or has insufficient airflow. Check gas input following the instructions in Section 14, "Checking Gas Input Rate." If air temperature rise is still above temperature rise range specified, more heating airflow is needed. Change blower heating speed to a higher setting following instructions in Section 18, "Adjusting Blower Speed."

??If air temperature rise is below temperature rise range specified in Table 9, furnace is underfired or has too much airflow. Check gas input following the instructions in Section 14, "Checking Gas Input Rate." If air temperature rise is still below temperature rise range specified, less heating airflow is needed. Change blower heating speed to a lower setting following instructions in Section 18, "Adjusting Blower Speed."

??After making adjustments, you must check air temperature rise to verify that resulting air temperature rise is within allowable range. If air temperature rise is still outside temperature rise range specified in Table 9, check duct system design with a qualified heating engineer. It may be necessary to re-size duct work. Recheck air temperature rise after revising duct systems.

10.Set room thermostat to desired setting.

11.Remove thermometers and seal ductwork holes.

SECTION 21. CHECKING

CONTROLS

Before leaving work site, check to see that all controls are functioning properly.

You will need a 0 to 15 inch water manometer with 0.1 inch resolution and a 1/8" NPT manual shut-off valve.

Follow this procedure:

1.Turn off electricity at electrical disconnect switch next to furnace.

2.Remove three screws holding burner access panel in place. Remove burner access panel.

3.Turn gas control switch to OFF position.